Funded Grants

Pollination Services and Adaptive Management

The global loss of biodiversity is perhaps the largest calamity and also the greatest challenge facing humanity in the 21st century. Estimates of the magnitude of species extinction vary greatly, but some suggest that several species are lost each hour. Largely, this is due to human influence: humans now dominate all global environmental systems through resource consumption and land use, resulting in levels of extinction rivaling those causing the disappearance of the dinosaurs at the end of the Cretaceous or marine invertebrates at the end of the Permian era. Modern-day human-caused extinctions irreversibly terminate the products of hundreds of millions of years of evolution, and also threaten the life support systems on which we depend. Ecosystems, and the biodiversity that they contain, provide us with a flow of goods and services vital to our existence. These include purification of our air and water, stabilization of our climate, generation of soil, prevention of flooding and soil loss, pollination of our crops, pest-control, production of fish, forests, and non-timber products including vital medicines, and generation of life-fulfilling conditions, such as aesthetic and recreation pleasure.

To stem the growing tide of extinction, conservationists have proposed and fieldtested a variety of strategies over the past century, with varying success. Early strategies for conservation aimed to protect biodiversity by establishing reserves that were offlimits to people, and disregarded the often-negative social and economic consequences of such policies. These strategies were replaced in the late 80's by a paradigm seeking more equitable and long-lasting ways to balance human and wildlife needs: involving local people in co-management of protected areas for the dual goal of sustainable resource use and biodiversity conservation. Recently, however, such integrated models have come under fire due to their limited success, leading to a resurgence of advocacy for strict nature reserves. In contrast, another new strategy is emerging that seeks to integrate human and wildlife needs in a novel way: here, ecosystems are seen as valuable "natural capital" that produce a flow of goods and services of value to humans. Creative new financing mechanisms aim to preserve these ecosystem service values by recompensing land owners for stewarding services that traditionally had no market value, such as the production of clean water or the sequestration of carbon.

Along with other conservationists, I have been deeply involved over the past 13 years in testing some of these strategies in countries as different as Madagascar and the USA. I have seen limited successes and absolute failures, and thus my quest for alternative conservation strategies continues. My current work focuses on testing this latest approach to conservation: the ecosystem service model.

While promising, it is not yet clear whether ecosystem service arguments can always provide sufficient economic motivation for conserving biodiversity. Ecosystem services can be provided by a spectrum of ecosystems, from pristine, natural habitats to restored or highly disturbed systems. When services could be generated more economically from highly modified systems (e.g. using fast-growing non-native tree plantations rather than slower-growing native plant communities to fix nitrogen and stabilize soils), ecosystem arguments are unlikely to generate support for biodiversity conservation. Ecosystems are inherently complex and unpredictable; managing them for financial benefit can therefore be risky since we still lack much basic information. Many land-owners and investors may therefore steer clear of stewarding services for their cash values. Finally, the relationship between biodiversity and ecosystem function is still unclear. The strategy for using the value of ecosystem services to promote conservation of biological diversity relies upon a positive relationship between diversity and ecosystem function. While some studies support this positive relationship, others suggest that only a few species are sufficient to provide ecosystem function. Only a few services have been studied to date, however, so we still lack fundamental information about the relationship between diversity and ecological function.

If natural or restored ecosystems cannot provide ecosystem services in some or all cases, it is important to know this and to develop alternative motivations and policies for biodiversity conservation. Alternatively, if they can, we need to understand ecosystem functions better in order to manage them for their service value. In particular, we need to understand the complex relationships between ecosystem services and biological diversity, their value to humans, and the influence of alternative land-use management strategies upon them. To this end, two years ago, I began to study pollination services in California. Initially I asked the question, do patches of natural habitat in the landscape around farms enhance the diversity and abundance of native bee pollinators, and thus the level of pollination services that crops experience? There are over 4000 species of native bees in North America alone; so far we have found over 20 species visiting several agricultural crops at our study sites. My preliminary results suggest that crops on farms near natural habitat patches benefit greatly from the higher abundance of native bee pollinators found there, presumably because these patches of natural habitat provide bees with resources critical for their own survival and reproduction.

This study is especially topical because of a growing concern about declines in vertebrate and invertebrate pollinator populations around the globe. As pollinators go extinct, then the plants that they pollinate (including many crops that we ourselves rely upon for food) will no longer be able to reproduce. Failures of critical ecological linkages such as plant-pollinator interactions can also have cascading effects throughout ecological communities, causing other organisms to suffer from scarce resources or even to go extinct themselves.

In my McDonnell Foundation proposal, I am asking four sets of interrelated questions aimed at understanding the values of the services native bee communities provide to us, and how we might manage the landscape to enhance those services for our own benefit.

o Value: How important are native bee pollinators for crop pollination, and what is the value of the service they provide? Is this value sufficient to motivate conservation and/or restoration of natural habitat? If not, what other ecosystem services could the natural habitat provide? Could the total ecosystem service value provide sufficient value to motivate conservation? This information can be used to generate an economic motivation for restoring pollination services across the landscape, and is a critical element for determining an optimal allocation of land between agriculture and conservation to maximize pollination service and other service values.

o Diversity: How are these pollination services related to biological diversity of pollinators? Does pollinator diversity confer an insurance value for maintaining pollination services to crops that will increase ecological "resilience" to ecological change such as global warming? These studies address the fundamental question of the role of biodiversity in maintaining are life support systems.

o Spatial patterning: How do these pollination services vary across the landscape? Do they depend on the proximity, abundance, diversity and/or composition of natural habitat? Do native pollinators move between natural and agricultural habitats? These studies will allow us to design explicit restoration strategies that will maximize maintenance of pollination services.

o Management: What resources in natural habitats or agricultural habitats are required to maintain populations of native pollinators? What areas of natural habitat are required to maintain bee populations sufficient to provide agricultural pollination services? These studies will allow us to identify the optimal allocation of land uses to maximize pollination services across the landscape;

My project is a "demonstration project": a detailed case study on the economic value and ecological conditions affecting management of a specific ecosystem function of value to humans. Ultimately, the objective of my research is to go beyond investigating pollination services and their dependency on biodiversity, in order to develop and implement management plans that will maintain pollination services across natural and human-dominated landscapes.

Case studies are also the first step towards "scaling up" to generalize to other systems and locales. I will use the results from this study, in conjunction with related work that I am conducting on other ecosystem services at other scales, to assess when ecosystem arguments can provide adequate motivation for biodiversity conservation, and to draw general conclusions about the policy and economic issues of conserving, restoring, and managing ecosystem services using natural ecosystems. The funds from the McDonnell Foundation would allow my research team and I to generate conceptual and mathematical models that explore complex systems at the interface of ecology, economics, and policy towards better environmental management.