Anthropogenic land use is a major threat of species diversity in semiarid savannahs of southern Africa. However, land use affects species diversity not only in a direct way, but also indirectly via changes in the spatial pattern of vegetation, i.e. the structural diversity of vegetation and landscape. In semiarid savannahs, structural diversity is characterized by a typical pattern of scattered trees and shrubs in a wide grass matrix, which forms the habitat for animal and plant species, living in this area. Changes in this pattern, as they occur due to overgrazing (shrub encroachment) and tree harvesting, lead to a shift in habitat structure and imply changes in species composition.

The aim of BIOTA subproject S09 is a mechanistic understanding of this interrelationship between the two key elements of biodiversity, i.e. structural diversity of vegetation and species diversity, under the impact of landuse. Our studies combine a multidisciplinary approach of field studies (zoological, botanical and genetic), and spatial-explicit simulation models to integrate the knowledge gained by several disciplines.

In the first phase of BIOTA empirical as well as modelling studies gave insight into the specific response of the occurrence and abundance of animal and plant species to vegetation structure, and elucidated the mechanisms behind these responses. In the second phase, these studies are expanded into three directions: (i) scaling up patterns and processes from single farms/ landuse units to larger landscapes consisting of a mosaic of landuse units, (ii) strengthening the socio-economic aspect as the key driver of landuse by linking socio-economic and ecological models, and (iii) testing a functional type approach as means to close the gap between understanding the dynamics of selected species and species diversity in general.

Studies are located in two savannah sites of the BIOTA transect: Observatory Alpha in the southern Kalahari, and the observatories Gellap Ost/ Nabaos in southern Namibia.