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.
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.
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.
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
|Science, technology and agency in the development of droughtprone areas: a cognitive history of drought and scarcity
Vincent, L.F. - \ 2004
The Open University. Promotor(en): D.V. Wield. - - 396
droogte - aride klimaatzones - droog klimaat - woestijnvorming - waterbeheer - watervoorraden - sociaal milieu - sociale instellingen - politiek - schaarste - sociale factoren - agentschappen - bureaucratie - drought - arid zones - arid climate - desertification - water management - water resources - social environment - social institutions - politics - scarcity - social factors - agencies - bureaucracy
Land-surface and boundary layer processes in a semi-arid heterogeneous landscape
Jochum, A.M. - \ 2003
Wageningen University. Promotor(en): Bert Holtslag, co-promotor(en): H.A.R. de Bruin. - Wageningen : S.n. - ISBN 9789058088246 - 155
atmosfeer - droge gebieden - droog klimaat - woestijnvorming - wiskundige modellen - spanje - aardoppervlak - grenslaag - atmosphere - arid lands - arid climate - desertification - mathematical models - spain - land surface - boundary layer
The European Field Experiment in a Desertification-threatened Area (EFEDA) provides a comprehensive land-surface dataset for a semiarid Mediterranean environment. It is used here to study heat and moisture transport processes in the atmospheric boundary layer (ABL), to derive grid-scale surface fluxes for numerical weather prediction models, and to evaluate the performance of the High-Resolution Limited-Area Model (HIRLAM).
Boundary layer budgets were derived for two sub-regions of the EFEDA area with different moisture characteristics. The budget analysis is based on the synergistic combination of the observational dataset and a simple coupled canopy-mixed layer model. The mixed layer (ML) warming is balanced by a combination of the heat flux divergence and the radiative divergence (directly measured by aircraft). The large radiative warming is consistent with the high aerosol load and low visibility observed in the area. The moisture budgets reflect the influence on non-ABL scales on the entrainment moisture flux, which changes sign over time as the ABL grows into the observed heterogeneous moisture structure of the residual layer (RL). Accurate high-resolution vertical humidity profiles are needed to properly estimate the moisture flux divergence, which varies in space and time. The coupled canopy-ML slab model proves to be a valuable tool in this complex environment, if it is regularly provided with updated RL gradients. The potential for moisture flux divergence and associated ML moistening is higher at Barrax, where irrigation enhances the surface evapotranspiration.
The area-aggregated fluxes (in particular of moisture) depend strongly on the location of the area boundaries, whenever a significant fraction of irrigated land is present. This confirms the importance to adequately account for tiles of irrigated land in surface schemes and the corresponding physiographic databases of large scale models. A simple way to accommodate a minimum information on canopy water status is proposed in terms of the distinction of at least two seasonal classes of irrigated crops, one of spring and one of summer growing cycles.
The HIRLAM performance evaluation reveals model shortcomings essentially in four areas. The moisture assimilation makes the model surface and ABL too moist. The ABL entrainment description cannot resolve the observed temporal and spatial variations of entrainment moisture fluxes. The landuse and soil classification with its associated physiographic database attribute too much green vegetation to the EFEDA grid cells, thus causing a wet bias in the surface energy balance. The aerosol parameterization in the radiation code does not account for the typically higher aerosol load of semiarid environments, which introduces a high bias in solar and net radiation. Practical steps for model improvement are proposed. They focus on the landuse classification and the aerosol parameters, both adapted to dry Mediterranean landscapes.
|Land cover and the climate system
Hutjes, R.W.A. ; Kabat, P. ; Dolman, A.J. - \ 2003
In: Global environmental change and land use / Dolman, A.J., Verhagen, A., Rovers, C.A., Dordrecht : Kluwer - ISBN 9781402013461 - p. 73 - 110.
