Human Development Drives Global Estuary and Delta Loss

Economy and population growth along coastal environments are rapidly increasing, and threaten estuarine and deltaic systems. Recent anthropogenic alterations have led to changes in sediment supply, so that estuaries and deltas in sediment depleted areas remain vulnerable to marine processes. Here, we compared the 20^th century extent of estuaries and deltas to modern aerial images throughout the world to identify long-term and short-term drivers of estuarine change, and how they vary with coastal development. We identified the extent and shape (change in width throughout the estuary) of more than 4,000 estuaries and deltas worldwide, and compared to local dam construction and land use practices to determine main drivers of estuarine change. Preliminary results suggest that global estuaries and deltas have decreased by more than 5,000 km² within the last 30 years, where areal loss is influenced primarily by local farming activity and dam occurrence. Therefore, estuaries tend to contract following dam installment and where agriculture practices are high. Interestingly, post-industrial estuarine change (early 1900s – 1975) may greatly exceed modern change (1984 – 2015). These observations suggest that estuaries and deltas respond quickly to anthropogenic alterations, and the possibility that further human changes may lead to long-term loss of major coastal environments.