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Why tropical species are at greater climate risks

Why tropical species are at greater climate risks

why tropical species are at greater climate risk

The effects of climate change – extreme heat waves, wildfires of unprecedented magnitude and devastating floods – have now been occurring for several decades, and the COP26 climate agreement reached in Glasgow will not be enough to keep global warming below 2°C, as the French climatologist Benjamin Sultan recently said.

These disruptions do not leave any species alone. The report is from the IPBESThe equivalent of the IPCC on biodiversity, ecologists highlight dramatic declines All over the worldYou can also find it in regions that have been preserved.

Future projections are not better. Studies that attempt to predict the effects of climate changes suggest that there will be winners as well as losers. But they are mostly losers – not to mention the risks of invasion by the “winners”.

Although the idea of containing global warming to less than 2°C is making headway, that endeavour would nonetheless remain insufficient, as stressed in a Study published in the leading journal Climate Change.

Clearer signals in the tropics

Climate change, as we know, will affect all of us, even in temperate areas. A growing number of studies shows that climate change has a gradient effect on species’ responses. The greater the severity of the effects, the closer one is to the equator. This is true for European birds, which suffer greater declines in their southernmost population. Similar patterns can be observed in the North American mountainsBirds track the cold to higher altitudes by using this method, but it is usually seen in the tropics.

This gradient was also observed when it came to the body size French passerines. A study that I conducted with the French National Museum of Natural History. Global Change and BiogeographyHigh temperatures had a negative effect on juvenile growth, but only in the south, according to a study. In the following rap song, I summarize this research with Benjamin Freeman from University of British Columbia.

“Species, climate change and latitude (Scientific Rap Sessions, 6 octobre 2021).”.

Species that live closer to their tolerance threshold

How is this possible? Are the species found in the southernmost parts of the world not adapted for warmer climates? Yes, they are, but heat or drought are still the main challenges in these areas. In the Mediterranean region, warming would increase aridity, and hence decrease plant production – the basis of the food chain. Warmth equals more aridity, which means fewer plants and insects, and therefore less food for birds in spring.

What about the tropics? Although species have adapted to these climates, their thermal tolerance threshold is the same as that for temperate species. The limit of tropical species is always within reach. A very slight temperature shift may be necessary. Drive them beyond their physiological comfort zone.

Alarming projections

Predictive models are able to help predict the impact of climate change. After identifying the best climate conditions for a particular species, ecologists use the future climate scenarios created by climatologists.

These models were used in a study that was done in collaboration with the University of Porto as well as the NGO Madagasikara Voakajy. Two species will experience a dramatic decrease in climate conditions by 2070: A bright-coloured frog hailing from Madagascar and a gecko, a sticky toed lizard hailing from Reunion island.

Phelsuma inexpectataA collection of gecko species that live on the island Reunion.
B. Navez/Wikimedia, CC BY -NC – SA

Both species are restricted geographically to a small area with very specific climate conditions. The study takes into account a variety sources of uncertainty related to the scenario and the methods. In all cases, the climate will be largely unsuitable not only for their current range, but also for their entire island. Climate change is now one of the many threats to their environment.

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A glimmering hope

These models show that the ideal climate conditions required for these species are unlikely to be met in future. However, they ignore the species’ capacity to adapt to new conditions. Some species may alter their habits to avoid the most warm periods of the day (or the year). Others may seek micro-climatic refuges either in urban areas or in the wild. It is possible that these species may be more tolerant to heat than expected.

Reunion has already seen conservation actions. The NGO Nature Océan IndienPlans for restoration of the natural habitat have been made. These steps enable climate risk to be anticipated by favoring existing populations.

What’s the point of all this research if the climate is unsuitable in future? This study allowed us to pinpoint the areas that will be most favorable in the future with high precision. These results will serve as guidelines to conservation professionals and will allow them to maintain or build habitats that will be a haven.

This study was limited to two species due to the inconsistency of the data. For many other tropical species, however, these grim predictions could become a reality. This is a further alarm bell in an increasingly hot world.

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