COMMENT CLIMATE From Kyoto to ECONOMICS Michael Mann CULTURE A poet’s clarity ENERGY There’s no free campaigning: an advocate- debates Naomi Klein’s Green navigates our rapidly lunch on a finite planet turned-activist reflects p.337 New Deal manifesto p.340 shifting world p.343 —do the maths p.344 THE OCEAN AGENCY/XL CATLIN SEAVIEW SURVEY SEAVIEW CATLIN THE OCEAN AGENCY/XL A green sea turtle (Chelonia mydas) swims over corals bleached by anthropogenic global heating. Save reefs to rescue all ecosystems An approach that tackles the underlying causes of coral-reef decline could be applied to other habitats, argue Tiffany H. Morrison, Terry P. Hughes and colleagues. ll the coral reefs in the world could floor, but they support almost 30% of the safeguard reefs: ecologists, conservationists, be gone by 2070 if global heating world’s marine fish species. Their loss has non-governmental organizations, national continues on its current path1,2. Since huge implications for biodiversity and for and regional policymakers, and philanthro- A1998, heatwaves have bleached or killed cor- the roughly 400 million people who depend pists. Such groups must address the causes of als in more than 90% of reefs listed as World on them for work, food and protection from reef ecosystem decline — not just focus on Heritage sites worldwide (including in the waves, storms and floods in more than biodiversity, or on trying to restore a particu- Galapagos Islands, Hawaii and Australia)2 100 countries across Australasia, southeast lar reef or region to some idealized ‘prior state’, (see ‘Under pressure’). In the Great Barrier Asia, the Indo-Pacific, the Middle East, the for instance by establishing marine parks. Reef, the world’s largest reef system, half of Caribbean and the tropical Americas. Policymakers in Australia, say, should try to the corals died in 2016 and 2017 alone3. We think a change in approach is urgently change land use in the 425,000-square-kilo- Coral reefs cover only 0.5% of the ocean needed from the slew of groups striving to metre catchment of the Great Barrier Reef. ©2019 Spri nger Nature Li mited. All ri ghts reser19ved . SEPTEMBER 2019 | VOL 573 | NATURE | 333 COMMENT Currently, they funnel some US$14 million diabetes, cardiovascular disease and cancer, can convey a misleading message: that the each year into local-scale approaches such as have risen in part because of the dietary and decline of coral reefs is solvable without rapid, coral gardening to restore damaged reefs. lifestyle changes that have accompanied peo- co ordinated action on climate change caused Instead, they should replace coal-fired power ple’s increased reliance on imports. (Six years by human activity. with renewable energy sources, develop land- ago, these diseases caused 80% of all deaths; We think that a bolder approach to the based aquaculture (which avoids the release in 2017, they caused 86%6.) governance of coral reefs should be inspired of animal waste and anti biotics into the sea), The decline of reefs, especially in the past in part by ecological theory on synergistic and restore or rehabilitate terrestrial vegeta- five years, has prompted scientists, policy- effects11. tion, wetlands, mangroves and seagrass. All makers, non-governmental organizations of these actions would simultaneously reduce and philanthropists to undertake increasingly MAKE CHANGES ON LAND AND SEA emissions, capture carbon, curb agricultural desperate attempts to Over the past decade, ecologists have found runoff onto coastal reefs and enhance people’s “Done right, save or restore targeted that the response of reefs to any one pressure, livelihoods and food security. Thus, the ben- efforts to save coral species. (The such as overfishing or pollution, is typically efits would extend far beyond the preservation reefs could most recent 2014–17 non-linear. Numerous feedbacks and multi- of coral reefs. protect other global bleaching event ple drivers reinforcing each other can lead to There is enormous interest in coral reefs ecosystems.” was the longest ever new stable states11. For example, agricultural worldwide, and growing concern about the recorded, and caused runoff can promote the growth of algae that pace of their decline. Done right, efforts to save around 70% of the world’s reefs to bleach once compete with corals for space — a problem reefs could protect other ecosystems by safe- or more in consecutive, record-breaking hot that is exacerbated by the overfishing of her- guarding coastal catchment areas and provid- years7.) bivores. Under many pressures, the capacity ing a model for similar approaches that could In Australia, engineers are using a robot of corals to reassemble after disturbances be applied to diverse systems. Indeed, the to disperse coral larvae