Predicting the distribution of an increasingly vulnerable ecosystem: The past, present, and future of the Polylepis woodlands.

摘要

Polylepis woodlands are an important and highly threatened ecosystem in the high altitudes of the tropical and subtropical Andes, providing unique habitats for diverse flora and fauna and vital resources for local human communities. Species within this Andean region, a biodiversity hotspot, are predicted to be extremely susceptible to future climate change. In response to increased annual temperatures, Polylepis woodlands are predicted to shift their elevational extent, as paleoecological evidence suggests with past climate fluctuations. However, our understanding of Polylepis species distribution is severely limited by centuries of woodland fragmentation, beginning with pre-Colombian Andean civilizations and continues to today. This research aimed to predict current Polylepis species and woodland distribution, distribution during the Last Glacial Maximum (LGM), and changes in species distribution resulting from doubled atmospheric CO2. Regions of high Polylepis species richness were characterized, as well as the extent Polylepis woodlands within international and national protected areas throughout the region. Current, LGM, and future distribution as a result of doubled atmospheric CO2 were predicted for 21 species of Polylepis using the Maxent algorithm over South America. Several environmental layers, including climate, optical, and microwave remote sensing data, were used for particular climate scenarios. Range contraction was predicted to occur for most species, from LGM to future climate, as a result of upslope range shifts to smaller land area as a result of increasing annual temperatures. However, the expansion several species ranges were predicted to occur within the Altiplano of Peru and Bolivia as greater land area becomes available. This is contrary to most models of climate change that solely predict contraction in mountain regions. The sites of highest Polylepis species richness did not closely match the current location of protected areas, indicating that the expansion and addition of protected areas are necessary to preserve key areas of high altitude tropical ecosystems. Overall, the management of remaining Polylepis woodlands must take into account the natural distribution of Polylepis species and their response to future climate change to protect this vulnerable ecosystem and the flora, fauna, and human populations that depend on them.