Using paleoecological data to define main vegetation dynamics along the savanna-forest ecotone in Colombia: implications for accurate assessment of human impacts

n recent decades there has been increasing interest, from scientists of many disciplines, in the origins and dynamics of tropical savanna-forest boundaries. These boundaries are rarely present as a smooth gradient from tropical forests to scattered trees and open grassland (Bond and Parr 2010); rather, they are often patchy and irregular, occurring where at first sight no apparent driver for an ecosystem shift is apparent (Sarmiento 1984). In general terms, savanna ecosystems cover approximately 40% of the tropics or 23 million km2 (Cole 1986; Gardner 2006) and host around one-fifth of the world’s human population (Young and Solbrig 1993). These people are imparting a growing impact on savanna systems, as agriculture and other subsistence activities occupy increasingly larger land areas (Gardner 2006).