Aaron Matthius Eger, Ezequiel Marzinelli, Rodrigo Baes, Caitlin Blain, Laura Blamey, Paul E. Carnell , Chang Geun Choi, Margot Hessing-Lewis, Kwang Young Kim, Julio Lorda

Underwater kelp forests have provided valuable ecosystem services for millennia. However, the global economic value of those services is largely unresolved. Kelp forests are also diminishing globally and efforts to manage these valuable resources are hindered without accurate estimates of the services kelp forests provide to society. We present the first global economic estimation of services - fisheries production, nutrient cycling, and carbon removal - provided by four major forest forming kelp genera (Macrocystis, Nereocystis, Ecklonia, and Laminaria). Each of these genera provides between $135,200 and $177,100/ ha/ year. Collectively, they contribute $684 billion/year worldwide. These values are primarily driven by fisheries and nitrogen removal, but kelp forests also have the potential to sequester 2.7 megatons of carbon from the atmosphere/year and may be considered blue carbon systems valuable for climate change mitigation. These findings highlight the value of kelp forests to society and will enable informed marine management decisions.