Defenders' Experts
Farallon National Wildlife Refuge - California
The Farallon NWR, sometimes referred to as the Galapagos of California, is comprised of rocky islands 28 miles west of the Golden Gate Bridge. The refuge sustains the largest Pacific Coast sea bird nesting colony south of Alaska and is home to the largest colonies of Brandt's cormorant and western gulls found anywhere. Fifty percent of the world's ashy-storm petrel population, thousands of endangered California brown pelicans, and six species of marine mammals can all be seen on the Farallon Islands. The key to the islands' rich and variable marine ecosystem is the plant plankton that blooms when spring wind and water currents saturate the ocean with nutrients from deep within. Animal plankton, such as shrimp-like krill, eat the plant plankton and are, in turn, consumed by juvenile rockfish and other animals. The intricate food webs expand from here.
The Threat
Global warming is contributing to the rattling of food chains and shifting of species composition in delicate marine ecosystems including that of Farallon National Wildlife Refuge. Rising ocean temperatures off the coast of California have suppressed the upwelling of cold, nutrient-rich, plankton-sustaining waters and altered the food available to fish and birds. Some prey species have declined in number. Others have moved north to cooler, more productive waters and been replaced by species from the south.
While many marine animals have adapted to the changing food supply, several of the species that make up the refuge's huge seabird colony have not fared as well. The refuge's Cassin's auklet population is unlikely to adapt to this sudden loss of its main food source, the zooplankton krill, and has dropped 75 percent; 2006 is the second year in a row that almost none of the 20,000 nesting pairs raised a healthy chick. Researchers on the Farallon islands agree that the decline of krill and Cassin's auklets corresponds with a 3-5 degree increase in California ocean temperatures.
This absence of krill is also afflicting entire food chains. Dramatic declines have been noted in pigeon guillemots, common murres, and two species of cormorants. These seabirds share the same primary food source- the declining, nonmigratory rockfish.
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