Paleosol-derived data used for the reconstruction of environmental conditions during the Holocene in the upper part of the Kali Gandaki valley, Central Nepal
Menges, Johanna ; Hovius, Niels ; Andermann, Christoff ; Dietze, Michael ; Swoboda, Charlie ; Cook, Kristen L. ; Adhikari, Basanta R. ; Vieth-Hillebrand, Andrea ; Bonnet, Stephane ; Reimann, Tony ; Koutsodendris, Andreas ; Sachse, Dirk - \ 2019
degradation - paleosols - climate - desertification - isotopes - drought - precipitation
This data publication contains the data sets of a study aiming to reconstruct environmental conditions during the Holocene in the upper part of the Kali Gandaki valley, Nepal. The data are for samples taken from paleosol sections in the Upper Mustang region (Menges et al. 2019). On these samples we measured the grain size distribution to gain information about the depositional processes, pollen data to reconstruct past vegetation, 14C isotopes in the humin fraction of organic matter for soil formation ages, and hydrogen isotopic composition on n-alkanes to reconstruct past hydrological conditions. This is complemented with optically stimulated luminescence data for additional depositional age information, surface water samples and modern soil samples to constrain modern hydrological conditions, and sediment concentration data to gain insights into erosion processes. The data was generated between 2013-02 and 2018-12. The data files are provided in Excel and tab-delimited text versions.
Can we infer plant facilitation from remote sensing? A test across global drylands
Xu, C. ; Holmgren, M. ; Nes, E.H. van; Maestre, F.T. ; Soliveres, S. ; Berdugo, M. ; Kefi, S. ; Marquet, P.A. ; Abades, S. ; Scheffer, M. - \ 2015
Ecological Applications 25 (2015)6. - ISSN 1051-0761 - p. 1456 - 1462.
positive interactions - vegetation patterns - spatial-patterns - ecosystems - desertification - distributions - environments - competition - dynamics - ecology
Facilitation is a major force shaping the structure and diversity of plant communities in terrestrial ecosystems. Detecting positive plant-plant interactions relies on the combination of field experimentation and the demonstration of spatial association between neighboring plants. This has often restricted the study of facilitation to particular sites, limiting the development of systematic assessments of facilitation over regional and global scales. Here we explore whether the frequency of plant spatial associations detected from high-resolution remotely-sensed images can be used to infer plant facilitation at the community level in drylands around the globe. We correlated the information from remotely-sensed images freely available through Google EarthTM with detailed field assessments, and used a simple individual-based model to generate patch-size distributions using different assumptions about the type and strength of plant-plant interactions. Most of the patterns found from the remotely-sensed images were more right-skewed than the patterns from the null model simulating a random distribution. This suggests that the plants in the studied drylands show stronger spatial clustering than expected by chance. We found that positive plant co-occurrence, as measured in the field, was significantly related to the skewness of vegetation patch-size distribution measured using Google EarthTM images. Our findings suggest that the relative frequency of facilitation may be inferred from spatial pattern signals measured from remotely-sensed images, since facilitation often determines positive co-occurrence among neighboring plants. They pave the road for a systematic global assessment of the role of facilitation in terrestrial ecosystems.
Armed conflict distribution in global drylands through the lens of a typology of socio-ecological vulnerability
Sterzel, T. ; Lüdeke, M. ; Kok, M. ; Soysa, I. De; Walther, C. ; Sietz, D. ; Lucas, P. ; Janssen, P. - \ 2014
Regional Environmental Change 14 (2014)4. - ISSN 1436-3798 - p. 1419 - 1435.