landgebruik - vegetatie - landbouwklimatologie - klimaatverandering - bodemwater - ontbossing - woestijnvorming - land use - vegetation - agroclimatology - soil water - deforestation - desertification - climatic change
Catastrophic vegetation dynamics and soil degradation in semi-arid grazing systems
Rietkerk, M. - \ 1998
Agricultural University. Promotor(en): L. Stroosnijder; H.H.T. Prins. - S.l. : s.n. - ISBN 9789054859413 - 155
beweidingssystemen - aride klimaatzones - bodemdegradatie - woestijnvorming - vegetatie - bodemwater - sahel - tanzania - burkina faso - grazing systems - arid zones - soil degradation - desertification - vegetation - soil water - sahel - tanzania - burkina faso - cum laude
When vegetation is drastically reduced as a result of drought or an increase in herbivore numbers, it does not simply recover if periods with normal rainfall follow or if herbivores are removed. These are commonly recognized catastrophic phenomena of semi-arid grazing systems in general and of the African Sahel in particular. The main aims of this thesis are to provide an effective explanation of the catastrophic properties of vegetation dynamics in these systems and to predict under which conditions they might be expected.
We start with a description of Sahelian rangeland vegetation dynamics, to reveal its catastrophic properties. This exercise appeared a very useful first step in the growth of our ideas about catastrophic vegetation dynamics because: 1) it translated rather vague concepts into a verifiable format by deducing hypotheses about the conditions under which catastrophic vegetation dynamics might be expected, and 2) it generated the notion that soil degradation could somehow be an important factor attributing to catastrophic vegetation dynamics in semi-arid grazing systems. This is in contrast with models that emphasize herbivore feeding characteristics or plant competition as possible mechanisms underlying catastrophic vegetation dynamics. We tested the hypothesis that soil degradation, i.e. soil erosion by run-off and wind and the consequent loss of water and nutrients, is sufficient to explain catastrophic vegetation dynamics by mathematical modelling.
Our model studies indeed show that soil degradation can effectively explain the catastrophic properties of semi-arid grazing systems. Soil degradation can cause a positive feedback between reduced resource (soil water and nutrients) availability and reduced vegetation biomass which may lead to collapse of the system. This positive feedback loop can be triggered by grazing. We argue on the basis of a large body of literature that this is an important mechanism causing catastrophic vegetation dynamics in semi-arid grazing systems. Furthermore, our model studies predict for which site-specific properties catastrophic vegetation dynamics may be expected, that is on loamy or clayey soils in case of water-limited vegetation biomass production, and on sandy soils in case of nutrient-limited biomass production. This is because sandy soils have higher water infiltration rates but are more vulnerable to nutrient loss through erosion than loamy or clayey soils.
Based on our models, we hypothesized that the removal of aboveground herbaceous biomass would lead to a reduced soil water content and biomass production because of reduced water infiltration and increased run-off. We tested this hypothesis in a semi-arid savanna in Tanzania (East Africa). Indeed, as a consequence of biomass removal, a reduction in soil water content and biomass production occurred. But it appeared that increased loss of soil water through increased soil evaporation as a consequence of litter removal ultimately outbalanced all other effects on soil water content. Several factors might have contributed to the importance of increased soil evaporation, overriding that of reduced water infiltration and increased run-off. The soil in the research area was a sandy loam, with higher water infiltration rates than soils with a lower percentage sand and higher perentage clay, while rainfall primarily occurred in light showers. Thus, under these conditions, when the positive feedback between reduced water infiltration and reduced biomass does not operate, another positive feedback that is between increased soil evaporation and reduced biomass may become prominent.
We further hypothesized that at a certain range of herbivore impact small initial differences in plant cover and amount of soil resources can magnify to alternative states which persist in time due to positive plant-soil feedbacks. We tested this hypothesis in a semi-arid grazing system in Burkina Faso (West Africa), where we studied vegetation patchiness along a gradient of herbivore impact. Indeed, the occurrence and likely persistence of a spatial pattern of vegetated patches alternating with bare soil at a certain range of herbivore impact could be explained by the positive plant-soil feedback between vegetation biomass and water infiltration.
We stress the general applicability of our models by comparing catastrophic vegetation dynamics of the semi-arid grasslands of the African Sahel with the arctic salt marshes along the Hudson Bay in Canada. We argue that in both systems, an increase of herbivory triggered a catastrophic vegetation shift, which was ultimately caused by a positive plant-soil feedback, leading to desertification.
