A more accurate portrait of the loss of wetlands to better protect them

Old studies have overestimated the extent of their destruction. Instead of declaring victory, researchers see it as an opportunity to act to better preserve these environments of high ecological value.

A young fish in a wetland near Mumbai, India.

By combing through thousands of drainage and land-use change records, researchers have established that at least 3.4 million square kilometers of wetlands have been lost from 1700 to 2020, the equivalent of the area of ​​India. Human activity would thus have caused the disappearance of 21% to 35% of these environments on a planetary scale.

This portrait contradicts the estimates made previously by other studies, which evaluated the loss of these environments from 50% to 87%. For lack of sufficient data, these studies have tended to extrapolate based on the cases of regions that have experienced greater losses.

A team of around twenty researchers from Stanford, Cornell and McGill universities this time searched nearly 3220 national and regional databases from 154 countries in order to arrive at this reconstruction which spans more than 300 years.< /p>

What differs from previous studies is that we wanted to represent geographical disparities, by including and quantifying wetlands that have not yet been affected on the globe, explains Etienne Fluet- Chouinard, postdoctoral researcher at ETH Zurich and specialist in environmental data.

Using mathematical models, researchers were able to estimate this loss since 1700 to account for the upheavals brought about by the pre-industrial era. This continuing trajectory of wetland destruction provides links to human-induced carbon emissions and biodiversity loss over time, according to Fluet-Chouinard.

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Although the destruction of these environments turns out to be less serious than we thought, the researchers warn anyone who might be tempted to see in these results the sign that there is no danger in delay.

“You could misinterpret [these data] and think you're scaring yourself for nothing. But our message is rather that there is still time to protect wetlands in places where we have them, like in Canada. »

— Etienne Fluet-Chouinard, postdoctoral researcher at ETH Zurich

Countries have seen their wetlands disappear at a breakneck pace. The United States has lost 39.1% of its wetlands since 1700, representing 15.6% of all recorded losses globally.

With the United States, China, India, Russia and Indonesia alone share more than 40% of all media losses wetlands in the world from 1700 to 2020.

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Over the same period, Canada lost 83,000 km2, or 3.8%, of its wetlands. The country thus contributed to 2% of global losses, according to the researchers. However, this estimate does not take into account the destruction and degradation attributable to mining and the extraction of fossil fuels.

We know that industries like that of the oil sands in Alberta lead to the conversion of wetlands, land and forests, but we have been unable to quantify their effects, specifies Etienne Fluet-Chouinard, who underlines that the results put forward by the researchers are intended to be conservative. /p>

They note that untouched wetlands in Canada are mostly peatlands found in arctic and boreal regions. In their case, the main threat would not be directly related to human activities, but rather to the effects of climate change, such as melting permafrost, droughts and fires.

Damaged by drainage, in addition to the impacts of climate change and sea level rise, wetlands are among the most threatened ecosystems in the world.

Most of the wetlands that disappeared were in the basins of large rivers where people settled, such as the Danube in Central Europe, the Indus in South Asia, the Yangtze in China, and the Mississippi in the United States.

To date, the Amazon and [River] Congo basins have been able to retain most of their riverine wetlands, the researchers point out, but they have come up against the lack of available data on this subject.

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For too long seen as environments of no real value, wetlands were particularly abused during the 1950s. At the time, government programs in North America, Europe and China subsidized their drainage for the purposes of #x27;agriculture and forestry.

Peat extraction for fuel or fertilizer, the development of urban areas and extensive grazing are among the many of the activities that have harmed these communities over the years. They are among the most threatened ecosystems in the world.

Today, however, the ecosystem services provided by these wetlands no longer need to be proven. Studies have led to an understanding of their essential role, particularly for carbon sequestration, flood regulation, groundwater recharge and water purification.

• The drainage of environments for the establishment of cultivated land
• The conversion of flooded rice fields and agricultural production in wetlands (40% of all losses in Asia and sub-Saharan Africa)
• Urban planning
• Forestry (45% of wetland loss in Sweden, Finland and Estonia)
• Pastures
• Peat extraction (mainly in Ireland, Northern Europe and Western Russia)

Although wetland conversion has slowed in most countries, researchers note that destruction continues in some areas. In Indonesia, where wetland loss accounts for 4.3% of the global toll, tropical peat swamps are being destroyed for industrial plantations and small-scale agriculture.

We must slow down the transformation and degradation of these environments, and restore, rebuild in the regions which have experienced great losses, insists Etienne Fluet-Chouinard.

Today we present a global portrait, but the issue remains local, he adds.

In other words, protecting large swaths of intact wetlands in northern Canada or Siberia has its benefits, but will not compensate for the destruction of areas that are thousands of kilometers away. Hence the importance, according to the researcher, of better understanding where the most sensitive environments are located, which require immediate action.

The researchers believe that x27;a better understanding of these environments will also allow for more targeted action and monitoring of progress towards the protection goals set by the international community.