Species & Habitat

Endangered Species Listings Accelerate

Why Is This Important?
Two hundred years ago, several thousand Ohlone Indians were the only people living in the southern San Francisco Bay area. The region was rich with a great variety of habitat types and plant and animal life. Grizzly bears, elk, and wolves were common then.

Destruction of habitat is the primary reason why species become endangered. When habitats are reduced, species decline and become more vulnerable to natural and man-made stresses.

We are living at a time with the greatest rate of species extinctions since the dinosaurs disappeared approximately 65 million years ago. Although it is yet unclear what effect continued loss of biological diversity will have on the world's ecosystems and human welfare, scientists believe it could be severe. Each species occupies a unique niche in the delicate web of life. If too many species are removed, ecosystems risk collapse.

Healthy ecosystems enrich and sustain human life, providing services valued at many trillions of dollars. Examples of ecosystem services include: pest and disease control, fresh water and flood regulation, pollination and crop dispersal, commercial and recreational products such as fish and timber, climate moderation, production of oxygen by plants, new medicines, and disease-resistant wild strains of crops.

Data Sources: U.S. Fish & Wildlife Service,
California Department of Fish & Game, and
California Native Plant Society

How Are We Doing?
In the last 200 years the human population in our area grew from a few thousand to more than 2 million. Along with these people came development and filling in large sections of the Bay and wetlands. Immigrants brought plants from their native lands, many of which now crowd out native California species. Domestic and imported game animals, hunting, and recreational activities have also contributed to species decline.

Map Source: Environmental Defense Fund

Santa Clara County is one of the few endangered species "hot spots" in the U.S. Thirty-three federally or state-listed endangered or threatened plant and animal species may occur, or be affected by projects, in the County, along with 3 proposed species, one candidate species, 79 species of concern, and 46 additional rare species not federally or state listed. In all, there are 162 rare species in the County, or rare species that may be affected by projects in the County, including 11 plant species that are locally extinct. Many more species qualify for listing than are actually federally or state listed as endangered or threatened. The dramatic increase in listed species since 1992 is mainly due to recent court decisions requiring the U.S. Fish & Wildlife Service to list more species according to the Endangered Species Act.

Much of the land in threatened areas is privately owned, where enforcement of the Endangered Species Act has often been a problem. This is why it is so important to add privately-held lands to our public preserves and to work with landowners to join in voluntary efforts to protect species. Preserving continuous greenbelts and large expanses of habitat is a top priority for saving endangered species.

Federally or State-Listed Endangered and Threatened Species That May Occur, or Be Affected By Projects, In Santa Clara County

Salt marsh harvest mouse
San Joaquin kit fox
Riparian brush rabbit

California clapper rail
California black rail
California brown pelican
California least tern
Bank swallow
American peregrine falcon
Marbled murrelet
Western snowy plover
Bald eagle

San Francisco garter snake
Giant garter snake

California red-legged frog

Tidewater goby
Winter-run chinook salmon
Spring-run chinook salmon
Delta smelt
Central California steelhead
South Central California steelhead
Sacramento splittail
Coho Salmon

Bay checkerspot butterfly
Vernal pool fairy shrimp

Tiburon paintbrush
Coyote ceanothus
Santa Clara Valley dudleya
Metcalf Canyon jewelflower
Showy Indian clover
Robust spineflower
Contra Costa goldfields
California sea blite

Tidal Marshes Decrease by 84%

Why Is This Important?
The San Francisco Baylands ecosystem is the largest estuary on the West Coast of North and South America. Since wetlands are one of the most productive ecosystems on earth, San Francisco Bay wetlands are recognized as among the nation's most valuable natural resources.

The San Francisco Bay wetlands are critical habitat for more than 500 species of fish, birds, mammals, and other wildlife. Tidal marshes and seasonal freshwater wetlands are especially important because they are used by more than 60 of the estuary's endangered, threatened, rare, or candidate species such as the California clapper rail and the salt marsh harvest mouse. The wetlands also improve water quality, protect against flooding, aid in groundwater recharge, deter erosion, absorb air pollutants, and provide open space and recreational opportunities.

Data Source: San Francisco Bay Area Wetlands Ecosystem Goals Project

How Are We Doing?
The most striking thing to note about South Bay wetlands is not the total change in acres, but the overall change in the types of wetlands. Because South Bay wetlands were too saline to support agriculture, they were converted to shallow salt ponds for salt production. As a result, South Bay tidal marshes have been reduced 84% since 200 years ago, most of which have been converted to less biologically productive salt ponds. In addition to salt production, urbanization and farming have contributed substantially to these changes.

