Snowlines and Treelines in the Tropical Andes

Examination of the dynamism of snowlines and treelines could provide insights into environmental change processes affecting land cover in the tropical Andes Mountains. Further, land cover at these ecotones represents a powerful lens through which to monitor and understand ecological processes across biophysical gradients while acknowledging their socioenvironmental dimensions. To illustrate this approach, we draw on recent research from two sites in the high tropical Andes where, at the regional scale, land cover assessments document retreating glaciers and changing amounts of forest cover, even though steep topographic gradients impose spatial shifts at much finer scales. Our results show that heterogeneous patterns of glacier recession open up new ecological spaces for plant colonization, potentially forming new grasslands, shrublands, and wetlands. In addition, treeline shifts are tied to changes in woody plant dominance, which can vary in rate and pattern as a result of aspect, past land use, and current livelihoods. We suggest that the telecoupling of regional and global biophysical and socioeconomic drivers of land use and land cover change to specific landscape combinations of elevation, aspect, and slope position might explain much of the spatial heterogeneity that characterizes landscape stasis and flux in mountains.