Researchers say they’re not sure these iconic coastal ecosystems will be able to make a comeback anytime soon.

Satellite images comparing bull kelp canopy cover (gold shading) 2008 and 2019 off the coast of Mendocino and Sonoma Counties in Northern California.

The coastal waters of Northern California are changing. A decade ago, hundreds of miles of the rugged seaside were flanked by thick, swaying underwater forests of amber-green bull kelp that were home to fish, abalone and a host of other species. Now, those forests have been nearly wiped out by a series of environmental events that have been falling like ill-fated dominos since 2013.

A healthy patch of bull kelp forest photographed at Pescadero Point

A new study using satellite imagery and underwater surveys is the latest to confirm that these majestic marine ecosystems have all but disappeared, reports Tara Duggan for the San Francisco Chronicle. Satellite images dating back to 1985 show that bull kelp forests off Sonoma and Mendocino counties have declined by a devastating 95 percent since 2013, and, according to the Chronicle, researchers are concerned the kelp may not be able to bounce back anytime soon.

The results, reported last week in the journal Communications Biology, are the first to use satellite images to quantify the ecological losses that have racked up over the last eight years, the Associated Press reports. Across the more than 200 miles of coast encompassed by the study, kelp forests have been almost completely replaced by barren stretches of sea floor covered in spiky purple sea urchins.

Purple sea urchins are marine grazers that love to munch on kelp, and in 2013 one of their biggest predators, the sunflower sea star, abruptly started wasting away due to a still-mysterious disease that has ravaged the many-armed invertebrates from Mexico to Alaska.

Many of Northern California’s kelp forests have been replaced by so-called urchin barrens made up of purple sea urchins like these.

As the unchecked purple urchin populations began exploding in number, bull kelp got hit with successive marine heatwaves that made life even harder for the cold water-loving kelp from 2014 to 2016. While these ocean conditions can’t be wholly attributed to climate change, such marine heatwaves are predicted to become more common under climate change.

“There were a lot of disruptions at one time that led to this collapse, and the system now persists in this altered state,” Meredith McPherson, an ocean scientist at the University of California, Santa Cruz and the paper’s first author, in a statement. “It’s a naturally dynamic system that has been really resilient to extreme events in the past, but the die-off of sunflower stars caused the resilience of the ecosystem to plummet. As a result, the kelp forests were not able to withstand the effects of the marine heatwave and El Niño event combined with an insurgence of sea urchins.”

https://www.smithsonianmag.com/smart-news/satellite-imagery-shows-northern-california-kelp-forests-have-collapsed-180977214/

It is sad. I recall seeing these vast kelp forests on a number of documentaries.

Bubblecar said:

It is sad. I recall seeing these vast kelp forests on a number of documentaries.

Tasmania has it’s own problem with the same issue in the southeast waters.

.
Ecology Of Seaweed And Its Environmental Significance

Even if you don’t care about a bunch of giant seaweed,
the fact that it’s a home & nursery of many other species
that entire industries depend upon to provide an important
source of protein for both man and other important species
(the same as coral) that populate every strata of the ocean.

It doesn’t take Einstein to figure out how dire the situation has
become when you add up the die-off of the Arctic krill population
the coral bleaching/die-off and the crash of the giant kelp forests.

Makes me want to grab the climate deniers and force them to see
what’s happening, Of course if that fails to get there attention we can
simply keep holding their heads under the water until the bubbles stop.

On a similar subject:

Blue carbon
Seagrasses and mangroves can suck carbon from the air
They do an even better job than forests on land

Science & technology
Mar 6th 2021 edition

Off the coast of Formentera, an island in the Spanish Mediterranean, lives an organism that stretches 15km from one end to the other. Posidonia oceanica, more prosaically known as seagrass, spreads by sending shoots out beneath the sediment. Entire meadows, covering several hectares, can thus be made up of a single organism. The grasses are long-lived, too. The vast meadow in Formentera is thought to have been spreading for tens or hundreds of thousands of years.

But the seagrass is more than just a biological curiosity. Along with two other kinds of coastal ecosystem—mangrove swamps and tidal marshes—seagrass meadows are particularly good at taking carbon dioxide from the air and converting it into plant matter. That makes all three ecosystems important for efforts to control climate change.

