Assistant Professor Univeristy of Florida Gainesville, Florida, United States
Animals are often seen as merely inhabitants of a biogeochemical landscape that is shaped by microbial and vegetation communities. However, animals can strongly influence that landscape through their metabolic processes, modifications of the physical landscape, and movements across ecosystem boundaries. When animals consume resources in one location and deposit them in another through excretion, death, or reproduction, they can provide resource subsidies to the recipient habitat that influence community structure and ecosystem function. These animal-vectored subsidies are distinct from abiotic subsidies in their ability to move against natural gradients or along natural gradients at faster rates, their tendency to be aggregated in time and space, and their quality relative to other resources. Animals are also able to physically alter ecosystems in ways that can shape the environmental context in which subsidies are deposited, influencing the way in which recipient ecosystems respond. In many ecosystems, these animal subsidies have declined or been lost in concert with declines in animal populations. In East African savannas, abundant populations of large wildlife enable us to study the potential role of animal resource subsidies in shaping ecosystem processes. Large herbivores, including hippos and wildebeest, regularly transport terrestrial resources to aquatic ecosystems. These terrestrial subsidies can alter rates of nutrient cycling and ecosystem production in aquatic systems, effectively transforming into aquatic subsidies that in turn move into terrestrial ecosystems via emerging insects and riparian scavengers. Thus, the movement patterns of animals create a dynamic and reciprocal flux of resources across the land-water interface that belies traditional conceptualizations of ecosystem processes. These types of animal networks occur across the Earth, creating a biotic circulatory system that moves and transforms resources over landscapes in ways that are fundamentally different than would occur in their absence.