to degraded sites and might be so reduced that a new stable eco- plight of coral reefs could finally help to push experimenting with underwater fans to cre- system results, often consisting mainly of nations past a societal and political tipping ate cooling, artificial upwellings. In Florida, mats of algae or cyanobacteria. point, where the protection of ecosystems, surviving corals are being transferred from The sustained protection of coral reefs with their multiple services and functions, is degraded reefs to aquaria to rescue them similarly requires making many changes at seen as socially and politically necessary. from disease. In many countries, artificial once: reducing greenhouse-gas emissions, reefs are being built to promote biodiversity, rebuilding fish stocks and improving water HEAT STRESS or corals are being reared in the laboratory or quality. This requires policymakers to work Raised sea temperatures during heatwaves can in underwater ‘nurseries’ and later transferred with a much broader range of social actors, kill sensitive corals or prompt them to expel to reefs. Coral sperm are even being frozen in including commercial and recreational the beneficial microscopic algae (Symbio- the hope that populations could be restored fishers, farmers, the tourism industry, min- dinium and related genera) living in their tis- in the future8. ing companies, energy providers, property sues, resulting in mass bleaching. Over one or Such interventions are difficult, expen- developers and individual citizens. two decades, most coral populations depleted sive and labour-intensive. Replanting coral The importance of such broader-scale, by bleaching can recover. But the gap between fragments grown in a nursery costs between synergistic policy interventions to protect consecutive bleachings has shrunk drastically $1 million and $4 million per hectare9. Thus, ecosystems is starting to be recognized in — from an average of 25 years in the 1980s to even without factoring in ongoing mainte- multilateral policy agreements; by major just 6 years since 2010 (ref. 4). nance, restoring 10 km2 of reef would cost environmental non-governmental organi- Already, people in the 22 small-island in the region of $1 billion9. None of these zations and international aid agencies; and nations and territories of the southwest approaches will restore the ecological func- even by some countries. Pacific have increased their reliance on tions of reefs at a meaningful scale. (Indeed, The Ramsar Convention on Wetlands of imported foods, including canned meats given the current levels of human influence International Importance, for example, now and packaged products, in part because of on the environment, restorations to past highlights how the conservation of wetlands depleted fish stocks. Food imports to coun- ecological conditions and past levels of bio- can help to achieve multiple goals. They can tries such as Samoa and Tonga now exceed diversity are no longer possible10.) What’s conserve biodiversity, act as carbon sinks total exports5. What’s more, deaths in the more, small-scale attempts at coral garden- and provide ecosystem services such as pro- Pacific from preventable diseases, such as ing, aquarium breeding and cryopreservation tection against flooding. (In 1971, when the convention was established, it focused much UNDER PRESSURE more on the conservation of species than on Coral reefs listed as World Heritage sites have been increasingly the broader benefits of wetlands.) aected by regional and global bleaching since 1980. Likewise, non-governmental organizations Regional bleaching event Global bleaching events are beginning to combine ecological, eco- 30 nomic and social interventions to help sustain ecosystems. For instance, environmental char- 25 ity the Nature Conservancy in Arlington, Vir- ginia, is considering funding the installation 20 By 2017, 27 out of the 29 of sewage-treatment plants and other infra- World Heritage reefs had structure that would improve public health experienced bleaching. 15 as well as prevent sewage from reaching coral INFORMATION SOURCE: SEE SUPPLEMENTARY reefs12. And agricultural research and develop- 10 ment agencies, such as CGIAR in Montpel- lier, France, are supporting integrated national Cumulative number reefs of 5 policies for agriculture and the environment in Pacific island nations to address the declin- 0 ing supply of reef fish and the altered move- 1978 1981 1984 1987 1990 1993 1996 1999 2002 2005 2008 2011 2014 2017 ment of pelagic stocks due to climate change. 334 | NATURE | VOL 573 | 19 SEPTEMBER 2019©2019 Spri nger Nature Li mited. All ri ghts reserved. ©2019 Spri nger Nature Li mited. All ri ghts reserved. ALEXIS ROSENFELD/GETTY Biologists track corals in nurseries amid renewed