Tropical Alpine Ecosystems under climate change: Paramos and moorlands in peril

Tropical Alpine Ecosystems are high-altitude grasslands located above 3000 m.a.s.l. along the tropical belt of three continents. Their unique vegetation and soil characteristics, in combination with low temperature and abundant precipitation, create the most advantageous conditions for regulating and storing surface and groundwater. However, increasing temperatures and changing patterns of precipitation due to greenhouse-gas-emission climate change are threatening these fragile environments, reducing their extent and modifying their altitudinal distribution range. Here, we investigate the impact of climate change on the distribution and extent of global Tropical Alpine Ecosystems. We use an ensemble of historical and projected climate data (SSP585) from seven General Circulation Models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to estimate annual average values of temperature and annual accumulated values of precipitation for reference (1985-2014) and far future (2070-2100) 30-year periodos. We produced the 95% probability current and future hydroclimatic spaces for every ecosystem to determine the range at which Tropical Alpine Ecosystem currently thrives in the climatic space, and investigate a number of hydroclimatic variables. Then, we used the projected climate time-series data to assess the current Tropical Alpine Ecosystem areas that will be unable to keep up with the temperature and precipitation changes by exceeding their reference climatic boundaries in the far future. Overall, our results showed that the Tropical Alpine ecosystem would drastically reduce its extent. Approximately 45% of its current extent will experience hydroclimatic conditions beyond their reference climatic boundaries. For example, the Ethiopian montane moorlands in Africa will be the most impacted ecoregion with a reduction of approximately 95% of its current extent. For the case of páramos in the North of the South American continent, increasing temperatures and changing precipitation will render ~50% of the current extent unsuitable for these ecosystems during the dry season. Our results highlight the magnitude of the impacts of climate change on Tropical Alpine Ecosystem and the vulnerability of water security of millions of people who depend on its ecological functioning. These results also have implications for biodiversity conservation, as endemic species will be threatened by habitat reduction and shifts in their distribution ranges.