Weathering the storm of mangrove deforestation

Loss

Straddling the intertidal zone between saltwater and muddy soil, in 1997 mangroves covered over 18,100,000ha of the world’s coastlines. Since then, this number has rapidly diminished to less than 13,776,000ha in 2011 and further decreased to 8,349,500ha in 2016 meaning that we have now lost over 50% of mangroves in just over two decades. The main causes of loss are urban development, aquaculture, conversion into agriculture for rice farming and timber exploitation, all a result of human impact.

Conservation

Mangroves provide an abundance of environmental and economic benefits. They are adapted to withstand anoxic soils, extreme tides and sweltering tropical climates. Ecologically, mangroves are an invaluable habitat for juvenile fish species and in the Galapagos, found to be a nursery ground for endangered hammerhead and blacktip sharks. The structural complexity of their roots helps juvenile sharks evade predation and mangroves are often home to a wealth of small invertebrates, a convenient food source.

By far the most vital role of mangroves is their ability to absorb carbon and nitrogen. Carbon is drawn into mangrove wood and soil, accumulating there, removing and isolating it from the atmosphere. In addition, with the help of soil-dwelling microbes’ nitrogen is fixed from its inorganic to its organic form in mangrove mud. Whilst mangroves only cover 3% of Earth’s forests, they account for over 10% of the reduction of carbon emissions globally, significantly more than their rainforest counterparts.

The most direct benefit from mangroves is their ability to buffer coastlines against storm surges and tsunamis, reducing the loss of human life in catastrophic natural disasters. A report after the 2004 Indian Ocean tsunami highlighted how the presence of mangroves provided protection to coastal communities. In a Sri Lankan village with dense mangrove forests, only two people lost their lives yet in settlements that had suffered major mangrove deforestation up to 6000 people died. This led to worldwide calls for pioneering mangrove restoration projects.

Restoration

After the Indian Ocean tsunami, many governments looked to mangrove restoration projects to protect coastlines for the future. However, many of these efforts failed for reasons such as planting the wrong species, unsuitable for the specific level of salinity, wave exposure and submergence.

Since this discovery, there has been a shift to a more holistic approach, taking consideration of the mangrove beds as an entire ecological unit. To make the system more resilient planting a mixture of natural species, ages and root types is required. As a consequence, a more diverse range of fruit, fodder and timber is produced, benefitting all stakeholders.

In general, researchers agree that to save these habitats, policies enacted and enforced by governments in isolation are not enough. For mangrove protection and restoration to be effective, engagement and commitment from local communities is essential. One initiative involves locals in data collection for citizen science projects which can then be assessed for protective area planning, natural resource monitoring and threat to disease. These types of approaches have been met with increased enthusiasm towards restoration and offer hope for the future.