Kelp forests grow along roughly 25 percent of the world’s coastlines and provide valuable habitat and nutrients for many types of aquatic life. Now, research by the “Floating Forests” project is shedding light on how these underwater kelp forests are affected by climate change. The project is using NASA satellite data to observe changes in kelp forests over a period of more than four decades. The catch: No accurate way to automate the process exists, so the researchers rely on an international team of nearly 3,500 citizen scientists to mark the bright green kelp forests, which stand in stark contrast to the deep blues of the ocean in the images. In addition to the California coast, shown above, the project has focused on kelp forests off the coast of Tasmania, where a 95-percent decrease in kelp forest populations led the Australian government to classify kelp forests as an endangered ecological community — the first time the country has granted such protection to an entire community. Elsewhere, kelp populations have been negatively affected by warmer waters with fewer nutrients, new types of invasive species, and severe storms, underlining the importance of keeping these ecosystems under close observation in the face of climate change.