New Study Shows a Drastic Decline in NorCal Kelp Forests

A new study using satellite images and underwater surveys shows an almost 95 percent decline in Northern California kelp forests.

NORTHERN CALIFORNIA一 A new study published in Communications Biology using satellite imagery and underwater surveys shows that 95 percent of Northern California kelp forests have disappeared since 2013.

The study showed the dramatic decline in bull kelp forests through an abrupt ecosystem shift that began in 2013 and continued through 2019 along 200 miles of Northern California’s coast primarily in Mendocino and Sonoma counties.

Through the study, researchers used satellite imagery to show the effect of a multi-year marine heatwave that they believe caused a decline in keystone predator populations. They theorized that historically kelp forests were resilient and had the ability to regenerate easily but that with recent environmental and biological events the ecosystem has shifted to a state of low primary activity causing a severe decline and no way to bounce back without intervention.

In 2013 there was an outbreak of sea star wasting syndrome (SSWS) which caused a dramatic decline in the sea star population up and down the west coast of North America.

Typically lesions appeared on the outside of the sea star which caused decay and eventual death and fragmentation, sunflower sea stars were among the first to succumb to the disease according to an article on the University of California, Santa Cruz website that was last edited on March 25.

The sunflower sea star is considered a keystone species because of the large effect they have on the ecosystem as a primary predator of sea urchins, which primarily survive on kelp.

Part of the decline in the kelp forests is attributed to the loss of the sunflower sea star, which has still not recovered in kelp forests or coastal tidal areas but, the decline is not solely responsible.

A year later in 2014, there was an ocean warming event in the Pacific Ocean which became known as “The Blob.”

“The biggest marine-warming event ever was the original 2014-2016 “Blob,” which resulted in unprecedented harmful algal blooms, invasive species, shifts in migratory ranges for animals, including humpback and gray whales, and changes in the marine food web that, among other things, depressed salmon returns for years.” said a Feb. 19, 2020, article from The Seattle Times.

The satellite imagery that was used provided the researchers with a perspective going back 34 years. Through the historical data and a series of first-hand data gathered through the study, researchers believe that it was a combined effort of two events that created an opportunity for a shift to urchin barrens, barren areas of the coastline covered in unchecked populations of sea urchins that have made it difficult for bull kelp to grow back.

The loss of the kelp forests has been devastating to local fisheries that depend on kelp forest ecosystems, and various species that depend on the kelp forests for their home.

The study suggests the implementation of “ecosystem-based and adaptive management strategies.” Hopefully by monitoring kelp growth and the density of sea urchins and their predators; creating management techniques of these levels; and creating restoration and educational efforts, the study theorizes that we can bring kelp forests back.


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