Conservation news

Island species and endemics will bear brunt if warming exceeds 3°C: Study

A Coquerel's dwarf lemur. Image by Rhett A. Butler/ Mongabay.

  • Endemic species on islands, especially plant species, are at the greatest risk of disappearing because of climate change, a study has found.
  • In general, species found exclusively in one region face a greater threat from a changing climate than native and introduced species, with the latter likely to face almost no negative effects at all.
  • Places like the Caribbean, the Indian Ocean islands, including Madagascar and Sri Lanka, the Philippines, and biomes like India’s Western Ghats could be bereft of all their endemic plant life in three decades, according to the analysis.
  • Introduced species could outcompete and replace endemic species in the world’s biodiversity hotspots if warming continues unchecked.

Endemic species face a greater risk of going extinct because of climate change than native or introduced species, a recent study in Biological Conservation has found. Species that are exclusive to islands could disappear from the planet altogether if the global climate warms by more than 3° Celsius (5.4° Fahrenheit) above pre-industrial levels.

Some of the world’s most unique creatures fall into this category: lemurs from Madagascar, rare orchids from the Caribbean, the marine iguanas of the Galápagos.

“Of special concern are those rich-spots that are on islands or mountains because due to geographical restrictions, these areas are usually isolated and have very limited space,” Stella Manes, first author of the paper, told Mongabay in an email. “As climate change worsens, species have less ‘ways to get out’ of threat with such limited conditions.”

A marine iguana on one of the Galápagos Islands. Image by Rhett A. Butler/ Mongabay.

The authors looked at 273 biodiversity hotspots worldwide to understand how sensitive flora and fauna are to climatic changes. Threats to island hotspots jumped out in the analysis. The isolation that gives rise to higher levels of endemism is also a reason that species face higher risks. Many species occupy narrow niches within such regions, making their situation even more precarious.

Places like the Caribbean, the Indian Ocean islands, including Madagascar and Sri Lanka, the Philippines, and biomes like India’s Western Ghats could be bereft of all their endemic plant life in three decades, according to the analysis. In Africa, too, endemic plants in higher-altitude biodiversity hotspots are in grave danger.

On a continental scale, the largest negative impacts will be seen on endemic wildlife in South America, Africa and Oceania.

A troubling conclusion arising from the work is that introduced species will remain relatively unscathed. For land-based species, the scientists calculated that the risk from climate change to endemic species is 10 times higher than for introduced species. The researchers also considered impacts on native species that are not endemic and found that introduced species fare better than native ones as well.

They observed a similar pattern for marine species. However, more research is needed on this group because out of the 200 or so papers considered in the analysis, less than a fifth dealt with marine ecosystems. The available data show that non-native organisms will cope better with a changing climate in this realm too.

“Ultimately, the replacement of endemic species by fewer, generalist and widespread opportunists would lead to homogenization in biodiversity rich-spots, causing ecosystem simplification,” the authors write.

The risk increases disproportionately with the intensity of predicted global warming. If, instead of rising by less than 1.5°C — as the Paris Agreement calls for — average global temperatures rise by more than 3°C, the proportion of terrestrial endemic species menaced by extinction will swell 10 times. “Our study provides evidence that species deeply benefit from climate change mitigation and that risks accelerate with every degree of warming left unchecked,” Manes said.

However, even mitigating climate change may not be enough, since biodiversity threats come in many forms.

“Our analysis is likely underestimating the risk of extinction for biodiversity because we are evaluating the threat of climate change alone — however, we know that concomitant risks, such as land-use change, overexploitation or urbanization, are external sources of threat and deeply impact species as well,” Manes said.

Citation:

Manes, S., Costello, M. J., Beckett, H., Debnath, A., Devenish-Nelson, E., Grey, K., . . . Vale, M. M. (2021). Endemism increases species’ climate change risk in areas of global biodiversity importance. Biological Conservation, 109070. doi:10.1016/j.biocon.2021.109070

(Banner Image: A Coquerel’s dwarf lemur. Image by Rhett A. Butler/ Mongabay.)