Nature, the international journal of science, published a study on April 24, 2019 titled “Greater vulnerability to warming of marine versus terrestrial ectotherms.” This is the first study that draws comparisons between the impacts of higher temperatures in the oceans and on lands,for a range of cold-blooded wildlife, from fish and mollusks to lizards and dragonflies.
2018 became the hottest year for oceans as they continue to absorb the heat trapped in the atmosphere due to carbon dioxide pollution. Since ocean-dwelling species have fewer ways of seeking refuge from the global warming, they are disappearing from their natural habitats at twice the rate than the land-dwelling ones.
According to Malin Pinsky, an ecologist and evolutionary biologist at Rutgers University, who led the research, “marine animals live in an environment that, historically, hasn’t changed temperature all that much. It’s a bit like ocean animals are driving a narrow mountain road with temperature cliffs on either side.”
For the purposes of the study, the scientists calculated “thermal safety margins” for 88 marine and 318 terrestrial species. The aim was to determine how much warming can they tolerate and how much exposure do they already have to those heat thresholds. Marine ectotherms experience hourly body temperatures closer to their upper thermal limits. This occurs in terrestrial ectotherms only if they do not have access to thermal refugia.
The margins of safety are the slimmest near the equator for ocean dwellers and near the mid-latitudes for those on land. This is not a direct prediction of population decline. However, the thermal safety margin provides an index of the physiological stress caused to marine species due to the global warming.
Across the marine and terrestrial realms, different processes exacerbate thermal vulnerability. Thus, in the marine realm, higher sensitivities to warming and faster rates of colonization can result in faster and frequent extirpations as well as species turnover. In contrast, in the terrestrial realm, species are more vulnerable to loss of access to thermal refugia. Thus, the critical factors causing loss of species on land are habitat fragmentation and changes in land use.
The study has established that for many species, the current levels of heat is already excessive. So, more than half of the marine species had disappeared from their historical territory, at the warm edges of the ranges. The contention here is that even though the narrow safety margins for the tropical marine animals, averages to about 10 degrees Celsius, the populations actually become extent long before experiencing warming to that degree.
A boost in warming by even half- or one-degree can create impediments and devastating impacts vis-à-vis searching for food, reproducing etc. In such a situation, some species successfully migrate to new territories, but others, like sea anemones and coral, cannot move and simply become extinct. In this context, the study provides hard data to reiterate the long-standing assumption that marine systems are more vulnerable to climate warming.
Multiple measures can limit the destruction being caused to ocean habitats and address the loss of marine species. These include: curbing greenhouse gas emissions, eliminating overfishing, rebuilding populations that have been overfished, establishing networks of marine protected areas as stepping stones for species to move to higher latitudes etc.
Thus, the report lays emphasis on the fact that an understanding of which species and ecosystems will be most severely impacted by warming, with the advancement of climate change, is crucial for guiding conservation and management. This implies that it is important to measure temperature changes but also determine their impact on marine and land-based animals. It provides yet another wake-up call for the dire need to protect natural environments for the temperature buffer that they provide for wildlife in an increasingly warming world.
India Outbound
April 24, 2019
source https://indiaoutbound.org/increasing-thermal-vulnerability-of-marine-species-due-to-global-warming/
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