Mangroves are among the most important ecosystems on the planet. They provide food and protection for a huge variety of marine and land-based species, sustain livelihoods of coastal populations, and provide protection from ocean swell and extreme weather events. Today, however, the worlds mangroves are under threat from several sources including coastal development and the impacts of climate change. This document, the second in a series of booklets on coastal ecosystems, is aimed at the general public, as well as decision-makers and coastal developers. It provides an overview of the worlds mangroves, a description of the threats to which they are subject and a summary of some of the actions being undertaken to protect them.