climate-change - civil-war - violent conflict - african sahel - dataset - desertification - institutions - patterns - risk
Motivated by an inconclusive debate over implications of resource scarcity for violent conflict, and common reliance on national data and linear models, we investigate the relationship between socio-ecological vulnerability and armed conflict in global drylands on a subnational level. Our study emanates from a global typology of smallholder farmers’ vulnerability to environmental and socioeconomic stresses in drylands. This typology is composed of eight typical value combinations of variables indicating environmental scarcities, resource overuse, and poverty-related factors in a widely subnational spatial resolution. We investigate the relationships between the spatial distribution of these combinations, or vulnerability profiles, and geocoded armed conflicts, and find that conflicts are heterogeneously distributed according to these profiles. Four profiles distributed across low- and middle-income countries comprise all drylands conflicts. Comparing models for conflict incidence using logit regression and ROC (Receiver Operator Characteristic) analysis based on (1) the set of all seven indicators as independent variables and (2) a single, only vulnerability profile- based variable proves that the non-linear typology-based variable is the better explanans for conflict incidence. Inspection of the profiles’ value combinations makes this understandable: A systematic explanation of conflict incidence and absence across all degrees of natural resource endowments is only reached through varying importance of poverty and resource overuse depending on the level of endowment. These are non-linear interactions between the explaining variables. Conflict does not generally increase with resource scarcity or overuse. Comparison with conflict case studies showed both good agreement with our results and promise in expanding the set of indicators. Based on our findings and supporting literature we argue that part of the debate over implications of resource scarcity for violent conflict in drylands may be resolved by acknowledging and accounting for non-linear processes.
Making land management more sustainale: experience implementing a new methodological framework in Botswana
Perkins, J. ; Reed, M. ; Akanyang, L. ; Althopheng, J. ; Chanda, R. ; Magole, L. ; Mphinyane, W. ; Mulale, K. ; Sebego, R. ; Fleskens, L. ; Irvine, B. ; Kirkby, M. - \ 2013
Land Degradation and Development 24 (2013)5. - ISSN 1085-3278 - p. 463 - 477.
degradation - desertification - africa
It is increasingly recognised that tackling land degradation through more sustainable land management depends on incorporating multiple perspectives by using a variety of methods at multiple scales, including the perspectives of those who manage and/or use the land. This paper reports experience implementing a previously proposed methodological framework that is designed to facilitate knowledge sharing between researchers and stakeholders about land degradation severity and extent, and sustainable land management options. Empirical findings are presented from the Botswana site of the EU-funded Desertification Mitigation and Remediation of Land project. The paper reflects upon the challenges and benefits of the proposed framework and identifies a number of benefits, notably related to insights arising from the integration of local and scientific knowledge, and the ownership of the sustainable land management strategies that emerged from the process. However, implementing the framework was not without challenges, and levels of poverty and formal education may limit the implementation of the framework in some developing world contexts
Zaaien op dorre bodem : wereldwijde aanpak van verwoestijning
Lynden, Godert van - \ 2013
land degradation - rehabilitation - soil degradation - soil conservation - world - desertification
Ecosystem engineering by seagrasses interacts with grazing to shape an intertidal landscape
Heide, T. van der; Eklof, J.S. ; Nes, E.H. van; Zee, E.M. van der; Donadi, S. ; Weerman, E. ; Olff, H. ; Eriksson, B.K. - \ 2012
PLoS ONE 7 (2012)8. - ISSN 1932-6203
spatial vegetation patterns - geese branta-bernicla - brent geese - arid ecosystems - zostera-noltii - wadden sea - dynamics - organisms - desertification - exploitation
