Most people can appreciate the majesty of a terrestrial forest. Deep in the woods there is a sense of spirituality that comes from being surrounded on all sides by trees that soar skywards. Forests aren’t known as nature’s cathedrals for nothing, made all the more beautiful by the fact that these forest ecosystems seem to positively vibrate with life. The ocean harbors forests of its own, forests that far fewer people will ever see for themselves. Made of kelp instead of wood, these underwater forests are recognized as one of the most productive and dynamic ecosystems on Earth.
Comprising several species of vertically growing brown algae, kelp requires cool, relatively shallow coastal waters to flourish. It favors areas rich in nutrients, and due to its dependency on natural light for photosynthesis, it is rarely found deeper than 130 feet (40 m). Under the right conditions, kelp strands can grow as much as 18 inches (45 cm) per day, and are kept vertically buoyant by gas-filled bladders located at the base of each frond. In some temperate parts of the world, groups of these towering kelp strands have formed far-reaching forests that provide food and shelter for an astounding number of marine organisms. Kelp forests are particularly important as nurseries for juveniles, and as such, are vitally important to the marine environments in which they occur.
Humanity has found countless uses for kelp throughout our history. Fishing communities have depended upon the rich bounty generated by kelp ecosystems while others have harvested the algae as food in its own right. Today, kelp is used as feed for aquaculture species and in the manufacture of several cosmetic and pharmaceutical products. Kelp forests also constitute some of the world’s most unique dive sites, and wherever they occur, scuba divers flock to discover their secrets for themselves.
California
North America’s Pacific coast is home to the world’s most prolific kelp forests, which stretch all the way from northern Baja to the frigid waters of Alaska. California is perhaps the most well known kelp-diving destination, thanks to the magnificent forests that flourish along the shores of several spots, including Monterey Bay, the Northern Channel Islands and Catalina Island. The California coast boasts the ideal conditions required to encourage kelp growth, particularly at Monterey, where the plunging depths of the Monterey Submarine Canyon cause significant upwellings of life-giving, nutrient-rich water.
California’s kelp forests provide sanctuary and grazing for an incredible number of marine species, including sharks, whales, cormorants, great blue herons, and of course, a multitude of fish. California’s kelp forests are particularly famous for their pinnipeds. Seals and sea lions create their rookeries near the kelp forests, and use them alternatively as a hunting ground, as a source of refuge, and as a playground. Some California kelp forests are also home to the endangered sea otter, an iconic species that has long been associated with these unique marine ecosystems. Kelp provides an anchor for the otters, who wrap themselves in its strands while they sleep; in turn, the otters help maintain the kelp forests by eating the urchins that prey upon the lower sections of the strands, consequently severing and killing them.
Cape Town, South Africa
The cool waters of South Africa’s cape are also home to abundant kelp forests, comprised of two species that are both endemic to South Africa. These forests fulfill a similar function to their California counterparts, providing food and shelter for a wealth of marine life, ranging from commercial species like lobster and abalone to top predators like the Cape fur seal. Perhaps the most fascinating aspect of the cape kelp forests is the variety of shark species that call these pseudo-arboreal environments home. The kelp forests of False Bay are home to a number of rarely seen shark species, including the charismatic pyjama catshark and the shy spotted-gully shark.
By far the most famous inhabitant of False Bay’s kelp forests, however, is the sevengill cow shark, or broadnose sevengill shark as it is also sometimes known. This bizarre-looking animal is one of the most prehistoric of all shark species, and is the only extant member of its genus. It is notably recognizable by its gills, having seven gill slits instead of the conventional five possessed by other sharks. Sevengill cow sharks are social feeders, and can be observed in groups of up to 18 individuals. To see these prehistoric predators in action is a truly memorable experience that should be on every diver’s bucket list.
Tasmania
Giant kelp forests were once plentiful along the shores of southern Australia and Tasmania. Today, these ecosystems have shrunk to small pockets, centered around Munro Bight and Bruny Island. There, the towering kelp forests still sustain exceptional concentrations of biodiversity, most famously providing a home for endemic species like the weedy seadragon, the pot-bellied seahorse and the golden weedfish.
Sadly, Tasmania’s kelp forests are now more famous as examples of the fragility of these incredible ecosystems than for the marine creatures that live there. According to The Institute for Marine and Antarctic Studies, there has been a 95 percent decline in Tasmania’s east-coast kelp forests since the 1940s. It is thought that the most significant contributor to this drastic loss is the rising temperature of Tasmanian waters as a direct consequence of climate change. Tasmania is particularly susceptible to the effects of this phenomenon, with sea temperatures here increasing by up to 35 F/1.5 C in the last decade alone. Additionally, overfishing has caused the explosion of benthic herbivores like sea urchins, which in turn have negatively impact the region’s kelp beds. Climate change and overfishing are global problems, and, as such, all kelp forests are at risk of suffering similar declines in the near future.
Charles Darwin recognized the importance of kelp forests over 180 years ago, when he wrote “I can only compare these great aquatic forests with the terrestrial ones in the intertropical regions. Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here, from the destruction of kelp.” As divers, we can contribute to the conservation of the world’s remaining kelp ecosystems simply by paying to visit them. Kelp is already financially important in its harvested form, but dive tourism makes these majestic underwater forests valuable in their untouched, natural state as well. California, for example, is the kelp-diving capital of the world. It is also home to a statewide network of Marine Protected Areas, many of which work to ensure the future health of the region’s spectacular kelp forests.
So, when you next get the chance, go kelp diving. Experience the wonder of these utterly unique, entirely majestic aquatic forests; and in the process, discover for yourself precisely why they are so worth protecting.
