Australia’s most protected marine habitats are likely to suffer extreme impacts from climate change by 2040, according to a new study.
Even under today’s optimistic climate scenarios, ocean conditions considered extreme today will become the new normal in Australian waters in just 15 years, increasing threats to thousands of marine species, the study warns.
At that level of warming, the study also found, the effects will be so widespread that almost none of Australia’s ocean territory will be able to provide “safe havens” to shelter marine life from the brunt of those impacts. Refuge from climate change, in other words, will all but disappear.
The study appears in “Earth’s Future,” the American Geophysical Union’s journal for research on the state of the planet and its inhabitants and their future resilience in the Anthropocene.
According to said lead author Alice Pidd, a former fisheries researcher now undertaking a PhD in quantitative ecology at the University of the Sunshine Coast:
“When we think about marine protected areas, we might imagine fences or boundaries in the ocean. In reality, these boundaries are ethereal and porous to a changing climate.”
Marine protected areas, which comprise about half of Australia’s 7 million square kilometers (2.7 million square miles) of marine real estate, are legally designated to conserve biodiversity in vital habitats such as coral reefs, kelp forests, seagrass beds and mangroves. But little research has delved into how these protected areas will handle the mounting impacts from climate change that threaten the marine life living within them, including whales, sharks, turtles and commercial fish species such as billfish and tuna.
Pidd said:
“Marine protected areas are important tools in reducing the impacts of human activities such as fishing, shipping, mining and tourism. But they weren’t designed with the realities of climate change in mind, and their location alone won’t protect them from its impacts.”
To predict how Australia’s waters would respond to various levels of climate change over the course of this century, the researchers fed four different greenhouse gas emissions scenarios into 11 different Earth system models — an effort involving several terabytes of data to process.
According to Pidd:
“It took us over six months and many late nights of babysitting the code for errors.”
Under all but the most hopeful of those scenarios, they found that global warming of more than 1.8 degrees Celsius (3.2 degrees Fahrenheit) above preindustrial levels would cause Australian marine climate “refugia” — areas where climate change’s impacts appear more slowly — to almost entirely disappear by 2040.
Rapidly reducing greenhouse gas emissions could allow some refugia to reappear after 2060, Pidd said, but “we have already crossed several climate tipping points. Biodiversity will need to adapt.”
Past the 1.8 degrees Celsius of warming seen in the lowest-emissions scenario, Australian waters would also experience more extreme conditions than any seen from 1995 to 2014, including higher temperature and acidity, lower oxygen and more frequent and intense marine heatwaves. These changes would also occur faster than during any period of climatic change in the recent past, amplifying the pressure on marine species to either adapt or relocate in search of more livable habitat.
Pidd said analyzing impacts from 1.8 degrees of warming, rather than only the most extreme scenarios of over four degrees, makes the findings more tangible, offering a picture of the results we might expect given the current suite of global commitments to mitigate climate change.
Even safe harbors offer no safe harbor
When the team looked specifically at impacts to Australia’s marine protected areas, they found virtually no difference.
According to co-author David Schoeman, a professor of global change ecology at the University of the Sunshine Coast:
“The results are unfortunately not surprising. Marine protected areas will be as vulnerable as unprotected ocean areas when faced with rapid warming, oxygen loss, acidification and heatwaves.”
Protected areas off northwestern and eastern Australia bear the highest vulnerability.
Traditionally, marine protected areas have been designed to cover as wide a range of species as possible based on their historical habitats. But “the past is no longer a good guide to the future,” Schoeman said. That becomes increasingly true as many species’ ranges migrate across static protected area boundaries in response to climate change. As a result, marine protected areas may become inadequate as biodiversity conservation tools.
More climate-smart marine protected area design, the team wrote, might instead focus on protecting remaining climate refugia, where species may have more time to adapt to changes, or corridors between those refugia so that species can more easily relocate as ocean conditions change. Pidd is interested in further research to investigate where these “stepping stone” corridors might be most valuable:
“The key is to protect where biodiversity is likely to be in the future, not just where it is now.”
Australia’s upcoming review of its marine protected area management in 2028, she added, could be a good opportunity to incorporate these considerations into marine conservation planning. At the same time, the team stressed that adaptive measures like these are not enough and that urgent, aggressive action to reduce carbon emissions must remain the top priority to delay or limit the projected climate impacts.
Pidd said:
“Doing nothing is not an option. Every fraction of a degree counts.”
