South Florida has the largest remaining subtropical wilderness in the United States, and contains the only shallow coral reef formation in the continental United States. The lush seagrass beds, mangrove-fringed shorelines, and nearshore coral reefs in Florida Keys National Marine Sanctuary provide food and shelter to more than 6,000 species of marine life and contribute $4 billion annually in tourism. South Florida is also on the front lines of climate change. Record-breaking water temperatures and other stressors such as ocean acidification, hypoxia (low oxygen), harmful algal blooms, and excessive nutrients are putting the future of these reefs at risk.