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Deep green infrastructure

Introduction

A wetland, chucua,[2] or humid zone, is an area of land, generally flat, whose surface is permanently or intermittently flooded.[3] By being regularly covered with water, the soil becomes saturated, becoming devoid of oxygen and giving rise to a hybrid ecosystem "Hybrid (biology)") between purely aquatic and terrestrial ones.

Considering that the fundamental concept of a wetland is not water as such but "humidity", we can speak of "wet ecosystems" interdependent on water, whether surface or underground.

The biological category of wetland includes areas with diverse geological properties such as swamps, estuaries, marshes, swamps, peat bogs, as well as maritime coastal areas that present periodic flooding due to the tidal regime (mangroves).[4].

In addition to being very important environments and ecosystems today, wetlands were also very common throughout the history of the Earth, as many sedimentary rocks have been interpreted as formed in ancient wetlands, both freshwater[5] and coastal.[6].

World Wetlands Day has been celebrated every February 2, since the Ramsar Convention was held in 1971.

Wetlands cover at least six percent of the Earth and are estimated to be home to 40% of all animal and plant species.[7] They have become a central issue for conservation due to the ecosystem services they provide. More than three billion people, approximately half of the world's population, obtain their basic water needs from inland freshwater wetlands.[8] They provide essential habitats for fish and various wildlife species, and play a vital role in purifying polluted waters and mitigating the damaging effects of floods and storms. Additionally, they offer a wide range of recreational activities, such as fishing, hunting, photography and wildlife viewing.[9].

Since the year 1700, humanity has destroyed 87% of the planet's wetlands.[10] Since the year 1900, humanity has destroyed 64% of the wetlands.[10].

Definition

The Ramsar Convention defines wetlands as:

"A wetland is an area of the earth's surface that is temporarily or permanently flooded, regulated by climatic factors and in constant interrelation with the living beings that inhabit it."[11].

According to article 1 of paragraph 1, they are considered wetlands.

Likewise, contained in article 2 of paragraph 1, it is stipulated that,.

Deep green infrastructure

Introduction

Considering that the fundamental concept of a wetland is not water as such but "humidity", we can speak of "wet ecosystems" interdependent on water, whether surface or underground.

World Wetlands Day has been celebrated every February 2, since the Ramsar Convention was held in 1971.

Since the year 1700, humanity has destroyed 87% of the planet's wetlands.[10] Since the year 1900, humanity has destroyed 64% of the wetlands.[10].

Definition

The Ramsar Convention defines wetlands as:

"A wetland is an area of the earth's surface that is temporarily or permanently flooded, regulated by climatic factors and in constant interrelation with the living beings that inhabit it."[11].

Characteristics

Contenido

El carácter distintivo de los humedales está en la escasa profundidad del nivel freático, con la consecuente alteración del régimen del suelo. La vegetación específicamente adaptada a estas condiciones se denomina hidrófita, cuando se ubica sobre zonas inundadas de agua; y freatofita cuando estas zonas se ubican sobre zonas de agua oculta (criptohumedales); en estos casos se reemplaza a las especies terrestres normales.

Las peculiaridades del entorno hacen que la fauna presente sea por lo general endémica y netamente diferenciada de las zonas adyacentes; grandes familias de aves y entornos de este tipo.

La función principal del humedal, aparte de ser un gran ecosistema y un importante hábitat para muchos seres vivos, es que actúan como filtradores naturales de agua, esto se debe a que sus plantas hidrófitas, gracias a sus tejidos, almacenan y liberan agua, y de esta forma comienzan con el proceso de filtración. Antiguamente los humedales eran drenados por ser considerados una simple inundación de los terrenos, pero hoy en día se sabe que los humedales representan un gran ecosistema y se los valora más.[12].

Los humedales son diversos según diferencias existentes a nivel regional o local, en la topografía, hidrología, vegetación y otros factores como la actividad humana..

Hydrology

The hydrology of a wetland is associated with the temporal and spatial dispersion, flow, and physicochemical attributes of its surface and groundwater. Based on hydrology, wetlands can be categorized as riparian zone "Ribera (shore)") (associated with rivers), lacustrine (associated with lakes and reserves), and palustrine (isolated, without water flow).

