By Siobhan Murphy, Marine Conservation Institute Communications Intern
In our exploration of blue carbon so far, we’ve swum through dense mangrove forests and snorkeled over swaying seagrass meadows. Now, let’s head to cooler waters. Grab your wetsuit and dive with us into a towering kelp forest!
Kelps are large, typically brown seaweeds, of the order Laminariales. The 27 species of kelp and their ecosystems grow on rocky reefs in shallow, temperate waters around the world. For some marine fish and invertebrates, kelp towers and their canopies are an essential refuge from predators and storms. Seabirds, such as kelp gulls and great blue herons, use kelp forests as floating buffets of flies, maggots and crustaceans.
Kelps are also very valuable to humans, as we use them in products like toothpastes, salad dressings and even pharmaceuticals. Kelp contains an emulsifying and bonding agent called algin, which is used in many products as well. The environmental benefits of kelp go far beyond these everyday uses though!
Like seagrass and mangrove ecosystems, kelp capture ‘blue carbon’ and help mitigate climate change. Kelp takes up carbon and respires oxygen the same way terrestrial plants do. If its stored a very long time, some kelp-sequestered carbon can even reach deep-sea sediment and enter the rock cycle. Sadly, more and more kelp forests are being lost, limiting their role in the carbon cycle and ability to fight climate change.
Kelp forests are highly dynamic ecosystems that are sensitive to physical, chemical and biological changes in their environment. Climate change, coastal development, increased nutrient run-off and fishing all threaten kelps globally. Along the northern California coast alone, kelp cover has decreased by 90% since 2014! Researchers have theorised that the decrease is a consequence of a recent heatwave and invasive species. Australia’s shores have similarly experienced a 38% decrease in kelp cover, and have seen it replaced by tightly-packed bushy seaweeds that accumulate sediment and block kelp regrowth. Other recent ecological changes have hurt kelp populations as well.
One threat posed to kelps are the growing sea urchin populations around the world. Within kelp ecosystems off California, sea otters and sea stars used to feast on these spikey invertebrates. Due to previous hunting pressure and newer threats like coastal development, the number of sea otter pups in California remains low relative to historic levels. As for sea stars, a mysterious disease called sea star wasting disease (SSWD) has crippled U.S. sea star populations along the West Coast. SSWD causes lesions and tissue decay all over the echinoderm’s bodies, eventually causing death. With fewer sea stars and sea otters around, sea urchin numbers have grown by 300% and this exploding population has devoured 30% of U.S coastal kelp density. This decimation is worsened by the rising human demand for kelp.
Demand for kelp as a food product, source of algin and aquaculture feed is increasing. Commercial harvesting of kelps can harm these forests: for example, the kelp industry in Norway has adopted a dredging technique that rips canopy-forming kelp from the rock. Because of this technique, the abundance of kelp-supported small fish in some study areas has declined by 85% in comparison to non-harvested areas. A recent kelp harvesting proposal in Scotland also faced backlash for potentially destroying these ecosystems. Thankfully, it is not all doom and gloom for kelp forests today.
With their carbon sequestering powers gaining increased recognition, kelps are receiving more conservation attention. In the U.S. National Marine Sanctuaries, harvesting kelp for commercial use is now strictly regulated. The Channel Islands National Marine Sanctuary off California even has a Kelp Forest Monitoring Program dedicated to boosting their protection. Across the Pacific, Australia is also stepping up to protect its kelp forests: after Tasmania saw 95% of its kelp vanish, the Australian government granted its kelp forests ‘endangered’ status. It marked the first time an entire ecological community has been given this protection under their federal law. Please explore our Marine Protection Atlas to find other marine reserves that protect kelp ecosystems.
It is encouraging to see more nations recognising the importance of kelp and protecting these forests. Kelp still faces many threats, so we will keep raising awareness of kelps and working to expand and improve marine protected areas to save their vital ecosystems. Together, we can ensure that kelp forests thrive again!