Last year, a major United Nations climate report underscored a grim reality: Humanity is pushing the world’s oceans to the brink. By the end of the century, the report’s authors wrote, more of the world’s seas could be hot, acidic and lifeless — with catastrophic implications for marine life, the climate and for the food security of billions of people. But as grave as the report’s findings were, experts say, there is reason for hope. Through ambitious alliances and innovative engineering, conservationists are working tirelessly in 2020 to prevent the UN’s stark warning from becoming reality. Here are three approaches that Conservation International scientists are pioneering to conserve the oceans on a global scale. Mixing “green” with “gray” to protect coastal communities Limb for limb, the mangrove is perhaps the most important tree species on Earth .…