By Malintha Halkewela –
Human civilizations have grown and thrived in river valleys and coastal plains with abundant wetlands for thousands of years. These wetland systems, with their rich natural resources, have been critical to the development and survival of humanity and are part of our natural wealth. Wetlands exist in every country and in every climatic zone, from the polar regions to the tropics, and from high altitudes to dry regions. They are places where the land is covered by water, either salt, fresh or somewhere in between, including marshes and ponds, the edge of a lake or ocean, the delta at the mouth of a river or low-lying areas that frequently flood. Wetland ecosystems include mangroves, peatlands and marshes, rivers and lakes, deltas, floodplains and flooded forests, rice-fields, and even coral reefs.
Wetlands, a Lifeline for All Beings
The scientific community estimates that wetlands cover 6% of the world’s land surface with mangroves covering some 15.2 million hectares and coral reefs are estimated to cover 60 million hectares. Further reach indicates that wetland ecosystems contain about 12% of the global carbon pool, playing an important role in the global carbon cycle. Important wetland functions include water storage, groundwater recharge, storm protection, flood mitigation, shoreline stabilization, erosion control, and retention of carbon, nutrients, sediments and pollutants. Wetlands also produce goods that have a significant economic value such as clean water, fisheries, timber, peat, wildlife resources and tourism opportunities.
In Sri Lanka, wetlands have been a lifeline for both humans and animals for well over two thousand years. Sri Lankan ecosystems include a variety of wetlands including inland natural freshwater wetlands, numerous lakes, marshes, streams, swamp forests and villus as well as marine and salt water wetlands such as lagoons, estuaries, mangroves, seagrass beds, and coral reefs and man-made wetlands. Bundala, Anaiwilundawa and Maduganga wetlands are renowned worldwide for their unique biodiversity.
Threats of Climate Change
Climate change is recognized as a major threat to the survival of species and integrity of ecosystems worldwide. Scientific data predicts the ecological and hydrological impacts expected to result from climate change have increased considerably over the past decade. Potential climate change impacts on wetlands are likely to be caused through changes in hydrology, direct and indirect effects of changing temperatures, and changing land use patterns.
Hydrologic impacts due to climate change may range from sea level rise and salt water intrusion to increased inundation on a seasonal or annual basis and loss of soil moisture due to drying or drought. As wetlands move nutrients, pollutants and sediments from land to water, decreasing water flows due to drought will cause these substances to accumulate in the wetlands and seriously endanger animal and plant life. As water levels decrease it would also increase the exposure of wetland sediment and increase the concentration of salt in the soil. In drier areas it will decrease the movement of water from regions of higher potential to regions of lower potential, overall restraining the ability of plant life to take up water from the soil. The concentration of other toxics in the soil may also increase and cause problems to both plants and animals due to the increased rates of evapotranspiration.
As our planet becomes warmer, in general, biological productivity increases with temperature. Most aquatic birds in coastal areas depend upon seasonal flood pulses and gradual water reduction. Changes in the timing and severity of this flood pulse due to climate change will affect the availability of safe breeding sites for birds and amphibians, causing some wetland species to move away from their natural habitats and paving the way for extinction.
Fighting Climate Change
Despite the impact of climate change upon wetlands, recent reports have indicated that coastal wetlands are among the best marine ecosystems to fight climate change. Coastal wetlands take in carbon quickly and hold it for a long time. If they are not protected, these ecosystems could release huge amounts of greenhouse gases into the atmosphere, especially when temperatures rise, limiting the scope of some nations to meet their international climate commitments in the Paris Agreement.
The ability of wetlands to buffer climate change impacts can be considered a natural adaptation measure. For example, mangrove forests provide protection and shelter from extreme weather events such as storm winds and floods. Mangroves absorb and disperse tidal surges and can reduce the destructive force of a tsunami by up to 90%. They also play a major role in climate change mitigation, as coastal wetland vegetation such as mangroves stores so-called “blue carbon” and thereby acts as a carbon sink. It has been estimated that the world has lost around 3.6 million hectares of mangroves since 1980, and that this has been a major reason for the decline in coastal fisheries of many tropical and subtropical countries, including Sri Lanka.
Protecting and Restoring Mangroves
Protecting and restoring mangrove habitats is vital in the fight against climate change and its impacts. New zones of mangrove habitat should be established where they do not clash with human development, so they are capable of replenishing themselves landwards as the sea level rises.
To ensure that the wetlands are protected, it is important that restoration practitioners take climate change into account when implementing restoration projects. Also, policymakers need to ensure that wetland restoration is part of climate change adaptation and mitigation strategies for Sri Lanka. As wetlands help to maintain clean air, health, economy, human quality of life and the well-being of the natural environment, restoring and protecting them is key to addressing climate change and protecting the environment.