Just as wild plants and animals have their environmental champions, so foodies are seeking to preserve the biodiversity of cultivated species and rescue rare delicacies such as California's Sebastopol Gravenstein apple. The big difference? With endangered foods, you save them by eating them. A century ago, 1,600 varieties of apples were cultivated in the United States. Today, grocery shoppers are lucky to find 11 in their local stores. Slow Food Russian River, a northern California chapter of Slow Food USA, has launched a campaign to promote the crunchy Gravenstein, brought to California about 1790 by Russian settlers. In the early 1900s, thousands of Gravenstein orchards made Sonoma County the world capital of that tasty variety. Streets and schools were named after the apple and annual Gravenstein festivals celebrated its delights in pies, juice, vinegar, sauces and brandy. Today fewer than 10 Sonoma farmers make a living selling apples, according to the group. 'It is part of our local agricultural heritage, and yet it is disappearing so fast that it could become commercially extinct.' Six years ago, the Russian River activists applied to the Slow Food Foundation for Biodiversity, which named the Sebastopol Gravenstein one of six 'Presidia' projects in the U.S. (Presidia are groups that promote regional foods). Now the local Apple Corps, a volunteer organization, is working with farmers markets and chefs to develop 'high-value marketing channels,' publishing on its Slow Food website the photos and phone numbers of Gravenstein growers and links to more than 60 northern California eateries featuring 'Gravs' on their August menus from Berkeley to Yountville. But if scientists' predictions of the effects of global warming on California agriculture are correct, food preservationists have their work cut out for them. According to a University of California, Davis study last month, large swaths of California's Central Valley, the nation's most productive fruit and nut-growing region, will be unsuitable for growing apples, peaches, apricots, plums, cherries, walnuts and pistachios by the end of the century. 