The Danish Nature Agency flooded the river valley in the Omme Å area by removing barriers and closing fisheries. US National Oceanic and Atmospheric Administration (NOAA) spent 181$ million on a two-phased project in Louisiana, where 6.4 million m3 of sediment from the Mississippi river was piped to Barataria Basin creating marshland. Slovakian team of environmentalists at Broz in collaboration with the Mossy Earth are flooding the forest near Danube River by opening the dam and digging trenches for the water from the main river canal to spread around in the lower parts of the forest. There are many examples like this across the globe, but what is the point?
The answer is wetlands – an immensely varied and biodiverse ecosystem, that is flooded or saturated in water. Wetlands are among the most productive ecosystems on the planet, often referred to as the "kidneys of the earth" due to their ability to filter water. There are different types of wetlands depending on the water source and the ways they are created. The main four types are:
Disappearance of Wetlands
In the past 100 years wetlands have been disappearing at an alarming rate, with nearly 50-70% of it gone since the 1900s. The inland has been more affected than the coastal wetlands, and while in Europe and North America, the degradation rate has slowed down recently, it remains high in Asia and South America. The main culprits of this disappearance are as usual humans, and we contributed in the past and continue to contribute to this decline in many different ways. As people move from the countryside to the cities driving the urbanization, wetlands are drained and filled to make place for new infrastructure, city expansion, and timber production. Additionally, wetlands are often converted to farmlands, particularly for crops that require extensive irrigation, since this type of land is often closely located to water sources and is rich in nutrients. The construction of dams for hydroelectric power also plays a massive role in the loss of wetland areas, as we divert rivers from their natural course for our benefit and encapsulate them in concrete. Indirect consequences of anthropogenic activities, such as pollution and climate change, exacerbate the problem even more. Pesticides and heavy metals contaminate wetland ecosystems and rising temperatures and changing precipitation patterns disrupt wetland hydrology, affecting their health and functionality.
Importance of wetlands
Wetlands are among the most diverse ecosystems in the world, comparable to rainforests and coral reefs. They host an immense variety of microbes, plants, fungi, and animals, which use wetlands for part or all of their life cycle. The combination of shallow waters and high levels of nutrients create ideal conditions for young offsprings of many species, acting as giant nurseries, thus many species of birds, mammals, and fish rely on wetlands for food, water, and shelter, especially during migration and breeding.
However, the preservation and restoration of wetlands is important not only for the conservation of countless species living in those habitats but also for our survival. Wetlands provide values that no other ecosystems can since they act as natural water purifiers, trapping sediments and toxins, thereby improving water quality. Moreover, wetlands offer protection against natural disasters. They absorb excess rainwater, reducing the severity of floods, and act as buffers against storms and coastal erosion. In arid regions, wetlands can recharge groundwater supplies, ensuring a steady water source during dry periods.
Net carbon source or sink?
Just like in any other ecosystem, wetland plants and trees absorb CO2 from the atmosphere through plant growth and peat formation. However, while in the forests the organic material decomposes on the forest floor after its life, in wetlands it becomes trapped under water without oxygen, allowing it to store carbon for many years. That is the primary process behind fossil fuel formation. And this process is very effective, as peat bogs for example make up only about 3% of the earth's land mass, but still store twice as much carbon as all the world's forests combined.
On the other hand, the same principle of water-trapping organic material in oxygen-deprived environments leads to the creation of much more potent greenhouse gases than CO2, namely methane (CH4) and nitrous oxides (NOx). The production of NOx gases is especially intensive in nitrogen-rich locations, e.g. in areas used for agriculture, and a great example of that is rice paddies, which account for nearly a third of all wetlands’ methane production. Thus, a great challenge lies in optimising wetlands conditions to maximise carbon sequestration while minimising CH4 and NOx emissions when considering wetlands creation projects. We cannot mindlessly flood the areas hoping for a beneficial result. Understanding the complex biogeochemical processes in wetlands, researching the area’s ecosystem, and use prior to major human interventions are essential to ensure that wetlands remain net contributors to climate mitigation efforts.
Who works on restoration and how can you help?
As it was mentioned before in this article, there are many projects and organisations across the world researching the wetlands as ecosystems and studying the carbon sequestration processes behind them. Among the currently undergoing projects in Denmark are the Wet Horizons and Global Wetland Center. In Europe overall the new law is aiming to restore at least 20% of the EU's land and sea areas by 2030 and all ecosystems in need of restoration by 2050. At the same time, it is stated that the restoration of wetlands will continue to take place on a voluntary basis for farmers and private landowners.
Bearing in mind the delicate balance of CO2 sequestration and CH4 and NOx production in wetlands, every such project needs to undergo careful consideration and evaluation if it would actually bring climate positive or negative results. Thus, if you choose to support wetlands creation projects, be it through donations, volunteering, or any other way, here are some tips to ensure that your help is directed to the right cause:
Danube River wetland in Slovakia
A great example of a successful wetland restoration project currently undergoing can be found on the Danube River delta in Slovakia, where 650m of water channels have been excavated to flood 64ha of floodplain forest. The initial results of these efforts were observed immediately on the first flooding in spring 2022 – as the fish and frogs reclaimed the lands turning them into their nurseries for the young; the area was filled with the sound of insects buzzing, birds chirping, and amphibians humming in the background. That same autumn a gradual botanical shift has also started to be observed as the native wetland plant species took root around the water canals, while the invasive dry land species found it harder to survive. The researchers from Comenius University even found a female representative of the endangered Pannonian root vole (Microtus oeconomus mehelyi) species creating a new home for its offspring next to the flooded area. Fast forward to the summer and then winter of 2023-2024, and the water spreads further into the forest, as clay (which prevents water from quickly being absorbed into the ground) accumulates along the water channels, giving new life to the area.
References:
Mitsch, W. J., Bernal, B., Nahlik, A. M., Mander, Ü., Zhang, L., Anderson, C. J., Jørgensen, S.E., Brix, H. (2012). Wetlands, carbon, and climate change. Landscape Ecology 28 (4). https://doi.org/10.1007/s10980-012-9758-8
Genskab naturlige forhold med mange vildfisk. (2023, June 4). https://www.fiskepleje.dk/vandloeb/restaurering/vaadomraade/genslyngede-vandloeb-i-vaadomraade/vaadomraade-genskabe-naturlige-forhold
Davidson, N. C. (2014). How much wetland has the world lost? Long-term and recent trends in global wetland area. Marine and Freshwater Research 65 (10):936-941. https://doi.org/10.1071/MF14173
Vådområders kæmpe betydning for klimaet skal kortlægges. (2024, June 13). https://www.danskskovforening.dk/skoven/vaadomraaders-kaempe-betydning-for-klimaet-skal-kortlaegges/
Twomey, A. J., Nunez, K., Carr, J. C., Crooks, S., Friess, D. A., Glamore, W., Orr, M., Reef, R., Rogers, K., Waltham, N. J., Lovelock, C. E. (2024). Planning hydrological restoration of coastal wetlands: Key model considerations and solutions. Science of The Total Environment 915. https://doi.org/10.1016/j.scitotenv.2024.169881
Nyt projekt vil fremskynde genopretning af vådområder i hele Europa. (2022, October 4). https://agro.au.dk/aktuelt/nyheder/vis/artikel/nyt-projekt-vil-fremskynde-genopretning-af-vaadomraader-i-hele-europa