The Amazon basin, with the river it’s named for, is crucial to the global water cycle. As deforestation lays waste to this vast region, funding, investment, and deep understanding of the issues at stake are needed to stem the onslaught. In 2019, 30 global financial managers pleaded with Brazil's leaders to bring fires and deforestation in the Amazon under control—pleas that were rejected for economic and political reasons. But estimates show that a shift to a low-carbon and sustainable economy could immediately benefit Amazonia, creating more than 2 million jobs and adding US$535 billion to Brazil’s GDP alone. Many investors and donors want to help the region but fear criticism and political and market risks, and are perplexed by the complexity and lack of information. As deforestation nears a tipping point, investing in the Amazon's conservation may be the climate-mitigation investment opportunity of the current decade. How do investors find the balance between sustainability and profitability?