Even as the controversy around genetically modified (GM) crops escalates, few people are aware that a biotech revolution in forestry is also underway, with GM trees being developed and tested around the globe. Some have been engineered to grow cherries in unusual colors or apples that don’t turn brown even hours after being sliced. Others have been developed to grow quickly, which proponents say could help meet growing demand for lumber and paper products without the logging of existing forests. But GM opponents say not enough is known about the possible environmental impacts of the trees, which live hundreds of times longer than food crops. The critics say the long-term effects of the trees on forest-dwelling critters is unknown and they fear that genes inserted in the trees to make them resistant to leaf-eating bugs or chemical herbicides could spread via windblown pollen to related tree species, upsetting whole ecosystems.