Along much of the California coast, throughout Oregon and into Washington, thick kelp forests became urchin barrens after a combination of intense marine heat waves, a die-off of urchin predators, and a purple urchin population explosion, tipped the balance from kelp forest ecosystems to urchin barrens.
Urchin barrens form where unchecked populations of sea urchins feed on kelp forests untll almost nothing is left except bare rock.
Urchins in urchin barrens will slowly starve, but they may survive for decades. Our project is working to reduce urchins so that kelp forests can reestablish and flourish.
Short video by National Marine Sanctuaries on urchin barrens.
Video showing a dive through the urchin barren off of Coral Street in Pacific Grove by Stephen Pacetti.
Look at a 360° view of an urchin barren.
Kelp forests are one of the most productive and biodiverse ecosystems on the planet. In addition to providing food and habitat for hundreds of species of invertebrates, fish, birds, and mammals, kelp provides important benefits to us humans. Kelp forests photosynthesize and produce oxygen that we breathe and they absorb 20X more carbon dioxide per acre than forests on land. Not only do kelp forests help reduce climate change, they help protect coastal communities by dampening wave action and preventing coastal erosion. Kelp is economically important as extracts from kelp are used in products that we come across in our everyday lives. A compound called alginate comes from kelp and is used in medicines, cosmetics and even as a food thickening agent. So if you’ve ever had pudding, ice cream, or used toothpaste, you’ve probably eaten this kelp compound.
Sadly, Monterey's once-lush kelp forests are rapidly being consumed by sea urchins. In a healthy kelp forest, native sea urchin numbers are very low. Urchins usually hide in cracks to avoid being eaten by predators and wait for bits of kelp to fall to the reef to eat. In late 2013, a marine heat wave coincided with a wasting disease that wiped out many species of sea stars, including huge sunflower stars, a major urchin predator. Without many predators, the urchin population exploded. Kelp likes cold, nutrient-rich water, and did very poorly during the marine heat wave. With less kelp available to eat, urchins changed their feeding behavior. Instead of hiding in cracks, urchins began coming out of the cracks and actively grazing on the reef and mowing down kelp. The results are underwater deserts known as urchin barrens. Very few other animal species can survive in an urchin barren. According to Reef Check CA, urchin populations grew to 260 times higher than normal, and we’ve seen a huge reduction in Monterey’s giant kelp forests. This means that hundreds of animals are being left without food and habitat.
Even starving urchins may live for many years by scraping diatoms off of rock and grabbing bits of seaweed debris and phytoplankton as it floats past them. In many parts of the world kelp forests have been mowed down by urchins, forming urchin barrens that have persisted for decades. Unless there is some perturbation in the environment, urchin barrens are unlikely to go away. Possible perturbations are: several consecutive years of cold water, pollution, predation, and disease. California sheephead, spiny lobsters, sun stars, and sea otters are urchin predators, but otters are the only significant predators in Monterey Bay. Without human intervention or a disease outbreak, Monterey urchin barrens are not expected to disappear.
See what the Monterey Bay National Marine Sanctuary says about this question.
No, at least not the starving urchins in urchin barrens.
Sea otters must consume at least 25% of their body weight every day. Urchins in urchin barrens have eaten all seaweeds, including kelp, and are starving. If you cut open an urchin from an urchin barren, you'll see that all of their tissues and reproductive organs have shriveled to almost nothing and have little nutritional value or calories. Sea otters eat a wide variety of foods and some specialize in eating urchins, but they are clever enough to avoid eating the starving urchins in barrens.
Uni is harvested sea urchin reproductive organs. Most uni comes from large red urchins. Purple urchin uni is tasty too, but it is not harvested commercially.
Urchins in the urchin barrens have eaten all edible seaweeds and are starving. Their tissues and reproductive organs have shriveled to almost nothing and have little nutritional value or calories. Unfortunately, it can take them years to die of starvation. The urchin at left was taken from an urchin barren in Monterey. Notice that the test (shell) is mostly empty because this urchin was starving.
