afforded through habitat restoration are poorly understood. Given the relatively high-per-unit area costs of marine habitat restoration, making the case for such work requires a thorough examination of the ecosystem service benefits of such new habitat creation. Global distribution Seagrass meadows are found in the shallow seas of the continental shelves of all continents except Antarctica. Continental shelves are underwater areas of land surrounding each continent, creating areas of relatively shallow water known as shelf seas. The grasses live in areas with soft sediment that are either intertidal (uncovered daily by seawater, as the tide goes in and out) or subtidal (always under the water). They prefer sheltered places, such as shallow bays, lagoons, and estuaries (sheltered areas where rivers flow in to the sea), where waves are limited and light and nutrient levels are high. Seagrasses can survive to maximum depths of about 60 metres. However, this depends on the availability of light, because, like plants on the land, seagrass meadows need sunlight if photosynthesis is to occur. Tides, wave action, water clarity, and low salinity (low amounts of salt in the water) control where seagrasses can live at their shallow edge nearest the shore; all of these things must be right for seagrass to survive and grow. The current documented seagrass area is , but is thought to underestimate the total area since many areas with large seagrass meadows have not been thoroughly documented. Most common estimates are 300,000 to 600,000 km2, with up to 4,320,000 km2 suitable seagrass habitat worldwide. Ecosystem services Seagrass meadows provide coastal zones with significant ecosystem goods and services. They enhance water quality by stabilizing heavy metals and other toxic pollutants, as well as cleansing the water of excess nutrients, and lowering acidity levels in coastal waters. Further, because seagrasses are underwater plants, they produce significant amounts of oxygen which oxygenate the water column. Their root systems also assist in oxygenating the sediment, providing hospitable environments for sediment-dwelling organisms. Additionally, the conservation of seagrass meadows contributes to 16 of the 17 UN Sustainable Development Goals. As shown in the image above on the left, many epiphytes can grow on the leaf blades of seagrasses, and algae, diatoms and bacterial films can cover the surface. The grass is eaten by turtles, herbivorous parrotfish, surgeonfish, and sea urchins, while the leaf surface films are a food source for many small invertebrates. Blue carbon The meadows