(defendant's environmental plan to protect plants and animals in two national monument areas in Arizona upheld; plaintiffs, consortium of environmental activist groups, claimed that off-road vehicle use and grazing in subject areas would destroy historic artifacts and critical habitat for endangered species; court determined that defendant satisfied its obligation under federal land policies and President's Clinton's proclamation that created the areas in 2000; court also rejected claim that use of lead ammunition by hunters in subject areas is poisoning endangered species).