Fishermen like Jose da Cruz have made their living for decades hunting for crabs among Brazil's vast coastal mangrove forests, dense thickets of twisted plants in deep black mud that grow where fresh-water rivers meet the brackish Atlantic Ocean. Cruz doesn't use a rod and reel or a net. Instead he parks his two-foot-wide boat at the shore of the Caratingui river and wends his way on foot through the tangle of mangroves to dig out crabs with his hands from the dark muck. The four or five dozen he captures in a day will earn Cruz about 200 reais ($50) per week, enough to get by, he said. But this tenuous livelihood is facing a series of threats, including rapid alterations to the environment caused by climate change, and Cruz's average daily catch is half of what it was 10 years ago. In that time, the water line has advanced 3 meters inland from where it used to be, according to Cruz. Climate scientists lend credence to Cruz's interpretation of what he sees. Rising water levels, they say, are a sign of global warming, which also causes water temperatures to rise, killing off some marine life. Globally, scientists have warned that water temperatures are increasing far faster than expected, which drives rising sea levels. Climate change and human development are putting 1 million species, a large share of which live in marine environments, at risk of extinction, according to a report published this year. These changes in turn are threatening the dozen or so families in Cruz's village that depend on the coastal ecosystem.