Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Response to commentary ‘towards more meaningful scenarios of biodiversity responses to land-use change in Central Asia
    Nunez, Sarahi ; Alkemade, Rob ; Kok, Kasper ; Leemans, Rik - \ 2020
    Regional Environmental Change 20 (2020)3. - ISSN 1436-3798
    Biodiversity change - Grasslands - Grazing intensification - Land-use scenarios

    With this letter, we respond to the commentary by Kamp et al. on our paper (Nunez et al. in Reg Environ Chang 20:39, 2020) that reports on potential biodiversity change in Central Asian grasslands using climate and land-use change scenarios. In their commentary, Kamp et al. criticize data and methods employed and discuss several shortfalls of our approach. In this response, we argue that in our paper projections of future biodiversity already acknowledge the issues indicated by Kamp et al. We elaborate on the reasons why. We maintain our main finding that, based on a number of contrasting scenarios (shared socioeconomic pathways and representative concentration pathways combinations), biodiversity in grasslands in Central Asia will potentially decline under each scenario. We conclude that while our data and methods conservatively estimate potential biodiversity changes in the Central Asian grasslands, they could be enriched with more elements. The results, however, are likely to confirm the vulnerability of these grasslands and the possible decline in their biodiversity.

    Outcome prediction of head and neck squamous cell carcinoma by MRI radiomic signatures
    Mes, Steven W. ; Velden, Floris H.P. van; Peltenburg, Boris ; Peeters, Carel F.W. ; Beest, Dennis E. te; Wiel, Mark A. van de; Mekke, Joost ; Mulder, Doriene C. ; Martens, Roland M. ; Castelijns, Jonas A. ; Pameijer, Frank A. ; Bree, Remco de; Boellaard, Ronald ; Leemans, C.R. ; Brakenhoff, Ruud H. ; Graaf, Pim de - \ 2020
    European Radiology (2020). - ISSN 0938-7994
    Factor analysis - Head and neck neoplasms - Magnetic resonance imaging - Prognosis

    Objectives: Head and neck squamous cell carcinoma (HNSCC) shows a remarkable heterogeneity between tumors, which may be captured by a variety of quantitative features extracted from diagnostic images, termed radiomics. The aim of this study was to develop and validate MRI-based radiomic prognostic models in oral and oropharyngeal cancer. Materials and Methods: Native T1-weighted images of four independent, retrospective (2005–2013), patient cohorts (n = 102, n = 76, n = 89, and n = 56) were used to delineate primary tumors, and to extract 545 quantitative features from. Subsequently, redundancy filtering and factor analysis were performed to handle collinearity in the data. Next, radiomic prognostic models were trained and validated to predict overall survival (OS) and relapse-free survival (RFS). Radiomic features were compared to and combined with prognostic models based on standard clinical parameters. Performance was assessed by integrated area under the curve (iAUC). Results: In oral cancer, the radiomic model showed an iAUC of 0.69 (OS) and 0.70 (RFS) in the validation cohort, whereas the iAUC in the oropharyngeal cancer validation cohort was 0.71 (OS) and 0.74 (RFS). By integration of radiomic and clinical variables, the most accurate models were defined (iAUC oral cavity, 0.72 (OS) and 0.74 (RFS); iAUC oropharynx, 0.81 (OS) and 0.78 (RFS)), and these combined models outperformed prognostic models based on standard clinical variables only (p < 0.001). Conclusions: MRI radiomics is feasible in HNSCC despite the known variability in MRI vendors and acquisition protocols, and radiomic features added information to prognostic models based on clinical parameters. Key Points: • MRI radiomics can predict overall survival and relapse-free survival in oral and HPV-negative oropharyngeal cancer. • MRI radiomics provides additional prognostic information to known clinical variables, with the best performance of the combined models. • Variation in MRI vendors and acquisition protocols did not influence performance of radiomic prognostic models.

    Turning the tide: how marine ecosystem-service assessments contribute to preserve healthy seas
    Böhnke-Henrichs, Anne - \ 2020
    Wageningen University. Promotor(en): R. Leemans, co-promotor(en): R. de Groot. - Wageningen : Wageningen University - ISBN 9789463953894 - 196

    Healthy marine ecosystems are essential for human well-being because they sustain livelihoods, shape traditions and identity of coastal communities, provide food, moderate extreme weather events or mitigate effects of anthropogenic climate heating by uptaking and storing carbon dioxide. These ecosystem contributions to human well-being are conceptualized as ecosystem services and certainty and scientific consensus increases that they are at risk due to globally degrading marine ecosystems.

    International policies have responded to the decline of marine ecosystems. In Europe, the Marine Strategy Framework Directive sets the frame for conserving and sustainably using European seas. The directive aims at biologically diverse and dynamic seas that are clean, healthy and productive. To implement these aims, the Directive requires to adopt an Ecosystem Approach to marine management. This approach is characterized by the so-called Malawi Principles which also reflect several challenges involved in implementing this approach. For instance, human pressures that degrade marine ecosystems need to be reduced to sustainable levels, the preferences of stakeholders and society in general, need to be considered in management decisions, and management effects on ecosystem services need to be taken into account. These three challenges are addressed by my thesis which aims to develop, adapt and apply marine ecosystem service assessments and to understand how these assessments assist to achieve the policy goal of healthy seas. I approach this objective by three case studies in the Black Sea, in the Mediterranean Sea and in the North Sea. These case studies apply a similar marine ecosystem service typology at different spatial scales to assess management effects on marine ecosystem services.

    Chapter 2 develops a marine ecosystem service typology with a particular focus on sustainable marine management that restores habitats or reduces human pressures. Such measures improve ecosystem processes and functions as prerequisites for ecosystem service supply. To reflect ecosystem service supply changes, my typology includes only those marine aspects that depend on ecosystem processes and functions. This implies to exclude from the typology marine aspects that are purely abiotic or utilize the so-called carrier function of marine ecosystems. My thesis applies its marine ecosystem service typology to assess marine management effects in three different case studies in the context of the EU’s Marine Strategy Framework Directive and the EU’s Habitats Directive. All three case studies assess ecosystem services at different spatial scales that range from the entire regional sea to a sub-regional part of the North Sea, to a local case study on a part of a Mediterranean lagoon. The typology proved for all these different policy contexts and spatial scales sufficiently comprehensive and flexible but required adaptations to specific assessment conditions. For the indicator-based assessment, the typology was refined by distinguishing particular sub-ecosystem services. For the survey-based assessment, the terminology of the particular ecosystem service definitions and descriptions were re-phrased to avoid technical terms and improve comprehensibility by interviewees.

    The ecosystem service typology assists in structuring and guiding the ecosystem service assessments regarding which ecosystem services to include. Moreover, a joint typology can facilitate the transfer of assessment methods (e.g. ecosystem service indicators) and the comparison of assessment results (e.g. to integrate findings from different assessments). However, even an agreed general typology leaves room for interpretation that can question the comparability of different assessments. Particularly the Black Sea case study illustrates that each ecosystem service is linked to a number of sub-services. This makes it unlikely that different assessments investigate the same and thus comparable sub-services. To apply a general, pre-defined ecosystem service typology can also involve the risk to restrict an assessment because even a comprehensive typology may fail to capture very specific local ways of how ecosystems contribute to human well-being.

    To summarize, ecosystem service typologies can be a very useful tool that should be carefully applied. Even comprehensive typologies most likely need adaptation to case study conditions. Perhaps even more relevant than a general typology is to agree on what is to be considered an ecosystem service (and what not)? Particularly regarding purely abiotic ecosystem components and the carrier function, current typologies reveal large disagreement.

    Chapter 3, aims to understand how nutrient and fisheries management affect marine ecosystem services in the Black Sea. This chapter also considers the cumulative effects of both management aspects. The study compares three different management scenarios that combine fishing at maximum sustainable yield with different levels of primary production (that reflects the Black Sea’s eutrophication status). The study reveals trends of marine ecosystem service supply under the three management scenarios at the scale of the entire Black Sea. The study developed a set of indicators for ecosystem processes, functions and ecosystem services and mapped how these indicators are interlinked in ecosystem service supply. Results suggest that sustainable fisheries management is most favourable from an ecosystem service perspective, because it involves many ES increases and the least decreases. However, this is a rather tentative result due to remaining knowledge gaps.

