Democratic presidential hopeful Bill Bradley attacked Al Gore yesterday on Gore’s signature issue, the environment, accusing him of being all talk and no action. Bradley, speaking in San Francisco, ticked off a list of environmental promises that Gore had made before the 1992 election that the administration had failed to follow through on. He also accused the administration of bending environmental rules to help big campaign contributors. Bradley proposed what he called a “land ark,” a system that would use federal funds to create protected habitats for endangered species on federal land. Gore barely mentioned the environment during his campaigning yesterday, but his staff issued a three-page paper summarizing his record and a statement noting that dozens of prominent enviros have endorsed him.