A new study reveals that 2023–2024 experienced an unprecedented surge in marine heatwave days, triggering extreme weather, coral bleaching, and fisheries collapse.
Record-breaking marine heatwaves (MHWs) have wreaked havoc across global oceans in recent years, with Asia emerging as one of the most severely affected regions. The extreme rise in sea surface temperatures (SSTs) during 2023–2024 has amplified climate-related disasters, disrupted marine ecosystems, and imposed significant socio-economic costs on coastal communities, according to a new study published in Nature Climate Change. Despite advance warnings, inadequate mitigation strategies have left the region vulnerable to escalating climate risks.
Record-setting heatwaves and their triggers
The study highlights that SSTs in 2023 and 2024 reached unprecedented levels, driven primarily by human-induced climate change, amplified by El Niño conditions and record-low cloud cover. The number of MHW days in 2023–2024 surged 240% higher than any other recorded year, with over 8.8% of global oceans experiencing the highest-ever temperatures.
According to the study, Asia’s surrounding waters—especially the western Indian Ocean, the southwest Pacific, and the eastern Pacific—were among the worst-hit regions. The extreme heat in these oceanic zones intensified atmospheric and oceanic disturbances, influencing monsoons and typhoon activity, which had far-reaching consequences for coastal nations.
The risk to climate vulnerable regions
The study finds that the link between MHWs and extreme weather events was evident in 2023 when Typhoon Doksuri struck China, Taiwan, the Philippines, and Vietnam, affecting over two million people and causing nearly 200 fatalities. Similarly, Japan witnessed severe coastal flooding due to intensified storm activity. In the Indian Ocean, marine heatwaves likely contributed to the strengthening of cyclonic events, increasing the risk of displacement and economic loss in vulnerable regions.
Beyond storms, prolonged heatwaves fueled a series of biological impacts. The study reports that the Gulf of Thailand, a vital fishing region, saw mass fish mortalities, leading to severe economic losses for the local fishing industry. Coral reefs, crucial to marine biodiversity and coastal protection, suffered bleaching events as part of a global coral bleaching event, with documented losses off the coast of Japan. Such coral loss not only endangers marine life but also threatens tourism and fisheries-dependent economies.
The socio-economic fallout
According to the study, the ecological distress caused by marine heatwaves has translated into significant socio-economic losses. In Thailand, aquaculture industries suffered due to rising sea temperatures and harmful algal blooms, leading to lower yields and higher mortality rates among farmed fish. In Japan, the loss of marine productivity impacted the seafood trade, forcing adjustments in fishery quotas and affecting livelihoods.
Moreover, the study notes that changes in species distribution have disrupted local economies. The movement of commercially important fish, such as anchovies off the Peruvian coasts, forced the closure of fisheries, leading to economic losses amounting to billions of dollars. These shifts have created instability for fishing communities and necessitated government interventions in the form of subsidies and relief programmes.
The urgent need for preparedness
Despite early warnings and predictive models, the study finds that Asia’s response to MHWs has largely been reactive rather than proactive. Unlike Australia and the United States, where national-level response plans were implemented, most Asian nations lacked coordinated interventions. In Australia, a quarter of the population of endangered red handfish was taken into aquariums before the marine heatwave hit, and released again when waters cooled. In the US, some corals and conches were moved into deeper, cooler waters. In Peru, the government paid benefits to the fishers who could not go to sea when they were forced to close the anchovy fishery.
“While the scale of marine heatwaves is alarming, some proactive interventions have made a real difference. One of the success stories has been in Australia, where marine heatwave forecasts helped reduce impacts. If more regions had access to and acted on these forecasts, we could better protect fisheries, aquaculture, and coastal communities from devastating losses,” said Dr. Alistair Hobday, Research Director for CSIRO’s Sustainable Marine Futures Program.
Potential strategies outlined in the study include enhanced monitoring of SSTs, implementation of coral conservation projects, and adaptation measures such as relocating vulnerable species. Governments must also prioritize financial support for affected industries and develop sustainable fisheries management practices, the study stated.
With the frequency and intensity of marine heatwaves set to rise, the study warns that Asia faces a pressing need to bolster its climate resilience. Failure to act swiftly may result in irreversible damage to marine ecosystems, economic instability, and heightened risks for millions living along its coastlines.
“Ultimately, to prevent marine heatwaves and their impacts from worsening we need to reduce/stop our use of fossil fuels. In the interim, preparation for marine heatwaves and interventions to reduce loss of species have shown some success stories, but these are not permanent solutions,” said Dr. Kathryn E Smith, The Marine Biological Association of the UK.
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