    This chapter concludes with recommendations for ecosystem service assessments in the context of the Marine Strategy Framework Directive and beyond: (1) To deal with knowledge gaps, marine ecosystem service assessments should combine qualitative and quantitative methods and an interdisciplinary team that includes several regional sea experts is crucial; (2) to split up ecosystem services into several sub-ecosystem services increases the specificity of the assessment; (3) to analyse cumulative management effects is relevant for identifying synergies and useful antagonistic effects. To combine such synergistic and antagonistic effects smartly can assist in alleviating negative management outcomes.

    Chapter 4 analyses how participatory salt-marsh restoration affects local residents’ appreciation of salt marshes and their support for conservation. This study surveyed local residents twice at an early and at the final stage of a restoration project and compared the results of both surveys. Results suggest that salt marshes are widely appreciated in the Venice lagoon region and are associated with nature conservation but also with a range of different ecosystem services and social benefits. This appreciation increased between both surveys and the participatory restoration approach is supposed to have contributed to this increase. Results further show a general understanding and acceptance that salt marsh conservation and restoration comes at a cost because they express a willingness to pay for restoration, to support restoration works in their free time and to accept restrictions in fishing and boating. Despite this overall support for restoration, a coherent, lagoon-wide and long-term funded salt marsh management scheme is lacking so far, although these protected habitats are disappearing at high rates. This chapter presents suggestions on how this pressing challenge in Venice lagoon management can be addressed: (1) Salt marsh management benefits from involving local residents. (2) Information and education measures should accompany salt marsh conservation to ensure long term conservation support. (3) Spatial zoning can be used to solve conflicts between different saltmarsh uses and conservation.

    Chapter 5 applies three different methods to understand the effects of nature conservation, offshore wind farm construction and fisheries on the Dogger Bank (North Sea) and aims to understand how these different methods can be combined for a more comprehensive understanding of management implications. The three methods involve an indicator assessment to understand ecosystem service supply, a Discrete Choice Experiment to reveal ecosystem service demand and a Citizens’ jury that reveals the public’s management preferences for the Dogger Bank. Integrating the findings of such different methods proved challenging because they differ regarding the ecosystem services covered and regarding their output units. These differences hamper a smooth comparison of individual ecosystem services’ supply and demand. Instead, findings were integrated based on their major management implications for the three management foci: conservation, fisheries and wind farms. All three methods largely agree in favouring conserving the Dogger Bank. Results for the other management foci are, however, rather mixed. Yet, even contradicting results can still provide valuable information to management decisions because they highlight management issues that require attention and can also reveal underlying reasons for management conflicts. This Chapter exemplifies that applying and integrating different methods improves the basis for decision making and is thus relevant for marine management.

    My thesis shows that ecosystem service assessments provide information that is relevant for improving marine management. However, marine management decisions in Europe frequently lack consideration of ecosystem service implications. Since current management approaches failed to preserve our life-sustaining oceans the application of the ecosystem service concept offers a way forward to turn the tide in marine ecosystem management towards more healthy seas.

    Potential biodiversity change in Central Asian grasslands : scenarios for the impact of climate and land-use change
    Nunez, Sarahi ; Alkemade, Rob ; Kok, Kasper ; Leemans, Rik - \ 2020
    Regional Environmental Change 20 (2020)2. - ISSN 1436-3798
    Biodiversity change - Climate change - Grasslands - Grazing intensification - Land-use scenarios

    Central Asian grasslands are extensively used for pastoral livestock grazing. This traditional land use is nowadays characterized by intensifying grasslands into more productive pastures. This change affects biodiversity and diminishes grasslands’ ecological role. Biodiversity impacts are probably also exacerbated by climate change. These changes in biodiversity are poorly studied in Central Asia. Here, we estimated potential biodiversity changes in the Central Asian grasslands using the latest shared socio-economic pathways and the representative concentration pathways (i.e., SSP-RCP scenario framework). We selected scenarios with contrasting socio-economic and climate conditions (i.e., SSP1-RCP4.5, SSP3-RCP8.5, SSP4-RCP4.5, and SSP5-RCP8.5) and further detailed the land-use scenarios for the region using stakeholders’ input. We indicated future biodiversity by the mean species abundance indicator. The contrasting scenario combinations showed that grasslands’ biodiversity will decline under each scenario. The strongest impact on biodiversity is expected in SSP5-RCP8.5, where half of the grasslands are likely to lose most of their local originally occurring species by 2100. The lowest impact is expected in SSP4-RCP4.5. Our study stresses the potential vulnerability of this region to increasing land-use intensity and climate change. These impact projections can help regional decision makers to develop and implement better biodiversity-conservation and sustainable management policies for these grasslands.

    Projecting terrestrial biodiversity intactness with GLOBIO 4
    Schipper, Aafke M. ; Hilbers, Jelle P. ; Meijer, Johan R. ; Antão, Laura H. ; Benítez-López, Ana ; Jonge, Melinda M.J. de; Leemans, Luuk H. ; Scheper, Eddy ; Alkemade, Rob ; Doelman, Jonathan C. ; Mylius, Sido ; Stehfest, Elke ; Vuuren, Detlef P. van; Zeist, Willem Jan van; Huijbregts, Mark A.J. - \ 2020
    Global Change Biology 26 (2020)2. - ISSN 1354-1013 - p. 760 - 771.
    anthropocene - biodiversity scenarios - global environmental change - land-use downscaling - mean species abundance

    Scenario-based biodiversity modelling is a powerful approach to evaluate how possible future socio-economic developments may affect biodiversity. Here, we evaluated the changes in terrestrial biodiversity intactness, expressed by the mean species abundance (MSA) metric, resulting from three of the shared socio-economic pathways (SSPs) combined with different levels of climate change (according to representative concentration pathways [RCPs]): a future oriented towards sustainability (SSP1xRCP2.6), a future determined by a politically divided world (SSP3xRCP6.0) and a future with continued global dependency on fossil fuels (SSP5xRCP8.5). To this end, we first updated the GLOBIO model, which now runs at a spatial resolution of 10 arc-seconds (~300 m), contains new modules for downscaling land use and for quantifying impacts of hunting in the tropics, and updated modules to quantify impacts of climate change, land use, habitat fragmentation and nitrogen pollution. We then used the updated model to project terrestrial biodiversity intactness from 2015 to 2050 as a function of land use and climate changes corresponding with the selected scenarios. We estimated a global area-weighted mean MSA of 0.56 for 2015. Biodiversity intactness declined in all three scenarios, yet the decline was smaller in the sustainability scenario (−0.02) than the regional rivalry and fossil-fuelled development scenarios (−0.06 and −0.05 respectively). We further found considerable variation in projected biodiversity change among different world regions, with large future losses particularly for sub-Saharan Africa. In some scenario-region combinations, we projected future biodiversity recovery due to reduced demands for agricultural land, yet this recovery was counteracted by increased impacts of other pressures (notably climate change and road disturbance). Effective measures to halt or reverse the decline of terrestrial biodiversity should not only reduce land demand (e.g. by increasing agricultural productivity and dietary changes) but also focus on reducing or mitigating the impacts of other pressures.

    Archetyping shared socioeconomic pathways across scales: An application to central Asia and European case studies
    Pedde, Simona ; Kok, Kasper ; Hölscher, Katharina ; Oberlack, Christoph ; Harrison, Paula A. ; Leemans, Rik - \ 2019
    Ecology and Society 24 (2019)4. - ISSN 1708-3087
    Multiscale scenarios - Narratives - Scenario archetypes - Shared socioeconomic pathways - Worldviews

    The complex interactions of drivers represented in scenarios and climate change impacts across scales have led to the development of multiscale scenarios. Since the recent development of global shared socioeconomic pathways (SSPs), which have started being downscaled to lower scales, the potential of scenarios to be relevant for decision making and facilitate appreciation and inclusion of different perspectives has been increasing, compared with a single-scale global scenario set. However, in practice, quantitative downscaling of global scenarios results in narratives that are compressed from the global level to fit the local context to enhance consistency between global and local scales. We brought forward the concept of scenario archetypes to analyze multiscale SSP scenario narratives and highlight important diverging assumptions within the same archetype. Our methodology applied scenario archetypes both as typologies, to allocate specific cases of scenarios into existing scenario archetypes, and building blocks, conceptualized with worldviews from cultural theory. Although global SSPs generally match existing archetypes and tend to be well defined, the socially unequal SSPs at subglobal scales are more nuanced, and dominant worldviews are much less straighforward to interpret than in global scenarios. The closest match was the great transition–sustainability (SSP1) archetype, whereas the most divergent was the market forces– fossil fuel development (SSP5) archetype. Overall, our results highlight the need to improve uptake of bottom-up approaches in global scenarios to improve appreciation of different perspectives as sought after in multiscale scenarios.

