California Agriculture, November-December 1995
Volume 49, Number 6
Biological diversity: What is it and why do we care?
peer-reviewed research articles
Can we stop farmland losses? Population growth threatens agriculture, open space
by Albert G. Medvitz , Alvin D. Sokolow
California, the nation's top agricultural producer, also leads the states in the number of new residents added annually. California's population is projected to double to 63 million by 2040. If the resulting increase in urban acreage replaces farmland, California agriculture will lose nearly 5 million acres — 17% of today's total farmland base. With it will go open space, which is now a refuge for some wildlife. In the past, population growth did not reduce farmland acres because there was always more land to convert to agriculture. That scenario no longer exists due to limited cultivable land and water. Adaptations in farming practices and urban form such as higher densities and more compact development could limit the conversion of farmland to urban uses.
Sidebar: Mono Lake compromise: A model for conflict resolution
by Deborah L. Elliott-Fisk
Abstract Not Available – First paragraph follows: Mono Lake is a unique natural resource in California and the rest of the world. The lake evolved as a hydrologically closed basin, having no ocean outlet. Estimated to be 1 million years old, it is a remnant of the much larger ice-age Lake Russell. Lake Russell created a series of linked ecosystems: saline lake waters linked to hot and cold springs, fringing wetlands, riparian corridors and terrestrial uplands. Such a series of ecosystems is found nowhere else in the world. The unique ecology of this lake has been greatly threatened in this century by the development of California's water resources.
Inventory first step to conserving plant diversity
by Bruce M. Pavlik
After 200 years of exploration and study, botanists have found California's native flora to be diverse and unique. Despite having great economic, scientific and aesthetic values, many species are close to extinction. Conserving the flora will require additional scientific efforts to catalog, map, preserve and restore diversity at the level of the gene, species and natural habitat.
Displaced by agriculture, urban growth: California wildlife faces uncertain future
by Thomas E. Kucera , Reginald H. Barrett
California supports one of the greatest diversities of terrestrial wildlife of any state. However, many wildlife species have been lost or have become imperiled since the mid-1800s. Much of this biodiversity loss has been due to habitat loss caused by the conversion of wildlands to agriculture, facilitated by numerous water projects. Although certain agricultural practices can benefit wildlife, continued population growth and urban sprawl are consuming much of California's agricultural land, threatening even these benefits.
How economic incentives for growers can benefit biological diversity
by Richard E. Howitt
Reduction in biological diversity is an inevitable outcome of economic pressures and technological innovations in the initial stages of agricultural development. However, some research shows that economic incentives steer agricultural development to areas where the impact on biological diversity is minimized. As agriculture has developed in California its effect on biological diversity has increased and the value of biological diversity is increasingly recognized. The effect of several economic and technical trends on California agriculture suggest that incentives can be modified to reconcile continued profitability of the agricultural industry with sustaining the current biological diversity.
Millions of generations old: Once lost, diversity of gene pools cannot be restored
by Michael T. Clegg
The present diversity of species is the result of a very long and slow process of genetic change and adaptation. The time necessary for the emergence of new species, and even for the accumulation of genetic variants at individual gene loci within species, greatly exceeds the time since the emergence of Homo sapiens. New techniques of molecular biology combined with recent theories in population genetics allow us to assess the time dimension of genetic change; these suggest that some genetic polymorphisms may have originated over a million generations ago. In other words, once lost, any particular genetic adaptation cannot be regained in any realistic time interval. We depend on biological systems for food, fiber, energy and medicinal needs. Continued advances in each of these areas may be compromised by losses of the biological resources — that is the genetic variants — that provide the raw material for innovation.
Sidebar: Hot-button issues for Endangered Species Act reauthorization
by Patrick Y. O'Brien
Abstract Not Available – First paragraph follows: The Endangered Species Act (ESA) establishes protection of threatened and endangered species as a national goal. However, human use of land and water often conflicts with the habitat needs of other species, which means that protective measures can interfere with economic development and other socially beneficial public works projects. This is the basic friction point that sparks most of the issues included in the debate over reauthorizing the ESA.
Biodiversity indicators in California: Taking nature's temperature
by Michael E. Soulé
Several habitats and ecosystems in California, including those that have been converted to agriculture, are severely threatened — the remnants of these disappearing communities constitute only 10% or so of their original extant. As a society we have begun a last-ditch effort to salvage and protect these remnants and the species that depend on them. To succeed, we must develop and agree on criteria for ecological integrity. These criteria must include “indicators” — ways to take nature's temperature. But more is needed than good science; saving this diverse living legacy also requires a moral consensus.
