The interplay between African protected savannas and their surrounding pastoral rangelands

PhD ceremony: Ms. N.D.P. Bhola, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: The interplay between African protected savannas and their surrounding pastoral rangelands

Promotor(s): prof. H. Olff

Faculty: Mathematics and Natural Sciences

With limited resources for conservation and increasing human population densities surrounding protected areas, it is necessary to identify the conditions required for maintaining diverse assemblages of plants and wildlife. Nina Bhola modeled the species richness of large mammals in 300 protected areas across Africa using the size of an area, variation in habitat types (heterogeneity) and vegetation productivity as key determinants of diversity. Surprisingly, habitat heterogeneity had a stronger influence on species richness than the size of an area.

An even more important factor in maintaining diversity is located beyond the protected area boundaries. Protected areas do not always encompass both wet-and dry-season resources that wildlife require. Often one of these resource types lies outside the protected area, which is also used by livestock herders. Bhola studied the distribution of the densities of different sized species of wild herbivores and carnivores in the protected Mara-Serengeti ecosystem and its adjoining livestock ranches.

In the wet season when food and water are plentiful, small and medium-sized herbivores are attracted to the livestock ranches by short, nutritious grasses and better visibility of ambush predators due to livestock grazing. In contrast, in the dry season when food and water supplies are low, the medium sized herbivores avoid competition with livestock in the ranches by moving into the Mara reserve.

The areas surrounding the nature reserves are increasingly dominated by rapid human population growth and economic development. In addition to these changes, shifts in rainfall patterns and rising temperatures make it increasingly important, yet, more difficult for animals to migrate outside the protected areas. This results in a decline of densities of almost all species.

The study of Bhola highlights the importance of landscape heterogeneity and connectivity between protected areas and their surrounding rangelands for wildlife conservation in the context of global change.