    Vier jaar na Parijs
    Leemans, Rik - \ 2019
    Meteorologica / Nederlandse Vereniging van Beroeps Meteorologen 28 (2019). - ISSN 0929-1504 - p. 10 - 12.
    Wageningen expertise in the IPCC climate report
    Nabuurs, Gert-Jan ; Biesbroek, Robbert ; Leemans, Rik - \ 2019
    Modelling the response of net primary productivity of the Zambezi teak forests to climate change along a rainfall gradient in Zambia
    Ngoma, Justine ; Braakhekke, Maarten C. ; Kruijt, Bart ; Moors, Eddy ; Supit, Iwan ; Speer, James H. ; Vinya, Royd ; Leemans, Rik - \ 2019
    Biogeosciences 16 (2019)19. - ISSN 1726-4170 - p. 3853 - 3867.

    Understanding climate change effects on forests is important considering the role forests play in mitigating climate change. We studied the effects of changes in temperature, rainfall, atmospheric carbon dioxide (CO2) concentration, solar radiation, and number of wet days (as a measure of rainfall intensity) on net primary productivity (NPP) of the Zambian Zambezi teak forests along a rainfall gradient. Using 1960-1989 as a baseline, we projected changes in NPP for the end of the 21st century (2070-2099). We adapted the parameters of the dynamic vegetation model, LPJ-GUESS, to simulate the growth of Zambian forests at three sites along a moisture gradient receiving annual rainfall of between 700 and more than 1000 mm. The adjusted plant functional type was tested against measured data. We forced the model with contemporary climate data (1960-2005) and with climatic forecasts of an ensemble of five general circulation models (GCMs) following Representative Concentration Pathways (RCPs) RCP4.5 and RCP8.5. We used local soil parameter values to characterize texture and measured local tree parameter values for maximum crown area, wood density, leaf longevity, and allometry. The results simulated with the LPJGUESS model improved when we used these newly generated local parameters, indicating that using local parameter values is essential to obtaining reliable simulations at site level. The adapted model setup provided a baseline for assessing the potential effects of climate change on NPP in the studied Zambezi teak forests. Using this adapted model version, NPP was projected to increase by 1.77% and 0.69% at the wetter Kabompo and by 0.44% and 0.10% at the intermediate Namwala sites under RCP8.5 and RCP4.5 respectively, especially caused by the increased CO2 concentration by the end of the 21st century. However, at the drier Sesheke site, NPP would respectively decrease by 0.01% and 0.04% by the end of the 21st century under RCP8.5 and RCP4.5. The projected decreased NPP under RCP8.5 at the Sesheke site results from the reduced rainfall coupled with increasing temperature. We thus demonstrated that differences in the amount of rainfall received in a site per year influence the way in which climate change will affect forest resources. The projected increase in CO2 concentration would thus have more effects on NPP in high rainfall receiving areas, while in arid regions, NPP would be affected more by the changes in rainfall and temperature. CO2 concentrations would therefore be more important in forests that are generally not temperature- or precipitation-limited; however, precipitation will continue to be the limiting factor in the drier sites.

    Assessing biodiversity responses to changes in climate and land use
    Nuñez Ramos, Sarahi - \ 2019
    Wageningen University. Promotor(en): R. Leemans; R. Alkemade, co-promotor(en): K. Kok. - Wageningen : Wageningen University - ISBN 9789463950428 - 143

    Biodiversity loss due to changes in climate and land use has been assessed recently. The earliest biodiversity assessments already showed that species are declining faster than at any time in the past and that ecosystems are rapidly deteriorating. Moreover, these assessments indicated that the projected changes in climate and land use likely drive further biodiversity losses in the 21st century, both directly and in synergy with each other. This accumulated evidence positions climate change and land-use change among the major human-induced direct drivers of biodiversity loss. Climate change affects biodiversity as climate variables, such as temperature and precipitation, largely determine the geographical distributions of species. Hence, in areas where climate is less suitable, species shift their geographical ranges and go extinct locally. Land-use change poses immediate threats to biodiversity as the conversion of natural habitats (e.g. forests, wetlands and grasslands) into agricultural land results in populations decline and extinctions become more likely. These adverse effects consequently change ecosystems functioning and potentially affect the supply of ecosystems services and thus human well-being.

    Although research on climate and land-use change impacts on biodiversity and the consequent implications was repeatedly conducted, the range of estimates for these impacts remains disturbingly large. Moreover, such research relied on climate-change scenarios that depict relatively small increases in global mean temperatures (i.e. <2°C). Nowadays, the plausibility of climate-change scenarios which overshoot the 2°C policy target from The Paris Agreement, is rapidly increasing. Advances are thus needed to better understand how biodiversity will respond to such larger changes, including quantifications of the expected biodiversity decline at different climate and land-use change levels, and the effect derived from interaction mechanisms between these drivers. Furthermore, the global efforts to combat climate change and to keep global average temperature to well-below 2°C will require large mitigation commitments from the land sector with potentially both positive and negative consequences for biodiversity. These implications of land-based mitigation efforts have to be further assessed.

    My PhD thesis therefore aimed to explore future biodiversity trends under projected direct and synergistic changes in climate and land use and to advance understanding of climate-change mitigation consequences for biodiversity. In this thesis, climate change was indicated by global mean temperature increase (°C) and land-use change by land-use intensity levels (i.e. grazing and cropland levels) and land-cover type transitions.

    In Chapter 2, I assessed the magnitude of expected changes of biodiversity by systematically reviewing studies and performing a meta-analysis of the responses of species distributions to climate change. I proposed two indicators to quantify the local response of terrestrial biodiversity to climate change: the fraction of remaining species (FRS) and the fraction of remaining area (FRA) with suitable habitat for each species. The FRS and FRA calculate deviations from the original biodiversity state and both they indicate biodiversity intactness. The biodiversity response was quantified for different intervals of global mean temperature increase and for different taxonomic groups and ecosystems. The results showed that projected climate-change impacts likely cause changes to the distribution of many plants and animals and this leads to severe range contractions and local extinction of some species (i.e. decreasing biodiversity). The FRS and FRA were projected to gradually decrease with significant reductions of 14% and 35% between 1°C and 2°C increases in global mean temperature, and 32% and 54% beyond 4°C increase. This chapter showed that already at moderate temperature increases the original biodiversity significant decreased.

    In Chapter 3, I estimated biodiversity decline from changes in climate and land use in grassland ecosystems, which are among the most extensive ecosystems in the world. The analysis was conducted in the Central Asian grasslands, which are nowadays transforming by changes in land use and climate. I used a scenario analysis based on the latest Shared Socio-Economic Pathways (SSPs) and Representative Concentration Pathways (RCPs) (i.e. SSP-RCP scenario framework) and further detail land-use scenarios for the region. I selected contrasting socio-economic and climate conditions (i.e. SSP1-RCP4.5, SSP3-RCP8.5, SSP4-RCP4.5 and SSP5-RCP8.5). In this analysis, the climate-change impact for the selected RCP4.5 and RCP8.5 was indicated by the FRS for grasslands as estimated in Chapter 2; the land-use change impact was indicated by changes in land-use intensity derived from the land-use scenarios; and the future biodiversity was indicated by the Mean Species Abundance (MSA). The MSA expresses the mean abundance of originally occurring species in disturbed conditions (e.g. after climate change) relative to their original abundance in undisturbed habitats. The contrasting scenario combinations showed that grasslands’ biodiversity remained under continuous threat and will further decline under each scenario. The strongest impact on biodiversity was projected in SSP5-RCP8.5, where half of the grasslands will likely undergo a large decrease in their species abundance by 2100. This chapter stressed the potential vulnerability of the Central Asian grasslands to increasing land-use intensity and climate change.

