Risk of Ectotherm Heat Failure Increases as Global Warming Worsens

Ectotherms (cold-blooded creatures) on land and in water might face severe consequences due to global warming. Recent studies show that for every degree the temperature rises, the frequency of heat damage among ectotherms doubles.

(Photo : Sippakorn Yamkasi)

Impacts of Climate Change

Climate change has a significant negative influence on ectothermic creatures. It is generally known that their body temperature and, consequently, their metabolic functions are dependent on both the surrounding environment's temperature and sunlight.

Even the researchers who carried out the new study were astonished by the finding that heat harm doubles for every degree the ambient temperature exceeds the animals' tolerance limit.

Five zoophysiologists from Aarhus University conducted the study, which was just published in the prestigious scientific magazine Nature and featured on the publication's cover. The results were based on information from earlier investigations on ectothermic animals.

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Geographic Distribution

(Photo : by Christopher Furlong via Getty Images)

The geographic distribution of ectotherms and their tolerance to ambient temperature conditions are known to be correlated. They can only endure extreme winter and summer conditions that are neither too cold nor too hot for extended periods of time, as well as temperatures that allow them to grow and reproduce.

If temperatures rise over what the animals can tolerate, they become injured. The cumulative effects of these wounds eventually decide whether the species can endure the current temperature circumstances.

According to postdoc Lisa Bjerregaard Jensen, one of the study's co-authors, "And the more the temperature surpasses the tolerance range of the species, the quicker they will acquire damage."

The researchers have examined 112 ectothermic species' temperature sensitivity to heat stress. According to the data, a 1°C increase in temperature causes the rate of heat injury accumulation to more than double.

Due to the exponential nature of the growth, a temperature increase of 2°C will accelerate the accumulation of heat injuries by more than four times, and a temperature increase of 3°C will accelerate them by more than eight times.

Comparing Studies

After that, the researchers compared their findings about temperature sensitivity to models that predicted an increase in maximum temperatures due to global warming. According to this research, the rate of heat damage for ectotherms might rise globally by an average of 700% and on land in many habitats by more than 2000%.

The comparable percentages for aquatic ectotherms are 180 and 500 percent.

Regional analyses point to significant effects, particularly in the seas around the Arctic and the northern temperate zone, which includes most of Europe and North America.

Although the underlying physiological and biochemical mechanisms that cause heat stress and mortality remain unknown to the researchers, their investigation shows that these processes are highly temperature-sensitive in all types of ectotherms. This could mean that comparable pathways govern the severity of heat harm.

Nuanced Discussion

"Since the threshold for heat stress varies greatly among species, we cannot forecast how many species and individuals may perish as temperatures rise. Additionally, many ectothermic terrestrial animals may control their body temperature by seeking shade, lowering the danger of heat-related injuries. According to research co-author Professor Johannes Overgaard, this is more complex for aquatic creatures.

"The point is that we run the danger of underestimating the consequences of future heatwaves due to this extremely high sensitivity to heat harm," he continues. Our findings suggest that future heatwaves will have significant effects, even if not every species will be negatively affected to the same extent.