Climate change is increasingly affecting wildlife habitat distribution. Globally, many plant and animal species move to higher elevations in search of cooler areas that resemble the climatic conditions to which they have adapted over millions of years.However, species do not all migrate at the same speed. In a recent study published in the scientific journal Nature Communications, some species move to higher altitudes faster than others due to their climatic preferences as well as evolutionary background, which makes them more or less adaptable to a warming Earth.The paper analyses paired lower and upper-edge shifts across 845 plant and animal species records worldwide and finds that the two distribution limits often respond differently to warming. Tropical species shifted their lower edges upslope faster than temperate species, while globally prevalent species expanded by advancing their upper edges more quickly and contracting their lower edges more slowly.Conducted by researchers from the Chinese Academy of Sciences and Rice University, the study analysed observations from around the world and is among the largest of its kind on climate change impacts at high altitudes.Not all species react in a similar mannerScientists have long known that species move upslope as temperatures rise. Nevertheless, according to previous studies, there had been huge variations in how quickly or slowly these movements occurred, and in some cases, no movement at all. In order to understand these differences better, scientists looked into changes occurring in both the lower and upper range limits of these species. The lower range limit refers to the warmest habitat a species can occupy, while the upper range limit refers to its expansion into cooler, higher areas.These results showed that factors affecting these two boundaries differ from each other.Species in tropical zones moved faster than species in temperate zones in terms of lower range limits. According to scientists, this is attributed to the fact that species inhabiting tropical zones live closer to their temperature limits and therefore have less tolerance for increasing temperatures. The research also found that species preferring warmer, wetter environments expanded their upper range limits faster than others.
Image of Alpine meadows. Image Credit: Wikimedia Commons
Evolution is still relevantOne of the key findings from the research is that the evolutionary history of the species is a crucial factor in how the species will react to changes in the climate. Species belonging to the same taxonomic category displayed similar trends when it came to movements, which implies that evolutionary history affects the ability of the species to adapt to new conditions. The researchers describe this as ‘phylogenetic conservatism,’ in which traits passed down through evolution continue to shape how species respond today. Simply put, some species may find it difficult to adapt because evolution has made them inflexible in certain ways.According to the research, evolutionary history was able to explain quite a large proportion of variation in elevational shifts.Common species have an edgeIn addition, it was found that species that occur worldwide seem to adjust better to changes. They were prone to shift their distribution upwards on the mountain slopes and to lose their distribution less rapidly at low elevations. Their increased tolerance to varying climates, especially to dry conditions, may be responsible for this.On the other hand, species that are adapted to a narrower range of environments may face difficulties in adjusting due to their reduced habitats. This finding reveals an issue that needs to be considered by conservationists. While some climate conditions might exist at high mountain altitudes, not all species can make use of them biologically.Importance of the mountainsIt is well recognised that mountain ecosystems are among the regions that have been hit hardest by climate change. With rising temperatures, organisms get pushed uphill. Over time, mountaintop species could be forced higher and may eventually face extinction. According to the Intergovernmental Panel on Climate Change (IPCC), rising global temperatures are shifting species distributions on land and at sea.In its Sixth Assessment Report, the IPCC says climate change is affecting biological processes, altering species distributions and increasing biodiversity risks globally. Similarly, the International Union for Conservation of Nature (IUCN) considers climate change a major threat to global biodiversity, especially for species with small ranges or specific ecological requirements.An even more complicated view on climate changeInstead of assuming the same reaction for all species, the new approach provides a much more sophisticated view of the issue. According to the findings of the study, species’ reactions to climatic changes are formed as a result of the interaction between certain ecological features and the long evolutionary histories of the species in question. Such knowledge could be useful when trying to predict the survival rates of certain species.With increasing temperatures, such information becomes highly valuable when it comes to preserving biodiversity. The study shows that species are not responding to climate change in the same way. While evolution might give some species an advantage, others would have to suffer from it.