    In Chapter 4, I explored interaction mechanisms between climate and land-use change effects on biodiversity. Climate change and land-use change are often addressed as drivers that interact synergistically in several ways and alter their mutual effects on biodiversity. I identified interaction mechanisms in which species in heavily modified landscapes may respond differently to climate change than species in pristine landscapes. These interactions arise if 1) species adapted to modified landscapes differ in their sensitivity to climate change from species adapted to natural landscapes and if 2) land-use composition restricts climate-change induced dispersal of species in fragmented landscapes. To verify these conditions, I performed systematic reviews and a meta-analysis of bioclimatic studies on species distributions in landscapes with varying proportions of cropland (first condition) and species’ dispersal under climate change in fragmented landscapes (second condition). I used the FRS as the effect-size metric in this meta-analysis. Based on the results of this analysis, I found no significant interaction effect for the first condition. This indicates that the influence of global mean temperature increase on the FRS did not change with different cropland levels. No quantitative studies were found to verify the second condition for climate-change induced dispersal of species. This chapter emphasized the need to assess interactions between land-use and climate-change effects on biodiversity, integrating other conditions, such as spatial location, adaptive capacity and time lags.

    In Chapter 5, I assessed carbon-dioxide-removal options in the Agriculture, Forestry and Other Land Use sectors (i.e. land-based mitigation options) implemented in different mitigation pathways that keep global temperature increase to well-below 2°C for their biodiversity impacts using the MSA indicator. Land-based mitigation options may preserve, increase or deteriorate biodiversity, because of their land-use impact. In this chapter, I reviewed climate change mitigation studies that assessed each of the selected land-based mitigation options and indicated the land transition needed to achieve a significant climate change mitigation (i.e. potential land-cover and/or land-use change). I found that reforestation of cultivated and managed areas together with restoration of wetlands deliver the largest increase of MSA, if provided the opportunity to reach mature states over time. Contrary, intensification of agricultural areas and bioenergy with carbon capture and sequestration decreased MSA locally. Options such as afforestation and reduced deforestation, either positively or negatively affect MSA. This depends on their spatial implementation and the precise forest conservation schemes. This chapter provided insights on possible synergies that emerge from certain scenarios and their benefits for current and future biodiversity conservation in regions with large land-based mitigation potential.

    My PhD thesis advanced scientific understanding of climate and land-use change impacts on biodiversity that can feed into the current UN Conventions on Biological Diversity and Climate Change agendas. It showed future biodiversity trends and proposed methods that translate relevant information of socio-economic and climate-change drivers to assess interactions between climate and land-use change effects on biodiversity. Such knowledge is quickly becoming an important element to develop strategies for regional and global biodiversity conservation and thus to minimize biodiversity loss. I stress the importance of holding climate change well-below 2°C as this helps to maintain the composition of local communities and their climatically suitable areas, while seeking for the desired combinations that will reduce the use of detrimental land-based mitigation options to biodiversity.

    Assessing the impacts of climate change on biodiversity: is below 2 °C enough?
    Nunez, Sarahi ; Arets, Eric ; Alkemade, Rob ; Verwer, Caspar ; Leemans, Rik - \ 2019
    Climatic Change 154 (2019)3-4. - ISSN 0165-0009 - p. 351 - 365.

    Large changes in biodiversity are expected to occur if climate change continues at its current pace. Adverse effects include changes in species habitats and compositions, and consequently changes in ecosystem functioning. We assessed the magnitude of expected changes of biodiversity by performing a meta-analysis of the responses of species distributions to climate change. We focused on the proportion of local remaining species and their habitats. We summarized 97 studies and calculated two effect-size metrics from their results to quantify changes in biodiversity. These metrics are the fraction of remaining species (FRS) and the fraction of remaining area (FRA) with suitable climate for each species. Both metrics calculate deviations from the original biodiversity state and together they indicate biodiversity intactness. We found an expected gradual decrease in both FRS and FRA with significant reductions of 14% and 35% between 1 and 2 °C increase in global mean temperatures. Strong impacts are projected for both mammals and plants with FRS reductions of 19%. The climate-change response of biodiversity varies strongly among taxonomic groups and biomes. For some taxonomic groups the FRA declines strongly beyond 3 °C of temperature increase. Although these estimates are conservative, as we assume that species are unable to disperse or adapt, we conclude that already at moderate levels (i.e., 1–2 °C) of temperature increase a significant decrease of original biodiversity is projected. Our research supports the pledge to limit climate change to 1.5 °C and preferably lower to protect biodiversity.

    Effects of changes in climate and land cover on Tanzanian nature-based tourism in national parks : How are tourist attractions affected?
    Hassan, Halima Kilungu - \ 2019
    Wageningen University. Promotor(en): R. Leemans, co-promotor(en): B. Amelung; P.K.T. Munishi. - Wageningen : Wageningen University - ISBN 9789463439213 - 136

    The impacts of environmental change are generally recognised as the major threats to humans and biodiversity. With respect to nature-based tourism (NBT), the impact of environmental change not only changes the types and distributions of tourist attractions but also interfere with tourists’ comfort and safety. In Tanzania, some environment impact assessments are available, but these do cover neither NBT nor specific attractions and destinations. A major knowledge gap is that tourist attractions are poorly defined in coarse categories, such as ‘wildlife’, without details on types or species, and knowledge on how individual attractions are rooted in the environmental properties in which they occur. This knowledge gap is primarily related to the current lack of approaches to link individual attractions with their supporting environments (i.e. microclimate, soil, water and vegetation types and hydrology).

    My thesis fills this knowledge gap as it assesses how tourist attractions react to climate and land-cover change for the key Tanzanian NBT destinations: Serengeti and Kilimanjaro National Parks. To achieve this, Chapter 2 reviews and synthesizes the major factors that drove the Tanzanian NBT since the 19th century. This review provides the state-of-the-art information on the Tanzanian contemporary NBT and its destinations.

    Subsequently, I developed a tourism-resource assessment approach referred to as the ‘eco-parcel’ approach (Chapter 3). The eco-parcel approach is a three-step approach that classifies tourist attractions in fine categories and firmly links individual attractions with their supporting environments of discrete landscape patches. Each well-described discrete landscape patch is an eco-parcel. An eco-parcel is a landscape patch with distinct physical features on which one or multiple attractions occur and whose supporting environmental properties are known. I applied the eco-parcel approach in Serengeti National Park (SENAPA) and Kilimanjaro National Park (KINAPA) to identify all attractions in details. ‘Wildlife’ is now classified into types and species. In addition, plants and physical features are as well identified as key attractions for NBT. The eco-parcel approach uses land-cover type as a proxy to link attractions with their supporting environment so that land-cover change would be an approximate of environmental change. I use this link to assess the impacts of environmental change on individual tourist attractions and tourism in KINAPA and SENAPA (Chapters 4 and 5).

    Chapter 4 assesses the impacts of climate and land-cover change on the physical and sightseeing aspects of trekking in KINAPA for the past forty years. Trekking is the main tourism activity in KINAPA and sightseeing is an add-on to the experience. In this Chapter, I use a hazard-activity pairs approach to link trekking with the impacts of environmental change, especially changes in climate and land cover. Hazard-activity pairs’ is an approach to structure the analysis of the complex interactions between environmental change and tourism for particular destinations. Chapter 5 assesses the implications of climate and land-cover change on the key tourist attractions and tourism in SENAPA for the past forty years. I focus on wildebeest migration as the key tourist attraction although important attractions in SENAPA are many (cf. Chapter 3). In this chapter, I use the inferential statistics approach to make judgments on the probability of causal relationships between happened environmental impacts and observed changes on attractions through climate and land-cover statistical analysis. In Chapters 4 and 5, an increase in a specific land-cover type suggests an increase in types and distribution of attractions supported therein. Land cover is a basis for wildlife and plant to breed and grow. An adverse change in land-cover types is, therefore, an indicative threat to tourist attractions.

