Our Wetlands: Our Defence
by Dr. Rahanna Juman
Deputy Director or Research
The frequency of disasters worldwide has more than doubled in just 35 years; and 90% of these disasters are water related. More and more, climate change is driving weather-related hazards such as flooding and hurricanes. This pattern is already having a significant impact on Small Island Developing States in the Caribbean; and it’s unlikely to get any better. The most we can do is to develop strategies to manage the impacts of climate change and reduce carbon emissions and this is where wetlands come into their own importance.
In the Caribbean Region, it is estimated that changes in annual hurricane frequency and intensity could result in annual losses of as much as USD 446 million by 2080, arising from interruptions to business particularly in the tourism sector. Further, the Caribbean Development Bank estimates that the Region could lose up to 5% of Gross Domestic Product (GDP) over the next decade if governments fail to step up their efforts to improve the Region’s resilience and adaptation to climate change.
Globally, human activity is releasing increased amounts of carbon dioxide (CO2), methane, and other greenhouse gases (GHG) in the atmosphere fuelling the rise of temperatures. As temperatures rise, oceans become warmer, snow and ice caps melt and sea levels rise; faster now, than in any other time recorded in the previous century. Our wetlands can play a role in mitigating, and adapting to the negative impacts.
- Wetlands play a significant role in stabilizing GHG emissions and blunting the impacts of climate change. Coastal wetlands, particularly tidal marshes, seagrass beds and mangrove forests, trap and store carbon within their biomass and soils and are referred to as “blue carbon” ecosystems because of their relevance to the global carbon cycle. Mangroves, for example, store 50 times more carbon than tropical forests. Also called “blue carbon” ecosystems because of their relevance to the global carbon cycle, mangroves also support coastal livelihoods in addition to their mitigatory and adaptation functions. The Caroni Swamp and the Bon Accord Lagoon are some local examples of
a blue carbon ecosystems.
- Coastal wetlands such as coral reefs act like shock absorbers, reducing the intensity of waves, storm surges, and tsunamis; shielding the coastline and protecting human activity along the coasts from flooding, property damage and loss of life during severe weather events. Coral reefs act as offshore wave barriers. Annually, this protection from extreme events is estimated to be valued up to USD 33,556 per hectare.
- Mangroves can be an important defence against sea level rise. If mangroves are allowed to colonize landward areas where space is available, they can provide coastal defence services against waves and storms. Typically, wave height is reduced 13-66% for every 100 metres of mangrove. Every hectare of mangrove and coastal marsh is estimated to be worth USD 15,161 a year in disaster-related services.
What’s more and of particular significance to many of us in Trinidad and Tobago, wetlands, particularly floodplain wetlands, have the capacity to temporarily store flood waters during high runoff after torrential rain events. While wetlands have often been referred to as natural sponges that soak up water; they actually function more like natural tubs, storing either flood waters that overflow riverbanks or surface water that collects in isolated ponds. As flood waters recede, the water is released slowly from the wetland soils. By holding back some of the flood waters and slowing the rate that water re-enters the stream channel, wetlands can reduce the severity of flooding and erosion. The effectiveness of wetlands for flood abatement may vary, depending on the size of the area, type and condition of vegetation, slope, location of the wetland in the flood path and the saturation of wetland soils before flooding, Typically, a one-acre wetland, can store about 3.7 million litres of water. In Trinidad, floods are the most common and widespread of all natural disasters and there is strong evidence that, in a warming world, destructive floods will become more common and intense.
In spite of their important role, wetlands across the globe continue to be degraded by human activities and in Trinidad and Tobago our coral reefs, mangroves and seagrasses have not been spared. Land-based sources of pollution (excessive sediments and nutrients from run off following rains) are negatively impacting our coral reefs, decreasing their resilience and making them more susceptible to impacts from climate change (warmer sea waters leading to coral bleaching) and diseases. Many coral reefs around Tobago have also been experiencing phase shifts in benthic cover away from hard coral to species more tolerant of nutrient enriched water. Mangrove coverage declined in Trinidad by 252.4 ha from 2007 to 2014, while in Tobago it declined by 16.6 ha. This decline can be attributed to the removal of mangrove trees to facilitate built development. The only remaining extensive seagrass community is located within the Buccoo Reef Marine Park. Seagrass beds that were decimated along the northwest peninsula of Trinidad and on the Atlantic side of Tobago (La Guira, Kilgwyn Bay) have not recovered.
When we destroy wetlands, we lose the climate change mitigation and adaptation services they provide. National strategies to address climate change must therefore include the wise use of our wetlands. Individuals, communities, the private and public sectors must all work together to protect and where necessary restore these amazing ecosystems, which help us prepare for, cope with, recover and rebound from the impacts of climate change.
As we join the rest of the world on February 2nd 2019 to celebrate World Wetlands Day, let us remember the role our wetlands play in protecting us from impacts of climate change. We must conserve our wetlands so they can continue to protect us in the unforeseeable future. Healthy wetlands are our defence and our key to coping with climate change!
The Institute of Marine Affairs… Supporting Vision with Science since 1978.