Bengaluru: Over 40 per cent of all land vertebrates will be exposed to extreme heat events before the end of the century if the current fossil fuel trends continue without interventions, finds a study published in the journal ‘Nature’ Wednesday.
Under the Shared Socioeconomic Pathways (SSP) 8.5 — the scenario of the continued rise in temperatures following current emission trends — the world is likely to be at least 4.4 degrees Celsius warmer than the pre-industrial period by the year 2099. Central India among other places is at considerable exposure to frequent extreme thermal events under this particular scenario.
The SSPs are a set of future scenarios offering a broader view of what a world without future climate policy might look like. The SSPs integrate different sets of population, economic growth, and other socioeconomic assumptions into future emissions scenarios.
This rise in temperatures will expose 31.1 per cent of mammals, 25.8 per cent of birds, 55.5 per cent of amphibians, and 51 per cent of reptiles — which together make up 41 per cent of land vertebrates — to extreme thermal events previously never experienced by the species. Amphibians and reptiles are at the highest risk, as compared to birds and mammals.
Extreme thermal events are periods where the temperature vastly exceeds a historical threshold. These events are becoming increasingly common when compared to historical weather and climate records. Worsening rapidly with each passing year, such extreme events exert great heat stress on infrastructure and life.
An average of 3,773 species or over 11.2 per cent of land vertebrates will face extreme heat for over half the year. The constant and severe thermal stress causes a number of physiological and psychological changes in animals, resulting in lower reproduction rates, lower fitness and even death.
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Consequences for humans
The findings fill a large gap in understanding which species and which locations are most prone to the consequences of extreme temperatures on biological systems and warn of substantial threats to future biodiversity around the world.
Under heat stress, the human body (and those of other animals) loses its ability to cool down properly through sweating, leading to a rapid rise in temperature within the body and harm to the brain and organs. It can result in heat exhaustion, heat stroke, rashes, reduced overall health, and reduced productivity. As for animals, it can lead to an increased death rate.
It is thought that by the end of the century, many places — notably India and sub-Saharan Africa — will have 30-40 days a year when humans should not be outdoors for any amount of time.
However, short-term effects on animal populations dealing with heat stress and heat damage have not been assessed widely in academic literature in general.
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Scenario-based outcomes
In the study, a team of scientists from Israel and America mapped the exposure of 33,600 land vertebrates, which make up about 90 per cent of land vertebrates, to extreme heat events under the various greenhouse gas emissions scenarios.
These scenarios are SSP 1.9 (a rise of 1.9 degrees celsius above pre-industrial times by 2100 with very low greenhouse gas (GHG) emissions), SSP 2.6 (low GHG emissions), SSP 4.5 (intermediate GHG emissions), SSP 7.0 (high GHG emissions), and SSP 8.5 (very high GHG emissions continuing present day’s fossil fuel trends).
The researchers projected the frequency, duration, and intensity of extreme thermal events between 1950 and 2099.
Under the SSP 8.5 scenario, where global temperatures would rise to a minimum of 4.4 degrees Celsius above pre-industrial times and a maximum of 8.5 degrees Celsius, they found that 41 per cent of species will experience extreme thermal events in all three metrics. This will affect at least half of the land distribution for terrestrial vertebrates.
For intermediate to high scenarios (3.6 degrees Celsius), that number is expected to decrease to 28 per cent and for low emission scenarios (warming limited to 1.8 degrees Celsius), it is likely to drop to 6.1 per cent.
“As the planet enters a new state of the climate in which extreme temperatures that were once regarded rare become the norm, it is crucial to establish conservation practices that minimise and tackle the impact of heat extremes,” said the paper.
The scientists suggest approaches such as establishing or protecting microhabitats, open water sources that lower the impact of short-term heat stresses or rewilding to maintain the intactness of communities after extreme events are essential.
“Importantly, we find strong effects of SSP scenarios on the impact on land vertebrates, with warming below 2 degrees Celsius fully preventing exposure in many regions. Our study, therefore, stresses the importance of lowering greenhouse gas emissions in reducing the impact of heat extremes on biodiversity, highlighting the urgent need for international collaborations to mitigate the magnitude of climate change,” the authors conclude in their paper.
(Edited by Theres Sudeep)
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