Mangroves and seagrass meadows are coastal ecosystems that cover a small portion of the total ocean area but collectively are widely distributed on every continent except Antarctica. Mangroves are found in 123 countries worldwide with an estimated area of 15.2 million hectares while seagrasses occur in 159 countries covering over 30 million hectares. These ecosystems are highly productive and form biologically rich habitats that play a major role in providing highly valuable ecosystem goods and services for human well-being. In spite of their importance to people, mangroves and seagrasses are amongst the coastal ecosystems that face the highest rates of loss globally, with estimated annual losses of 1–3% of mangroves area and 2–5% seagrass area. Over a quarter of the original mangrove cover has already been lost and almost 30 per cent of global seagrass area has been lost since the late nineteenth century.