The value of ecosystem services in global marine kelp forests

Article https://doi.org/10.1038/s41467-023-37385-0 The value of ecosystem services in global marine kelp forests Received: 24 May 2021 Accepted: 14 March 2023 1234567890():,; 1234567890():,; Check for updates Aaron M. Eger 1,2 , Ezequiel M. Marzinelli3,4,5, Rodrigo Beas-Luna 6, Caitlin O. Blain7, Laura K. Blamey 8, Jarrett E. K. Byrnes 9, Paul E. Carnell Chang Geun Choi 11, Margot Hessing-Lewis12,13, Kwang Young Kim14, Naoki H. Kumagai 15, Julio Lorda 16, Pippa Moore17,18, Yohei Nakamura19, Alejandro Pérez-Matus20,21, Ondine Pontier 12, Dan Smale 22, Peter D. Steinberg1,4,5 & Adriana Vergés 1,5 10 , While marine kelp forests have provided valuable ecosystem services for millennia, the global ecological and economic value of those services is largely unresolved. Kelp forests are diminishing in many regions worldwide, and efforts to manage these ecosystems are hindered without accurate estimates of the value of the services that kelp forests provide to human societies. Here, we present a global estimate of the ecological and economic potential of three key ecosystem services - fisheries production, nutrient cycling, and carbon removal provided by six major forest forming kelp genera (Ecklonia, Laminaria, Lessonia, Macrocystis, Nereocystis, and Saccharina). Each of these genera creates a potential value of between $64,400 and $147,100/hectare each year. Collectively, they generate between $465 and $562 billion/year worldwide, with an average of $500 billion. These values are primarily driven by fisheries production (mean $29,900, 904 Kg/Ha/year) and nitrogen removal ($73,800, 657 Kg N/Ha/year), though kelp forests are also estimated to sequester 4.91 megatons of carbon from the atmosphere/year highlighting their potential as blue carbon systems for climate change mitigation. These findings highlight the ecological and economic value of kelp forests to society and will facilitate better informed marine management and conservation decisions. “The number of living creatures of all Orders, whose existence intimately depends on the kelp is wonderful.” – Charles Darwin 18451 Vast underwater forests of kelp (defined here as brown macroalgae in the order Laminariales) along polar to subtropical coastlines have enormous value to peoples across multiple continents and eras. Archaeological excavations show how kelp forests facilitated southward travel for early peoples in the Americas some 20,000 years ago. During this migration, people relied on the food provided by kelp forests to survive2. Subsequently, ecological management of kelp forests has occurred since approximately 3000 BCE in the NE Pacific, with peoples regulating harvest and transplanting kelp to enhance growth and trap fish roe3. In the NW Pacific, kelp harvesting has played A full list of affiliations appears at the end of the paper. Nature Communications | (2023)14:1894 an important role in Japanese, Korean, and Chinese economies since the 8th century, where it is eaten as food and supports a myriad of associated plants and animals, many of which are also harvested. In Europe, kelp has been used for many centuries to fertilize soil and increase crop yields, treat illnesses caused by iodine deficiency and, for many centuries, as the base in the production of soda ash4. In the 20th and 21st centuries kelp forests have become the main source of alginate (also known as algin from alginate-yielding seaweeds), a common food, medical and bioengineering additive5. Globally, kelp forests provide habitat for important fisheries of abalone, lobsters, reef fishes, and kelp itself6. Additionally, through their high productivity, kelp forests draw carbon from the atmosphere7, release oxygen8, and help e-mail: 1 Article https://doi.org/10.1038/s41467-023-37385-0 reduce marine nutrient pollution9,10. Long before Charles Darwin wrote his essay on the Patagonian kelp forests, these habitats provided essential services for human society that continue to this day. The fact that kelp forests have cultural and socioeconomic importance is not disputed, but the magnitude and economic values of these ecosystems are poorly understood11–13. Relevant research on kelp forests to date has generally grouped kelp with other marine habitats as “coastal systems”14, treated values from limited genera as representative of not just kelps but all macroalgae15, or has not assigned a monetary value to the services provided16. This knowledge gap leads to an underappreciation of their contribution to nature and people. Since both the economic value of ecosystems and the recognition of their ecological and cultural importance are increasingly major considerations for conservation and natural resource management, the lack of value estimates for kelp ecosystems is a barrier to effective management and policy17. For example, societies are increasingly considering active kelp forest restoration and management strategies to combat regional declines in kelp forests18,19. However, restoration may not be pursued if the costs outweigh the perceived benefits20. Furthermore, while kelp forests are valued to some degree by ocean users21,22, they are not perceived to be high-value ecosystems to the public23,24, which can limit public support for kelp conservation and restoration25,26. Moreover, quantifying and valuing services provided by marine ecosystems is an important goal in the context of the UN Decade of Ocean Sciences, achieving the UN Sustainable Development Goals, growing the field of ocean accounting, and cost-benefit analyses27–29. Regional economic valuations of kelp forests which have incorporated various ecosystem services (e.g. harvest, fisheries, and tourism) have estimated regional kelp forests to be worth between $290 million (e.g. Ecklonia and Laminaria forests in South Africa)30 and USD $540 million per year (e.g. Lessonia and Macrocystis forests in CentralNorthern Chile)12. In Australia, Bennett et al. (2016)23, valued the ~71, Fishery biomass (Kg Ha−1year −1) 20000 3412 Kg 668 Kg 1868 Kg 2269 Kg $28,307 $33,382 $ 8,309 $26,353 $61,971 N = 264 2426 Kg N = 370 N = 44 N = 610 N = 68 15000 Ocean Region NE Atlantic NE Pacific NW Atlantic NW Pacific S Atlantic SE Pacific Southern SW Pacific 10000 5000 0 Ecklonia Laminaria Lessonia Macrocystis Nereocystis & Saccharina Fig. 1 | Fisheries biomass and associated economic value provided by kelp forests. Site (unique time and location) yearly total biomass and the economic value of the harvestable fisheries production per hectare per year. The values are represented for each kelp genus, colours represent the ocean region, the black triangle and number values represent the mean value for the genus, the error bars are the standard error. Note: the sample size represents the number of points used for calculation, though 70–90% of points for Ecklonia, Laminaria & Saccharina (previously classified as Laminaria in some regions), and Macrocystis have been randomly removed from the graph fo (...truncated)