Sometimes we say we would “move mountains” for people we care about or causes we are committed to. However, scientifically speaking, moving mountains can be a very bad idea, especially for biodiversity.

 

Globally speaking, biodiversity distribution reflects the presence of latitudinal gradients, with the tropics generally displaying higher diversity than the northern and southern temperate zones. Within the tropical and subtropical zones, mountain ranges seem to boast the most species, as the elevation of mountains enables a variety of microhabitats that allow for correspondingly high local biodiversity [1]. 

 

A typical elevation-dependent ecological zonation will divide mountain habitats into lowland, montane, alpine and nival zones. Such a distinction, along with geographical barriers such as rivers, valleys and glaciers, creates an ideal set-up for speciation, i.e., the formation of new and distinct species [1]. With its high-relief mountains and various geographic barriers, the Third Pole centered on the Tibetan Plateau has been a hotspot for speciation. For example, what were thought to be two subspecies of red panda, the endangered furry mammal native to the eastern Himalayas and southwestern China, have recently been found to be genetically distinct enough to be classified as two species: the Chinese red panda and the Himalayan red panda. Scientists believe the dividing line between the two species should be the geographical barrier of the Yarlung Zangbo River, and their divergence occurred about 220,000 years ago [2]. 

 

But this is not the only reason why we should not move mountains. We also need mountains for refuge during climate change. Scientists expect fewer challenges from rapid climate change to those living in the mountains than to those in lowland areas, since the steeper the mountains, the shorter the distance people (or other living things) will have to travel to cope with climate change [1]. Therefore, running to the Third Pole for refuge in disaster films such as 2012 does make some sense. 

 

However, it is crucial to remember that even the roof of the world is not immune to climate change. The Third Pole has acted as a “species pump” during periods of extreme cooling and warming throughout Earth’s history [1]. Tibetan fossils have shown that the snow leopard and Arctic fox first evolved at the Third Pole. The cold winters at the Third Pole prepared them for the later Ice Age, a period of extreme cooling during which their habitats expanded to Eurasia and beyond [3].

 

The global warming we are experiencing now is being amplified over the Third Pole[4]. The Third Pole has seen an increase in vegetation growth over the past three decades [5]. “The greening of the Third Pole has both local and remote impacts on climate change,” said PIAO Shilong, professor at CAS center for excellence in Tibetan Plateau Earth Science. This greening, on the one hand, enables plants to convert more carbon dioxide into sugars and starches through photosynthesis, pulling carbon dioxide from the atmosphere and mitigating global warming. On the other hand, the greening could cause more water to evaporate from the leaves and help cool the local climate, thereby contributing to a slowdown of rapid warming over the Third Pole. PIAO noted that this evaporative cooling process will “modify the atmospheric heat source of the Third Pole, and possibly induce a remote impact on downstream Asian climate.” However, he also noted that quantifying this connection requires further exploration. 

 

Of course, it is still too early to tell whether this greening will have an overall positive outcome or not. For example, another study by PIAO’s team has found that warming-induced earlier greening may induce more water loss through enhanced evapotranspiration. This would create drier summer soils across the northern hemisphere, which might result in more frequent heat waves [6]. Moreover, the Third Pole holds large quantities of soil carbon in permafrost. The thawing permafrost would return more soil carbon to the atmosphere, which possibly overwhelms greening-induced atmospheric carbon dioxide drawdown and then accelerates the warming. An experimental platform has been built (the Naqu Ecological and Environmental Observation and Research Station, Institute of Tibetan Plateau Research of Chinese Academy of Sciences) in the central Third Pole to explore how thawing ecosystems “breathe” with permafrost thawing. By controlling temperature and moisture of alpine meadows in the experiment fields, scientists found that while warming has changed the thawing pattern of the permafrost, local ecosystems’ “breathe” for now seems steady, as there is no significant increase in CO2 release [7]. This finding is consistent with another experiment conducted in northeastern Third Pole[8]. 

 

Amid the warming across the Third Pole[9], scientists are also studying how temperature will affect species richness and biodiversity. There are three potential consequences for species under climate change: adaptation in situ, tracking climate change in spatial and/or temporal dimensions, and local extinction. Simulated warming may reduce species richness. However, over larger spatial and temporal scales, species remain in original community will eventually meet with species newly arrived tracking climate change. A transplanting experiment at Third Pole suggests that new species tracking climate change have outnumbered the lost species[10]. 

 

Another reason not to move the mountains is that it was the love for mountains that brought Profs. YAO Tandong, Lonnie G. Thompson and Volker Mosbrugger to a Chicago hotel bar in 2009, where they initiated the international science program now known as Third Pole Environment (TPE). “All three of us felt that the Third Pole is such an important key area of planet Earth that it requires an international and interdisciplinary research program involving the best experts worldwide,” said Prof. Mosbrugger. TPE has since enabled a series of productive workshops, research and observation networks as well as training courses for young scientists. It is also endorsed by UNESCO as a flagship program and is in close partnership with UNEP and WMO. With TPE, the three cochairs embody the quote by John Muir, “You are not in the mountains. The mountains are in you.”

 

References:

1. Mosbrugger, V., et al., Cenozoic evolution of geo–biodiversity in the Tibeto–Himalayan region, in Mountains, climate and biodiversity. 2018. p. 448.

2. Hu, Y., et al., Genomic evidence for two phylogenetic species and long-term population bottlenecks in red pandas. Science advances, 2020. 6(9): p. eaax5751.

3. Deng, T., et al., Out of Tibet: Pliocene woolly rhino suggests high-plateau origin of Ice Age megaherbivores. Science, 2011. 333(6047): p. 1285-1288.

4. Chen, D., et al., Assessment of past, present and future environmental changes on the Tibetan Plateau. Chinese Science Bulletin, 2015. 60(32): p. 3025-3035.

5. Piao, S., et al., Characteristics, drivers and feedbacks of global greening. Nature Reviews Earth & Environment, 2020: p. 1-14.

6. Lian, X., et al., Summer soil drying exacerbated by earlier spring greening of northern vegetation. Science Advances, 2020. 6(1): p. eaax0255.

7. Wang, Q., et al., Annual ecosystem respiration is resistant to changes in freeze–thaw periods in semi‐arid permafrost. Global Change Biology, 2020. 26(4): p. 2630-2641.

8. Lv, W., et al., Net neutral carbon responses to warming and grazing in alpine grassland ecosystems. Agricultural Forest Meteorology, 2020. 280: p. 107792.

9. Yao, T., et al., Recent Third Pole’s rapid warming accompanies cryospheric melt and water cycle intensification and interactions between monsoon and environment: Multidisciplinary approach with observations, modeling, and analysis. Bulletin of the American Meteorological society, 2019. 100(3): p. 423-444.

10. Wang, Q., et al., Richness of plant communities plays a larger role than climate in determining responses of species richness to climate change. Journal of Ecology, 2019. 107(4): p. 1944-1955.