Associate Professor of Wildlife Ecology and Conservation
Institute of Food and Agricultural Sciences
Emilio Bruna strives to understand the impact of human activities on tropical ecosystems. Much of his work is conducted in Latin America’s two largest biodiversity hotspots – the Amazonian rain forest and the Brazilian savannas known as the Cerrado. Understanding the inherent complexity of these ecosystems and investigating the consequences of the myriad threats they face requires creative, multidisciplinary, and collaborative approaches.
Many studies have found that plant species go extinct in the fragments of forest that remain following deforestation. Although the mechanisms responsible for these extinctions are usually unknown, reductions in seedling establishment are thought to be among the most important. In the first comprehensive tests of this hypothesis, Bruna and his collaborators found that reduced recruitment could indeed lead to population declines in fragments. However, they also found that elevated seed dispersal by birds into forest fragments appeared to help populations overcome the negative consequences of fragment isolation. With support from the National Science Foundation, Bruna and his colleagues are now testing this hypothesis. To do so they are integrating detailed data on plant reproduction, information collected with radio telemetry on the diet and movements of birds, and genetic paternity analyses into sophisticated mathematical models. They expect the research they will conduct in the coming years will help resolve a longstanding controversy in plant ecology – whether seedling abundance is limited by the availability of suitable habitat in which seeds can germinate or the abundance of seed dispersers.
Human activities such as the combustion of fossil fuels and the application of chemical fertilizers have more than doubled the quantity of nitrogen in terrestrial ecosystems. This increase can have profound consequences for ecosystem properties, but how it influences plant populations remains unknown. With recent support from NSF and the Packard Foundation, Bruna and his collaborators are investigating how nitrogen enhancement influences plant populations and communities in the Cerrado. Bruna’s research will address a major gap in our understanding of how tropical plant populations are regulated. Furthermore, anthropogenic nitrogen deposition is widely recognized as an emerging threat to ecosystems throughout the developing world – one that is likely to worsen as the global demand for biofuels increases. Because the Cerrado is an increasingly important producer of sugarcane used for ethanol, this work will also have important implications for conservation in this agricultural and biological hotspot.