Self-facilitation through ecosystem engineering (i.e., organism modification of the abiotic environment) and consumer-resource interactions are both major determinants of spatial patchiness in ecosystems. However, interactive effects of these two mechanisms on spatial complexity have not been extensively studied. We investigated the mechanisms underlying a spatial mosaic of low-tide exposed hummocks and waterlogged hollows on an intertidal mudflat in the Wadden Sea dominated by the seagrass Zostera noltii. A combination of field measurements, an experiment and a spatially explicit model indicated that the mosaic resulted from localized sediment accretion by seagrass followed by selective waterfowl grazing. Hollows were bare in winter, but were rapidly colonized by seagrass during the growth season. Colonized hollows were heavily grazed by brent geese and widgeon in autumn, converting these patches to a bare state again and disrupting sediment accretion by seagrass. In contrast, hummocks were covered by seagrass throughout the year and were rarely grazed, most likely because the waterfowl were not able to employ their preferred but water requiring feeding strategy ('dabbling') here. Our study exemplifies that interactions between ecosystem engineering by a foundation species (seagrass) and consumption (waterfowl grazing) can increase spatial complexity at the landscape level
A process for effective desertification mitigation
Schwilch, G. - \ 2012
Wageningen University. Promotor(en): Leo Stroosnijder; H. Hurni, co-promotor(en): Jan de Graaff. - S.l. : s.n. - ISBN 9789461732880 - 178
woestijnvorming - grondbeheer - duurzaamheid (sustainability) - besluitvorming - participatie - stakeholders - bodembescherming - milieueffect - mitigatie - desertification - land management - sustainability - decision making - participation - stakeholders - soil conservation - environmental impact - mitigation
in these ecosystems can easily result in widespread and severe land degradation and thus desertification.
Methods for Detecting Early Warnings of Critical Transitions in Time Series Illustrated Using Simulated Ecological Data
Dakos, V. ; Carpenter, S.R. ; Brock, W.A. ; Ellison, A.M. ; Guttal, V. ; Ives, A.R. ; Kefi, S. ; Livina, V. ; Seekell, D.A. ; Nes, E.H. van; Scheffer, M. - \ 2012
PLoS ONE 7 (2012)7. - ISSN 1932-6203
critical slowing-down - climate tipping points - regime shifts - catastrophic shifts - leading indicator - ecosystems - system - states - models - desertification
Many dynamical systems, including lakes, organisms, ocean circulation patterns, or financial markets, are now thought to have tipping points where critical transitions to a contrasting state can happen. Because critical transitions can occur unexpectedly and are difficult to manage, there is a need for methods that can be used to identify when a critical transition is approaching. Recent theory shows that we can identify the proximity of a system to a critical transition using a variety of so-called ‘early warning signals’, and successful empirical examples suggest a potential for practical applicability. However, while the range of proposed methods for predicting critical transitions is rapidly expanding, opinions on their practical use differ widely, and there is no comparative study that tests the limitations of the different methods to identify approaching critical transitions using time-series data. Here, we summarize a range of currently available early warning methods and apply them to two simulated time series that are typical of systems undergoing a critical transition. In addition to a methodological guide, our work offers a practical toolbox that may be used in a wide range of fields to help detect early warning signals of critical transitions in time series data
Desire for greener land : options for sustainable land management in drylands
Schwilch, G. ; Hessel, R. ; Verzandvoort, S.J.E. - \ 2012
Bern [etc.] : University of Bern [etc.] - ISBN 9789461733290 - 282
droge gebieden - grondbeheer - duurzaamheid (sustainability) - duurzaam bodemgebruik - woestijnvorming - bodembescherming - waterbeheer - teeltsystemen - begrazingsbeheer - bosbedrijfsvoering - arid lands - land management - sustainability - sustainable land use - desertification - soil conservation - water management - cropping systems - grazing management - forest management
