In general my research programme is directed towards testing formal models in ecosystem dynamics using large-scale natural or semi-natural experiments. I am concerned that the results of my work are of relevance to conservation of the environment and to the priorities of society.I have used models developed from the behaviour of individuals, for example in predation theory or the behaviour of migration, and applied them to population and ecosystem dynamics.
Predator Sensitive Foraging This work has tested theory on the interaction of predation and food resources on foraging behaviour of animals. I developed models predicting that animals facing food shortage should take greater risks and hence die earlier from predation. My studies compared the mortality of animals in food rich with food poor conditions using data accumulated over 27 years and demonstrated that mortality conformed to predictions of Predator Sensitive Foraging theory (Sinclair & Arcese 1995 Ecology).
Predator-Prey Theory Analysis of population dynamics in predator-prey systems has confirmed predictions based on the behaviour of predators. First, my studies with colleagues in Australia have shown that populations can be held down by predators, but that these populations can breakout from predator control, cause outbreaks and become pests. Secondly, analysis of declining populations has confirmed predictions that the characteristics of predator behaviour results in the extinction of populations. This work has provided a protocol for conservation of endangered mammals and birds in Australia and New Zealand (papers in Conservation Biology 1997, and with Olsen 1990 Oikos, Pech et al. 1992, Oecologia).
Migration Systems Long distance annual movements (migrations) are characteristic of many mammal and bird species. Studies of the migrations of large mammals in Serengeti demonstrated both the cause and function of migration. Migration is an adaptation to track seasonally changing food resources. Its significance for understanding ecosystem dynamics is that it results in much larger numbers than would occur with sedentary populations. The consequences of migration are that the population escapes from predator regulation. It therefore determines all components of the ecosystem. The switch between sedentary and migratory behaviour is one way a population can have multiple states. This result explains effectively all migration systems in the world. It provided the basic understanding for the repeated human famines in northern Africa, migration systems that had become sedentary and unstable. (Sinclair & Fryxell 1985) and provides the basis for conservation in Africa (In Serengeti, and Fryxell et al. 1988).
The Regulation of Populations A major part of my research has examined the mechanisms that lead to the regulation of populations, focusing on the large mammals of Africa. I used a natural experiment from the disappearance of a disease, rinderpest, to test theories of regulation in two large mammal species in the Serengeti, the African buffalo and the wildebeest. This work demonstrated that regulation was non-linear, accelerating at high density, and resulted in system stability. I am interested in how various factors such as disease interact with food supply and predation in affecting populations. These studies were synthesized in The African Buffalo, A study in regulation of populations in 1977, and two books I edited, Serengeti (1979) and Serengeti II (1995).
My results are relevant to how natural areas are managed for conservation, for they address how much human interference is necessary in management.
Trophic dynamics The large-scale experiments in ecosystem dynamics in northern Canada with Charles Krebs and other colleagues, has allowed us to explore the ecosystem effects of top-down and bottom-up processes. Our most significant finding was that both resource supply and predation occurred simultaneously and their effect was more than just additive - there was a synergistic interaction of food and predators in determining the abundance of the dominant species, snowshoe hare. As with the Serengeti ecosystem indirect interactions determine trophic dynamics.
Future research activities The above outline illustrates my approach to ecosystem research by using natural experiments. It requires teamwork, often in different countries because these provide different opportunities for understanding. My approach, therefore, is to build teams and to develop links and collaborations with other groups. My future interests lie in five areas:
1. The role of protected areas as baselines for measuring the impacts of human exploitation on ecosystems. I am conducting research in Serengeti using this approach but I would like to establish this in other areas of the world including Britain and other parts of Europe because of the extensive human impact. In particular, I am interested in how to provide scientific advice for conservation.
2. Understanding the consequences of biodiversity loss on ecosystem dynamics. This can be approached by looking at whole systems and comparing with ones where major components have been lost through various human activities. Again protected areas play a role in this and biodiversity has become the major theme of my Serengeti work. I have recently been developing a research proposal in Canada to experiment with this approach. We propose to use a gradient of natural diversity from the high Arctic to the prairies. This Biodiversity Knockout Experiment (BioKO) is intended to become the research program for this Centre for the next ten years.
3. Reconstitution of ecosystems. Related to the above, I am interested in whether we can reconstitute ecosystems that have become degraded. Ecosystems that lose species seem to unravel once important species are lost. This predicts that reconstitution may also follow a non- linear course. If this is so then it has profound consequences for conservation.
4. Processes leading to extinction of small populations. I am involved with both New Zealand and Australian research groups in this aspect. Experiments in the conservation of endangered marsupial prey and their exotic predators, the red fox and feral cats, have been conducted in Australia since 1992. This is being carried out in conjunction with the CSIRO, Sustainable Ecosystems division, Commonwealth Government of Australia. Similar experiments are being conducted in New Zealand by their Crown Research Institute, Landcare Inc. I am working them on their research in the conservation of endangered bird species threatened by exotic weasels, ferrets and cats; and on ecosystem studies and biodiversity loss.
Within British Columbia we have a program on the dynamics of declining populations of endangered species, in particular the Vancouver Island Marmot.
5. Setting priorities for conservation sites. Other work in British Columbia include developing ways to prioritize conservation sites.