The hydrological input flows in a humid area are mainly precipitation, surface water and groundwater, while the output flows are evaportranspiration, runoff, and movement of groundwater.[13].

Salinity plays a key role in the water chemistry of humid areas, especially those located on the coast, and in regions with large precipitation deficits "Precipitation (meteorology)").

Floor

Most nutrients, such as sulfur, phosphorus, carbon and nitrogen, are found in the soil of humid areas. Depending on whether aerobic or anaerobic respiration occurs in the soil, it will influence the carbon, hydrogen, oxygen and nitrogen cycles of the soil,[16] and the solubility of phosphorus,[17] contributing to chemical changes in the water.

Biodiversity

Wet zones cover a relatively small part of the Earth's surface. Even so, they are ecosystems rich in biodiversity. Coastal wetlands such as mangroves, coral reefs, estuaries and seagrass beds have the most productive and biologically diverse communities in the world.[18] However, the role of wetlands as reservoirs of biodiversity is threatened, as they are an ecosystem that is being lost and degraded at a faster rate than any other[19] (since 1900, more than 64% of wetlands have been lost worldwide). world).[20].

Some species of fauna and flora are completely dependent on humid areas,[18] as is the case of the fartet, a freshwater fish that only lives in humid coastal areas of the Iberian Mediterranean coast and is threatened with extinction.

The vegetation that we can find in a humid area are aquatic or hydrophytic plants, which are those adapted to aquatic environments. Four categories can be differentiated: the emergents are rooted in the flooded soil but most of them are out of the water (boga, phragmites); plants with floating leaves are those with roots fixed to the submerged soil, but floating leaves (Nymfea); submerged are completely submerged and are the most adapted to aquatic environments (miriofile); floating float completely with free roots in the water, they can have a very reduced morphology and since they do not have roots fixed to the substrate, they must absorb nutrients directly from the water (salvinaceae, water lettuce).[21].

• - Mammals: only about 100 mammals are strictly dependent on humid areas,[14][22] including some of the smallest mammals in the world such as some species of shrews, some of the largest in the world such as hippopotamuses, or others also known as otters, beavers, minks or muskrats.[23].

• -

Wetland Birds, in the photo a black heron and a biguá on trees on the coast. Bs.As. May 2025.

Birds: more than 1,800 species of birds are somewhat dependent on humid areas.[14][22] Some groups are loons, grebes, pelicans, sea crows, anseriformes (ducks, geese, swans), waders, etc.[24].

• - Photo of tadpoles swimming in wetland, from the Urban Natural Reserve, in Buenos Aires. Photo taken in October 2024.

Photo of tadpoles swimming in a wetland, from the El Corredor Urban Natural Reserve, in Buenos Aires. Photo taken in October 2024.

Amphibians: more than 5,000 species have been described worldwide, all of them depend on humid freshwater areas (except for some species that can tolerate brackish water) at some point in their life cycle.[22] Most adult amphibians feed on invertebrates, making them an important link in the food web between insects and other vertebrates.[25] They are animals very sensitive to changes in the quality of terrestrial habitats and aquatic species that they inhabit, since they have a semi-permeable skin and present different stages of the biological cycle. Due to this high sensitivity, amphibians are used as bioindicators to know the environmental quality of a habitat.[26][27].

Despite their importance, wetlands around the world are under threat. These hazards come from intensive conversion to agriculture or aquaculture, industrial development, artificial hydrological changes, or degradation through overexploitation. This being one of the most important issues regarding its future conservation.[28].

Structural types

From the structural point of view, wetland types can be differentiated based, on the one hand, on the hydrological criterion of the external or surface structure; and on the other hand, in the hydrogeological criterion that includes the internal structure or underground connection. The combination of these two aspects can also be understood as a "hydrological-structural" criterion.[30] They are:.

• - Hydrological structural criterion (External aspects):

Hydrowetland: they almost always have a sheet of outcropping water (practically throughout the year)

Hygrowetland: they almost always have a hidden layer of water (practically all year round).

• - Hydrogeological structural criterion (Internal aspects):

Epigenic: its structure is detached from nearby localized underground flows.

Phreatogenic: its structure is linked to nearby localized underground flows.

