The Great Oceanic Die-Off Now Underway

A new report in Nature Climate Change warns that heat waves are sweeping the oceans causing a die off of sea grasses, kelp and corals, leading to a dangerous loss of marine biodiversity.

It's a very technical paper of the sort utterly unsuited to a blog post. I'll fall back on the digested report in The Guardian, "Heatwaves sweeping the oceans 'like wildfires.'"

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 the atmosphere, they say. 

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.  ...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 plankton to invertebrates, to fish, mammals and seabirds,” Smale said.

I have great memories of swimming over coral reefs, across acres of sea grass and into kelp forests.  Anyone familiar with them would find the impending loss of these magnificent ecosystems devastating.