Some 100 environmentalists convened in Reno, Nev., yesterday to push for an end to all livestock grazing on federal lands in the U.S., a notion once considered radical but now gaining more mainstream support. The activists argue that grazing causes serious environmental damage in the West, particularly soil erosion and deterioration of streamside areas. They also argue that grazing on public lands amounts to a costly subsidy from taxpayers because the federal government charges below-market rates for grazing rights. More than 20,000 livestock owners have permits to graze cattle and sheep on 170 million acres of federal land in 13 Western states. On Friday, nine environmental groups asked a federal judge to enforce a 1934 law that requires the Interior secretary to define which public lands are “chiefly valuable for grazing,” a move the enviros hope would lead to many areas being declared valuable for other uses, such as wildlife protection and recreation, and therefore put off-limits to livestock.