SAN FRANCISCO (CBS SF) -- Over the last 10 years, an ecological disaster has taken place along the coast from San Francisco north.
Bull kelp forests, which provide some of the most productive habitat for sea life anywhere on the planet, have declined by 96%. The once thriving undersea forests have been replaced by seemingly endless beds of purple urchins. These "urchin barrens" as they are called by scientists are exactly what they sound like. Nothing else can live there now.
It's a crushing loss for communities along our coast who have depended on the diverse bounty kelp beds once provided. Most notably, the abalone fishery and the far-more-palatable red urchin have all but vanished.
Like so many other stories of ecological disruption, this one has a strong link to climate change- specifically, the warming of our ocean. In 2015, the year our kelp forest collapsed, scientists documented the largest and most intense marine heatwave on record.
Marine heatwaves are classified as prolonged periods of well-above-average temperatures throughout a sizeable expanse of the ocean. Kelp likes water temperatures in the mid-50s, but during some of the more extreme heat waves of the last seven years, the temperatures off our coast have reached near 70°. Temperatures that warm have weakened the defenses of the kelp, enabling purple urchin to over graze the forest.
Unfortunately, the urchin got some help right about the same time when their primary predator was wiped out by a pathogen. While it's not as clear, it is believed ocean warming lead to the loss of the sunflower sea star as well. Without a natural predator, the urchin have been free to completely devour the kelp forests.
While it's unclear what the solution is, researchers from many different branches of ocean science and biology are working hard to find solutions.
One possibility is the work being done by associate professor Brent Hughes of Sonoma State University to cultivate a strain of kelp more resistant to the warmer temperatures now found off our coast. If successful, he hopes to re-introduce a new strain of kelp which will be better able to thrive in a warmer ocean.
Perhaps the first line of attack has to be removal of the purple urchin. A company called Urchinomics is leading the charge to create a market for purple urchin to inspire enough people to harvest them off our coast thereby creating enough open space for kelp to once again gain a foothold.
Regardless how creative our efforts, the 800-pound gorilla in the room is climate change and the fact that marine heat waves like the one we saw 2015, as well as several others since, will almost certainly now be a regular feature off our coast going forward. How this plays out with re-introducing a stable population of kelp is still unknown.
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