And within the phreatogenic wetlands, according to their hydrogeological flow areas, which is why they are considered "wet ecosystems" interdependent on groundwater (that is, they can be generated by these and in turn those can also generate them, depending on the hydrogeological gradient, in space and time), they can be subdivided into 3 other groups:

• - Recharge wetlands (at the localized piezometric recharge thresholds): Navas, infiltration ponds, river recharge sections, etc.

• - Transit wetlands (in areas of flow circulation subparallel to the terrain or flat trend): Continental cryptowetlands, coastal cryptowetlands, outcropping sheet lagoons, etc.

• - Discharge wetlands (in hydrogeological flow convergence zones): Flooded springs, bottom discharges, seepage areas, etc.

Therefore, combining both sets of nomenclatures, for each external and internal criteria, 7 hydrological-structural types would result:

- Exclusive epigenic: coastal salt flats, lagoons, reservoirs, ponds, etc.

- Recharge hydrowetland: infiltration lagoons, rice fields, filtering rivers, etc.

- Transit hydrowetland: steppe lagoons, phreatic pools, water tables, etc.

- Discharge hydrowetland: spring surges, river lagoons, coastal lagoons, spring pools, inland salt marshes, seeps, etc.

- Recharge hygrowetland: mountain basins "Nava (geomorphology)"), ponds in permeable boulevards, etc.

- Transit hygrowetland: continental cryptowetlands, coastal cryptowetlands, etc.

- Discharge hygrowetland: seasonal karst upwellings (trop plein), karst extrusions, etc.

Functions and value of wetlands

Los humedales sirven como ecosistemas multifacéticos con una amplia gama de funciones esenciales que contribuyen tanto al medio ambiente como a las sociedades humanas.

Floodwater storage and filtration

Wetlands can help mitigate the impacts of flooding in certain areas due to their floodwater storage function. According to the Vermont Department of Environmental Conservation, many wetlands, particularly those located in floodplains, have the ability to temporarily retain excess flood waters during high runoff conditions. Although wetlands have been compared to natural sponges in the past, their function is more precise when compared to that of natural reservoirs. They store flood waters that overflow from the banks of the rivers "Bank (geography)") or accumulate in low areas. As flood waters gradually recede, these wetlands slowly release the water stored in their soils. This function of retaining some of the flood waters and regulating the rate at which water re-enters the stream can effectively reduce the intensity of downstream flooding and erosion.[31] Wetlands also aid in water filtration by removing excess nutrients, slowing the flow and allowing particles to settle and then be absorbed by plant roots. Its vegetation and soil trap sediments and pollutants, while beneficial wetland microbes break down harmful substances. In this way, these invertebrates are capable of eliminating up to 90% of the bacteria in the water.[32].

Habitat

Wetlands play a vital role in providing diverse and critical habitats for a wide variety of plant and animal species, and serve as a cornerstone of ecological diversity. Different species of fish and wildlife use wetlands in different ways. Some rely on wetlands as their primary habitat, while others use them seasonally for food and shelter. Wetlands are crucial for the survival of many species, while serving as essential seasonal habitats for others.[33] The synergy of shallow waters, abundant nutrients and high primary productivity creates a perfect environment for the growth of organisms that form the base of the food chain, providing food for various fish, amphibians, shellfish and insects. [34] Wetlands have also been a favored place by scientists to help the improvement and discovery of medicine. It is estimated that between 70 and 80% of the world's population depends on herbal medicine, as well as income from the harvest and trade of plants, due to its medicinal purposes. Although there is no global inventory of medicinal wetland species, the white willow is an example. This riverine plant is used in skin care products, as well as being the original source of salicylic acid.[35] In addition, numerous species of birds and mammals depend on wetlands for food, drinking water, and a safe place to stay, particularly during their long journeys or when they have young. [36].

Climate change mitigation

Wetlands play a crucial and multifaceted role in mitigating climate change through their natural processes and functions.[37] They capture carbon from the air when plants grow and trap sediment from water. This carbon is stored in plants, leaves, soil and mud, sometimes for thousands of years.[38] According to a paper published by AM Nahlik and MS Fennesy, globally, wetlands retain around 700 billion tonnes of carbon, mainly in peat soils, with an annual sequestration rate of 96 million tonnes. In the United States, wetlands are estimated to contain 11.52 billion tons of carbon, equivalent to approximately 1% of the global soil carbon stock, highlighting the carbon storage capacity of wetlands on a global scale.

