Casting the threat of wildfires next year as an emergency, the Bush administration today proposed rule changes that it said would speed up environmental reviews to allow the thinning of forests. Experts generally agree that a century of mismanagement of the forests — including fire suppression, allowing tinder to build up; selective logging of the biggest trees; and grazing — created conditions for the kind of catastrophic fires that swept across the West this summer. The fires burned more than 7.1 million acres, killed 21 firefighters, destroyed 23,000 structures and forced tens of thousands of people from their homes.