Will Mountains Become A Climate Refuge?

How high-elevation regions could become vital refuges for wildlife and biodiversity in the face of climate change.

Before I transitioned from my academic career, I published a series of papers that aimed to understand species’ responses to changing climates. As we all know by now, climate change is altering ecosystems worldwide. However, not all regions are affected equally. Indeed, some areas and ecosystems are more vulnerable to climatic changes than others, and many factors may affect these responses.

I like staying up-to-date with new discoveries and methodologies in this field. And a new paper on the subject caught my eye, suggesting that high-elevation areas may serve as crucial refuges for biodiversity in a warming world. But why?

The study led by Dr. Yanlong Guan and colleagues, and published in Geophysical Research Letters, delves into how elevation influences climate heterogeneity (the variety of climatic conditions within an area) and the implications for wildlife and plant species as they adapt to changing temperatures and precipitation regimes.

The researchers employed Shannon’s diversity index (SHDI) and the Köppen‐Geiger climate classification to understand how elevation affects climate heterogeneity.

SHDI measures the biodiversity in a given ecosystem. The idea behind this is that an ecosystem with 5 species with an even representation between all of them will be more biodiverse than an ecosystem where you only have 3 species, and one dominates 95% of the ecosystem.

When I studied SHDI for my bachelor’s degree, understanding how useful it was made me fall in love with the field of ecology. Over the years, I have consistently used this metric in my research in modern and past ecosystems. On the other hand, the Köppen‐Geiger classification categorizes climates into tropical, arid, temperate, continental, and polar regions based on temperature and precipitation patterns (which is a bit less love-eyes inducing, but just as useful).

Dr. Yanlong Guan’s study analyzed data from over 4,000 weather stations worldwide, covering a period from 1952 to 2020. Additionally, the researchers divided the global elevation range into nine intervals, from sea level to over 4,000 meters, in 500-meter increments. They then used high-resolution climate simulations from NASA’s NEX‐GDDP‐CMIP6 dataset to analyze historical (1950–2014) and future (2015–2100) climate scenarios.

By comparing SHDI (remember, it refers to biodiversity) across different elevations and time periods, the team aimed to identify patterns and drivers of climate heterogeneity (aka. climate variability). So, what did they find?

The Results

The most relevant results from the study indicate distinct patterns in climate heterogeneity between low and high elevations. At lower elevations (below 2,000 meters), SHDI tends to decrease as temperatures rise. This means that as temperatures increase, ecosystems become less biodiverse.

So far, so expected. The reduction in climate diversity is attributed to the expansion of similar arid and tropical conditions. As the article notes, “Shannon’s diversity index reduces at low elevations (less than 2,000 m) where temperatures rise higher and faster, leading to a proliferation of similar arid and tropical conditions over a wide expanse of area.”

But in contrast, higher elevations (above 2,000 meters) exhibit an increase in SHDI with rising temperatures. This means that as temperatures increase, high altitude ecosystems become more biodiverse.

These areas, characterized by cooler conditions and complex topography, maintain diverse climate types even as temperatures warm slowly. The study highlights that “higher elevations (more than 2,000 m) display greater climate heterogeneity, meaning that the diversity index continues to increase amidst the initially cooler but continuously slow warming environmental conditions until only small patches of cold climates remain at topographic highs.”

More importantly, climate simulations confirmed that these changes in climate heterogeneity are primarily driven by anthropogenic (human-driven) climate change. The simulations also projected future trends, identifying regions likely to experience reduced climate variability and those that might serve as climate refuges (areas where species can move to as climate changes).

For instance, North America, with an average elevation of about 1,600 meters, is expected to experience a mean temperature of 14.2°C by the end of the century. Meanwhile, the Qinghai-Tibet Plateau, at over 4,100 meters, is predicted to have temperatures of 5.9°C but is already warming at a rate of 0.44°C per decade, twice the global average.

The study’s findings underscore the critical role of high-elevation regions in maintaining climate heterogeneity and biodiversity. These areas may become vital refuges for species seeking cooler climates as global temperatures rise.

Preserving diverse climate types at higher elevations could help sustain ecosystems and provide safe havens for wildlife and plant species. For once, it’s nice to hear of a silver lining.

However, the research also highlights the challenges faced by low-elevation regions, where climate homogenization threatens biodiversity and ecosystem stability. As the article points out, “projections suggest up to 46% of land surfaces may transition to warmer and drier conditions by the end of the century, with this homogenization of climate types potentially threatening habitat and species distributions.”

Conservation efforts should consider the results of this study to protect high-elevation areas, their unique climates, and biodiversity while preserving habitat connectivity for species to migrate as climate changes. By understanding climate change patterns and impacts, we can develop strategies to mitigate these effects and support climate-adaptive migrations for at-risk species.

Dr. Yanlong Guan and colleagues’ research provides valuable insights into how elevation influences climate heterogeneity in a changing world. Luckily, high-elevation regions hold promise as refuges for biodiversity, offering a glimmer of hope amid the mountain of challenges posed by climate change.