Blue Forests Basics

What are Mangrove forests?

Mangroves are shrubs and trees that grow in coastal waters. Mangroves are halophytes, meaning they are salt-tolerant trees that thrive in intertidal conditions. These diverse and productive ecosystems provide essential habitats for species, coastal protection from storms, and livelihood opportunities for coastal communities.

There are approximately 70 species of mangroves world-wide, of which there are six primary species: red mangroves (Rhizophora mangle), black mangroves (Avicennia germinans), white mangroves (Laguncularia racemosa), palm mangroves (Nypa fruticans), and mangrove apple (Sonneratia caseolaris).

Where are Mangrove Forests Found?

Mangrove forests are only found in tropical and subtropical coastal zones around the world, as they do not tolerate freezing temperatures. However, mangroves have adapted to grow in a range of different coastal ecosystems. For example, red mangroves are predominantly found bordering coastlines where they face more direct impact from wave intensity and storm surge, necessitating more substantial submerged roots to keep them in place and more aerial roots to provide the trees with oxygen through thick mud. Black mangroves are also coastal, though often located higher up along the coastline, while white mangroves can sit at even higher coastal elevations and do not generally have any visible aerial roots.

What benefits do Mangroves provide?

Mangroves are the most productive carbon-storing blue forests ecosystem. They store carbon through above-ground tree biomass and below-ground roots and soil. Coastal nations around the world are increasingly incorporating mangrove carbon – and blue carbon more generally – into climate mitigation goals through Nationally Determined Contributions (NDCs) under the United Nations Framework Convention on Climate Change (UNFCCC). Because their carbon stocks can be reliably measured and monitored, mangrove forests are also ideal for blue carbon offsetting initiatives.

Additionally, mangroves provide nursery habitats, areas of refuge, and feeding grounds for many juvenile tropical fish species, shellfish, crustaceans and invertebrates. Terrestrial species benefit from mangrove ecosystems as well, with migratory birds, mammals and reptiles reliant on mangrove forests for breeding sites and feeding grounds.

Due to their complex root system, mangroves also absorb wave energy and stay in place through the rise and fall of daily tides. In this way, mangroves play a crucial role in protecting shorelines from coastal erosion and storm surge. Because they often border freshwater rivers and oceans, mangroves also trap and store sediments and pollutants which helps prevent nitrates and phosphates from flowing into the sea.

WHat are Mangrove forests threatened by?

Mangrove forests are one of the most threatened habitats around the world, with global mangrove populations declining by 1% annually – approximately 150,000 hectares per year.

Mangroves are predominately threatened by anthropogenic activity. Deforestation rates of mangroves can be attributed to large-scale shrimp aquaculture, agriculture (namely palm oil plantations and rice paddies), coastal development, pollution, and the harvest of mangrove wood for fuel and building materials.

When mangrove ecosystems become degraded from deforestation, the carbon once stored in their biomass is released back into the atmosphere, thus negating the carbon-storing benefits they naturally possess.