These people lacked the traditional knowledge needed to preserve swidden land. _________________________. For example, they would burn away large areas of forest or leave exhausted fields overgrown with cogon grass and other weeds. All in all, even though some methods of swiddening were more sustainable than others, the recent shift away from slash-and-burn farming is probably a good thing. This is because forest lands may be preserved to a greater extent now than in the past, when it was a widespread practice.