Desire for Greener Land compiles options for Sustainable Land Management (SLM) in drylands. It is a result of the integrated research project DESIRE (Desertification Mitigation and Remediation of Land - A Global Approach for Local Solutions). Lasting five years (2007–2012) and funded within the EU’s Sixth Framework Programme, DESIRE brought together the expertise of 26 international research institutes and non-governmental organisations. The DESIRE project aimed to establish promising alternative land use and management strategies in 17 degradation and desertification sites around the world, relying on close collaboration between scientists and local stakeholder groups. The study sites provided a global laboratory in which researchers could apply, test, and identify new and innovative approaches to combatting desertification. The resulting SLM strategies are local- to regional-scale interventions designed to increase productivity, preserve natural resource bases, and improve people’s livelihoods. These were documented and mapped using the internationally recognised WOCAT (World Overview of Conservation Approaches and Technologies) methodological framework, which formed an integral part of the DESIRE project. The DESIRE approach offers an integrated multidisciplinary way of working together from the beginning to the end of a project; it enables scientists, local stakeholders and policy makers to jointly find solutions to desertification. This book describes the DESIRE approach and WOCAT methodology for a range of audiences, from local agricultural advisors to scientists and policymakers. Links are provided to manuals and online materials, enabling application of the various tools and methods in similar projects. The book also includes an analysis of the current context of degradation and SLM in the study sites, in addition to analysis of the SLM technologies and approaches trialled in the DESIRE project. Thirty SLM technologies, eight SLM approaches, and several degradation and SLM maps from all the DESIRE study sites are compiled in a concise and well-illustrated format, following the style of this volume’s forerunner where the land is greener (WOCAT 2007). Finally, conclusions and policy points are presented on behalf of decision makers, the private sector, civil society, donors, and the research community. These are intended to support people’s efforts to invest wisely in the sustainable management of land – enabling greener drylands to become a reality, not just a desire.
Categorisation of typical vulnerability patterns in global drylands
Sietz, D. ; Lûdeke, M.K.B. ; Walther, C. - \ 2011
Global environmental change : human and policy dimensions 21 (2011)2. - ISSN 0959-3780 - p. 431 - 440.
water-use - rangeland degradation - multiple stressors - land degradation - rural poverty - south-africa - livelihoods - desertification - sustainability - mexico
Drylands display specific vulnerability-creating mechanisms which threaten ecosystems and human well-being. The upscaling of successful interventions to reduce vulnerability arises as an important, but challenging aim, since drylands are not homogenous. To support this aim, we present the first attempt to categorise dryland vulnerability at a global scale and sub-national resolution. The categorisation yields typical patterns of dryland vulnerability and their policy implications according to similarities among the socio-ecological systems. Based on a compilation of prevalent vulnerability-creating mechanisms, we quantitatively indicate the most important dimensions including poverty, water stress, soil degradation, natural agro-constraints and isolation. A cluster analysis reveals a set of seven typical vulnerability patterns showing distinct indicator combinations. These results are validated by case studies reflecting the cluster-specific mechanisms and their spatial distribution. Based on these patterns, we deduce thematic and spatial entry points for reducing dryland vulnerability. Our findings could contribute new insights into allocating the limited funds available for dryland development and support related monitoring efforts based on the manageable number of key indicators.
Cross-scale monitoring and assessment of land degradation and sustainable land management : a methodological framework for knowledge management
Reed, M.S. ; Buenemann, M. ; Atlhopheng, J. ; Akhtar-Schuster, M. ; Bachmann, F. ; Bastin, G. ; Bigas, H. ; Chanda, R. ; Dougill, A.J. ; Essahli, W. ; Evely, A.C. ; Fleskens, L. ; Geeson, N. ; Glass, J.H. ; Hessel, R. ; Holden, J. ; Ioris, A.A.R. ; Kruger, B. ; Liniger, H.P. ; Mphinyane, W. ; Nainggolan, D. ; Perkins, J. ; Raymond, C.M. ; Ritsema, C.J. ; Schwilch, G. ; Sebego, R. ; Seely, M. ; Stringer, L.C. ; Thomas, R. ; Twomlow, S. ; Verzandvoort, S. - \ 2011
Land Degradation and Development 22 (2011)2. - ISSN 1085-3278 - p. 261 - 271.