    Chapter 2 shows that environmental change is a root cause for the substantial changes in tourist attractions and, in turn, motives and preferences of tourists visiting Tanzania. As such, tourism activities changed from trophy hunting to mass tourism and finally, to environmental friendly tourism. These trends changed the management of tourism destinations from open areas and game reserves (mainly for hunting) or forest reserves (forest products) to national parks (mainly for experience tourism) to minimise the impacts and conserve wildlife.

    Chapter 3 concludes that, first; wildlife is not the only key attractions for NBT contrary to what is well-known. Attractions are diverse and the relative importance of each attraction for tourism varies widely. For instance, wildebeest migration and snow are indeed the key attractions but not the only important attractions in SENAPA’s and KINAPA’s tourism respectively. I found, however, high ratings for other identified attractions, such as big cats and kopjes in SENAPA, and high altitude, wildlife and flowers in KINAPA. These findings imply that assessing the relative importance of each attraction adds value in environmental-change impacts assessment from a tourism perspective. These details are likely to lead into the conservation of attractions at risk that have high tourism potential but are simultaneously marginalised in traditional and coarse assessments. Second, attractions emerge from and are connected to specific characteristic environments. This means that these characteristic environments regulate the attractiveness (e.g. breeding, migration or flowering) of many attractions. The spatial link between individual attractions and land-cover types enables the eco-parcel approach to localise the impacts assessment to individual attractions in time and space. The magnitude of environmental impacts on attractions, however, varies depending on their capacity to adapt, behaviour, sensitivity and resiliency.

    Chapter 4 shows that both, climate change and variability and land-cover change have positive and negative impacts on Mount Kilimanjaro’s tourism. Trekking is its key tourism activity and it needs conducive weather and preferably dry weather conditions and other attractions to enhance the trekking experience. Consequently, trekking Mount Kilimanjaro is mostly done during the dry months of June and September to avoid the long-rain period of March through May. The results indicate that mean annual temperature increased by 1.3oC (p< 0.05) between 1973 and 2013 and no significant trend for annual rainfall. Rainfall’s seasonality, however, did change with backward shift from May to March. This change extends the favourable trekking conditions. Moreover, land-cover changed substantially. This change has had substantial impacts on the extent and distribution of tourist attractions and, in turn, trekking experience. Heathlands that are known to attract tourists because of their flowers and giant groundsels, have increased by 38% and currently covers most of the Shira plateau. The montane forests that are also known to attract tourists because of their rich attractions including, Black-and-White Colobus monkey, birds and other wildlife species and high-crest waterfalls, have decreased by 15% in the past two decades. Snow cover, which is the mountain’s second most attraction, lost more than 50% of its extent in the last two decades.

    As these changes resonate with previous studies, in the short-term, the rapid decline in snow is likely to add to the mountain’s appeal through an increase in ‘last chance tourism’ (i.e. tourism in disappearing destinations). Warmer temperatures and reduced rainfall create better trekking conditions. In the long-term, however, the loss of snow and the montane forest cover will likely decrease the number of tourists. With this knowledge, I argue that climate and land-cover change should be considered more systematically and interactively to device appropriate management practices to adapt the Tanzanian NBT sector to current and future impacts.

    In Chapter 5, the key findings are that since the 1970s climate and land cover have changed significantly with potential influence on wildlife migration tourism and tourist comfort in SENAPA. Temperature has warmed by 0.8oC (i.e. approximately .0.2oC per decade). Mean monthly minimum and maximum temperature during the high tourism season (June to September) shifted from 17.5oC and 28.1oC in the 1970s to 18.3oC and 28.7oC in the 2000s. As a result, daily temperatures during high tourism season sometimes exceed 30oC. This rise likely interferes with comfort temperature (~21oC to 30oC) adapted for outdoor tourism activities. Rainfall totals have become highly variable despite long-term data showing no significant change. The rainfall amount received in different zones within the park varied substantially. In the northwest and eastern Serengeti, the amount of annual rainfall received in the short-rain season of October through December increased by 8%, while in the south-central Serengeti rainfall decreased by 4%. In the long rain season of March through May, the rainfall decreased by 5% in the northwest-eastern and increased by 6% in the southern-central zone. Furthermore, savannah grasslands, which form the main food for wildebeest migration, increased by 21% between 1970 and 2010. Woodlands and the riparian forests, which are the alternative food during the critical dry season, decreased by 87% and by 30% respectively. The surface water (i.e. lakes Ndutu and Magadi) shrank by 14%.

    As these changes resonate with previous studies, the implications of these results in SENAPA’s tourism include disruption of wildebeest migration patterns and timing. The disruption makes fulfilling tourists’ expectations to see wildebeest migration tourism to experience a challenge. Wildebeest-migration tourism is largely conducted between December and March in the southern-central Serengeti when the wildlife synchronously breeds and between June and September in northern Serengeti when the migration aggregates along the Mara River and ready to migrate to the Masai Mara in Kenya. The findings in Chapter 5 imply that this calendar is slowly changing and affects tourism. Personal communication in 2013 with park ecologist and tourism wardens acknowledge that the odds of delayed migration in the southern and northern Serengeti have increased and sometimes make tourism a chaotic experience. In the future, the likeness for tourists to visit Serengeti only to find no migration is increasing. Strategies to adapt tourism to the impacts of climate and land-cover change require active and integrated management approaches to improve or maintain the park’s attractiveness. The results in Chapters 4 and 5 can be used to develop climate and land-cover change adaptation strategies to inform tourism planning.

    The pioneering environmental-change impact assessments presented in my thesis bring new methods and mindset to NBT researches. This assessment is timely and indispensable. Very few studies exist that quantify the implications of environmental change on the Tanzanian NBT. My research potentially makes a substantial contribution to science and society. A detailed temporal and spatial link between tourists and attractions, and between attractions and their supporting environments provides a platform to assess the impacts of weather or climate change and land-cover change on individual tourist attractions. Chapters 4 and 5 demonstrate that the eco-parcel approach developed in Chapter 3 supports impacts assessment and allows the inclusion of tourists’ and other stakeholders’ perspectives or interests to support their decision-making process.

    My research, therefore, presents the eco-parcel approach as a generic tourism-resources assessment approach that can be used to study the impacts of environmental change on attractions in any tourism destination. The eco-parcel approach is timely. It provides NBT and recreation sectors with reliable spatial and temporal tourist attractions information to support impacts assessment. The spatial link between individual attractions with their characteristics environments not only allows to assessing changes in the distribution of attractions but also determine the attractions likely to be lost or gained when environment changes. With the ongoing rapid rate of forest loss and snow melting, the odds of complete loss of key attractions increase. I, therefore, argue that the impacts of environmental change on individual attractions and, in turn, NBT should not be ignored.

    Because attractions emerge from and are connected to specific environments, the integration of remote sensing in data collection and GIS-data analysis tool within the eco-parcel approach to determine changes on attraction is not an option. In fact, the majority of tourism destinations in developing countries are located in remote areas that are either difficult to access or poorly equipped with weather stations. As such, to acquire long-term environmental data including climate and types of attractions is difficult. This situation presents a challenge in addressing the impacts of environmental change on NBT in Africa’s tourism destinations. The IPCC 2014 and 2007 Africa reports acknowledge this knowledge gap. The use of land-cover within the eco-parcel approach makes a substantial contribution to tourism researches. Land-cover data are often freely acquired from satellites. Thus, the link between attractions and specific land-cover types makes the eco-parcel approach a model and a cost-effective approach to assessing the impacts of environmental change on NBT. The eco-parcel approach is the key contribution to the scientific arena

    My thesis informs the importance of the NBT sector to adapt to the impacts of environmental change. The tourism sector has long taken climate and environmental change for granted. This has hindered the mainstreaming of climate and environmental change adaptation in tourism management, planning and policies, particularly in Africa. My thesis is, therefore, timely to inform at least the three on-going policy processes. First, most Tanzanian National Parks are reviewing or about to review their general management plans and information provided in my thesis particularly the discussed impacts and implications of changing climate and land cover on tourist attractions is a valuable input. Second, Tanzania is reviewing its almost twenty-year-old tourism policy from 1999 and my research argues that the new policy should pay serious attention to the effects of environmental change. Third, in April 2018 Tanzania ratified the 2015 Paris Climate Agreement, which not only covers mitigation but also adaptation. The discussion in my thesis about the tourism-specific adaptation plans and diversification of tourism products to match with the current rate of environmental change may be taken as part of Tanzania’s adaptation efforts.

