Climate Change related heatwaves are affecting not just the land but the oceans too
The Guardian reports, 4th March 2019: The number of heatwaves affecting the planet’s oceans has increased sharply scientists have revealed, killing swathes of sea-life like “wildfires that take out huge areas of forest”.
The damage caused in these hotspots is also harmful for humanity, which relies on the oceans for oxygen, food, storm protection and the removal of climate-warming carbon dioxide from the atmosphere, say the scientists.
Global warming is gradually increasing the average temperature of the oceans, but the new research is the first systematic global analysis of ocean heatwaves, when temperatures reach extremes for five days or more.
The research found heatwaves are becoming more frequent, prolonged and severe, with the number of heatwave days tripling in the last couple of years studied. In the longer term, the number of heatwave days jumped by more than 50% in the 30 years to 2016, compared with the period of 1925 to 1954.
As heatwaves have increased, kelp forests, seagrass meadows and coral reefs have been lost. These foundation species are critical to life in the ocean. They provide shelter and food to many others, but have been hit on coasts from California to Australia to Spain.
“You have heatwave-induced wildfires that take out huge areas of forest, but this is happening underwater as well,” said Dan Smale at the Marine Biological Association in Plymouth, UK, who led the research published in Nature Climate Change. “You see the kelp and seagrasses dying in front of you. Within weeks or months they are just gone, along hundreds of kilometres of coastline.”
As well as quantifying the increase in heatwaves, the team analysed 116 research papers on eight well-studied marine heatwaves, such as the record-breaking “Ningaloo Niño” that hit Australia in 2011 and the hot “blob” that persisted in the north-east Pacific from 2013 to 2016. “They have adverse impacts on a wide range of organisms, from planktonplankton Plankton is a generic term for a wide variety of the smallest yet most important organisms form that drift in our oceans. They can exist in larger forms of more than 20cm as the larval forms of jellyfish, squid, starfish, sea urchins, etc. and can be algae, bacterial or even viral down to as small as 0.2µm. They are nutrient and light dependent, and form the essential foodchain baseline for larger dependent aquatic lifeforms. Fish species rely on the density and distribution of zooplankton to coincide with first-feeding larvae for good survival of their larvae, which can otherwise starve. Man-made impacts such as dredging, dams on rivers, waste dumping, etc can severely affect zooplankton density and distribution, which can in turn strongly affect larval survival and thus breeding success and stock strength of fish species and the entire ecosystem. They also form the essential basis of CO2 take up in our seas ecosystem, hence Global Warming. to invertebrates, to fish, mammals and seabirds,” Smale said.
“This [research] makes clear that heatwaves are hitting the ocean all over the world… The ocean, in effect, is spiking a fever,” said Prof Malin Pinsky, at Rutgers University, US, and not part of the team. “These events are likely to become more extreme and more common in the future unless we can reduce greenhouse gas emissions.”
Dr Éva Plagányi at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia also likened ocean heatwaves to wildfires. “Frequent big hits can have long-lasting effects,” she said. “This study shows that record-breaking events are becoming the new normal.”
The damage global warming is causing to the oceans has also been shown in a series of other scientific papers published in the last week. Ocean warming has cut sustainable fish catches by 15% to 35% in five regions, including the North Sea and the East China Sea, and 4% globally, according to work published by Pinsky and colleagues.
“We were stunned to find that fisheries around the world have already responded to ocean warming,” he said. Another study showed that achieving the 2°C climate change target set out in the Paris agreement would protect almost 10m tonnes of fish catches each year, worth tens of billions of dollars.
Separate work by Plagányi’s team showed that climate change will reverse the recovery of whales in the Southern Ocean by damaging the krill on which they feed. “Models predict concerning declines, and even local extinctions by 2100, for Pacific populations of blue and fin whales, and Atlantic and Indian Ocean fin and humpback whales,” they said.
“In the space of one week, scientific publications have underscored that unless we take evasive action, our future oceans will have fewer fish, fewer whales and frequent dramatic shifts in ecological structure will occur, with concerning implications for humans who depend on the ocean,” said Plagányi.
Source: The Guardian, 4th March 2019. For the full story, see www.theguardian.com/environment/2019/mar/04/heatwaves-sweeping-oceans-like-wildfires-scientists-reveal
