The decline of California's kelp forests since the marine heat wave of 2013–17 has seen only minor recovery despite heroic efforts at restoration carried out by scientists, fishermen, coastal tribes, volunteer divers and conservationists. Nor is the threat to kelp localized. Rather, the loss, like the expansion of mega-wildfires on land from Los Angeles to Siberia and from Canada to Australia, comes in response to an ever-warming world where 90% of the human-generated heat from the burning of fo...