    In conclusion, my thesis quantified the impacts of environmental change on tourist attractions by using empirical environmental data (i.e. climate and land-cover) and societal data (i.e. tourist visits and preferences). Although I acknowledge that my research alone will not solve all the environmental problems that Tanzanian NBT face, my research process and methods bring innovations in tourism-resources and environmental impact assessments. In addition, my research also provides insights on how to (1) identify the impacts, (2) proactively address the impacts on individual attractions and (3) identify opportunities to invest and adapt. This knowledge is indispensable to informing decisions and actions to better manage individual attractions and the Tanzanian NBT under the current rate of environmental change.

    Carbon markets under the Paris Agreement: how can environmental integrity be ensured?
    Schneider, Lambert - \ 2019
    Wageningen University. Promotor(en): N.E. Höhne; R. Leemans. - Wageningen : Wageningen University - ISBN 9789463439138 - 162

    The 2015 Paris Agreement allows countries to use international carbon market mechanisms to achieve their nationally determined contributions (NDCs). Carbon markets provide flexibility where and when emissions are reduced and could thereby lower the cost of mitigating climate change. This can help countries to enhance the ambition of their NDCs. If not designed and implemented robustly, however, carbon markets could lead to higher emissions and increase the cost of mitigating climate change. Ensuring environmental integrity of carbon market mechanisms is thus an important prerequisite for achieving their objectives.

    This thesis assesses how the environmental integrity of international carbon market mechanisms can be ensured in the new context of the Paris Agreement in which all countries have NDCs. The thesis assesses how environmental integrity could be defined – here it is assumed to be ensured if the engagement in international transfers of carbon market units leads to the same or lower aggregated global emissions –, what the risks for undermining environmental integrity are, what approaches could be used to address these risks, and what this means for the future role of international carbon market mechanisms.

    The thesis identifies four factors that influence environmental integrity (Chapter 2):

    • The accounting for international transfers of carbon market units;

    • The quality of units generated (i.e. whether the market mechanism ensures that the issuance or transfer of units leads to emission reductions in the transferring country);

    • The ambition and scope of the mitigation target of the transferring country; and

    • Incentives or disincentives for future mitigation action, such as possible disincentives for transferring countries to define future mitigation targets less ambitiously or more narrowly in order to sell more units.

    Robust accounting is a key prerequisite for ensuring environmental integrity. The diverse scope, metrics, types and timeframe of NDC targets is an important challenge, in particular for avoiding double counting and for ensuring that the accounting for carbon markets units is representative for the mitigation efforts by countries over time. The thesis identifies three ways in which double counting can occur: through double issuance (e.g. by issuing units from the same project under two crediting programs), through double claiming of the same emission reductions by the country where the emission reductions occur and the entity using the carbon market units, and through double use of carbon market units. A key finding is that double counting can also occur in rather indirect ways which can be challenging to identify. Effectively avoiding double counting mainly requires rules for accounting of unit transfers, appropriate design of carbon market mechanisms, and consistent tracking and reporting of units (Chapter 3).

    Unit quality can, in theory, be ensured through appropriate design of carbon market mechanisms; in practice, existing mechanisms face considerable challenges in ensuring unit quality. The thesis assesses an interesting real-world example of how carbon markets can create perverse incentives and thereby undermine unit quality. It shows that projects abating HFC-23 and SF6 waste gas emissions under the Kyoto Protocol’s Joint Implementation mechanism increased waste gas generation to unprecedented levels as a means to increase credit revenues. Due to these perverse incentives, about two third of the issued credits do not represent actual emission reductions. This case study provides important lessons for carbon markets under the Paris Agreement because Joint Implementation was implemented in countries that had mitigation targets, and thus in a similar context as for countries with NDC targets (Chapter 4).

    Unit quality is also an important matter for the new Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) adopted by the International Civil Aviation Organization. The scheme requires airline operators to purchase carbon market units to offset the increase in emissions above 2020 levels. It could constitute the single largest demand for carbon market units after 2020. The thesis shows that environmental integrity would be undermined if the scheme allows the unlimited use of credits from already implemented projects. While additionality and the quantification of emission reductions are, in principle, key considerations for unit quality for crediting mechanisms, the greenhouse gas (GHG) emissions impact from using credits from already implemented projects is more complex. If the supply of credits considerably exceeds demand, a key consideration for the global GHG emissions impact is whether already implemented projects would continue to reduce GHG emissions even without credit revenues, or whether they are ‘vulnerable’ to discontinuing GHG abatement. A detailed assessment of the status and operating conditions of projects under the Clean Development Mechanism, and their marginal costs of supplying credits, shows that most projects would continue GHG abatement even if they cannot sell credits. If CORSIA allows airline operators the unlimited use of offset credits from these projects, this will not only undermine its environmental objectives but also lead to continued low carbon prices, and thus neither offer incentives for new investments nor lead to any significant revenues for already implemented projects. The thesis recommends limiting eligibility under CORSIA to new or ‘vulnerable’ projects (Chapter 5).

    Unit quality is also a key consideration when linking emissions trading systems (ETSs). As linking of ETSs faces several practical and political challenges and risks, including with regard to whether allowances have ‘quality’ and whether linking provides incentives or disincentives to enhance the ambition of caps, policy-makers are considering also restricted forms of linking ETSs. The thesis uses a simple economic model and three criteria – abatement outcome, economic implications, and feasibility – to assess three different options for implementing restricted linking of ETSs: quotas, exchange rates, or discount rates. The analysis shows that quotas can enhance cost-effectiveness relative to no linking and allow policy-makers to retain control on the extent of unit flows. Exchange rates could enhance abatement and economic benefits or have unintended adverse implications for cost-effectiveness and total abatement, depending on how rates are set. Due to information asymmetries between the regulated entities and policy-makers setting the exchange rate, and uncertainties about future developments, setting exchange rates in a manner that avoids such unintended consequences could prove difficult. Discount rates, in contrast, can ensure that both cost-effectiveness and total abatement are enhanced. The thesis recommends the consideration of quotas or discount rates, but to refrain from using exchange rates, due to the environmental integrity risks (Chapter 6).

    The varying scope and ambition of current NDC targets, and possible disincentives to broaden their scope and enhance their ambition, could be addressed by facilitating the adoption of ambitious and economy-wide mitigation targets and by preventing the transfer of carbon market units in situations of high environmental integrity risks. This latter approach could be implemented through eligibility criteria or limits on the generation, transfer or use of carbon market units. Limits could in particular address the risk that some countries have mitigation targets that correspond to higher levels of emissions than independent projections of their likely emissions. If such ‘hot air’ can be transferred to other countries, it could increase aggregated emissions and create a perverse incentive for countries not to enhance the ambition of future mitigation targets. The thesis proposes a typology for such limits, explores key design options, and tests different types of limits in the context of fifteen countries. The analysis indicates that limits to international transfers could, if designed appropriately, prevent most of the hot air contained in current mitigation targets from being transferred, but also involve trade-offs between different policy objectives (Chapter 7).

    The thesis concludes by discussing how four strategies to mitigate environmental integrity risks – robust accounting, ensuring unit quality, facilitating economy-wide and ambitious mitigation targets, and restricting international transfers – could be implemented under the Paris Agreement and CORSIA (see Figure S-1). Crediting mechanisms pose higher risks for environmental integrity than linking of ETSs and should therefore have a limited role in the future. International oversight can reduce the risks to environmental integrity to some extent. Acquiring countries could also reduce risks by only acquiring units from countries that also have ambitious NDC targets. Overall, policy-makers should not regard carbon market approaches as the one and only ‘silver-bullet’ to mitigating climate change but carefully assess what policy instrument or mix of instruments is best suited achieve and balance different policy objectives, in particular in light of the rapid transition that is necessary to achieve the goals of the Paris Agreement (Chapter 8).

