Yes, they do, but not in such a way that existing forest totally disappears or that they prevent forest development at all. Grazers slow down forest succession in such a way, that a semi-open mosaic landscape remains intact for longer. Because grazers nibble trees and peel tree bark in the winter, they stop the sap flow, which means not all trees survive. Young trees germinating and growing up in open terrain have a though time to withstand grazing. However, armed with spines, poisons or through root shoots, they eventually conquer the open ground. In many cases, grazing even creates the conditions for the return of forest to open land by spreading seeds through manure and via their coats, or by creating suitable germination sites for tree seeds. Through this combination of forest formation in one place and forest degradation in another, the forest seemingly 'moves' through the landscape.