natural-resource management - local-communities - kalahari - desertification - rangeland - science - system - impact
For land degradation monitoring and assessment (M&A) to be accurate and for sustainable land management (SLM) to be effective, it is necessary to incorporate multiple knowledges using a variety of methods and scales, and this must include the (potentially conflicting) perspectives of those who use the land. This paper presents a hybrid methodological framework that builds on approaches developed by UN Food & Agriculture Organisation's land degradation Assessment in Drylands (LADA), the World Conservation Approaches and Technologies (WOCAT) programme and the Dryland Development Paradigm (DDP), and is being applied internationally through the EU-funded DESIRE project. The framework suggests that M&A should determine the progress of SLM towards meeting sustainability goals, with results continually and iteratively enhancing SLM decisions. The framework is divided into four generic themes: (i) establishing land degradation and SLM context and sustainability goals; (ii) identifying, evaluating and selecting SLM strategies; (iii) selecting land degradation and SLM indicators and (iv) applying SLM options and monitoring land degradation and progress towards sustainability goals. This approach incorporates multiple knowledge sources and types (including land manager perspectives) from local to national and international scales. In doing so, it aims to provide outputs for policy-makers and land managers that have the potential to enhance the sustainability of land management in drylands, from the field scale to the region, and to national and international levels. The paper draws on operational experience from across the DESIRE project to break the four themes into a series of methodological steps, and provides examples of the range of tools and methods that can be used to operationalise each of these steps.
Climate Science, Development Practice, and Policy Interactions in Dryland Agroecological Systems
Twyman, C. ; Fraser, E.D.G. ; Stringer, L.C. ; Quinn, C. ; Dougill, A.J. ; Crane, T.A. ; Sallu, S.M. - \ 2011
Ecology and Society 16 (2011)3. - ISSN 1708-3087 - p. 14 - 14.
human-geography - past famines - food systems - vulnerability - livelihoods - scenarios - scale - desertification - resilience - strategies
The literature on drought, livelihoods, and poverty suggests that dryland residents are especially vulnerable to climate change. However, assessing this vulnerability and sharing lessons between dryland communities on how to reduce vulnerability has proven difficult because of multiple definitions of vulnerability, complexities in quantification, and the temporal and spatial variability inherent in dryland agroecological systems. In this closing editorial, we review how we have addressed these challenges through a series of structured, multiscale, and interdisciplinary vulnerability assessment case studies from drylands in West Africa, southern Africa, Mediterranean Europe, Asia, and Latin America. These case studies adopt a common vulnerability framework but employ different approaches to measuring and assessing vulnerability. By comparing methods and results across these cases, we draw out the following key lessons: (1) Our studies show the utility of using consistent conceptual frameworks for vulnerability assessments even when quite different methodological approaches are taken; (2) Utilizing narratives and scenarios to capture the dynamics of dryland agroecological systems shows that vulnerability to climate change may depend more on access to financial, political, and institutional assets than to exposure to environmental change; (3) Our analysis shows that although the results of quantitative models seem authoritative, they may be treated too literally as predictions of the future by policy makers looking for evidence to support different strategies. In conclusion, we acknowledge there is a healthy tension between bottom-up/ qualitative/place-based approaches and top-down/quantitative/generalizable approaches, and we encourage researchers from different disciplines with different disciplinary languages, to talk, collaborate, and engage effectively with each other and with stakeholders at all levels.
Slowing down in spatially patterned systems at the brink of collapse
Dakos, V. ; Kefi, S. ; Rietkerk, M. ; Nes, E.H. van; Scheffer, M. - \ 2011
American Naturalist 177 (2011)6. - ISSN 0003-0147 - p. E153 - E166.
