Background: Conflict between human livelihood needs and nature conservation; The destruction of natural, intact habitats is one of the main driver of global biodiversity loss as well as of the deterioration of ecosystem functions. Gallery forests along rivers in the semiarid tropics are important ecosystems and lifelines that provide habitats for many (endangered) plant and animal species as well as natural resources for the local human population. However, gallery forests are fragile ecosystems in semiarid environments that suffer under changing rainfall patterns and non-adapted agricultural regimes, leading to modified ecosystem functions. This becomes further aggravated by the increasing human demographic pressure on these fragile ecosystems. Such river systems lined by gallery forests comprise landscapes characterised by different degrees of disturbance, and thus provide a gradient from still intact and natural forests, transformed into agricultural land, to severely degraded habitats and functions.
The research focus: The fragility of gallery forests and the high demographic pressure along such rivers, home for many endangered, endemic species, provisioning important ecosystem functions, in the semiarid regions of Eastern Africa creates a conflicting situation between ecosystem conservation including species and local populations and land-use like habitat transformation and the exploitation of natural resources. The Tana River river system in south-east Kenya provides a unique system comprising different land-use intensities (from National Park to densely populated areas) (see Fig. 1). The local human population is the driving force for ecosystem depletion, but at the same time strongly depends on intact ecosystem functions. Consequently, a consortium of transdisciplinary scientists is required to elaborate a holistic study framework, which includes abiotic and biotic factors as well as the human being with social and economic aspects.
Central research aims (beyond single case-studies):
- Detection of coherences among biodiversity (including all three levels) and human behaviour (land-use regimes), bio-economy – in gallery forests with different disturbance levels;
- Delineating threshold values of the reliability and resilience of disturbed gallery forests;
- Elaborating management strategies to preserve gallery forests in semiarid Africa, including nature conservation interests and human livelihood needs.
Study framework and transdisciplinary character; The proposed framework for the research programme comprises gradually degraded conditions of East African riparian forests ranging from intact ones in protected areas (National Parks) and highly degraded ones in agricultural land (beyond protected areas). Abiotic, biotic and societal (culture, habits, economic constraint) factors are shaping the condition of gallery forests. Distinct sub-projects will create a transdisciplinary study-setup, including methods from natural and social sciences, and economy. In a first sub-project, ABIOTIC FACTORS (water, soil and climate) (1) will be assessed in gallery forests representing different levels of degradation. These factors directly influence biota (vegetation, animals, and its viability), and the ecosystem functions (natural sciences) and the services used by the human being (social sciences and economy). A second sub-project on LAND COVER (land use dynamics and land-cover change detection) (2) will provide relevant information affecting abiotic and biotic systems – including local communities, plant and animal populations, potential stressors from rapid habitat degradation and changing habitat configurations. The third sub-project will be focusing on the VEGETATION ECOLOGY (3), and how ecosystem disturbances affect the susceptibility to become invaded by exotic plant (and animal) species (including the river as trajectory and dispersion corridor). Three sub-projects in the field of zoology will be focusing on biodiversity sensu stricto: INTRASPECIFIC VIABILITY (population genetics and endocrinology of bird species) (4), POPULATION ECOLOGY (movement ecology of birds and mammals) (5) and COMMUNITY ECOLOGY (based on amphibians) (6). These three sub-projects will strongly dependent on data collected in SP 1 and 2. Furthermore, these three levels will strongly interplay, as within-taxon structure (population genetics and endocrinology), population structures (e.g. movement ecology), as well as communities may strongly experience potential environmental conditions (like stress). The next sub-project will focus on ECOSYSTEM FUNCTIONS (7) provided by gallery forests (here from a natural science point of view) and how these ecosystem functions (EF) are affected by different levels of disturbances, and how taxa and local populations are affected from modified EF. In the last sub-projects, EF will be analysed from a social science perspective, and create the sub-project ECOSYSTEM SERVICES (8). Data on abiotic and biotic factors, ecosystem functions and the human population living therein will be combined in this sub-project, to calculate threshold values on the vulnerability of an ecosystem (resistence, resilience). These two SPs create important links between natural and social sciences; Information from other previous SPs will feed SP 7 and 8. A final sub-project, RESTORATION AND POLICIES (9) will combine major data-sets to create a complete socio-ecological-economic picture on this system.