Andy Kerr, a well-known environmental activist who spent much of the 1980s and 1990s fighting a bitter war against logging in the Northwest, is turning his attention to another issue: population growth in Oregon. Kerr’s new organization, Alternatives to Growth Oregon, is still developing its agenda. But Kerr has already proposed some controversial ideas, including tax incentives for small families, the elimination of subsidies designed to attract new businesses, and limits on both foreign and domestic immigration.