Almost one-third of Maine’s 15 million acres of forest have been put on sale in the last two years, and conservationists are worried that a good deal of forestland now in private hands may soon be lost to development. Maine voters last year approved $50 million to buy and preserve land, and land trusts and enviro groups have been active in trying to acquire land in the state, too. Groups are also encouraging large landowners to put their lands under conservation easements, agreeing not to develop the property. The world’s biggest easement, a $30 million deal on a piece of Maine property larger than Rhode Island, is almost finalized, and a slightly smaller project on the West Branch of Maine’s Penobscot River is being negotiated.