Environment: Extensive wetland losses in past three centuries

The world lost about 20% of its natural wetlands between 1700 and 2020, according to a study published in Nature this week. The findings may provide a basis for assessing the impact of wetland loss on the wider environment.

Wetlands provide important ecosystem services but are often drained and converted for urbanization or agricultural development. It has been challenging to adequately map wetland loss at a global scale. Previous research has suggested that at least 50% of wetland has been lost since 1900, although estimates range between 28% and 87% net loss since 1700. Such a wide range of figures makes it difficult to assess the environmental impact of wetland conversion.

Etienne Fluet-Chouinard and colleagues reconstruct the timing and spatial distribution of wetland loss due to human intervention by combining 3,320 international and regional records of wetland drainage and land conversion from 154 countries with existing data on land usage and simulated wetland extent. They estimate that 3.4 million km2 of inland wetlands have been lost since 1700 — a net loss of 21% of global wetlands, which is supported by existing regional estimates of loss. The most common causes of wetland disappearance were drainage for upland crops, conversion to flooded rice fields, and urban development. The drivers for conversion varied by region, and the authors note that wetland loss has been concentrated in Europe, the United States and China.

This study documents an environmental shift at the global scale and could be a crucial resource for monitoring how human activity is influencing environmental change, the authors conclude.