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A2 - Crop Science

 

Functions and Uses of Wetlands in changing Savannah Environments


Research Areas:
Crop Science

With contributions from Biodiversity (H. Oyieke – African counterpart), and
Animal Science (T.P. Lanyasunya – African counterpart)

Principal Investigator:
Prof. Dr. Mathias Becker

Land and water shortages are currently driving the use of wetland sites in East African savannah environments. Pastoralists, traditional subsistence farmers, and commercial farms increasingly compete for limited land and water resources. Transfers between wetlands and surrounding dryland savannahs are changing both on a material level and the social level. International interests interfere with the decision-making of local resource users and changes in wetland use are frequently linked to global processes. Ecosystem collapse phenomena and social conflicts increasingly centre on wetlands. The dynamics of the coupled biophysical and socio-cultural processes are seen to determine the resilience, collapse or eventually the reorganisation of agriculturally used wetlands. The interdisciplinary sub-project will describe wetland ecosystem changes under intensified use and establish biophysical threshold values for land use by both agriculturalists and pastoralists. Activities in the areas of soil science, crop agronomy, animal nutrition and vegetation ecology will focus on the littoral areas of lakes Naivasha and Baringo in Kenya. In close collaboration with subprojects B1, B2 and C3 as well as the Kenya Agricultural Research Institute (KARI), the diverse economic and social strategies of various resource users in the face of changing bio-geophysical conditions will be described, and the rapidly unfolding political ecology of initially two contrasting wetland systems in the East African savannah will be documented.

East African savannahs are characterized by the presence of wetlands of different size. Ecologically but also economically these wetlands are key resources within otherwise dry savannah environments. Demographically and politically driven land shortages (high fertility rates, immigration, elite capture of natural resources) and upland degradation phenomena are currently driving the use of highly productive wetland sites in East Africa. Pastoralists, smallholder subsistence farmers, resource-poor vegetable producers, large commercial flower farms, and wildlife increasingly compete for limited land and water resources in these wetlands. Transfers between wetlands and surrounding dryland savannahs are changing both on a material level (e.g. the decreasing lake-levels due to heavy diversion of up-stream water for private use) and the social level (e.g. closure of corridors historically used by pastoralists and wildlife to access riparian resources). International interests in wetlands (e.g. agro-industry, tourism, conservation) interfere with the decision-making of local resource users and changes in wetland use are frequently linked to global processes. Ecosystem degradation phenomena (e.g. biodiversity loss, the spread of invasive species, soil fertility and production decline) and conflicts increasingly centre on wetlands. Two contrasting land use strategies practiced in East African wetlands involve a) the production of subsistence crops following wetland drainage and b) the expansion of agro-industrial crop production by irrigation. Drainage can result in rapid ecosystem degradation, initially by soil physical, later by biochemical deterioration, forcing farmers to progressively encroach and open new land within the fragile wetland ecosystem. Conflicts with other wetland dependants (pastoralists, wildlife) are inevitable and international conventions often exacerbate such conflicts. The dynamics of the coupled biophysical and socio-cultural processes are determining the resilience, regulation, collapse, or eventually the reorganisation of agriculturally used wetlands.

To understand the patterns, rates and socio-economical impacts of wetland ecosystem changes, this project seeks to comparatively evaluate case studies along gradients of intensified wetland management (chronosequences of drainage and land use). The research activities will determine wetland ecosystem changes under intensified use, establish threshold values for land use and document the rapidly unfolding political ecology of wetland systems. The activities will focus on urban and peri-urban communities in Naivasha and rural communities in Baringo and on chronosequences of land use on contrasting soil types in the riparian zone of both lakes in Kenya. While in Naivasha the impact of horticultural industries and global ideas of resource protection shape the land use change, in the Baringo case competition for wetland resource and heavy pastoral impact on the shoreline impact SES changes. These changes in land use will be quantified in a spatial-temporal analysis of historic aerial photographs (1984 – date, purchased from the Centre of Land Management and Remote Sensing in Nairobi). The crop cover and the agronomic potential of plots and the changing availability pastureland and quality of pastures (in collaboration with subproject A3) will be assessed along the identified chronosequences of land use. The response of the wetland soils to various durations and different types of agricultural land use will be assessed by soil physical, chemical and biological methods in the laboratory. In addition, in-situ measurements of soil moisture dynamics, and nutrient fluxes will be studied in relation to the crop and feedstock production potential. Key processes responsible for productivity declines or systems' collapse will be quantified for different land use scenarios.

These biophysical data will be linked to changes in social, economic and political parameters determined in Subprojects B1, B2 and C3. Economic and social anthropological information collected among smallholder farmer and migrant herder communities and wildlife authorities will inform about the driving forces of change and adaptive strategies. The implications for livelihood and conflict potentials and the needs and avenues of reorganisation and regulation of the social-ecological systems will be comparatively assessed by modelling approaches (together with subprojects A3 and B2) in a subsequent phase.

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