Research

Some animals play disproportionate roles in ecosystems relative to others. Often termed ecosystem engineers, these animals can shape the structure and functioning of landscapes in profound ways. Much of our work on these animals has focused on termites and elephants in African ecosystems. Future work on animal-driven ecosystem engineering includes planned studies on white and black rhinos, as well as hippos, in an effort to integrate the effects of multiple megaherbivores into our understanding of how landscapes look and function.

Termites

Termites are arguably the most important soil organisms in tropical and sub-tropical environments, where they facilitate a majority of litter decomposition and alter the nature and properties of soils through their foraging and mound building activity.  Their activity also leads to nutrient concentrations in their nests, often in the form of large epigeal mounds, which results in nutrient hotspots across the landscape. The vegetation communities on termite mounds are often very different to the vegetation in the surrounding matrix, due to the increased nutrients as well as increased moisture on and around mounds. These differences increase landscape heterogeneity and have cascading effects on invertebrate communities, mammalian foraging patterns and fire regimes. Our work seeks to better understand these termite-driven effects and to quantify their magnitude and importance for ecosystem functioning at landscape scales. 

 

 

 

Elephants

Elephants, when present, are among the strongest drivers of vegetation change in African ecosystems, altering patterns of treefall, vegetation cover and aboveground carbon stocks. Elephants also serve as a model organism for understanding the role of megafauna and provide clues as to how the now largely extinct megafauna of other continents shaped how these ecosystems look today. Our work on elephants seeks to quantify their role in driving vegetation change across landscapes in both savanna and thicket habitats, as well as to understand how they interact with other species shapes landscapes. 
Image courtesy of Antoine Marchal

A major theme of our work is to understand the interplay between landscape heterogeneity and biodiversity, how they interact to shape each other, and how animals affect the generation and sustainability of both. Landscape heterogeneity, the uneven distribution of resources and features across space, drives diversity and enhances the resilience of ecosystems to global change. Therefore, understanding how heterogeneity is generated, what enables it to persist, and how it influences ecosystem processes is of much importance. Biodiversity too can affect the generation and persistence of heterogeneity through the activities of different species that alter ecosystem processes. Diverse ecosystems also lead to increased stability through a range of mechanisms including asynchrony in species responses to disturbance, and a dampening of inter-specific competition. Moreover, management action, human land-use change, and global climate change have the potential to fundamentally alter many of the processes that generate heterogeneity, possibly stifling its formation and leading to homogeneous environments with reduced biodiversity.  

Our work in this area has focused on understanding the role of both biotic and abiotic, drivers of landscape heterogeneity and its effects on biodiversity. We have studied how biotically-driven heterogeneity alters the distribution and abundance of grasses and trees, the foraging activity of mammals, and the community structure of invertebrates. In terms of abiotic drivers, we have examined the role of fire, rainfall and woody encroachment in shaping biodiversity and ecosystem functions such as decomposition rates. Planned future work in this area aims to uncover how trophic interactions complement and/or mitigate the creation of spatial heterogeneity and the implications this could have on biodiversity. 

Predator activity can have profound impacts on the behavior and population size of prey species, with extensive ecosystem level effects and sometimes the emergence of trophic cascades. Comparably little is known about these effects in the complex multi-predator/multi-prey systems common to African ecosystems. Moreover, how these effects might vary across landscapes in response to changing levels of forage quantity and/or quality, predator numbers and vegetation structure are poorly understood. We have investigated the effects of vegetation structure on predator behavior, how the reintroduction of top predators alters the habitat use and behavior of herbivores, and how herbivore responses to predator induced ‘landscapes of fear’ change over varying landscapes. Future research will focus on when and how predators trigger trophic cascades that alter landscape structure and function, and how such cascades might be mitigated or enhanced by the activity of other species and variation in abiotic drivers. 

In addition to understanding how animals shape and respond to changing landscapes, we strive to aid the conservation of endangered species and to find solutions to management challenges that will facilitate the survival of these species. Research in this area has included studies on habitat use and reproductive success in African wild dogs, whether attempts by researchers to study wild dogs has in fact contributed to their plight, and habitat use and movement ecology of orangutans in disturbed forests. We plan to continue and expand this line of research to include other species, such as black and white rhino and African great apes in the future.