Australia has large areas of seagrass, rich in diversity, which flourish in clear, relatively low-nutrient coastal waters. Seagrass losses in recent years have been extensive with over 45 000 ha lost. The major widespread human-induced declines of seagrass, from 11 sets of locations around Australia, are summarized. The reasons for these losses are discussed, most being attributable to reduced light intensity, but in many cases, other factors interact to make the process of loss more complex. These declines result in loss of habitat and productivity, and increased sediment mobility. Recovery and recolonization from such losses are rare; thus, the destruction of seagrass has long-term consequences. Increasing awareness of the risks and better understanding of seagrass systems is leading to better management practices.