Future climate projections for the tropical Andes suggest that temperatures will increase by 2°C this century, and precipitation will become more variable. Enhanced seasonality and rising temperatures will lead to moisture stress for Andean ecosystems and increase the risk of extinction for many species. Microrefugia are recognised as being important in the past for supporting populations during periods of unfavourable climate change and in facilitating rapid migration as conditions ameliorate. A simple tool, however, has not been developed and tested to predict which settings were microrefugial. As a near-term return to preindustrial temperatures is highly unlikely, identifying areas of ecosystem resilience, such as microrefugia, will be important for maintaining Andean biodiversity into the future. Building on the premise that topography and landscape heterogeneity are important determinants of a site’s microrefugial potential, we seek to answer the basic research question: Can topography be used to predict the presence of Andean high-elevation microrefugia during the Holocene? Here we combine paleoecological data with catchment terrain ruggedness modelling of nine Andean lakes spanning the last period of millennial–scale drought, the mid-Holocene dry event (MHDE), to test the predictions of ecological resilience to warmer and drier times. The MHDE was a period of peak aridity for the last 100,000 years, with both warmer and drier conditions analogues to future climate scenarios. We use fossil pollen of Polylepis as an indicator of high Andean forest, and charcoal abundance as a proxy for fire.
Results/Conclusions
The results suggest that sites with high terrain rugosity have the greatest chance of supporting high Andean Polylepis forest during periods of adverse climate change, such as the MHDE. Fire is a feature of all catchments at all time periods, however an increase in fire and subsequent decrease in forest abundance is only recorded in low terrain rugosity settings. The results suggest high terrain rugosity is important in the tropical Andes for i) sustaining mesic conditions during drought and ii) moderating against large fires by creating firebreaks in the landscape. Due to rising temperatures and greater precipitation variability, Andean ecosystems are threatened by increasing moisture stress. Our results suggest that high terrain rugosity helps to create more resilient catchments that act as high elevation forest refuges during adverse climate change. On this basis, conservation policy should target protection and management of high terrain rugosity catchments as such settings have the greatest chance of sustaining high elevation ecosystems with on-going climate change.