Much of the decline in South Bay wetlands occurred prior to the establishment of the San Francisco Bay Conservation and Development Commission in 1965. Nonetheless, an expanding population and the associated need for housing, transportation, and employment opportunities continue to be a major threat to South Bay wetlands. Extraordinary measures to preserve, restore, and create functional wetland systems will be required to maintain the long-term health of the South Bay wetlands. Our ability to effectively achieve these goals may serve to demonstrate whether or not, or how, we can protect and enhance our valuable natural resources while continuing to grow and develop.

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Non-Native Species Crowding Out Native Plants and Animals

Why Is This Important?
Invasions by non-native species ranks second to habitat loss as a leading cause of harm to endangered species. With few predators and often impervious to local disease, non-native species crowd out local species and consume their food sources.

Non-natives also cause severe economic damage estimated to cost U.S. taxpayers $123 billion a year, according to the U.S. Interior Department. For example, the Chinese Mitten Crab, a non-native species introduced in San Francisco Bay in 1992 and now found in Santa Clara County's creeks, have clogged intake screens for the Central Valley Project, which supplies 28% of Santa Clara County's water supply.

Data Source: Andrew N. Cohen and James T. Carlton

How Are We Doing?
The San Francisco Bay is the most invaded aquatic ecosystem in North America. There are at least 234 species of foreign plants and animals in San Francisco Bay and its shores (145 excluding those for which the year of first siting could not be determined). In the shallower parts of the South Bay, introduced species account for the majority of species diversity.

Further, trends show an accelerating rate of invasion. About half of all invasions in the past 145 years were reported in the last 35 years, with about one new species now introduced every 14 weeks. Many of the non-native aquatic species have been introduced by the discharge of ballast water from international ships entering the bay.

In addition to aquatic invasions, non-native species have invaded the South Bay's land as well. For example, non-native red foxes and feral cats threaten the endangered California clapper rail's South Bay population.

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Clapper Rail Rebounds Thanks to Controls on Non-Native Species

Why Is This Important?
The California clapper rail is one of California's most endangered species. Endangered species are species that are in danger of extinction within the foreseeable future throughout all or a significant portion of its range.

Historically, thousands of California clapper rails could be found in the marshes of San Francisco Bay. However, excessive commercial and sport hunting depleted this bird species' population. Then, increased urbanization led to the diking of most of the Bay's productive tidal marshes -- the rail's habitat -- for salt ponds, industry, agriculture, and airports.

More recently, non-native red foxes and feral cats have established themselves in the Bay's marshes, preying on the California clapper rail and other species at risk such as the burrowing owl, least tern, snowy plover, and salt marsh harvest mouse.

Data Source: San Francisco Bay National Wildlife Refuge Complex

How Are We Doing?
In the South Bay, the California clapper rail's tidal marsh habitat has been reduced 84%. This habitat loss, and the associated reduction in population size, made the clapper rail more vulnerable to extinction when non-native species appeared. Numbering nearly 1,000 in the South Bay during the early 1980s, the rail was almost eliminated after red foxes migrated to the San Francisco Bay in the late 1980s. By 1991, 200 to 300 were left in the South Bay.

However, in recent years, the South Bay's fragile California clapper rail population has rebounded from the brink of extinction. Aggressive controls on red foxes and feral cats led to a dramatic recovery, with the rail populations jumping 160% since 1991, to an estimated 600 to 700 birds.

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Burrowing Owl Habitat Disappearing in Silicon Valley

Why Is This Important?
The Western burrowing owl is classified as a species of special concern by the California Department of Fish and Game. It is one of 78 species of concern in Santa Clara County. Species of concern do not receive specific habitat protection under the state or federal Endangered Species Acts, but impacts to these species must be mitigated under the California Environmental Quality Act.

The burrowing owl is an indicator of the presence of open space, especially grasslands, on Silicon Valley's floor. The owls nest on flat, open grasslands on Silicon Valley's alluvial plain, where land prices exceed $1 million an acre. These open grasslands are valuable recreation sites and improve our quality of life. But, because they are so highly prized for development, they are in danger of disappearing almost completely from the Valley floor.

Data Source: Lynne Trulio, Ph.D., Environmental Studies Department,
San Jose State University

How Are We Doing?
The burrowing owl is facing local extinction in Silicon Valley, where it once flourished. A survey of 123 sites known to be occupied by burrowing owls (a subset of the total number of burrowing owl sites) shows a steady decline, with 57% of the open grassland patches lost since 1988. At this rate of loss, an average of almost 6% per year, the remaining privately-owned sites could be gone in only 7 years.

With declines in its habitat, the number of owls in Santa Clara County fell by half, to about 150 pairs, between the early 1980s and the early 1990s. A major reason for this decline is habitat loss to urban development. One-third of Silicon Valley's remaining owls live on government-controlled or semi-protected land, while the rest live on private land that is rapidly being developed.

The burrowing owl is likely to require Endangered Species Act protection in the future if proactive grassland protection measures are not implemented.


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