The image at right shows a healthy urchin from a kelp forest. Notice the large yellow reproductive organs (gonads) that are rich in calories and nutrients. This is what people and otters enjoy eating.
At least one company, Urchinomics, is working to collect starving urchins from urchin barrens, then fatten them up. They aim to create a commercial market for purple urchins and help reduce the number of urchins in barrens, but even they admit that their efforts will make only a tiny dent in the billions of urchins that are consuming west coast kelp forests. Read more.
We were initially concerned that culling urchins could trigger a spontaneous spawning event among the surrounding unculled urchins. There is no scientific study showing this occurs in the ocean and we have not seen it happen.
Our advisory team, which includes marine biologists with NOAA, Ocean Protection Council, California Dept. of Fish & Wildlife, and Reef Check have advised us that incidental spawning during urchin culling would be insignificant. They suggested that we continue culling urchins year round, even during the winter spawning season, to allow kelp forests to reestablish.
No, both purple and red urchins are native species. They are an important part of a healthy and balanced kelp forest ecosystem. Before 2013 urchin numbers were kept in check by predators and their numbers were less than 1 per square meter of reef. Since 2014, urchin populations in many parts of Central California have exploded. According to Reef Check CA, urchin populations have grown up to 260 times higher than normal, and we’ve seen a huge reduction in Monterey’s giant kelp forests.
No, it is illegal to cull urchins in Marine Protected Areas. Monterey dive sites with the most extensive urchin barrens, such as Lovers Point, Coral Street, and Point Lobos, are all within Marine Protected Areas. Our project at Tanker's Reef is not in a Marine Protected Area and we have been given permission to cull an unlimited number urchins there.
With a fishing license, divers can take 35 urchins per day outside of the Marine Protected Areas—at Del Monte Beach, for example.
Plus, there are so many urchins in the barrens that randomly culling them is simply ineffective. Efforts to remove urchins must be coordinated so that entire area is cleared to a low urchin density where kelp has a chance to establish. If you are interested in helping us with our effort to gain permission to cull urchins within the MPAs, please sign up for our newsletter so we can keep you updated on our efforts!
Yes, divers can cull an unlimited number of only PURPLE urchins for kelp restoration purposes at Caspar Cove in Mendocino County. Culling of red urchins is NOT allowed here.
To find out more information on volunteer diver efforts at Caspar Cove, check out the Watermen's Alliance Urchin Removal Efforts Facebook group
This video by the Nature Conservancy explains what we know about what killed the sunflower stars and efforts to restore their populations: Sunflower Sea Stars Now Critically Endangered
In Monterey, a new project led by Vince Christian is working to raise sunflower stars for future reintroduction into California. To find out more, check out the Sunflower Star Laboratory Facebook page.
We are working to reduce the urchin population at Tanker's Reef to 2 per square meter or less. We are vigorously protecting small patches of kelp so they will be able to produce offspring that will settle on the rocky reef and gradually expand into a healthy kelp forest.
More urchins are constantly moving into our restoration area from the surrounding urchin barrens, so it will take a year-round effort to ensure the survival of our future kelp forest.
Urchin removal, rather than culling, was initially tried in the northern California urchin barrens. Divers would descend, gather urchins in nets, then bring them up to waiting kayaks or other boats. The boats would ferry the urchins to shore, load them into a truck, then drive them to a facility to be composted. Divers removed over 20,000 pounds of urchins this way.
The removal method was abandoned for a number of reasons: 1) Repeatedly descending and ascending creates pressure changes that are potentially hazardous for divers, 2) This process is complex and highly labor-intensive, making it inefficient and expensive, 3) The nutrients and minerals contained in the urchin tests (shell) and tissues are removed from the ecosystem, rather than staying in the ocean where they could be used by other organisms.
In Monterey we made the decision to carefully cull urchins in place using small hammers because it is the most efficient, environmentally sustainable, and cost-effective method available.
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