Sidebar: Setting priorities for conserving endangered species
by Katherine Ralls
Abstract Not Available – First paragraph follows: While the Endangered Species Act requires us to try to save every listed species, many argue that this is not feasible from an economic standpoint. The argument goes that because there is a limited amount of money for conservation, we need to decide which species are the most important to save.
In California: ‘Agrobiodiversity’ key to agricultural productivity
by Calvin O. Qualset , Patrick E. McGuire , Marilyn L. Warburton
California's rich agricultural productivity is founded on its biological diversity, both native and exotic. Native species contribute genetic resources and play a vital part in preserving land, air and water quality. Exotic species introduced from around the globe provide the raw genetic material for nearly all of California's agricultural commodities. Through generations of selective breeding, native and exotic biodiversity have been used to solve agricultural problems. Such biodiversity — termed “agrobiodiversity” — includes not only crops, livestock and their wild relatives, but the species that interact with and support them: pollinators, symbionts, competitors, pests, parasites, predators and biological control agents. Long-term security and flexibility of California agricultural production requires conservation of both exotic genetic resources and native California habitats.
Private landowners critical to saving California biodiversity
by Thomas Scott , Richard Standiford , Nanette Pratini
California has more than 2,000 kinds of unique plants and animals, making it the most biologically diverse region of the continental United States. Given the predicted increase in human population and the high cost of habitat preservation, we can only expect biological reserves to maintain a small fraction of the state's biodiversity. Just as most of our biodiversity is evenly scattered across the state, we need a conservation continuum to preserve these species across the wide range of present-day wildlands. Managing this continuum will be a huge task that depends on wildland stewardship by private landowners. One program designed to promote these goals through research, integrated management, and public education is the DANR Integrated Hardwood Range Management Program.
Sidebar: Nation's richest insect diversity in California
by Greg Ballmer
Abstract Not Available – First paragraph follows: The broad diversity of local conditions that permit California growers to produce the broadest range of agricultural products anywhere in the United States also yield the nation's richest diversity of insects. While no one has added up the number of known insect species in California and new species are still being discovered, one conservative estimate is that there are about 27,000 insect species in California. That is roughly 30% of the estimated total for all of North America north of Mexico.
Sidebar: UCR's Biological Resources Information Unit: Local conservation planning backed by UC expertise
by Nanette Pratini
Abstract Not Available – First paragraph follows: Riverside County is the site of some of the most expensive environmental conflicts nationwide, containing many rare and endangered species and a high rate of urban expansion. To help avoid these conflicts, a coalition of citizens, county officials and scientists sought to formalize the county's access to University of California expertise by creating the Biological Resources Information Unit (BRIU) in 1992.
Sidebar: Habitat fragmentation: the sum of the pieces is less than the whole
by Tom Scott , Nanette Pratini
Abstract Not Available – First paragraph follows: Most of us envision two Californias: one where we live and work, and another where the wild things roam free. This distinction enables us to live and build as we please as if there were a vast realm of untapped potential just over the next hill. But while we conjure dreams of separate and distant wildlands, the reality is that our pattern of land development has rearranged wild California into mosaic of wildlife habitat and human uses.
Conjunctive use of farmland adds value: Winter flooding of ricelands provides waterfowl habitat
by Sylvie M. Brouder , James E. Hill
California rice fields are home to a rich diversity of plant and animal species, and are an integral component of the waterfowl habitat in the Pacific Flyway. Adoption of novel straw incorporation techniques that leave residual rice seed accessible to foraging wildlife coupled with winter flooding to create stable winter wetlands habitat should greatly improve bird health and subsequent fecundity in northern nesting grounds. From the agronomic standpoint, however, the efficacy of these incorporation techniques and their long-term impact on rice production remain to be demonstrated. Recognizing that future straw management options must meet both production agriculture and environmental stewardship objectives, the University of California has undertaken a 5-year, multidisciplinary research and demonstration program to address these issues.
Sidebar: Residual rice seed is critical food for waterfowl
by Michael R. Miller , Glenn D. Wylie
Abstract Not Available – First paragraph follows: The most important wintering region for waterfowl migrating along the Pacific Flyway is the Sacramento Valley, but the valley no longer has enough wetlands to sustain the birds. As a result, rice seed left in fields after harvesting has become a critical food for waterfowl that winter in the valley.
