WCMC Global Seagrass Database

Seagrasses are valuable and overlooked habitats, providing important ecological and economic components of coastal ecosystems worldwide. Although there are extensive seagrass beds on all the world's continents except Antarctica, seagrasses have declined or been totally destroyed in many locations.

As the world's human population expands and continues to live disproportionately in coastal areas, a comprehensive overview of coastal resources and critical habitats is more important than ever. The World Atlas of Seagrasses documents the current global distribution and status of seagrass habitat.

Seagrasses are a functional group of about 60 species of underwater marine flowering plants. Thousands more associated marine plant and

animal species utilize seagrass habitat. Seagrasses range from the strap-like blades of eelgrass ( Zostera caulescens) in the Sea of Japan, at more than 4 m long, to the tiny, 2-3 cm, rounded leaves of sea vine (e.g. Halophila decipiens) in the deep tropical waters of Brazil. Vast underwater meadows of seagrass skirt the coasts of Australia, Alaska, southern Europe, India, east Africa, the islands of the Caribbean and other places around the globe. They provide habitat for fish and shellfish and nursery areas to the larger ocean, and performing important physical functions of filtering coastal waters, dissipating wave energy and anchoring sediments. Seagrasses often occur in proximity to, and are ecologically linked with, coral reefs, mangroves, salt marshes, bivalve reefs and other marine habitats. Seagrasses are the primary food of manatees, dugongs and green sea turtles, all threatened and charismatic species of great public interest.

Seagrasses are subject to many threats, both anthropogenic and natural. Runoff of nutrients and sediments from human activities on land has major impacts in the coastal regions where seagrasses thrive; these indirect human impacts, while difficult to measure, are probably the greatest threat to seagrasses worldwide. Both nutrient and sediment loading affect water clarity; seagrasses' relatively high light requirements make them vulnerable to decreases in light penetration of coastal waters. Direct harm to seagrass beds occurs from boating, land reclamation and other construction in the coastal zone, dredge-and-fill activities and destructive fisheries practices. Humaninduced global climate change may well impact seagrass distribution as sea level rises and severe storms occur more frequently. The World Atlas of Seagrasses makes it clear that seagrasses receive little protection despite the myriad threats to this habitat.

Most of our understanding of seagrass ecosystems is based on site-specific studies, usually in developed nations. Very little is known about the importance of seagrasses in maintaining regional or global biodiversity, productivity and resources, partly because seagrasses are under-appreciated and their distribution is so poorly documented. As a result, seagrasses are rarely incorporated specifically into coastal management plans and are vulnerable to degradation.

Seagrass ecosystems in the Caribbean, Indian Ocean, Southeast Asia and Pacific are especially poorly researched, yet it is in these regions that the direct economic and cultural dependence of coastal communities upon marine resources, including seagrasses, tends to be highest.

The purpose of the World Atlas of Seagrasses is to present a global synthesis of the distribution and status of seagrasses. Such syntheses are available for other coastal ecosystems and have been instrumental in creating awareness, driving clearer conservation and management efforts and focusing priorities at the international level. For example, over the last ten years, opinion on the status of coral reefs has changed from a predominant view that the majority of coral reefs were unaffected by human activities, to the present view in which the global decline of coral reefs, and the increasing threats to them, are widely acknowledged. A similar understanding of seagrass ecosystems is needed in order to achieve the visibility and recognition necessary to protect this valuable global resource. Public perception translates into political interest. Perceptions of seagrass ecosystems must achieve comparable status with those of coral reef and mangrove ecosystems, through the creation of global maps, global estimates of loss, knowledge of human impacts to the ecosystem, regular monitoring of ecosystem status and a global plan of action to reverse seagrass ecosystem decline. It is our hope that the World Atlas of Seagrasses will contribute to the more widespread recognition, understanding, and protection of seagrass ecosystems worldwide.