How do African savanna ecosystems get the biological properties they have? How do they reconstitute themselves after being torn apart? And what can basic, curiosity-driven science tell us about how to manage their recovery — if anything? My talk is about the role of large mammalian herbivores — the megafauna — in these processes. I will discuss the factors that shape the dietary choices of these animals, and how their foraging decisions shape large-scale ecosystem properties such as the diversity and distribution of tree species. Lastly, I will examine the effects of human warfare on African savannas, focusing in particular on one war-torn ecosystem, Mozambique’s Gorongosa National Park. Wildlife populations are highly sensitive to armed conflict, and the >90% declines of Gorongosa's large-mammal populations during the Mozambican Civil War (1977-1992) triggered profound ecological changes throughout the park. Yet Gorongosa’s history is also a testament to nature’s resilience. I will illustrate how our ever-improving understanding of species interactions has helped to steer the ongoing rehabilitation of one of Africa’s most spectacular protected areas.
Results/Conclusions
Selective herbivory by large mammals interacts with abiotic factors such as soil properties to create habitat specificity and beta-diversity in savanna tree communities. However, we know surprisingly little about "selective herbivory" -- i.e., dietary choices -- of free-ranging wild large herbivores. DNA metabarcoding reveals a remarkable degree of dietary niche partitioning at the level of plant species in diverse large-herbivore faunas. These insights have guided the investigation into postwar ecological recovery in Mozambique's Gorongosa National Park. The collapse of the large-herbivore fauna was associated with ecosystem-wide shifts in woody cover and understory species composition; field experiments showed this to be the result not of collapse per se, but of the subsequent irruption of a single species of selectively feeding medium-sized antelope. High-resolution dietary analysis further supported this hypothesis, and also showed that recovering herbivore populations were feeding most heavily on an invasive woody shrub. This discovery suggests that a "natural solution" to invasvie plant management will simply be to allow native large-herbivore populations to recover, rather than undertaking aggressive pesticidal measures.