America’s fourth largest lumber retailer, 84 Lumber, pledged yesterday that by 2003 it will phase out all wood from forests considered endangered and sell only wood independently certified as coming from sustainably managed forests. With this move, 84 Lumber, which has more than 400 stores in 30 states, follows the lead of the top two home-improvement giants, Home Depot and Lowe’s. The announcement came two days before protests were to have been staged at 84 Lumber stores by the Rainforest Action Network.