Biological Research at the Western Ecological Research Center

By Gloria Maender

The Western Ecological Research Center began in 1994 as a collection of field stations, shortly after the National Biological Survey was created by Secretarial Order; and in 1996, this biological research center joined USGS. While its scientists are recognized internationally, much of their research occurs from California to Arizona, or the Pacific Southwest.

The Pacific Southwest is filled with natural superlatives, including the world's largest and tallest trees, the oldest living organisms on earth, three deserts, the lowest point in the western hemisphere, and the highest peak in the contiguous United States. It is also a region of explosive human population growth, increased competition for scarce natural resources, and recurring natural phenomena like fire, drought and floods.

Natural resource managers in this region face a daunting array of critical natural resource decisions each day. Issues include wildland fires, invasive species, environmental contaminants, declining populations of native species and urban development. Decision-makers need to understand the impacts of land use change on habitats, biological resource systems, and individual and communities of species. The Western Ecological Research Center is responding to these needs and deploys more than 100 scientists and research support staff in proximity to primary research endeavors and client needs. Many are widely recognized leaders in their fields, whose long-term research has enabled them to make remarkable discoveries vital to the sound management of natural resources. Some examples of their efforts are described in the captions that accompany the photos that appear in this story.

Mountain yellow-legged frog is one of the most rapidly declining amphibians in California's Sierra Nevada. Dramatic population declines in this and other frogs have occurred in California over the last 10-15 years. USGS scientists discovered that pesticides from agricultural areas in the Central Valley, which are transported to the Sierra Nevada on prevailing summer winds, may affect populations of amphibians that breed in mountain ponds and streams. When these pesticides are absorbed by frogs, they can suppress an enzyme called cholinesterase, essential for the proper functioning of the nervous system.

USGS scientists collect data on a bobcat and place a collar on it for a radio telemetry study at a nature preserve in Orange County, CA. Bobcats are an indicator species of habitat connectivity. Conservation of wild cats in fragmented urban landscapes requires identifying and monitoring critical habitat linkages to determine how road building or other development may affect the animals' movements.

USGS scientists are studying the biology and habitat needs of the threatened desert tortoise throughout the Mojave Desert. Research focuses on long-term population trends and causes of ill health and high mortality rates of tortoises and includes effects of natural and human-induced changes to the environment. A recent study examining the effects on tortoises of an exploding population of common ravens in the Mojave found that young tortoises were at risk of raven predation wherever ravens occurred and especially where non-breeding ravens gathered, such as at landfills, and where pairs nested.

With repeated burning, invasive grass species can convert a Mojave Desert landscape into an annual grassland of low diversity and few native plants and animals. Exotic grasses have invaded many regions of the West, including the Great Basin, the Mojave and Sonoran deserts, the Sierra Nevada, and California's coastal chaparral. USGS researchers are working to better understand how increased fire size and frequency affect arid ecosystems of the West, how fire changes nutrients in the soil, how invasive plants and fire are related, and how to protect native plants and animals from further impacts of invasive annual grasses. Results from a recent USGS study indicate that increased levels of soil nitrogen from atmospheric nitrogen deposition, or from other sources, could increase the dominance of alien annual plants and possibly promote the invasion of new species into desert regions.

In California, chaparral ecosystems burn in large landscape-scale crown fires that are necessary for the ecology of these systems but pose a threat to people in nearby developments. USGS research shows that many species in these systems are highly dependent on recurrent fire because some seeds require smoke to induce germination. Unlike western forests where a century of fire exclusion has led to fuel accumulation and a risk of catastrophic wildfires, USGS research has shown that large, intense fires have burned in chaparral ecosystems for numerous decades. They occur, in league with powerful Santa Ana winds, as frequently today as before widespread fire management aimed at fire exclusion. Here the use of prescribed fire is not necessary for ecosystem health, nor is it able to prevent large-scale fires.

In some Western States, more than 100 years of excluding fire has led to a heavy build-up of fuels such as dead vegetation, dense brush, and dense tree stands, with a potential for larger, more intense fires and more rapid spread than before the fire-exclusion era. USGS scientists in the Sierra Nevada have just completed a 10-year study to determine fuel accumulation rates for the species that occur in mixed conifer ecosystems: giant sequoia, ponderosa pine, sugar pine, Jeffrey pine, incense-cedar, white fir, and Shasta red fir. They also related annual increments of fuel to stand characteristics. Such relationships allow predictions of fuel loadings to be made on a stand basis for each of these species under current and possible future conditions.

In California, USGS scientists are striving to understand why the growth rate of the threatened southern sea otter population is lower than expected. Their data have shown that many breeding-age otters are dying, and this discovery is important to those involved in recovery planning for conservation of this smallest of marine mammals. USGS scientists and colleagues are using radio transmitters and time-depth recorders in dozens of sea otters to monitor their behavior and vital signs as they dive and forage for food. In Alaska's Aleutian Islands, USGS research untangled the chain of events that led to the collapse of the once-thriving sea otter and kelp forest. The collapse in the 1990's was likely driven by increased killer whale predation of sea otters when other marine mammal prey became scarce, and ultimately was caused by human impacts on the oceanic ecosystem. (Photo courtesy U.S. Fish and Wildlife Service.)

Photo courtesy Cristina Sandoval, University of California, Santa Barbara.	Western snowy plover chick, courtesy Morgan Ball, University of California, Santa Barbara.
Before a rope fence was installed, threatened western snowy plovers vacated their preferred roosting areas on this beach when disturbed, as on this particularly busy day at the Coal Oil Point Reserve in February 2001. In 2003, however, 39 young western snowy plovers fledged on this same California beach, signifying the first evidence that a reduction in human disturbance can lead to the recovery of a formerly abandoned snowy plover breeding site. This success, which was nationally recognized, owes much to the combined effort of researchers, managers and volunteers from USGS, the Santa Barbara Audubon Society, and the University of California Natural Reserve System. USGS studies assessed the rate of different kinds of human disturbance, found that human use of parts of the beach shared by the plovers interfered with the shorebird's ability to find a predictable place to rest and nest undisturbed, and determined the smallest portion of the beach that could be closed to maximize protection of plovers with minimal inconvenience to beach users. Now a single strand of rope designates the plover zone yet allows people on the beach to continue to walk at the water's edge.

A team of waterfowl biologists led by USGS scientists is using satellite telemetry to track migrating pintails to identify critical spring staging areas; link important winter, spring, and nesting areas; estimate efficiency of spring pintail surveys; and measure exposure to botulism. Satellite tracking has shown that southern Oregon and northeastern California are important stopover areas for the migrating ducks. Scientists are also investigating the response of waterfowl to a decade of habitat change in California's Central Valley. In the San Francisco Bay Estuary, USGS scientists are radio-tracking wintering surf scoters to learn about their distribution, movements, and feeding behavior and to understand the risks of accumulating contaminants from food sources in the bay.