Research Interests
Over the past decade, my career has undergone a transition from discovery-based ecological research that has distant applications to conservation, to synthesis-based analysis and education that more immediately affects conservation practice.
The research agenda of many conservation biologists diagnoses the threats to biodiversity from human development and explores theoretical questions in model systems. Although I am proud of my work with Clarkia concinna, one example of the above approach, the aim of my recent work is to more directly conserve biodiversity, and to support sustainable human endeavors.
This project was born out of a set of conversations I had with Elizabeth Gray, director of conservation science at the Washington state branch of The Nature Conservancy. We were both concerned about a push within Washington, and across the US, the European Union, and indeed globally to expand biofuel production that seemed to us to ignore biodiversity considerations.
Accordingly, I completed a review of the ways in which expansion of biofuel production may affect biodiversity in the coming years, consulting frequently with Dr. Gray and also one of my graduate students, Patricia Townsend, for further vetting of the analysis. Although biofuels are widely considered one of the most promising sources of renewable energy by policy makers and environmentalists alike, production of certain biofuels (particularly corn-based ethanol) will cause severe environmental impacts and reduce biodiversity. Our paper summarizes these results (Groom et al. 2008), and qualitatively contrasts major potential sources of biofuels, including corn, grasses, fast-growing trees and oil crops to highlight their relative impacts on the environment in terms of land, water and fertilizer use, and roughly calculated the environmental footprint of each crop. We recommended a focus on biofuels of the future that can be developed in small spaces, rather than extensively on croplands or on biodiverse native habitats. Our work is timely, and of a high-profile nature. On the basis of this paper, I've been invited to speak at a symposium on biofuels and biodiversity this coming summer at the Society for Conservation Biology annual meetings, and numerous press reports have mentioned our work or comments from interviews in March-June 2008.
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Beginning in 1999, I collaborated with Jaime Collazo and groups of graduate student researchers to carry out a complex suite of studies in coffee plantations and secondary volcanic and karstic forests. We investigated how specific aspects of land use or plant community pattern affected bird communities in north-central Puerto Rico, and considered how we might influence land use policy to better support conservation of an endangered species, the Puerto Rican Parrot.
In the area we studied, the landscape is composed of mosaics of coffee plantations of various types, tree plantations, and recovering secondary forests. More than 98% of the forest cover of Puerto Rico was removed in the last century, yet few bird species went extinct, perhaps because of the ability of the birds to use coffee plantations.
Traditionally, coffee has been grown under a canopy of a diverse suite of species, particularly legumes, and presents a more open, but relatively diverse forest cover type. Recently, agriculturalists have promoted varieties of coffee that are able to grow in full sun, due to the far higher yields of these varieties. For more than a decade, studies from Central America have shown that only the traditional method of growing coffee under a diverse canopy (shade coffee) harbors diverse communities of birds. Our results are in accord with these studies, showing that shaded coffee plantations contain more bird species that enjoy higher breeding success than do areas dominated by other agricultural practices. An interesting twist in our research, however, is that not all shade coffee plantations are created equal. It appears that only plantations that include large "resting" areas of secondary forest, and a wide diversity of canopy and subcanopy tree species, are widely used by the avian community. Further, it may be that certain tree species provide particularly important fruit resources, such that shade coffee plantations are most useful when these species are present.
Our work has influenced plans for the release of captive bred Puerto Rican parrots, as well as policy on the management of coffee plantations.
An interest in the population and community effects of life in fragmented, or spatially-discontinuous patches, led me to initiate mechanistic investigations of how populations respond to isolation and reductions in size. From [year to year span], I studied an annual plant (Clarkia concinna concinna (Onagraceae)) that grows in a highly subdivided habitat in northern California. In this project I developed a mechanistic understanding of the ways in which habitat fragmentation can change a species' biotic interactions and how constraints from the physical environment can influence the joint dynamics of the metapopulation. My approach included both the use of field and greenhouse manipulations coupled with population models to reveal the critical factors that determine patterns of population and community dynamics.
One of the most striking results is that sufficiently small and isolated patches of the plant do not receive effective pollination services, and suffer higher extinction rates than plants in large, well-connected patches (Groom 1998 Am Nat 151:487-496). While limited reproduction of plants in small patches have been demonstrated by others, this study is unusual in documenting a threshold relationship between pollination success and patch size or isolation, and in linking pollination failure to risk of extinction.
My research efforts on C. concinna represent a long-term research program aimed at teasing apart the details of population dynamics across a diverse landscape. My work in progress includes a detailed examination of constraints to colonization in this species and interactions between patch phenology and pollination success. I have quantified pollinator visitation, pollen transfer efficiency, and flower constancy among the suite of pollinators that visit C. concinna. Across the study area, consistent differences in the level of pollination have a partial correlation with differences in the make-up of the pollinator community in distinct locales.
However, in the future I intend to expand on work that examines the role of genetic variability and inbreeding on population performance and extinction rates. One of my graduate students, Todd Preuninger, and I have just completed a set of experiments in the greenhouse and the field. We found that C. concinna populations experience inbreeding depression in several life history characters, but that there is no decrease in the magnitude of inbreeding depression in isolated subpopulations. This suggests that at least over time spans of a decade or so, inbreeding can lead to serious declines in performance regardless of the spatial configuration of subpopulations. In addition, I completed a pilot experiment that tests the idea that low genetic diversity can limit the performance of C. concinna populations. This pilot showed that germination success is influenced by the genetic diversity of the seeds in a founder group. I hope to expand my work on C. concinna to document the patterns of genetic diversity in this naturally fragmented species, and to explore more thoroughly the consequences of low genetic diversity for spatial spread, average individual performance, and long-term patch persistence.