What are Wetlands?

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Wetland Site is Algiers, Algeria

Wetland site is Algiers, Algeria

Wetlands are areas where water covers the soil, or is present either at or near the surface of the soil all year or for varying periods of time during the year. Wetland environments play a major part in the water cycle and possess a unique mixture of environmental conditions, flora and fauna. Wetlands have provided vital services to humanity for thousands of years and include a variety of ecosystems such as lagoons, marshes, rivers and their deltas, lakes, streams, peat bogs, water meadows, swamps, oases, mangrove forests, coral reefs and human-made lakes, dams and Salinas, shrimp and fish ponds, irrigated land and others.

In a more detailed sense, according to the Ramsar Convention for the Protection of Wetlands (Articles 1.1 and 2.1) wetlands are defined as:

“areas of marsh, fen, peat land or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres […..] and may incorporate riparian and coastal zones adjacent to the wetlands, and islands or bodies of marine water deeper than six metres at low tide lying within the wetlands”.

The Ramsar Classification of wetland types includes 42 types which can be broadly divided into:

  • Marine and coastal wetlands
  • Inland wetlands
  • Human-made wetlands

This classification simplifies the characterization of wetlands by dividing it based on geographic location and human parameters, but one must consider that overlaps occur since the categories are not always mutually exclusive.
A more in depth classification divides wetlands into five major categories:

  • marine wetlands (coastal wetlands including coastal lagoons, rocky shores, and coral reefs);
  • estuarine wetlands (including deltas, tidal marshes, and mangrove swamps);
  • lacustrine wetlands (wetlands associated with lakes);
  • riverine wetlands (wetlands related to rivers and streams); and
  • palustrine wetlands (meaning “marshy” – marshes, swamps and bogs).

The common denominator in all wetland types is the continuous or seasonal presence of water which creates a characteristic wetland soil – the hydric soil – and favours the growth of specially adapted plants.  These conditions support high biodiversity in terms of amphibians and reptiles that need both wet and dry areas to breed and resident and migratory birds that use wetlands as a breeding and resting place.

Wetlands can be found all over the world, in all climatic conditions from the tundra to the tropics. The UNEP- World Conservation Monitoring centre has suggested that roughly 6% of the Earth’s land surface is made up of wetlands, 2% of which are lakes, 30% bogs, 26% fens, 20% swamps and 15% floodplains. However, these figures may not represent the true extent as they are based on estimates; other studies have found a higher percentage of wetland cover on Earth).

Why are wetlands important?

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1. Wetlands are very diverse and productive environments.

Two Greater Flamengoes (Phinicopterus roseus) at the Gediz Delta, Turkey

Two Greater Flamengoes (Phinicopterus roseus) at the Gediz Delta, Turkey

They have high levels of biodiversity and are the primary habitat for many species; for example freshwater wetlands hold more than 40% of the world’s species and 12% of all animal species. Wetlands also store genetic material like rice, which is staple food for a large part of the population, while wetland fauna and flora has been extensively used in the medical industry. It is estimated that over 20,000 medicinal plant species are currently in use, some of them from wetlands, and over 80% of the world’s population depends on traditional medicine for their primary health care needs.

2. Flood protection: When water levels are high due to “heavy” rainfall and flooding, the vegetation slows the flow of water and stores part of it in the soil or in the surface which in turn reduces flooding and erosion downstream. Floodplain and wetland restoration as well as removal of man made structures is providing a partial solution to flooding in many countries.

3. Soil erosion: The vegetation of wetlands acts as a sediment source which holds together the banks of lakes, rivers and beaches. Increased soil loss and sedimentation is a common problem when wetlands are converted and the vegetation is removed.

4. Maintenance of water quality and pollution control:

Common reed (Phragmite australis)

Common reed (Phragmite australis), photo credit: J.C. Farinha

Wetlands are natural reservoirs and can be considered as a natural sewage system. The hydrophytes – specially adapted plants – not only slow the flow of water but also purify it. Any chemicals entering a wetland (from agricultural sources, human wastes and industrial discharge) and sediment are separated and settle on the bottom, they are then absorbed by the plants and converted into nutrients which are in turn passed on to the fauna. The sediment and chemical control, as well as the nutrient recycling, protects the blockage and eutrophication of downstream water bodies.

Wetlands functions of filtering water and controlling pollution are the most unique and critical functions of wetlands. Some types of wetlands are also the source of replenishment to groundwater aquifers, which provide a large part of the drinking water world wide.

5. Storm and wind buffer: Coastal wetlands buffer the effects of storms and wind by absorbing enormous amounts of wave and wind energy and reducing the damage caused inland.

6. Climate change mitigation and adaptation: Wetlands protect us from climate change in 2 important ways. Firstly they are carbon sinks, meaning they store greenhouse gases, with estimates showing that they may store as much as 40% of the global terrestrial carbon (especially peat and forested wetlands). Secondly, their water capturing and purifying functions as well as the storm and wind buffering can  protect us from some of the effects of climate change, such as changing rainfall patterns, higher storm frequencies, rising sea level and general extreme weather phenomena.

