It’s a fabulous journey to the heart of landscapes as little-known and misused as they are essential, where water and earth mingle for our greatest happiness, for our greatest good, too. In Water Lands (1)a scholarly but accessible work, the Swiss biologist Tobias Salathé makes us discover the incredible beauty of the ponds, marshes, deltas or lagoons here and elsewhere, the peat bogs of the Jura, the rainforests of the Amazon or the Indian mangroves … The author, who worked for a long time in the Camargue, at the Tour du Valat foundation, also opens our eyes to the extraordinary range of services and solutions that these wetlands offer us in the face of major challenges of our time, starting with the climate crisis and that of biodiversity.
The expression “waterlands” sounds a bit like an oxymoron…
Maybe, but at the same time, it’s very precise and clear. And it’s more poetic and sympathetic than talking about “wet zones” or “wet environments”, two expressions used by specialists. These are lands, areas, landscapes, soils which are particularly linked to water. This can be open bodies of water such as ponds, lakes and lagoons. Watercourses that connect them, such as torrents, streams, rivers and streams. And basins covered by lush vegetation rooted in waterlogged soil found in marshes, swamps, peat bogs or wet meadows. What links all this is the water cycle: the precipitation that falls on Earth, infiltrates into the subsoil, arrives in rivers, feeds the ponds in the fields to irrigate them, evaporates at new, etc.
Where are these wetlands found?
They are found almost everywhere on Earth, except in very desert places. They cover only 6% of the planet’s land surface, but are extremely rich: around 40% of plant and animal species live and reproduce there. They are often very close to us and we do not know it. I would like the reader, after reading my book, to go in search of water lands near their home. This could be the small village pond if it still exists, or the river not far away, or even a local lake or coastal bank.
Why did you choose to present in your book twelve ecosystem services that these water lands provide us?
I chose twelve, because it is a harmonious number, but I could have grouped them into twenty themes, or less. These water lands make it possible to supply and guarantee our drinking water, to recharge groundwater, but also to purify water. Marsh vegetation absorbs substances that can pollute the water. In a country like France where there is relatively much space, many municipalities purify wastewater using a lagoon system where it is the vegetation, the reeds, which do most of the work, with the help of the sun. Wastewater flows slowly over a few months into ponds, allowing ultraviolet rays from the sun to kill pathogens.
One of the largest lagooning stations in Europe is located in the heart of the ancient marshes of the coastal plain of the last loop of the Charente. The lagoon park in the town of Rochefort can treat the wastewater of 35,000 inhabitants. The sludge that accumulates during settling is transformed into compost for the city’s green spaces or fermented into biogas to produce electricity and heat. And the resort’s marshes benefit migratory birds that pass on the Atlantic coast: ducks, scaup, grebes, terns, seagulls and swallows stop over there. It’s a win-win.
There is also coastal protection…
Yes. Remember the big tsunami that basically hit Thailand at the end of 2004. It was shown that where there were mangroves, mangrove forests, the damage was much less because these coastal forests were able to break up the waves. Closer to home, in England for example, we realize that with the increase in sea level due to climate change, we must maintain a coastal belt, a certain extent of land which can act as a buffer against large tides. Flood prevention is also part of the services that water lands provide us. The alluvial plains of rivers absorb floods.
What about carbon sequestration?
This happens when vegetation, which has extracted and stored carbon dioxide from the atmosphere, finds itself trapped for a long time in waterlogged soil. Dead plant matter has been accumulating there in the form of peat, sometimes since the Ice Age, ten thousand to fifteen thousand years ago. A lot of carbon is sequestered in peatlands around the world. Like those of the Jura, which are now protected and restored, which also serves as a sponge and ensures that there is enough water for pastures, while summers are increasingly dry, and therefore to maintain an entire rural cheese and dairy economy.
Why do we need to protect and restore these waterlands?
Because they are among the most threatened ecosystems, the most destroyed by us humans. For three hundred years, we have drained a lot of land, created dikes and built canals, thinking with some reason that we could increase agricultural production if it were a little less marshy. It worked quite well at first. Except that in many places where this has been done very intensively, we are reaching the end of the process, because the quality of the soil is deteriorating. The carbon stored in the peat is again exposed to oxygen and returns to the atmosphere, the soil compacts and sags. In certain coastal areas, for example in Indonesia, where many oil palm fields have been planted on former peaty soils, this subsidence of the soil opens the way to marine flooding.
We have lost more than a fifth of all wetlands on the planet since the year 1700, exactly 21%. And this decline has clearly accentuated over the last fifty years: since 1970, the surface area of water has been reduced by a third. In densely populated, intensively exploited and processed regions, their loss can reach 80% to 90%. For example, on the Swiss plateau, between the Jura and the Alps, 90% of all wet landscapes have been drained. Ditto in the alluvial plains of rivers, for example in the large alluvial plain of the Rhine.
Wetlands have long been part of our landscape, but they also had a bad reputation. The marshes were described as “mosquito holes”…
Of course, in the 18th and 19th centuries, drainage improved the lives of poor peasants who lived in swamps and suffered from malaria, including here in Europe. But today, we have realized that it is not by draining the marshes that we will eliminate all zoonoses, that is to say diseases whose pathogen, bacteria, virus or parasite, can be transmitted from animals to humans. Rather, it is now a matter of bringing together epidemiologists, ecologists and economists to find a way to create “one health” for us humans and our ecosystem.
When did the renewed interest in water lands begin?
It started with a conference which took place in 1962 in France, in Saintes-Marie-de-la-Mer (Bouches-du-Rhône), which was the culmination of a UNESCO project aimed at implementing before the services provided by these ecosystems, and no longer just talk about malaria or land to be drained. During this conference, ornithologists and waterfowl hunters expressed concern about the disappearance of spaces allowing migratory birds to stopover between Siberia and North Africa, for example. They suggested the creation of an inventory of wetlands and the signing of an international agreement to protect them. This was done on February 2, 1971 in the Iranian city of Ramsar, on the shores of the Caspian Sea, which has a lot of marshes. The Ramsar Convention entered into force in 1975 and has been signed by nearly 90% of UN member states. And February 2 became World Wetlands Day.
The effectiveness of this Ramsar convention does not seem convincing, since the disappearance of water areas has accelerated since…
It’s true. But it is the same dilemma as for other international conventions, on biodiversity, climate, etc. These subjects are still too much discussed among insiders. The debate and knowledge should be extended to a wider audience. It is with this in mind that I wrote this book.
Where are we in France?
France is rather a country where there is a lot of interest in wetlands. Since the 1990s, there have been national plans for these, often coordinated by water agencies, by large basins. Waterlands are part of the history of France and the way we used the landscape. For example, north of Paris, there were many watercress farms, where watercress, an aquatic plant, was grown in small ponds, before selling it in the capital. In the Jura, frogs were raised. I also cite the example of the Audomarois marsh, near Saint-Omer (Pas-de-Calais and Nord), which is a large marsh and market gardening site, known for its cauliflower and endives. Agriculture had become a little commonplace there, we drained and created large fields. But recently there have been efforts to return to those local and identifiable products, which are of better quality and sell at a better price. We have every interest in reconciling ourselves with water lands.
(1) Ed. Buchet Chastel, October 2024, 288 pp., €22.
Source: www.liberation.fr
