Ecologist Erika Zavaleta receives prestigious Mellon Foundation grant

Erika Zavaleta, an assistant professor of environmental studies at the University of California, Santa Cruz, has received a prestigious grant from the Andrew W. Mellon Foundation to investigate the ecological impacts of the loss of plant species in California ecosystems.

Through a program that supports the research projects of outstanding junior faculty, Zavaleta has been awarded a three-year, $200,000 grant. A maximum of only three such awards are presented each year.

Zavaleta, who joined the UCSC faculty in 2003, conducts research on the ecological impacts of biodiversity change. She is particularly interested in understanding the ecosystem effects of a decline in the number of plant species, including impacts on nutrient cycling and retention, productivity, and community and ecosystem resilience.

The grant will support observational field research and an experimental study of the effects of removing vulnerable species from two key ecosystems: vernal pool and grassland habitats in central California.

Zavaleta's work fills a gap that persists because most studies on the ecology of species decline and extinction have focused on vertebrate animals, not plants.

"Despite the fact that plant species are declining and disappearing at an alarming rate around the world, we have only a marginal understanding of the ecological consequences of these declines," said Zavaleta, who described California as "a global hotspot for threatened plant diversity."

Zavaleta's project will focus on non-random loss of rare and vulnerable plants. "Most species in ecosystems, and most at-risk species, are relatively uncommon," said Zavaleta. "They exert what influence they have in relatively small numbers."

In a pilot study in 2003-04, Zavaleta found that losses of even very rare species have a large impact on ecosystem productivity, colonization by other species, and water consumption. Her finding that declining biodiversity greatly reduced resistance to invasive species has important implications for resource managers. The new grant will enable Zavaleta to improve and expand on the pilot study to explore the mechanisms underlying the documented effects.

The observational study will compare approximately 500 currently threatened plant species and their nonthreatened relatives to explore whether they possess, as a group, unique or distinct characteristics, such as size, structure, life history, and defenses. "This will be the first phylogenetically controlled study of plant species vulnerability that we know of," said Zavaleta.

In the experimental study, Zavaleta will manipulate a small number of species in a single type of ecosystem to measure the ecological consequences of removing or reducing species. UCSC doctoral candidate Kristin B. Hulvey and a postdoctoral researcher will collaborate with Zavaleta, who will also work with colleagues at other universities.


Editor's Note: Erika Zavaleta may be reached at (831) 459-5011 or via e-mail at