catastrophic shifts - arid ecosystems - ecological-systems - regime shifts - vegetation - dynamics - time - desertification - bistability - transitions
Predicting the risk of critical transitions, such as the collapse of a population, is important in order to direct management efforts. In any system that is close to a critical transition, recovery upon small perturbations becomes slow, a phenomenon known as critical slowing down. It has been suggested that such slowing down may be detected indirectly through an increase in spatial and temporal correlation and variance. Here, we tested this idea in arid ecosystems, where vegetation may collapse to desert as a result of increasing water limitation. We used three models that describe desertification but differ in the spatial vegetation patterns they produce. In all models, recovery rate upon perturbation decreased before vegetation collapsed. However, in one of the models, slowing down failed to translate into rising variance and correlation. This is caused by the regular self-organized vegetation patterns produced by this model. This finding implies an important limitation of variance and correlation as indicators of critical transitions. However, changes in such self-organized patterns themselves are a reliable indicator of an upcoming transition. Our results illustrate that while critical slowing down may be a universal phenomenon at critical transitions, its detection through indirect indicators may have limitations in particular systems
Experiences in monitoring and assessment of sustainable land management
Schwilch, G. ; Bestelmeyer, B. ; Bunning, S. ; Critchley, W. ; Herrick, J. ; Kellner, K. ; Liniger, H.P. ; Nachtergaele, F. ; Ritsema, C.J. ; Schuster, B. ; Tabo, R. ; Lynden, G.W.J. van - \ 2011
Land Degradation and Development 22 (2011)2. - ISSN 1085-3278 - p. 214 - 225.
degradation - desertification - participation - system
Although sustainable land management (SLM) is widely promoted to prevent and mitigate land degradation and desertification, its monitoring and assessment (M&A) has received much less attention. This paper compiles methodological approaches which to date have been little reported in the literature. It draws lessons from these experiences and identifies common elements and future pathways as a basis for a global approach. The paper starts with local level methods where the World Overview of Conservation Approaches and Technologies (WOCAT) framework catalogues SLM case studies. This tool has been included in the local level assessment of Land Degradation Assessment in Drylands (LADA) and in the EU-DESIRE project. Complementary site-based approaches can enhance an ecological process-based understanding of SLM variation. At national and sub-national levels, a joint WOCAT/LADA/DESIRE spatial assessment based on land use systems identifies the status and trends of degradation and SLM, including causes, drivers and impacts on ecosystem services. Expert consultation is combined with scientific evidence and enhanced where necessary with secondary data and indicator databases. At the global level, the Global Environment Facility (GEF) knowledge from the land (KM:Land) initiative uses indicators to demonstrate impacts of SLM investments. Key lessons learnt include the need for a multi-scale approach, making use of common indicators and a variety of information sources, including scientific data and local knowledge through participatory methods. Methodological consistencies allow cross-scale analyses, and findings are analysed and documented for use by decision-makers at various levels. Effective M&A of SLM [e.g. for United Nations Convention to Combat Desertification (UNCCD)] requires a comprehensive methodological framework agreed by the major players
Robust scaling in ecosystems and the meltdown of patch size distributions before extinction
Kefi, S. ; Rietkerk, M. ; Roy, M. ; Franc, A. ; Ruiter, P.C. de; Pascual, M. - \ 2011
Ecology Letters 14 (2011)1. - ISSN 1461-023X - p. 29 - 35.
spatial vegetation patterns - power laws - catastrophic shifts - ecological-systems - local interactions - leading indicator - arid ecosystems - regime shifts - desertification - criticality
Robust critical systems are characterized by power laws which occur over a broad range of conditions. Their robust behaviour has been explained by local interactions. While such systems could be widespread in nature, their properties are not well understood. Here, we study three robust critical ecosystem models and a null model that lacks spatial interactions. In all these models, individuals aggregate in patches whose size distributions follow power laws which melt down under increasing external stress. We propose that this power-law decay associated with the connectivity of the system can be used to evaluate the level of stress exerted on the ecosystem. We identify several indicators along the transition to extinction. These indicators give us a relative measure of the distance to extinction, and have therefore potential application to conservation biology, especially for ecosystems with self-organization and critical transitions
Estimation of evapotranspiration in the Mu Us Sandland of China
Liu, S. ; Bai, J. ; Jia, Z. ; Jia, L. ; Zhou, H. ; Lu, L. - \ 2010
Hydrology and Earth System Sciences 14 (2010). - ISSN 1027-5606 - p. 573 - 584.
