Tree of Life
“Tree of Life” by Aimee Kelley-Dickinson
Trees and the ocean have always been two loves of mine. They show two of the most essential elements of life on Earth: stability and change. Mangroves, or “forests of the tides,” are a beautiful blend between these two contradictory forces in life. Coincidentally, our experiences in this trip revolving around mangroves have been exact opposites.
In our first experience we were above the canopy on a stationary watch tower, and the second we were speeding through the roots on a motor boat that was going way too fast. Mangroves are an interesting organism that bring together differing parts of their environment and form an ecosystem completely unique to themselves.
Much of the Mekong Delta was originally covered with lush mangrove forests. Mangroves still exist in Vietnam, but they have been severely reduced largely from Agent Orange and other defoliants during the US-Vietnam War, but also from deforestation for urban and agricultural development. Still, Vietnam is home to the largest mangrove forest in Asia and the second largest in the world outside of the Amazon. Mangroves are an invaluable resource for Vietnam, however they are threatened by past deforestation, human development, and climate change.
Mangroves, which grow in the intertidal zone in tropical regions, are unlike any other tree: it holds its ground below and above water. Mangroves have several unique adaptations that allow them to be “salt-tolerant forest ecosystems.” One important and noticeable adaptation that allows mangroves to live in saline areas is their prop roots, which help to secure the trees during storms and tidal influxes. These roots have multiple layers of filters that only absorb fresh water, enabling the trees to live in both saline and fresh water environments. Many species also have hanging roots or protruding roots to obtain oxygen from the air because the sediment rich soil is oxygen poor.
Mangroves are a significant resource and provide many ecosystem services. Ecosystem services are free benefits that people obtain from a healthy, functioning ecosystem. Many of these services are overlooked such as protection from coastal erosion and reduction of the effects of storms. Other services include shelter and habitat for species, thus supporting biodiversity. They also improve water quality by capturing sediments and reducing large amounts of pollutants.
Shrimp farming and human development in the Mekong threaten the survival and growth of mangrove forests. Although mangroves act as a nursery for young shrimp, they are not conducive for high production shrimp farming. For high yields farmers repeatedly cut back forests. So far, it appears that the only way to protect mangrove forests is by government decree. In several places in the Mekong Delta the government has installed policies that ensure the survival of mangroves and the prosperity of farmers. In Can Gio farmers are “given” on average around 80 hectares of mangroves to manage and protect. They are responsible to monitor the forest and ensure that they are not destroyed or cut down. If there is any molestation they are required to report it to the authorities. At the same time, these farmers can raise shrimp to supplement the income from managing mangroves.
In Ca Mau National Park farmers are required to have a certain amount of hectarage of mangroves on their farm, or they will be expelled from their land. Farmers are still able to raise both natural and stocked shrimp while keeping the mangroves. This model also allows farmers to raise mud crab, fruit trees, livestock, vegetables, and other aquaculture products. Vietnam, and nations all over the globe should start looking at more sustainable and integrated systems; in the US we could do this by supporting more small, local farms that donʼt exploit the land by only raising one crop (monoculture). However, for these and other models to be widely implemented people will need to be shown the direct benefits and income. Also, the appropriate technologies will need to be supplied, which may not always be possible.
A slow change in temperature and CO2 is not expected to negatively affect mangrove forests, however,0rapid changes combined with human activity and development could have a fatal impact on mangrove forests. As sea levels rise and saline water protrudes farther inland, mangroves are slowly migrating inward and towards areas densely populated by people. A key example is the mangrove forest in Can Gio that is slowly moving towards Ho Chi Minh City. It is highly implausible that HCMC would move to accommodate migrating mangroves. Furthermore, mangroves are likely to be impacted by other effects of climate change such as increased intensity and occurrence of storms and increased precipitation.
Although the mangroves are threatened, domestic and international attention has helped them slowly bounce back. While they may never be restored to their natural grandeur due to human activity and the effects of climate change, efforts are being made to ensure their survival.