In addition to their capacity to store carbon, wetlands act as natural buffers against extreme weather events. They function like sponges, absorbing excess water during heavy rains and releasing it in periods of drought, helping to prevent flooding and keep water flowing year-round. This function is essential, since it regulates hydrological cycles and protects human communities and biodiversity.[39].

Biological productivity

Although wetlands only cover about 5% of the land area of the continental United States, they support 31% of plant species. Thanks to their ability to absorb nutrients, wetlands can be highly biologically productive (able to produce biomass "Biomass (ecology)") quickly). Freshwater wetlands are even comparable to tropical rainforests in plant productivity.[40] Their ability to efficiently create biomass may be important for the development of alternative energy sources.

Recreation, education and research

Wetlands, beyond their ecological importance, offer a wealth of recreational opportunities, serve as invaluable educational resources, and serve as living laboratories for vital research. These unique ecosystems attract outdoor enthusiasts, providing spaces for activities such as bird watching, hiking and photography, while also serving as educational platforms where people can learn about nature and environmental conservation. Additionally, wetlands provide researchers with dynamic environments to study diverse ecological processes and species, contributing to our understanding of the natural world.[41].

Threats to wetlands

Según ONU Cambio Climático, los humedales están desapareciendo tres veces más rápido que los bosques. Los humedales se enfrentan a amenazas crecientes que ponen en riesgo su salud. El desarrollo urbano, la contaminación, el drenaje de tierras y el cambio climático están poniendo en peligro estos valiosos hábitats que sirven como amortiguadores esenciales contra inundaciones y refugios para la vida silvestre.[42].

Habitat loss

Globally, it is estimated that continued habitat loss alone will cause the extinction of approximately 1,700 vertebrate species by 2070.[43] Coastal wetlands are highly vulnerable to this threat due to erosion, subsidence, sea level rise, development and drainage. "Approximately seven football fields every hour, and a twenty-five percent increase over the previous six-year study period."[44] Common direct impacts of habitat loss on wetlands include the removal of vegetation, fluctuating water levels, and the construction of buildings. The decline of wetland habitat has far-reaching economic and social implications. The degradation and loss of these habitats have caused the reduction of fish populations, both in size and diversity. This, in turn, has led to a decline in the availability of opportunities for both the commercial fishing industry and recreational fishing, affecting the livelihoods and leisure activities of many people and communities. This habitat loss not only affects the fish that reside in these wetlands and the recreational activities that result from them, but the reduction in fish populations resulting from the loss of habitat in the wetlands can upset the delicate balance of the ecosystem. As fish play a crucial role in the food chain, their decline can lead to changes in the abundance and behavior of other species, affecting the entire wetland ecosystem.[44].

Pollution

Wetlands are susceptible to the harmful effects of pollution, which can undermine their ecological health and diminish their vital functions. Pollution from various sources, including agricultural runoff, industrial discharges and urban pollutants, poses a significant threat to the delicate balance of wetland ecosystems, affecting not only their plant and animal residents but also the ecosystem services they provide. According to an article published by NOAA Fisheries, due to high concentrations of pollution, the capacity of a wetland's filtration system can be overwhelmed, allowing excess nutrients and toxic chemicals to concentrate in waterways, creating dead zones that leave organisms living in the water unable to survive. Wetlands not only serve as conduits for the passage of plastic waste, but they also act as sites where this waste accumulates over time, posing long-lasting challenges. [45] Human actions, including road construction and resource extraction, have significantly disturbed wetland ecosystems. This has made previously drained wetlands susceptible to bushfires, thus increasing the chances of air pollution from the toxic metals that the wetlands have absorbed and stored in the peat, and which can pose threats to people's health and the environment. Once a drained wetland ignites, "peatland fires are difficult to contain as they can burn for weeks, months or even years. They produce large amounts of smoke and ash, filling the air with microscopic particles." [46].

