4,000 km2 of valuable wetlands have disappeared in 20 years

A wet areait doesn’tair nothing, just like that. But from a nature conservation perspective, it can do a lot. Because in the world, wet area consist of a reservoir of biodiversity. They help reduce the natural disasters. They constitute a carbon sink. They also have significant economic value. And some Cambridge University researchers (United Kingdom) confirm today what the Convention on Wetlands recently implied: these ecosystems are more than ever in danger.

The researchers analyzed more than a million satellite images. From a very factual point of view, they announce that 4,000 km² from wetlands to tide — marshes or mangroves, for example — have disappeared in the past 20 years. It is the surface equivalent of the Alpes-Maritimes department. But thanks to theartificial intelligence and machine learning, they were able to better characterize these wetland losses.

Towards new wetlands

The researchers thus conclude that almost a third – 27% exactly – of the losses – or gains because preservation operations also make it possible to restore wetlands – are very directly linked to human activities: the conversion of the land for’agriculture, for example. This is particularly the case in Asia, which accounts for three quarters of the total loss of tidal wetlands in the world. The rest of the losses are attributable to human impacts on the Watershedeconomic development of coastal areas, coastal subsidence, global warmingbut also to natural coastal processes.

This work also shows that three quarters of the losses — nearly 14,000 km² in total — have been offset by the creation of new wetlands. Especially in regions where they did not exist before. With a significant expansion in the deltas of the Ganges and theAmazon, for example. Migrations which will have to be taken into account in the future for more efficient management of coastal areas low altitudes in which more than a billion people in the world still live.

Wetlands are disappearing when they are essential to our survival

Essential allies in the fight against global warming, wetlands are highly threatened and degraded all over the world. The United Nations estimates that 35% of wetlands have disappeared since 1970, even though they have many unrecognized benefits, such as disaster mitigation, carbon sequestration and human health.

Article of Karine Durand published on 07/01/2022

The Convention on Wetlands (or Ramsar Convention) has just updated its latest report on the state of wet area in the world and the importance of their backup. While all eyes are focused on the degradation of the Amazon forest or on the disappearance glacierswetlands are the most threatened ecosystems on the planet: marshes, bogs, wet meadows, lagoons, mangroves and other water points are currently disappearing at a rate 3 times faster than forests. 36% of species dependent on wet area are globally threatened. Yet little known, the role of wetlands is crucial in the functioning of the Earth: reservoir of biodiversity, but also disaster mitigation, human health, and carbon sink.

Threats: agriculture, livestock, pollution and climate change

Wetlands have a global surface area of ​​1.2 billion hectares in total; this gives a territory larger than that of Canada. But in just 50 years, they have already lost a third of their total surface.

The anarchic exploitation of the land (in particular agriculture and livestock) is the primary degradation factor for wet areawhile the Convention on Wetlands insists on the fact that “ the future of sustainable food production depends on healthy wetlands and their wise use”. Agriculture is responsible for the disappearance of more than half of wetlands since 1970. Then come the overexploitation of livestock, plants, pollution, invasive speciesbut also Forest explotationas well as hunting and sin of species essential to the functioning of these areas. And the Convention’s predictions are rather bleak about the future: all these threats to land and biodiversity. projected to continue or worsen in many future scenarios, in response to indirect drivers such as rapid human population growth, unsustainable production and consumption, and technological development related. »

Wetlands are also particularly affected by the consequences of climate change: sea level rise, coral bleaching and disruption of hydrology. Among all of the world’s wetlands, wetlands arctic and mountains are more exposed to climate risks. In areas at climate rather dry, brought to suffer even more from the drought with global warming, water stress is becoming more and more important, drying up many wetlands essential to biodiversity and the human population.

Another geographical area where the deterioration of wetlands is clear is the Mediterranean region. Since 1992, the marine biodiversity of the Mediterranean decreased by 52% and its biodiversitypure water by 28%. the debit of watercourses in the Mediterranean basin decreased by 25 to 70% between 1960 and 2000, with repercussions on seasonal wetlands. Intensive agriculture consumes two thirds of the fresh water resources of the Mediterranean. With more than 42% of the Mediterranean population settled on the coast, settlements, industry and tourism are degrading coastal wetlands and the demand for water is increasing.

The unknown benefits of wetlands

The interest of safeguarding and restoring the planet’s wetlands is multiple and often totally unknown to farmers, breeders and more generally to local populations. The Convention estimates that 4 billion people (out of a world population of almost 8 billion) are directly dependent on wetlands for their survival. The economic value of wetlands for the services they provide to humanity is estimated at 47,400 billion dollars per year!

Coastal wetlands, such as mangrovessequester the carbon dioxide 55 times faster than tropical forests. The bogs, which cover only 3% of the world’s surface, sequester 30% of the carbon present underground. Peatlands and coastal blue carbon ecosystems (salt marshes, mangroves, seagrass beds, etc.) in good condition are very effective carbon sinks, but if degraded they become important sources of carbon. greenhouse gas.

One of the objectives of the United Nations is to restore 50% of the peatlands destroyed by 2030. Mangroves, Coral reefs and the algae also play the role of barriers that mitigate the submersion ribs in case of storm and tsunami. On land, peat bogs, ponds, rivers and water points in general absorb excess water in case offlood and retain them in case of drought. These ecosystems are part of what are called Nature-Based Solutions.

The good health of the population also depends on well-managed wetlands: “ The control of emerging zoonotic diseases depends on the preservation of intact and well-managed ecosystems and local biodiversity. Adopting an ecosystem approach to wetlands can have health benefits for all. The degradation of ecosystems and the senseless wildlife trade increase the risks of pandemics devastating and three-quarters of new diseases are of zoonotic origin”. Furthermore, ” water-related diseases, such as diarrhea infants, transported in unsanitary waters, are also favored by poor management of wetlands and kill millions of people each year”.

In order to better publicize the importance of wetlands and encourage their protection and restoration throughout the world, the United Nations General Assembly of August 30, 2021 decided to dedicate a World Day to these ecosystems. February 2 of each year will henceforth be “World Wetlands Day”.