    Climate-change effects on the Zambezi teak forests' productivity in Zambia
    Ngoma, Justine - \ 2019
    Wageningen University. Promotor(en): R. Leemans; J.H. Speer, co-promotor(en): E. Moors; B. Kruijt. - Wageningen : Wageningen University - ISBN 9789463434348 - 194

    The study aimed at determining the effects of climate change on the productivity of the Zambezi Teak forests along a rainfall gradient in Zambia. To achieve this aim, six research questions guided my study: (1) Are biomass models available for the Zambezi teak forests and if so, what kind of data are needed to develop these models? (2) How are forests’ carbon stocks distributed in the wetter, intermediate and drier sites of the Zambezi teak forests? (3) How do contemporaneously and future climate affect the productivity of the forests in Africa? (4) What is the relationship between forest productivity and climatic variables in the wetter, intermediate and drier sites of the Zambezi teak forests? (5) Can the forests’ carbon stock realistically be reproduced for current climate conditions at the wetter, intermediate and drier sites? (6) How will climate change affect the productivity of the Zambezi teak forests in the wetter, intermediate and drier sites, and what are the main drivers of change? The study was carried out in the Zambian Zambezi teak forests across a south-north climatic gradient with annual rainfall ranging from 700mm in the south to 1100mm in the north. Following this climatic gradient, I conducted my study at the wetter Kabompo, intermediate Namwala and the drier Sesheke sites. At the Kabompo site, the study was carried out in Kabompo and Zambezi Forest Reserves, while the Ila Forest Reserve was surveyed at the Namwala site. I surveyed the Masese forest reserve at the Sesheke site. The aim was achieved by integrating information from biomass measurements, tree-ring analysis and dynamic vegetation modelling. Three above-ground biomass models, one below-ground biomass model and one stump model were developed. The power model fitted well and diameter at breast height (DBH, p < 0.0001) significantly affected tree biomass. Using the newly developed biomass models, I found that the forests’ carbon stock was highest at the wetter Kabompo site (36ton C ha¯¹), followed by the intermediate Namwala site (25ton C ha¯¹). The lowest carbon stock value was recorded at the drier Sesheke site (16ton C ha¯¹). A climate-to-growth study through the tree-rings of the dominant Baikiaea plurijuga species showed that evaporation had the highest influence on tree growth at all the three study sites compared to temperature and rainfall alone. Literature showed that from 1900 to 2011, mean annual Net Primary Productivity (NPP) increased by 4.8% in Africa, and from the year 1950, the combined NPP of all African biomes is projected to reduce by 8% by the end of the 21st century.

    We used local soil parameter values to characterize texture and measured local tree parameter values for maximum crown area, wood density, leaf longevity and allometry, and LPJ-GUESS simulated forest carbon values were closest to the measured forest carbon stock values at the wetter Kabompo site, followed by the drier Sesheke site and then the intermediate Namwala site. NPP related positively with mean annual temperatures of current year, previous year and previous two years at all sites and projections showed that NPP would increase by 1.77% and 0.69% at the wetter Kabompo, and by 0.44% and 0.10% at the intermediate Namwala sites under Representative Concentration Pathways 8.5 (RCP8.5) and 4.5 (RCP4.5) respectively, especially caused by the increased carbon dioxide (CO₂ ) concentration by the end of the 21st century. However, at the drier Sesheke site, NPP would respectively decrease by 0.01% and 0.04% by the end of the 21st century under RCP8.5 and RCP4.5. The projected decreased NPP under RCP8.5 at the Sesheke site results from the reduced rainfall coupled with increasing temperature. This distinct response indicates that differences in the amount of rainfall received in a site per year influence the way in which the projected changes in climate and CO₂ will affect forests resources. The projected increase in CO₂ concentration would have more effects on NPP in high rainfall receiving areas, while in arid regions, NPP would be affected more by the changes in rainfall and temperature. CO₂ concentrations would therefore be more important in forests that are generally not temperature or precipitation limited, while precipitation will continue to be the limiting factor in the drier sites.

    Minder vliegen: makkelijker gezegd dan gedaan
    Leemans, H.B.J. ; Wals, A.E.J. ; Schroen, C.G.P.H. ; Plaisier, Christine ; Zanten, H.H.E. van - \ 2019
    Review of the implementation of the IMO’s 2011 Biofouling Guidelines in the Netherlands
    Strietman, W.J. ; Leemans, E. - \ 2019
    Wageningen : Wageningen Economic Research (Wageningen Economic Research report 2019-013) - ISBN 9789463435963 - 29
    Biofouling (or rather: biological fouling) on ships refers to the process where micro-organisms, plants, algae, or animals accumulate on outside areas of the ship that are (mostly) underwater. Biofouling on ships can result in the transfer of (non-native) invasive aquatic species. This risk has been addressed in the International Maritime Organization’s (IMO) 2011 Guidelines for the control and management of ships’ biofouling to minimize the transfer of invasive aquatic species (MEPC.207(62)). In this report, the implementation of this guideline in the Netherlands will be reviewed, based on interviews and an online survey.
    Forty Years of Climate and Land-Cover Change and its Effects on Tourism Resources in Kilimanjaro National Park
    Kilungu, Halima ; Leemans, Rik ; Munishi, Pantaleo K.T. ; Nicholls, Sarah ; Amelung, Bas - \ 2019
    Tourism Planning and Development 16 (2019). - ISSN 2156-8316 - p. 235 - 253.
    attractions - climate - Kilimanjaro - land-cover - last chance tourism - tourism

    This study explores the effects of observed changes in rainfall, temperature and land cover on the physical and sightseeing aspects of trekking in Kilimanjaro National Park. The impact analysis is organised around hazard-activity pairs approach, combinations of environmental change aspects (such as higher temperatures) and tourism activities (such as trekking and sightseeing). The results suggest that higher temperatures and reduced rainfall have lowered the risks of landslides, rock fall and mountain sickness, improving physical trekking conditions. Changes in land cover have affected sightseeing: there now are more flowers and groundsels to admire and less wildlife, waterfalls and snow. In the short term, the disappearing snow may give rise to “last chance tourism”, increasing visitation, but eventually, the loss of snow and forest cover will likely decrease the number of tourists. The paper concludes that effective management of the attractions in the expanding heathlands is the most promising option to limit the losses.

    Effects of land-use change on grassland ecosystem services in Inner Mongolia and their implications for livelihoods and sustainable management
    Du, Bingzhen - \ 2019
    Wageningen University. Promotor(en): R. Leemans, co-promotor(en): R.S. de Groot; L. Zhen. - Wageningen : Wageningen University - ISBN 9789463433983 - 191

    Grassland degradation has become a major challenge in many parts of the world, especially in arid or semi-arid areas, such as the Chinese Inner Mongolian Autonomous Region (IMAR). Previous studies of the grassland ecosystems in IMAR focused on climate change and its environmental consequences or on the land-use conflicts between agrarian communities and nomads. For better planning and management, a more integrated analysis of the consequences of land-use change for the livelihood dependence and other benefits (services) of the grasslands in IMAR is needed.

    Studies on ecosystem services of IMAR’s grasslands are usually based on remote sensing data (TM images) to assess the total value of the grassland ecosystem services using benefit transfer. Thus far, to my knowledge no study collected original data on the detailed use of ecosystem services by pastoralists on the Mongolian Plateau or on their livelihood dependence on these services at the household level. Also, no data is available on the changes over time in contrasting situations for different grassland types (like meadow, steppe and desert steppe). I therefore aim to analyse the interactions between the people and the ecosystems in IMAR in an integrated manner, and especially focus on analysing the different utilization patterns of ecosystem services and the livelihood dependence of local herders and other stakeholders in selected study sites. The ultimate goal of my study is to contribute to sustainable management of the IMAR’s ecosystems.

    To achieve the goal of my PhD study, the changes in land use, household consumption patterns and their impacts have been addressed and investigated for four selected study sites: Hulun Buir, Xilin Gol, Ordos and Alxa Right. These sites are in a ‘transect’ from southwest to northeast to capture the gradient in use of ecosystem services in IMAR. The methodological framework of this research combines quantitative and qualitative tools to analyse ecosystem services. It specifies an integrative approach in specific spatial and temporal contexts to evaluate trade-offs between human activities, use of ecosystem services and human well-being. This framework enables to analyse the effects of multiple factors (e.g. policies or climate and geographic conditions) on utilization patterns of ecosystem services and the influence on society. The data used to apply the framework stems from a bottom-up approach by using household surveys and other local field data.