Invasive species

Invasive species are causing considerable damage to wetlands by competing with native plants and animals, disrupting the delicate balance of these ecosystems. These invaders often grow more aggressively and can change the structure and function of the wetland, reducing its flood control and water purification capacity. Additionally, invasive species can negatively impact the availability of suitable habitat for native species and contribute to the overall degradation of wetland health.[47] An example of one of the many organisms that pose an invasive species threat to wetlands is the otter. The otter is a semi-aquatic rodent native to South America that was brought to the United States in 1889 due to the popularity of its fur, but over the years it has taken over wetlands because it was released or escaped from ranches. Due to their high reproductive rate and lack of population control implemented, these rodents have caused damage to crops, declines in native plants due to consumption, and an increase in flood damage due to their low burrows.[48].

Climate change

Climate change has a significant impact on wetlands, primarily through increasing temperatures and altering precipitation patterns. These changes can lead to changes in wetland ecosystems, affecting the distribution of plant and animal species.[49] In addition, rising temperatures can lead to the loss of wetland habitat and contribute to sea level rise, which can further threaten the stability and function of coastal wetlands, as well as causing alterations in precipitation patterns "Precipitation (meteorology)") and prolonged droughts, leading to reduced water levels and drying of wetland areas. As temperatures rise, wetlands are susceptible to more frequent and severe wildfires. Increased fire risk can lead to the destruction of wetland vegetation, further decreasing their ability to support wildlife and maintain their ecological functions. [50].

Featured wetlands

• - Iberá Wetlands, in Argentina.

• - Bañado La Estrella, in Argentina.

• - RAMSAR Site Chaco Wetlands, in Argentina.

• - Los Haitises National Park, Dominican Republic.

• - Jaaukanigás Ramsar Site, in Argentina.[60].

• - Laguna de Rocha,[61] in Monte Grande, Buenos Aires, Argentina.

• - Bocas del Polochic Wildlife Refuge,[62] in Guatemala.

• - Brazilian-Paraguayan-Bolivian Pantanal.

• - Bañados de Otuquis, in Bolivia.

• - Bañados de Izozog, in Bolivia.

• - Bañados de Tichela, in Bolivia.

• - Lake Titicaca, both on the Peruvian and Bolivian sides.

• - Okavango Delta, Botswana.

• - Queen Maud Gulf, in Canada.

• - Moncul Wetland, in Chile.

• - El Yali Wetland, in Chile.

• - Río Cruces, in Chile.

• - Ojos de Mar Wetland, Chile.

• - Ciénaga Grande de Santa Marta, lagoon on the Caribbean coast, east of the mouth of the Magdalena River, in Colombia.

• - Wetlands of Bogotá, in Colombia.

• - Baudó River Delta, in Colombia.

• - Palo Verde, in Costa Rica.

• - Lake Enriquillo, in the Dominican Republic.

• - Zapata Swamp, in Cuba.

• - Doñana, Tablas de Daimiel, Albufera de Valencia, Ebro Delta, Mar Menor and Lagunas de Ruidera, in Spain.[63].

• - The galacho of La Alfranca and the galacho of Juslibol, in the province of Zaragoza, Spain.

• - Charca de Suárez,[64] in Motril, Andalusia, Spain.

• - Everglades Natural Park, in the United States.

• - Gulf of Fonseca, in Honduras.

• - Chilka Lake, in India.

• - Niger Delta, in Mali.

• - Centla Swamps, in Tabasco, Mexico.

• - Ría Lagartos wetlands, in the Yucatán Peninsula, Mexico.

• - Gulf of Darién, on the Colombia border.

• - Laguna Los Milagros"), in Peru.

• - Villa Swamps, in Peru.

• - Ventanilla Wetlands, in Peru.[65].

• - Villa María Wetlands, in Chimbote[66] Peru.

• - Santa Lucia Wetland Park, in South Africa.

• - Santa Lucía Wetlands, in Uruguay.[67].

• - Phú Quốc, in Vietnam.

• - Mar Menor, in Spain.

• - Daimiel Tablas, in Spain.

• - Ruidera Lagoons (La Mancha), in Spain.

• - Bajo Yuna Mangrove National Park), Dominican Republic.