complementary relationship - regional evapotranspiration - profile relationships - northern china - evaporation - water - flux - desertification - transpiration - grassland
Evapotranspiration (ET) was estimated from 1981–2005 over Wushen County located in the Mu Us Sandland, China, by applying the Advection-Aridity model, which is based on the complementary relationship hypothesis. We used National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR), Moderate Resolution Imaging Spectroradiometer (MODIS), and meteorological data. Our results show that the estimated daily ET was about 4.5% higher than measurements using an Eddy Covariance (EC) system after forcing energy balance closure over an alfalfa field from 22 July 2004 to 23 August 2004. At a regional scale, the estimated monthly ET was about 8.7% lower than measurements using the EC system after forcing energy balance closure over an alfalfa field in August 2004. These results were about 3.0% higher than ET measurements by microlysimeter over sand dunes during June 1988. From 1981 to 2005, the average annual ET and precipitation levels were 287 mm and 336 mm, respectively, in Wushen County. The average annual ET varied from 230 mm in western parts of Wushen County to 350 mm in eastern parts of the county. Both inter-annual and seasonal variations in ET were substantial in Wushen County. The annual ET was 200–400 mm from 1981–2005, and the seasonal pattern of ET showed a single peak distribution. The cumulative ET during the June–September 2004 period was 250 mm, which was 87% of the total annual ET. The annual ET, precipitation, and the maximum Normalized Difference Vegetation Index (NDVImax) showed positive correlations temporally and spatially
The local impacts of climate change in the Ferlo, Western Sahel
Hein, L.G. ; Metzger, M.J. ; Leemans, R. - \ 2009
Climatic Change 93 (2009)3-4. - ISSN 0165-0009 - p. 465 - 483.
range condition - dynamics - senegal - ecology - desertification - precipitation - variability - thresholds - ecosystems - viewpoint
Recent increases in the accuracy of climate models have enhanced the possibilities for analyzing the impacts of climate change on society. This paper explores how the local, economic impacts of climate change can be modeled for a specific eco-region, the Western Sahel. The people in the Sahel are highly dependent on their natural resource base, and these resources are highly vulnerable to climate change, in particular to changes in rainfall. Climate models project substantial changes in rainfall in the Sahel in the coming 50 years, with most models predicting a reduction in rainfall. To connect climate change to changes in ecosystem productivity and local income, we construct an ecological¿economic model that incorporates rangeland dynamics, grazing and livestock prices. The model shows that decreased rainfall in the Sahel will considerably reduce local incomes, in particular if combined with increases in rainfall variability. Adaptation to these climate change projections is possible if reductions in rainfall are followed by destocking to reach efficient grazing levels. However, while such a strategy is optimal from the perspective of society, the stocking rate is determined by individual pastoralists that face few incentives to destock
Exploring farmers' perceptions of drought in Tanzania and Ethiopia
Slegers, M.F.W. - \ 2008
Wageningen University. Promotor(en): Leo Stroosnijder, co-promotor(en): Jan de Graaff. - S.l. : S.n. - ISBN 9789085852407 - 217
droogte - boeren - perceptie - ethiopië - tanzania - klimaatverandering - woestijnvorming - drought - farmers - perception - ethiopia - tanzania - climatic change - desertification
Development actions focusing on land degradation in Sub-Saharan Africa have not been particularly successful in changing farmers’ agricultural practices towards a more sustainable use of natural resources. Over time, programs have become more localized and participative, which is a positive step forward. However, these programs still depart from the productivity-reducing problems that are identified and perceived by scientists. Subsistence farmers in this region believe that other problems, such as drought are bigger constraints to them. Very little is known about how subsistence farmers in semi-arid East Africa perceive drought. The aim of this research is to bridge this gap between farmers and scientists to improve the impact of interventions aimed at improving agricultural productivity. The research focuses on two study areas within Tanzania and Ethiopia, where during the period between 2004 and 2006, sociological and biophysical studies were conducted.
