Climate and biodiversity in the Andean Dry Puna

Thesis

Arid mountain systems and their biological diversity are particularly vulnerable to changes in climate. The aim of this thesis was to evaluate climate variability and its impacts on ecological systems at different spatial and temporal scales, focusing on the Dry Puna ecoregion in the Central Andes, around the triple frontier of Argentina, Bolivia and Chile, and using a combination of climate data, data from remote sensors, and ecological surveys. I expanded on earlier generalized climatic trends by empirically assessing climate variability since 1980 with a larger set of weather stations at high elevation. I found no consistent temporal trends in temperature and rainfall, but high inter-annual variation in rainfall associated with El Niño Southern Oscillation (ENSO) effects. Climate and topography affected vegetation productivity (measured as the Normalized Difference Vegetation Index NDVI) in the Dry Puna in various ways. Primary productivity was overall low but higher in the High Plateau, under the humid influence of the Amazon. There was no significant temporal trend in productivity in the study area since 1980 and NDVI variability was chiefly driven by ENSO conditions (lower during El Niño years, with dry and hot summers). At a finer scale, vegetation types responded to low rainfall in different ways; tussock grasslands were the most affected by low rainfall; wetlands and scrublands the most resilient. The aridity of the Dry Puna also poses particular ecological limitations to animals. Using species distribution models and resource selection functions I showed that mesocarnivores coexist in this low productive ecosystem by selecting key resources at different degrees and scales, including free water, clusters of prey and refuge. The endangered Andean cat Leopardus jacobita, the most specialized, was also the most selective at finer scales and showed the larger spatial overlap with its preferred prey the southern mountain viscacha Lagidium viscacia. Using bioclimatic models at the continental level, I predicted that suitable habitats for Andean cats will decline under future scenarios of climate change by up to a third by 2080. Although 15% would still be represented within the current network of protected areas, there will be a dramatic decline in the northern reach of the species range. Given the dearth of earlier climatic and ecological studies in the Dry Puna, this thesis makes a substantial contribution to better understand the impact of climate on the productivity of this dry environment, and how threatened species may interact and respond to current and projected climate conditions.

Authors: Bennett Manzano, M

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English