A second chance to protect wetlands

Wetlands are vitally important for our nature due to the storage of large amounts of carbon and the wealth of biodiversity. However, wetlands are among the most threatened ecosystems in the world. New research published in Nature shows that the loss of wetlands areas around the globe since 1700 has likely been overestimated. That’s good news, you might think. But there are still significant differences between regions, several of which are severely threatened. For example, floodplains in riverine areas have been highly impacted, while remote boreal-arctic peatlands remain comparatively unharmed. Kees Klein Goldewijk, co-author of this study and a researcher at Utrecht University, provided his HYDE database that forms an important foundation for this study. This research offers new perspective in the recovery and protection of these special areas.

Historical reconstruction offers new insights

While they are now understood to be vital sources of water purification, groundwater recharge, and carbon storage, wetlands were historically seen as unproductive areas teeming with disease-bearing insects and good only for draining to grow crops or harvest peat for fuel or fertiliser. Over time, unrelenting drainage for conversion to farmland and urban areas, combined with alteration caused by fires and groundwater extraction, have made wetlands among the world’s most threatened ecosystems.

Until now, a lack of historical data has hindered efforts to understand the full global impact of wetland loss, forcing scientists to make estimates based on incomplete collections of regional data. The database provided by Kees Klein Goldewijk reflects global agricultural land use over a period between 10,000 BCE to 2015 CE. This data has been further enriched by researchers at Stanford, Cornell and McGill universities with data from 154 different countries.

Decline less than expected, still area of concern

The researchers found that the area of wetland ecosystems has decreased by 21-35% since 1700 due to human intervention. This is far less than the 50-87% losses estimated in previous studies. The lower estimate is likely due to the fact that this study is not limited to regions with historically high wetland loss. Still, the authors estimate that at least 3.4 million wetlands have been lost worldwide over the past 300 years - an area about the size of India. Five countries with the largest losses - the U.S., China, India, Russia and Indonesia - alone account for more than 40% of global losses.

“Many regions of the world have sustained dramatically high wetland losses, but our results suggest that losses are lower than previously thought when aggregated globally. Yet, it remains urgent for us to halt and reverse the conversion and degradation of wetlands, particularly in high-loss regions. The geographic disparities in losses are critical because the local benefits from drained wetlands cannot be replaced by wetlands elsewhere,” said lead author Etienne Fluet-Chouinard, a postdoctoral associate in Stanford’s Department of Earth System Science at the time of the research, who conceived of this study during his master’s degree in McGill’s Department of Geography.

Another chance to act on wetland loss

“Wetlands, in their natural state, are among the most important ecosystems to regulate our water resources, which benefits both humans and the environment,” adds co-author Bernhard Lehner, a global hydrologist at McGill University. “Discovering that fewer wetlands have been  historically lost than we previously thought gives us a second chance to take action to ensure wetland cover does not decline further. As part of that, we need to improve our capacity to map their past and current extents and monitor their status using satellites. This will allow us to establish meaningful conservation goals and restoration targets.”

An accurate estimate of the extent, distribution and timing of wetland loss is key to understand their role in natural processes and the impact of wetland drainage on the water and carbon cycles. These new results will help evaluate the effects of historic wetland loss on greenhouse gases and can help inform plans to protect or restore these fragile ecosystems that are crucial to human health and livelihoods.

Publicatie

Fluet-Chouinard, E., Stocker, B.D., Zhang, Z. et al. Extensive global wetland loss over the past three centuries. Nature 614, 281–286 (2023). https://doi.org/10.1038/s41586-022-05572-6