One of our model assumptions was that herbivore density is not regulated by vegetation biomass. In the general discussion, I investigated the influence of a positive feedback between vegetation biomass and water infiltration on the dynamics of a plant-herbivore system, where herbivore density depends on vegetation biomass. As a consequence of the positive feedback and if herbivore reproduction is efficient, I predict that the plant-herbivore system could destabilize and collapse. In this chapter I also stress the practical relevance of our studies as our approach may finally lead to objective ecological criteria on which pastoral managers can base their decision how to evade the hazard of degradation of their rangelands.
I highlight three topics which deserve more priority on the reseach agenda concerning semi-arid grazing systems in the near future. Hereby, I want to stress that it is important to put experimental and empirical studies into a clear theoretical framework, whereby mathematical modelling should play an important role. The three topics are:
Catastrophic vegetation shifts and soil degradation in terrestrial grazing systems.
Koppel, J. van de; Rietkerk, M. ; Weissing, F.J. - \ 1997
Trends in Ecology and Evolution 12 (1997)8. - ISSN 0169-5347 - p. 352 - 356.
natuurlijke graslanden - extensieve weiden - plantensuccessie - vegetatie - milieuafbraak - woestijnvorming - overexploitatie - natural grasslands - rangelands - plant succession - vegetation - environmental degradation - desertification - overexploitation
It has long been recognized that alternative vegetation states may occur in terrestrial grazing systems. This phenomenon may be of great importance as small environmental fluctuations may lead to relatively sudden and irreversible jumps between vegetation states. Early theoretical studies emphasized saturation of herbivore feeding to explain multiple stable states and catastrophic behaviour. Recent studies on semi-arid grasslands and arctic salt marshes, however, relate catastrophic events in these systems to plant-soil interactions.
|Irrigation and the environment of the Aral Sea basin : an annotated bibliography
Trouw, L.A. - \ 1994
Wageningen : ILRI - 78
irrigatie - watervoorziening - waterbeheer - watervoorraden - milieu - verontreinigende stoffen - verontreiniging - nadelige gevolgen - vegetatie - milieuafbraak - woestijnvorming - ruimtelijke ordening - landgebruik - zonering - kazachstan - hydrologie - overexploitatie - irrigation - water supply - water management - water resources - environment - pollutants - pollution - adverse effects - vegetation - environmental degradation - desertification - physical planning - land use - zoning - kazakhstan - hydrology - overexploitation
|Participatie in milieuprojecten in West Afrika.
Dijk, H. van; Bruijn, M. de - \ 1989
Leiden : Leiden University (Memoranda "Environment and development" 3) - 118
woestijnvorming - ontwikkelingsprojecten - milieuafbraak - mali - natuurlijke hulpbronnen - niger - planning - bescherming - herstel - hulpbronnengebruik - plattelandsontwikkeling - plattelandsplanning - sociale economie - duurzaamheid (sustainability) - vegetatie - economische planning - overexploitatie - desertification - development projects - environmental degradation - mali - natural resources - niger - planning - protection - rehabilitation - resource utilization - rural development - rural planning - socioeconomics - sustainability - vegetation - economic planning - overexploitation
|The struggle of the green against the yellow dragon : the Chinese approach to desertification control and its usefulness for the Sahel
Breman, H. - \ 1987
Wageningen : CABO - 62
china - woestijnvorming - milieuafbraak - erosiebestrijding - bedrijfssystemen - flora - landgebruik - natuurlijke hulpbronnen - ruimtelijke ordening - planten - bescherming - herstel - hulpbronnengebruik - sahel - bodembescherming - duurzaamheid (sustainability) - vegetatie - oogsttoename - oogstverliezen - opbrengsten - zonering - overexploitatie - china - desertification - environmental degradation - erosion control - farming systems - flora - land use - natural resources - physical planning - plants - protection - rehabilitation - resource utilization - sahel - soil conservation - sustainability - vegetation - yield increases - yield losses - yields - zoning - overexploitation