This role was highlighted in a report published on March 2nd by unesco, an arm of the United Nations, on “blue carbon”—the sort captured by Earth’s oceanic and coastal ecosystems. In total around 33bn tonnes of carbon dioxide (about three-quarters of the world’s emissions in 2019) are locked away in the planet’s blue-carbon sinks. Research by Carlos Duarte, the report’s author and a marine ecologist at King Abdullah University in Saudi Arabia, has shown that one hectare of seagrass can soak up as much carbon dioxide each year as 15 hectares of rainforest.

All this is attracting interest in blue carbon from those keen to use natural processes, rather than human technologies such as direct-air capture, to suck greenhouse gases from the atmosphere. In 2018 Apple partnered with Conservation International, a charity, to protect 11,000 hectares of mangroves on the Colombian coast. The firm estimates the project could lock away around 1m tonnes of carbon.

One reason that blue-carbon ecosystems make such effective sinks is that submerged forests are denser than their land-based equivalents. They can also trap floating debris and organic matter, which settles on the sea floor and can double the amount of carbon stored away.

They posses another advantage, too. Unlike forests on land, blue-carbon ecosystems do not burn. Climate change is intensifying wildfires around the world. As forests burn, their carbon stocks are released back into the atmosphere. And fires can impede a forest’s ability to capture carbon even after they have burned out. In a study published on February 25th in Nature Ecology and Evolution, researchers at Stanford University found that repeated fires favour slow-growing tree species. These are better able to survive blazes, but they are also less effective at soaking up carbon than faster-growing species.

Submerged forests may be impervious to fires, but they remain vulnerable to other sorts of disasters. In May 2020 cyclone Amphan destroyed 1,200 square kilometres of mangrove forest on the border between Bangladesh and the Indian state of West Bengal. A marine heatwave in Australian waters in 2010 and 2011 damaged around one third of the world’s largest seagrass meadow, in Shark Bay. Over the next three years field studies showed that uprooted plants were releasing their carbon back into the atmosphere.

Fortunately, an older, man-made ecological disaster suggests that restoring damaged blue-carbon ecosystems is possible. During the Vietnam war, napalm and a cocktail of weaponised herbicides destroyed more than half of the mangroves in the Mekong delta. A report published in 2014 by the International Society for Mangrove Ecosystems showed that an intense post-war replanting programme was able to restore it within two decades.

And there is more to such ecosystems than simply acting as sponges for greenhouse gasses. They also serve as buffers for vulnerable shorelines, shielding them from storms that barrel in from the high seas. One study of 59 subtropical countries estimated that by dampening waves and providing natural barriers to storm surges, mangrove forests prevent more than $65bn in property damage each year, and help shelter more than 15 million people. Protecting and expanding them, then, appears to be a no-brainer.

https://www.economist.com/science-and-technology/2021/03/06/seagrasses-and-mangroves-can-suck-carbon-from-the-air

Witty Rejoinder said:

On a similar subject:

Blue carbon
Seagrasses and mangroves can suck carbon from the air
They do an even better job than forests on land

Science & technology
Mar 6th 2021 edition

Off the coast of Formentera, an island in the Spanish Mediterranean, lives an organism that stretches 15km from one end to the other. Posidonia oceanica, more prosaically known as seagrass, spreads by sending shoots out beneath the sediment. Entire meadows, covering several hectares, can thus be made up of a single organism. The grasses are long-lived, too. The vast meadow in Formentera is thought to have been spreading for tens or hundreds of thousands of years.

> snip <

Fortunately, an older, man-made ecological disaster suggests that restoring damaged blue-carbon ecosystems is possible. During the Vietnam war, napalm and a cocktail of weaponised herbicides destroyed more than half of the mangroves in the Mekong delta. A report published in 2014 by the International Society for Mangrove Ecosystems showed that an intense post-war replanting programme was able to restore it within two decades.

And there is more to such ecosystems than simply acting as sponges for greenhouse gasses. They also serve as buffers for vulnerable shorelines, shielding them from storms that barrel in from the high seas. One study of 59 subtropical countries estimated that by dampening waves and providing natural barriers to storm surges, mangrove forests prevent more than $65bn in property damage each year, and help shelter more than 15 million people. Protecting and expanding them, then, appears to be a no-brainer.

https://www.economist.com/science-and-technology/2021/03/06/seagrasses-and-mangroves-can-suck-carbon-from-the-air

weird that humans have this dual world view:

on one hand we think we’re so dammed amazing that we can re-make the world. “NO WORRIES!”
on the other hand we think we’re so insignificant that there’s NO WAY
that we can possibly impact this fragile planet.