Regulation of ecosystems and biodiversity loss

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The primary purpose is to conduct a long term research program on biodiversity and ecosystem dynamics in the Serengeti ecosystem, East Africa. We use Protected Areas as Ecological Baselines to compare with human-dominated ecosystems outside. The Serengeti provides a unique opportunity to understand (1) how a natural ecosystem works, (2) what role biodiversity plays in this system, and (3) what human influences are threatening this biodiversity. The Main Questions are: 1. What are the rules for the sustainability and resilience of ecosystems? 2. How do disturbances cause changes in state or destabilize ecosystems? 3. What are the consequences when components of biodiversity are lost from a system? The hypothesis that I test is that moderate (natural) disturbances are buffered by complex stabilizing negative feedbacks within the diverse community, but large disturbances (agriculture) result in shifts in community composition and form multiple states. I use 3 approaches: (1) Understanding the dynamics using large scale disturbance; (2) Analysis of the multispecies interactions by studies of individual movements; (3) Understanding the consequences of loss of biodiversity by experimental removal of some parts of the biota. 1. Dynamics of the ecosystem using large scale perturbations. There are 6 perturbations that affect this system: 2 abiotic (fire, drought), 2 biotic (grazing by migrants, disease epizootics), 2 human induced (agriculture, hunting). (i) What are the direct and indirect effects of these impacts? (ii) Which species are affected, does composition change, and do some go locally extinct? (iii) What is the time scale of change and return, and is there more than one state? A team of trained field technicians obtains data from systematic sampling on all the major biotic components of the system – soil organisms, plants, mammals, birds, insects, while other data are supplied from colleagues that work with us on large carnivores, and diseases. 2. Multispecies movement models. This project is concerned with the rules for the stability of communities. (i) what are the stability properties for living in groups? (ii) What are the rules for movement and how do they affect stability? (iii) How do herbivores trade-off the needs for food with reduction of risk of predation? We hypothesize that predator (lions) behavior is determined by prey herd size, encounter rates and population density for each prey species. We have four objectives. i. We develop mechanistic movement models for 6 herbivore species eaten by Serengeti carnivores. ii. We use GPS data to test carnivore movement models. iii. We use these models to see how carnivores can link to the movements of migrant prey. iv. We examine when resource-searching by herbivores switches to risk-aversion, and how this is modified by food quality and abundance. 3. The biodiversity knockout experiment (BioKO). This program is designed to understand the role that functional groups of our biota play in whole versus communities that have lost species. The essence of the experiment is to knock out different plant functional groups then compare the stability of this reduced system with systems that have their full biota. Significance: This system provides an example for understanding the mechanisms of change. The information will allow managers to assess stability of the ecosystem for conservation, the need to maintain habitat heterogeneity, and whether management interventions are needed to modify undesirable change from human modification (agriculture, hunting) or Climate Change.