| Presidents Tern - Polar Bears and Bolsa Chica By Dave Carlberg No, that’s polar bears AND Bolsa Chica, not polar bears IN Bolsa Chica. The U. S. Department of Interior announced late last year that it was planning to list the polar bear as a threatened species, due to the loss of its critical habitat, the Arctic sea ice. Normally such action takes several months for biologists to accumulate enough data to justify the listing, but a number of conservation groups filed a successful lawsuit forcing the government to act quickly. Responding to a court order, the Interior Department designated the polar bear as threatened in May of this year. What does “threatened” mean, how does it differ from “endangered”, and most importantly, what does all this have to do with Bolsa Chica? To begin, threatened and endangered are terms from the Endangered Species Act, legislation passed by the U. S. Congress in 1973. Many states, including California, have their own versions of the ESA. The act’s purpose is to protect species of plants and animals from extinction. Plants and animals can face extinction from a variety of threats, any one of which prevents them from reproducing. Obviously if a plant or animal fails to produce progeny to replace it when it dies, its population will soon dwindle until it becomes zero, that is, the species becomes extinct. Three major causes of extinction are: loss of habitat, overexploitation (including predation) and contact with toxins in its food or environment. Loss of habitat prevents polar bears from feeding on their natural prey, seals, and in the case of birds, from nesting. Most birds are very particular when it comes to finding that perfect honeymoon cottage. Lacking that, the species may be headed for extinction. Understanding overexploitation is pretty simple. If a particular species, such as a plant or a fish, is harvested to the point there are not enough members of the species to reproduce, in time extinction becomes inevitable. Think passenger pigeon. A number of popular food fish are on the brink of extinction because they are so popular. See www.mbayaq.org/cr/SeafoodWatch.asp for information about what seafood to order and what kinds to avoid. The most notable examples of the dangers of exposure to environmental toxins have been the California Brown Pelican, the American Peregrine Falcon and the California Condor. In the case of the first two, as you recall, consuming food that contained high levels of DDT led to an imbalance in the birds’ calcium metabolism and weakened egg shells, resulting in crushed eggs before they hatched. Fortunately action over the years to clear the environment of DDT has resulted in a dramatic come-back for the two species. Lead from hunters’ bullets in carcasses that condors feed on appears to be jeopardizing the survival of the few condors we have left in our state. In early May, a survey of condors in the San Joaquin Valley found toxic levels of lead in the blood of seven ill condors, one of which died during treatment. “Threatened” and “endangered” are two official classifications with which a species can be labeled. An endangered species is deemed closer to extinction than a threatened one and would obviously demand greater attention. A given species may be nominated for placement on the federal threatened or endangered list through direct action by a government agency such as the Fish and Wildlife Service or through petitions by private individuals or organizations. In either case, a fair amount of scientific data is usually required to justify the listing. At least 6 endangered or threatened birds can be seen in the Bolsa Chica. The first three nest there, others are visitors. They are: California Least Tern (on both state and federal lists as endangered), Belding’s Savannah Sparrow (endangered on state list only). Western Snowy Plover (threatened on federal list only), Light Footed Clapper Rail (endangered on both lists, potential nester in Bolsa Chica), American Peregrine Falcon (endangered on state list only, but a candidate for delisting) and California Brown Pelican (endangered on both lists). While there are many sites in California that can brag about hosting endangered or threatened species, because Bolsa Chica is so close to the highly urbanized patch we call Orange County, easily accessible to the public and heavily visited, it should be a major ground-zero to educate students and adults of the world-wide significance of protecting species that are on the brink of extinction. Why be concerned about the loss of a few species? Every organism on Earth is part of the Web of Life. As the loss of species continues, it makes the web that much closer to collapse. |