Corinna Riginos
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Corinna Riginos
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Grazing strategies for wildlife-livestock coexistence
One thing is clear about conservation in Africa: parks are not enough. If wildlife conservation succeeds, it will be because people and wildlife learn to live with each other in mixed-use lands. These mixed-use lands already make up a vast and critical part of most wild species' ranges, but many are undergoing rapid degradation from overgrazing. This degradation means less grass for wildlife as well as cattle. In a part of the world where many rural people live marginal existences and where livestock husbandry is a deeply-rooted cultural practice, simply reducing or eliminating livestock is not practical. Instead, we need creative solutions to minimizing the negative, competitive interactions and maximizing the positive interactions between livestock and wildlife.
As part of my postdoc work, I am working with a large team of collaborators to test and evaluate the effects of different livestock grazing strategies on wildlife and the vegetation. Specifically, I will be testing whether cattle can be used to simulate large-scale herbivore migrations - patterns of animal movement that have broken down as wildlife habitat has become increasingly fragmented and pastoralists have been forced to adopt more sedentary livelihoods. This research project will address very applied questions of land management as well as fundamental questions about how different species of ungulates coexist in species-rich African savannas.
My primary collaborators on the project are Dan Rubenstein (Princeton University), Wilfred Odadi (Egerton University), Jayne Belnap (USGS), Siva Sundaresan (Denver Zoo), and Margaret Kinnaird (Mpala Research Centre).
Consequences of tree density in savannas
Savanna ecosystems are among the most important ecosystems in the world. They support the highest diversity and biomass of large wild mammals, as well as some of the most productive rangelands in the world. They cover more than one fifth of the planet's land surface. Yet, some of the most fundamental questions about how savannas function - and how we should manage them - have not yet been addressed.
Savannas are, by definition, a mixture of trees and grasses. Human actions, however, are altering the relative abundance of trees and grasses in many savannas all over the world. In some areas, people are over-harvesting trees for fuel wood. In others, people and their livestock are causing increases in tree cover through overgrazing the rangeland. Increases in atmospheric carbon dioxide are also pushing savannas towards a more woody state. Yet, despite these widely-recognized changes in tree cover, few studies have addressed the consequences of these changes.
I am conducting an experimental test of the consequences of variation in tree density for wildlife, cattle, grass, and the trees themselves. This experiment is unique; it is the only replicated, large-scale manipulation of its kind. Already this experiment is validating and expanding upon my previous descriptive findings from the same ecosystem. For example, I am finding that most herbivores avoid areas of high tree density, with various consequences for the vegetation. I am also finding that both tree and grass growth are affected by tree density - further evidence that competition between savanna trees and grasses is fierce. I hope in the near future to begin a more thorough study of the physiological mechanisms underlying these patterns.
With this experiment, we are gaining a unique set of insights into how savanna structure affects savanna function. An understanding of the factors that underly healthy savanna functioning is vital to the maintenance of biodiversity in these ecosystems.
My primary collaborators on the project are Truman Young (UC Davis), Kari Veblen (USGS), and Kelly Caylor (Princeton University).
Consequences of wild and domestic herbivores - Kenya Long-term Exclusion Experiment
The above research agenda ("Consequences of tree density in savannas") is closely linked with the Kenya Long-term Exclusion Experiment (KLEE), of which I am a co-PI. KLEE is a large-scale, replicated set of herbivore exclosures. The experiment, which was conceived and initiated by Truman Young, has been running for 13 years now. The experiment is designed to test the separate and combined effects of cattle and wildlife on savanna structure and function. Numerous fascinating results have come out of this study already, and many more promise to emerge in the coming years. My own involvement in the KLEE experiment centers on two themes: first, how different guilds of herbivores may cause changes in savanna structure (e.g. tree density), and second, how these changes may translate into changes in savanna function. To address these questions I am collaborating with Truman Young (UC Davis), Kelly Caylor (Princeton University), and Kari Veblen (USGS).
