Climate change could turn high-altitude areas into wildlife refuges

As climate change progresses, its effects are not universally uniform, with temperatures increasing at different latitudes and altitudes. Climate heterogeneity is the study of this diversity in Earth’s climate patterns, and the focus of recent research published in Geophysical research letters.

Yanlong Guan, of Fujian Agriculture and Forestry University, China, and colleagues investigated the role that elevation plays in climate heterogeneity by analyzing changes in organism diversity using Shannon’s diversity index and the Köppen-Geiger climate classification. The latter divides climate into tropical, dry, temperate, continental, and polar regions based on seasonal precipitation and temperature connections with vegetation distribution.

Such temperature and precipitation data were derived from over 4,000 weather stations worldwide over a 70-year period starting in 1952. Topography adds further complexity, as surface roughness and elevation can affect surface temperature, precipitation, the hydrological cycle, energy budgets and vegetation cover, creating a patchwork of the five climate groups. This project examined nine elevations from 0 m to over 4,000 m at 500 m intervals.

The research team’s main finding is that Shannon’s diversity index decreases at low altitudes (below 2,000 m), where temperatures rise faster and higher. This leads to the spread of similar dry and tropical conditions over a large area.

In comparison, at higher altitudes (above 2,000 m) the climate is more heterogeneous. This means that the diversity index continues to increase despite the initially cooler but slowly warming environmental conditions, until only small patches of cold climate remain at topographic height.

In addition, the scientists used climate simulations to test what was driving these patterns. It was no surprise that human-induced climate change was the cause of this marked shift in climate heterogeneity between lower and higher elevations.

These simulations also extrapolated climate heterogeneity back into the century, identifying locations where climate variability may be lower, such as North America, which has an average elevation of ~1600 m and where the average temperature is expected to be 14.2 °C.

Meanwhile, colder refuges have been identified at high altitudes, such as the Qinghai-Tibet Plateau at over 4,100 m. Temperatures there are expected to reach 5.9 °C between 2070 and 2098, but temperatures are already rising at an accelerating rate of 0.44 °C per decade, twice the global average.

This research is important because projections indicate that by the end of the century, as much as 46% of the land surface will be warmer and drier. This homogenization of climate types could threaten the distribution of habitats and species.

By understanding the climate variability that prevails at higher altitudes, these areas could become future refuges for human, animal and plant communities as they seek more favourable conditions away from rising temperatures and the associated social, economic and ecological problems.

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