Both case studies demonstrate the inter-relationship of human and natural systems. This is also part of farmers’ knowledge. Farmers’ perceptions of drought relate to the scientific concept of agricultural drought. Rainfall patterns are perceived to be negatively affected by deforestation, while soil erosion and continuous cultivation diminish soil fertility and a soil’s capacity to retain water. Farmers recognize that one has to be an active farmer to be productive and to withstand drought conditions. No one-size-fits-all solution exists for which SWC strategies to use, or for strategies to deal with climate variability and drought. Actions have to be area-specific and focused on local practices and the constraints that farmers have to deal with. Farmers’ strategies for dealing with the insecurity of the rains are multifocal. Interventions should target these multiple sectors and spheres in which people are engaged. The seemingly different problems of land degradation and drought are linked. Rather than “bridging a gap”, the issue is to find where both paths are connected. To achieve this, emphasis should lie on integrated studies and on improving the interaction between farmers and scientists.
The impacts of grazing and rainfall variability on the dynamics of a Sahelian rangeland
Hein, L.G. - \ 2006
Journal of Arid Environments 64 (2006)3. - ISSN 0140-1963 - p. 488 - 504.
use efficiency - vegetation dynamics - species composition - ecology - systems - africa - desertification - nonequilibrium - senegal - precipitation
The impacts of grazing pressure and rainfall variability on rangeland dynamics have been the topic of much debate. Understanding the combined impact of these two factors is crucial for the development of efficient management strategies for rangelands. In this paper, the impacts of grazing and rainfall variability on the dynamics of a Sahelian rangeland in Northern Senegal are examined. Specifically, the paper assesses their combined impact on species composition, above-ground phytomass production and rain-use efficiency (RUE), on the basis of a 10-year (1981¿1990) grazing experiment conducted in the Widou-Thiengoly catchment in the Ferlo, Northern Senegal. The experiment included both a high (0.15¿0.20 TLU ha¿1, corresponding to current grazing) and a medium (0.10 TLU ha¿1) grazing pressure. It is shown that species composition, above-ground phytomass production and RUE markedly differ for these two grazing regimes¿and that the differences are most pronounced in years with low rainfall. In dry years, both above-ground phytomass production and RUE are significantly reduced in the plots subject to a high grazing pressure. Consequently, the impacts of high grazing pressures on the productivity of the Ferlo are hardly noticed during years with normal or above normal rainfall, but the rangeland's productivity is strongly affected during a drought. The findings have important implications for the management of rangelands; they indicate that high grazing pressures may increase the vulnerability of rangeland ecosystems and local people to droughts
Geomorphology and human palaeoecology of the Méma, Mali
Vries, E. de; Makaske, B. ; Tainter, J.A. ; McIntosh, R.J. - \ 2005
Wageningen : Alterra (Alterra-rapport 1244) - 119
archeologie - paleo-ecologie - mali - geomorfologie - woestijnvorming - paleoklimatologie - archaeology - palaeoecology - mali - geomorphology - desertification - palaeoclimatology
The Méma is a semi-arid region in central-Mali with a rich archaeological heritage indicating the former existence of large urban settlements. Previous investigations suggest that the Méma is an important area in which to study the origins of Sahelian agriculture, metallurgy, and urbanism, the continuing effects of long-term desiccation, the fluvial history of the Niger River basin, human responses to desertification, and regional abandonment. As a basis for such future studies, a geomorphological map of the Méma was made based on remote sensing and field data. In this report the geomorphological map is presented with a discussion of the origin and chronology of the landforms. Following upon this discussion, the archaeology of the Méma is described, with theoretical considerations about the origin of urbanism and the abandoment of the urban settlements