    The results show that the householders’ intake comprised a low amount of crops, including staple foods, vegetables and fruit with a high amount of meat. However, more crops and less meat are increasingly preferred now. From 1995 to 2010, fuel consumption patterns changed from bio-fuels (especially dung) to mainly electricity and gas. Beside the influences of different environmental conditions and economic development, the grassland restoration policy measures changed grazing activities and basic household consumption patterns. Grazing activities were less affected by seasonal grazing and rotational grazing measures than other policy measures. However, when grazing was prohibited, immigration and livestock rearing control policy measures (e.g. in Xilin Gol and Ordos) fundamentally changed the basic household consumption patterns (especially for food and fuel).

    Livelihood’s food-consumption highly links to potential water consumption. The results show that compared to the direct water consumption, the indirect water consumption through food production was a major share of total water consumption. From 1995 to 2010, indirect water consumption decreased in Xilin Gol and Ordos because meat consumption decreased and fruit and vegetable consumption increased. The grassland ecosystem degradation in IMAR leads to a shortage of meat production and this causes people to purchase food from outside, but the ability to purchase food also depends on income levels.

    The implementation of the grassland conservation policies significantly affected household livelihoods and this in turn, affected household use of natural assets (primarily the land), their agricultural assets (farming and grazing activities) and their financial assets (income and consumption). The households developed adaptation measures to account for the dependence of their livelihoods on local ecosystems by initializing strategies (e.g. seeking off-farm work, leasing pasture land, increasing purchases of fodder for stall-fed animals and altering their diet and fuel consumption) to compensate for their changing livelihoods. In general, the household dependence on local grasslands decreased. This indicates a transition from traditional pastoral grazing to control grazing, rising of modern dairy cattle (intensive animal husbandry), diversification of income sources and decreases in land-based employment and in the household food and fuel consumption. These changes increased the diversity of livelihoods, household resilience and environmental sustainability.

    Five grassland utilization patterns were identified, including no use (natural grasslands), light use, moderate use, intensive use and recovery sites (degraded sites protected from further use). The results show that light use generally provided higher levels of ecosystem services than intensive use and no use. Only supporting ecosystem services differed. Surprisingly, I found no consistently positive effects of the strict conservation activities across the sites, since the results varied spatially and with respect to differences in the land-use patterns. My results suggest that appropriate grassland-utilization patterns likely enhance the supply of ecosystem services and reduce negative effects on both household livelihoods and the environment. For example, in the Hulun Buir grasslands, the precipitation is 50% higher than in the other areas. Therefore the area tolerates a higher grazing intensity before degradation occurs and its grasslands provide more provisioning services but at the cost of decreased regulating and supporting services.

    After implementing grassland conservation policies, income from cultivation and animal grazing decreased, whereas income from compensation and off-farm activities increased. The herders preferred an annual payment of 99.2 US$ ha-1 for participating in conservation activities, but the government prefers to provide only 83.8 US$ ha-1, resulting in an annual gap of 15.4 US$ ha-1. These currently too low payments probably lead some herders to expand their grazing into restricted grasslands or increase their number of animals, particularly if such payment program ends. To create an improved and sustainable payment scheme, solutions are needed that enable the herders to sustain their livelihood, while conserving the grasslands. My findings can help to establish appropriate grassland-utilization patterns and more effective payment schemes for the grasslands of IMAR and similar regions.

    Advancing the development and use of climate-change scenarios : A multi-scale analysis to explore socio-economic European futures
    Pedde, Simona - \ 2019
    Wageningen University. Promotor(en): R. Leemans, co-promotor(en): K. Kok. - Wageningen : Wageningen University - ISBN 9789463435598 - 119

    Climate change is one of the greatest challenges of our time and requires unprecedented changes to mitigate greenhouse gas emissions and adapt to climate-change impacts. Different viewpoints and definitions are used by scientists, decision makers and stakeholders to meaning of this challenge. The complexity of this diversity is amplified by the lack of a clear goal and methodology for the exploration of alternative futures in the form of future climate-change scenarios. Such scenarios need, at the same time, to be scientifically credible (credibility) and to reflect different viewpoints (legitimacy) in order to be generalised enough while representing contextual diversity (consistency) to be relevant for decision-making (salience). This thesis develops and analyse European and Central Asian socio-economic scenarios based on the global Shared Socio-economic Pathways (SSPs) to evaluate their credibility, legitimacy, consistency and relevance, with novel analytical methodologies.

    State-of-the-art scenario methodologies are framed on grounds of the objectives (exploratory and normative) and their links across scales (tight and loose links) and types (qualitative and quantitative). The first methodology is based on a fuzzy-set methodology to link qualitative (narratives) and quantitative (input variables to integrated assessment modelling) scenarios by assessing the different uncertainties resulting from their inherent complexities. In the second and third methodologies, a quantitative pan-European urbanisation model, stakeholder-led narratives and a qualitative concept of archetype are used discuss both the quantitative and qualitative scalability of the scenarios in a multi-scale approach. The fourth methodology combines a capital-capacities framework to link the goal of exploratory scenarios in relation to their relevance to decision-making by assessing their potential to achieve a (normative) desirable future.

    Overall, results suggest that linking directly the uncertainties contributes to more transparent qualitative and quantitative conversion and therefore yield more credible scenarios. When analysed across scales, global and European scenarios are consistent with both downscaled scenarios and local stakeholder-led narratives contribute to the creation of holistic and more legitimate scenarios. However, important divergences have emerged too. For instance, the scenario with high challenges to mitigation and low challenges to adaptation (SSP5) varies hugely across the European continent. The local versions of SSP5 tend to diverge from the global archetype more than the other SSPs. This divergence reflects different worldviews that challenge state-of-the-art knowledge and can ultimately question the role of global scenarios in guiding local scenario versions with a nested approach. I recommend the role of both narratives and quantifications to be equally important in capturing different uncertainties, stakes and worldviews, as well as a reframing of SSP uncertainty space as one of challenges to societal transformation, rather than one of challenges to mitigation and adaptation.

    The Mekong's future flows under multiple drivers : How climate change, hydropower developments and irrigation expansions drive hydrological changes
    Hoang, Long P. ; Vliet, Michelle T.H. van; Kummu, Matti ; Lauri, Hannu ; Koponen, Jorma ; Supit, Iwan ; Leemans, Rik ; Kabat, Pavel ; Ludwig, Fulco - \ 2019
    Science of the Total Environment 649 (2019). - ISSN 0048-9697 - p. 601 - 609.
    Climate change - Hydrological impacts - Hydropower dams - Irrigation expansion - Mekong basin - VMod model

    The river flow regime and water resources are highly important for economic growths, flood security, and ecosystem dynamics in the Mekong basin – an important transboundary river basin in South East Asia. The river flow, although remains relatively unregulated, is expected to be increasingly perturbed by climate change and rapidly accelerating socioeconomic developments. Current understanding about hydrological changes under the combined impacts of these drivers, however, remains limited. This study presents projected hydrological changes caused by multiple drivers, namely climate change, large-scale hydropower developments, and irrigated land expansions by 2050s. We found that the future flow regime is highly susceptible to all considered drivers, shown by substantial changes in both annual and seasonal flow distribution. While hydropower developments exhibit limited impacts on annual total flows, climate change and irrigation expansions cause changes of +15% and −3% in annual flows, respectively. However, hydropower developments show the largest seasonal impacts characterized by higher dry season flows (up to +70%) and lower wet season flows (−15%). These strong seasonal impacts tend to outplay those of the other drivers, resulting in the overall hydrological change pattern of strong increases of the dry season flow (up to +160%); flow reduction in the first half of the wet season (up to −25%); and slight flow increase in the second half of the wet season (up to 40%). Furthermore, the cumulative impacts of all drivers cause substantial flow reductions during the early wet season (up to −25% in July), posing challenges for crop production and saltwater intrusion in the downstream Mekong Delta. Substantial flow changes and their consequences require careful considerations of future development activities, as well as timely adaptation to future changes.

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