On an overcast Tuesday in July, divers Mitch Johnson and Sean Taylor prepare for their mission as they shimmy into their wetsuits aboard the R/V Xenarcha, a 28-foot vessel anchored off the coast of Rancho Palos Verdes, just south of Los Angeles. Below them, the shimmering waters of the Pacific Ocean reveal a lush underwater landscape, where a forest of army-green kelp sways gracefully, reminiscent of mermaid hair. This expedition aims to survey the giant Pacific kelp, a once-thriving species in these frigid waters, which has witnessed an alarming decline of 80% over the past two decades due to a combination of warm ocean temperatures, pollution, overfishing, and an explosion of voracious sea urchins that consume the kelp.
In recent years, scientists have initiated one of the largest and most successful kelp restoration projects globally, enlisting a dedicated team of divers to combat the destructive urchins. Today’s dive provides a unique opportunity to witness the success of these restoration efforts firsthand. From the boat, the kelp fronds appear thick and robust, creating mats at the ocean's surface, offering a perch for egrets and herons as they hunt for fish below. The waters teem with life, hosting a plethora of species—from vibrant orange garibaldi fish to stealthy white sharks, and even majestic blue whales cruising through the deep channel just a few miles east.
Divers Johnson and Taylor are well-equipped for their task. On some days, they utilize rock hammers—an underwater counterpart to the tools of the seven dwarves—to shatter the ravenous purple urchins that devastate young kelp. However, today, they are armed only with a tape measure and a camera to assess the health of this vast, concealed forest. Fully geared up, the divers signal a thumbs-up to Tom Ford, the chief executive officer of the Bay Foundation, a nonprofit organization committed to restoring Santa Monica Bay and its coastal waters. With a small splash, Johnson and Taylor plunge into the depths, leaving Ford and me waiting on the boat, listening to the gentle lapping of waves against the hull of the Xenarcha.
Under Ford's leadership, divers in Santa Monica Bay have logged an impressive 15,575 hours underwater over the past 13 years. Their primary focus is to minimize the impact of the purple urchin, which has been a significant threat to kelp forests. Their efforts have yielded notable results: divers have successfully smashed over 5.8 million purple urchins and cleared 80.7 acres (approximately 32.7 hectares or the size of 61 football fields), allowing the kelp to make a remarkable comeback. Yet, with these results hidden beneath the waves and far from the public eye, Ford questions whether anyone has truly noticed this “forgotten forest.”
The fast-growing kelp ecosystems are often referred to as the “sequoias of the sea” due to their remarkable ability to store large amounts of carbon, provide habitat for over 800 marine species, and mitigate the powerful force of storm waves. As a type of macro-algae, kelp can grow as much as 2 feet per day, reaching heights of 100 feet from the seabed to the ocean surface. For those fortunate enough to experience diving through these underwater forests, it feels like entering a magical realm where sunlight streams through the kelp canopy like stained glass in a cathedral. Ford recalls his first dive, where he was captivated by the shimmering light and the vibrant colors of the fish swimming amongst the kelp.
However, these stunning environments faced significant threats in the past. When the Bay Foundation began its restoration efforts in 2012, the sea floor was a bleak sight, blanketed in purple, with endemic golf ball-sized spiky urchins dominating the landscape. This situation was symptomatic of an ecosystem in distress, suffering from various overlapping issues: sea otters, a natural predator of urchins, were nearly eradicated by hunters in the 19th century. Additionally, from the 1940s to the 1970s, a substantial amount of DDT was discharged from a chemical plant into the waters off Palos Verdes, further harming the ecosystem. More recently, local sea stars, which also prey on urchins, were devastated by a wasting disease, leaving behind only the insatiable urchins that ravaged the kelp.
To restore balance, Ford and the Bay Foundation conducted numerous tests to determine the optimal number of urchins per square meter: ideally, just two. In contrast, some areas were found to have a staggering 70-80 urchins per meter, functioning as “zombie urchins”—hollow shells that prevented kelp from growing. The Bay Foundation sought grants from state and federal authorities, recruited divers, and enlisted the help of 75 volunteers and commercial fishers. Ford emphasizes that their goal wasn’t to eliminate healthy urchins vital to local fisheries but to restore the ecosystem for future fishing opportunities.
One notable contributor to the restoration effort is Terry Herzik, a veteran red sea urchin fisher who has dedicated time to help the foundation since 2012, spending nine hours a day clearing urchins instead of collecting them for sale. “No one has more hours down there clearing urchins than Terry,” Ford remarks, highlighting the crucial role of collaboration in achieving restoration goals. Divers worked methodically, week after week, employing foot-long rock hammers to crush the urchins, a task described as satisfying yet labor-intensive. Johnson notes that while the work is repetitive, it’s rewarding, akin to fixing potholes in the ocean.
As the divers monitor the progress, they are encouraged by the rapid return of kelp following the removal of urchins. In some areas, kelp has reestablished itself within just a few months, thanks to microscopic kelp spores that drift in the water, waiting for the right conditions to take root. Johnson recalls one area where the kelp returned with astonishing density after just three months. As Taylor and Johnson resurface from their dive, they share their observations with Ford—lots of fish, a small shark, and a thriving kelp forest. However, they also note that some areas are still battling the expansion of urchins, leaving questions about why certain spots remain restored while others revert to barren landscapes.
The boat shifts to another location, and the divers descend once more. Here, the kelp forest is so dense that it forms a natural mat, holding the vessel in place. Ford humorously remarks about not needing an anchor. As we lift a kelp frond from the edge of the boat, we discover a colony of bryozoans—tiny filter-feeding invertebrates—nestled on the kelp's surface, along with shrimp and snails, showcasing the habitat's biodiversity. The kelp’s bulbs, which keep the structure buoyant, are just beginning to develop, a testament to the algae's remarkable growth rate.
The success of this project could serve as a model for kelp restoration efforts worldwide, with similar initiatives underway in Tasmania and South Korea. As climate change continues to impact ocean temperatures, kelp remains at risk; however, the restored sites are holding strong. Research from the Bay Foundation indicates that California spiny lobsters have returned to these areas, and fish such as kelp bass and sheepshead are now more abundant than before restoration efforts began. Furthermore, healthy kelp forests improve water quality by absorbing excess nutrients and stabilizing sediments, much like trees prevent soil erosion after heavy rains.
While the purple urchins have wreaked havoc on kelp forests, Ford reminds us that kelp has always faced challenges, including powerful waves that can uproot strands and summer temperatures that deplete essential nutrients. This resilience allows kelp to respond quickly to favorable conditions for regrowth. “The rapid response to restoration efforts is due to the system’s evolution to thrive under beneficial conditions,” Ford explains.
In light of these encouraging developments, it seems that the kelp forest may indeed have a fairytale future—one that supports the planet, enriches local communities, and enhances the coastline for generations to come.