Sidebar: Waterfowl and rice in California's Central Valley
by Frederic A. Reid , Mickey E. Heitmeyer
Abstract Not Available – First paragraph follows: Wetlands of California's Central Valley historically held one of the largest concentrations of wintering waterfowl in the world. In wet winters, some 2 million to 4 million acres of seasonal and semi-permanent wetlands were flooded in the Valley. It is estimated that as many as 40 million to 50 million waterfowl once funneled down the Pacific Flyway — from the arctic tundra of the Northwest Territories, the boreal forests of Alaska, the prairies of Canada, and the alkaline flats of the Great Basin — to the Central Valley. As recently as the 1970s, some 10 million to 12 million swans, geese, and ducks wintered in or migrated through California; large numbers of other waterbirds such as shore-birds, cranes, wading birds, rails, grebes and gulls also came.
Society responds to contamination: Changes in pest control practices reduce toll on wildlife
by Daniel W. Anderson
While biocides, or pesticides, are designed to kill agricultural pests, many of these toxicants have the unintended effect of depleting natural biodiversity. Determining the specific effect of a biocide on biodiversity is complicated because other factors, such as direct habitat loss, also decrease biodiversity. Both in California and nationwide, farmers have been among the first biocide-users to respond to the challenge of reducing unintentional contamination of the environment. As a result, today agriculture faces many fewer biocide-diversity conflicts than it did even a decade ago. Changes in use of biocides have led to recoveries of many previously affected populations of birds, which are perhaps the most studied aspects of biodiversity in these situations. The principal focus of ecotoxicology research today has now shifted from studies of direct toxicity to the more subtle effects of biocides, such as their interactions with other stressors, the identification and evaluation of toxic metabolites and biomarkers of toxicity, the physiological impairments caused by biocides such as immunosuppressions and hormone-mimics, and biocides' overall effects on ecosystem functions.
Sidebar: Unexpected side effects of chemicals acting as hormone mimics
by D. Michael Fry
Abstract Not Available – First paragraph follows: In addition to the toxic effects of pesticides and other environmental contaminants, some pollutants act like hormone mimics, causing disruption of the endocrine systems of fish and wildlife, and potentially, humans who might be exposed. These endocrine effects occur because the “foreign” chemicals bind to receptor molecules in hormone sensitive “target” cells (cells which respond to hormones, and produce effects related to the hormone action), and result in an abnormal response. Hormone disrupters are most injurious to developing embryos and to animals exposed during sensitive stages of the life cycle, such as during the breeding season.
The case of Putah Creek: Conflicting values complicate stream protection
by Michael P. Marchetti , Peter B. Moyle
Increasing human demands for water in California have led to a decline in the diversity and abundance of native aquatic organisms, including valuable salmon and steelhead. Declines worsen during drought years, a fact demonstrated in 1989 when lower Putah Creek dried out in the third year of the state's most recent drought. That year, the Putah Creek Council (a local environmental group), UC Davis and the City of Davis joined forces to purchase more water from the Solano Irrigation District, thereby saving the fish that had survived in a few isolated pools. Since then, these parties and numerous others have filed lawsuits to establish rights to the waters of Putah Creek. While legal questions about these water rights remain to be settled, the events surrounding Putah Creek underscore the need for communities and irrigation districts to develop long-term water policies that recognize environmental needs in the context of California's frequent droughts. Such problem-solving will depend on balancing the conflicting value systems of different groups of water users.
Sidebar: The decline of sea-run fishes in California: An ongoing tragedy
by Michael P. Marchetti , Peter B. Moyle
Abstract Not Available – First paragraph follows: California has the southernmost West Coast populations of sea-run or “anadromous” fish, which spawn in fresh water but spend part of their lives in the ocean. The 13 anadromous fish species native to California include chinook salmon, steelhead trout, river lamprey, white sturgeon and longfin smelt.
Sidebar: A truce in the water wars
by Michael P. Marchetti , Peter B. Moyle
Abstract Not Available – First paragraph follows: The conflict over water diversions from the Sacramento-San Joaquin Delta has been one of the longest and most severe of California's water wars. This conflict developed in 1951 when the massive pumps of the federal Central Valley Project began pumping water from the south Delta to supply water to San Joaquin Valley farms.
editorial, news, letters & science briefs
Farmers and ranchers: Stewards of the land
by W.R. Gomes
What is biological diversity? Why do we care?
Living with the Endangered Species Act: Conflicts, compromises arise at grassroots
Perspective: Incentives are key to ESA
by Bob Vice
Will the Endangered Species Act become extinct?
by William Robert Irvin
Common questions: the Endangered Species Act
Biodiversity Council aids land use planners
Pioneer in genetics, conservation: Q & A with Ledyard Stebbins