7. Wetland Products:

The range of products that wetlands provide humans directly is immense and in fact well managed wetlands can be very productive. Some such products are fruit, fish and shellfish, rice, timber, fuel wood, reed for thatching, meat like deer, crocodile and many others. Wetlands are exploited in many scales from subsistence, to cottage industries to commercial activities.

8. Recreation and Tourism: Many wetlands are spots of amazing beauty and animal and plant diversity and some are protected areas or World Heritage sites. They can offer many activities from fishing, boating, to bird watching and hunting. They can also be very educational for school children but also for the general public.

Why conserve wetlands?

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The various functions of wetlands, presented in the previous section, give them unique importance for both the plant and animal kingdom but also for mankind.  Wetlands are important for the people who live around them but also for the global freshwater supply. Our overuse of finite freshwater resources (which constitute 2.5% of the total water volume of our planet) and our projected future increased use paint a bleak picture for wetlands, but also for humans.

Water shortage has already started in many parts of the world and according to FAO by 2025 two-thirds of the world population could be under water stress conditions. Lack of freshwater and increased population growth present a real threat to humanity, however the solution to this problem can’t be found in a single response. Considering that wetlands store and purify water and replenish underground water sources, their conservation is vital for our future.

Wetlands are also important as part of the cultural heritage of humanity. Their ecological functions have overshadowed this aspect of their importance but it is now increasingly getting more attention. Wetlands are inextricably linked with the cultural heritage of humanity and are a cradle for local knowledge and tradition, religious beliefs and aesthetic values. Effectively, the conservation of wetlands contributes to the conservation of human tradition.

Major threats for wetlands

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Wetland habitats are among the most heavily impacted and degraded ecosystems (UN- millennium ecosystem assessment). In the last hundred years alone, half of the world’s wetlands have been lost mainly due to human interference and mismanagement.

  •  In Northern Greece 73% of marshes have been drained since 1930
  • In France 86% of the 78 most important wetlands were degraded by official public policies in the thirty years to 1994
  • Spain has lost an estimated 60% of its original wetland areas
  • In Northern and Central Tunisia 84% of the Medjerda Basin has disappeared during the 20th century.

These are only some examples of the extent of wetland loss in the Mediterranean basin.

The main reasons for the loss of wetlands are:

  1. Drainage and conversion for agriculture
  2. Pressures from settlements, urbanisation and tourist development
  3. Industrial activities
  4. Pollution from industrial, agricultural and urban sources.
  5. Introduction of invasive species that compete with native ones
  6. Changes in the hydrological regime through building of dams, diking and flow diversions
  7. Sedimentation from removal of vegetation in catchment areas through grazing and deposition of fill material for development
  8. Hunting
  9. Mosquito control in order to combat Malaria and other related diseases.


In order to protect wetlands from these threats it is important to involve stakeholders in all levels of governance and change the destructive practices that have been implemented until now. Wetland loss to a large extent is due to ignorance and misunderstanding of their role, so an important step in effective wetland conservation is informing public policy officials, decision makers and the general public about the true values and functions of wetlands.

Mediterranean Wetlands

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The Mediterranean region is unique because of its special type of climate and very long history of human use. For thousands of years, the wetlands around the Mediterranean basin have provided people not only with essential services like water, food, materials and transport, but have also played a major part in their social and cultural activities. Major civilizations were established in association with and depended on wetlands for resources like water; for example, the ancient Egyptians with the Nile, the Mesopotamians with the Tigris. Major cities like Venice and Tunis have been built in or very close to wetlands. Since major human settlements have been built in or around wetlands, significant archaeological remains can be found, like ancient ships in Marseille and Venice or even entire cities like Nikopolis in the Amvrakikos Gulf in Greece.

In the 20th century, with the advent of industrialization, intensive agriculture, urbanization, population pressures and legitimate health considerations, the bond between man and wetland was severed and hence many wetlands were destroyed (Benessaiah, 1998). Wetlands were perceived as dangerous places filled with dangerous animals, evil spirits and disease-carrying insects that needed to be “sanitized” or seen as unimportant, fallow land to be drained or converted to other uses.

Papayannis and Salathé (1998) define three specific features of   Mediterranean wetlands that should be considered:

  1. Mediterranean wetlands are very diverse, which is caused by the climatic variability of the region. In the North the wetlands are large river deltas and lagoons and in the South they are sebkhas and marshes that are seasonal and may appear every few years. Also, artificial wetlands range from oases and salinas to contemporary reservoirs created by hydroelectric and irrigation dams like in the Nile and the Neretva rivers.
  2. There are strong ties between local inhabitants and wetlands. These ties are evident by the fact that Mediterranean people not only used them but lived and still live in them, like in the archaic lacustrine settlements (Hourmouziades, 1996), the Empurias in Spain. Also, Venice and Tunis, two large Mediterranean cities are built in wetlands. These choices in settlement demonstrate how local communities in the Mediterranean basin have developed strong cultural bonds with wetland sites.
  3. Mediterranean wetlands are in degraded condition and they are under threat. The last century has seen the loss of more than half the wetlands, which has resulted in a dramatic degradation of their functions and loss of their values. Even though many attempts have been made to counteract this trend, the degradation and loss haven’t yet been stopped or reversed.