Mangroves And Climate Change

 

Mangroves are coastal forests found at the border between land and sea. They are also found at river mouths (estuaries). Half their acreage is in the land and some parts are in the sea. Mangroves form the blue carbon ecosystems of which sea grass and saltmarshes are the others. As an ecosystem, mangroves are very rich in terms of biodiversity and carbon stores. Mangroves house thousands varying and multiple species of animal life and fish, and over 80 plant species.

Mangoves are located in 123 nations and are found ringing the Indian Ocean and sections of Atlantic and Pacific Oceans. Research figures put their coverage to about 152,000 square kilometers globally. Mangroves are unique in many ways, because even though they are below 1 percent of tropical forests, they are faster and more effective at carbon storage. It is estimated that the soils beneath mangrove forests carry about 6.4 billion tonnes of locked carbon, spread at the rate of a thousand tons per hectare.

Majority of mangrove carbon is beneath ground, around 83 to 99%. These forests are not uniform and depend on environmental conditions, consisting widely of hardwoods to shrubs, very tall close canopy forests to open shrub like growth.

Mangroves are different because they are able to store 4 times the carbon inland forests do. Some of the reasons for this is because mangroves thrive in brackish (partly saline water), so the salty conditions and waterlogged soil prevent respiration, decomposition and the release of carbon dioxide or methane.

Mangroves at the equator trap more carbon than other tropical counterparts and 90 percent of mangroves are found in developing nations.

Lamu mangroves - The Star

Mangroves have special characteristics that set them apart from their terrestrial counterparts. The first is aerial roots known as pneumatophores. Because the ground beneath these trees is waterlogged, soil oxygen is unavailable, and so these trees use aerial roots to absorb oxygen from the air. They are known as breathing roots.

The second is the trees have buttresses, with some of the exposed roots forming a strong base of visible support for the tree. Because of their positioning, mangroves receive nutrients from the land in form of runoff or from rivers washing fertile sediment into the sea. They trap this silt/sediment using their elevated roots.

In this way, they filter water and stop further contamination outwards, stop further erosion and steady (geologically stabilize) the shores.

They have floating seeds and are able to remove salt from sea water.

Research has it that a quarter to third of all initial mangrove forests have been lost or degraded. This is through exploitation for timber and fuel wood, agriculture, aquaculture, tourism, industrial or urban growth and pollution. If things continue as usual all mangroves will be lost by the end of the 21^st century.

In terms of climate change, mangroves are affected by changes in atmospheric carbon dioxide concentration, higher sea and air temperatures, higher rainfall, stronger and recurrent storms and sea level rise which is the greatest threat.

 Usually, as their roots trap sediment, these trees are lifted up gradually and this raises the surface of the land (accretion), which acts as a barrier against rising waters. However, with sea level rise, mangroves would migrate inwards onto dry land, but this rapidly being hindered by physical development on the coastlands.

Sea level rise will physically drown mangroves when it’s faster than the accretion rate. Also, these coastal forests need a specific balance of water. They need an influx of freshwater from rainfall and rivers to dilute saline sea water. They thrive in a region that is not too salty and not too fresh. However too high volumes of river water would flood mangroves.

As mangroves grow landwards, there tends to be an ecological succession where terrestrial forests that grow on dry land and rely on freshwater take over.

Mangroves are very sensitive to disruption. Because the soils beneath them are extremely carbon rich and have remained undisturbed for centuries, destruction of these forests for whatever reason releases vast amounts of previously intact carbon. In fact, 20% of all deforestation emissions are from mangroves. And because of how valuable they are, mangroves are being lost 3-5 more times than tropical forests.

Mangroves are crucial for adaptation especially for coastal communities. They form part of the nature based solutions (NbS) to climate change. They protect the land from some of the harsher effects of climate change like storm surges, strong cyclones, flooding and resultant erosion.

As a result of their powerful and far-reaching network of roots, mangroves are able to slow waves brought about by winds and so slow the velocity of storm surge flowing inland. They delay and obstruct the pace of flowing water, which reduces the speed these storm surges. The same is true for tropical cyclones. Their whole bodies, roots to shoots slow down the action of intense storms.

In this way they dampen the full blown effect of hurricanes on land, preventing massive destruction to a strong degree. However, mangroves cannot do this in isolation, and need to be paired with manmade adaptation methods, such as sea walls.

In addition, their trapping of soil and increase of land mass protects the coast from sea level rise.

Because of their filtering abilities, these ecosystems protect coral reefs and sea grasses from inundation with soil or pollution by agrochemicals like phosphates and nitrates. They also help adjoining mudflats.

Apart from their climate services mangroves also serve a host of other functions. They are a part of nutrient cycling, genetic diversity, have cultural value and spiritual importance, are used for recreation, education, research, entertainment, tourism, pollination,  and have medicinal value. They are used in decorations, ensure food security, and promote fisheries and biodiversity.

The last three are very important because mangroves provide a direct livelihood to about 100 million people. It is estimated that mangroves in developing countries are worth between 33 to 57 thousand US$ per hectare. The forest products include timber and fuel wood, honey and syrups, tannins and dyes, barks and leaves used as medicine and for making handicrafts etc. Over 600 known species of fish make mangroves their home, with nesting grounds and nurseries for many fish species found here.

Additionally, they form the habitat for migratory birds, clams, shrimps and crabs.

Because of all these reasons, mangroves need to be protected, of which about 41% of them are. As part of NbS, they need to be conserved and restored. However, protection of existing mangrove forests is the first priority as more areas are restored.

Mangroves face threats from agriculture especially palm oil plantations, and aquaculture is one of the biggest pressures. Shrimp farming especially in Asia is intensive, and large areas of mangroves are cut down to make way for the ponds. In fact, 38% of mangrove losses are from the practice. When retired, these ponds do not favour the regrowth of mangroves because the water chemistry has already been altered. It is too saline or toxic as a result of the chemicals used.

Mangroves are also destroyed to make way for beachfront property, ports and harbours.

To counteract this, there has to be efforts at bringing more mangroves under legal and global protection. In fact, as wetlands, mangroves are covered by the Ramsar Convention, the Convention on Biological Diversity and the Paris Agreement article 5 which deals with protection of forests and reduction of their emissions.

However, more needs to be done in terms of funding, because restoration needs finance. More awareness needs to be created about the importance of mangroves inclusive of public education campaigns. Legal and regulatory framework needs to be mainstreamed into local and national governments. There needs to be more willing, direct and open partnerships between stakeholders especially the local populace. This is in order to ensure cohesion and progress in mangrove protection.

Such consultative forums induce sharing of knowledge which is mutually beneficial to all.

Corporations can undertake such projects as part of their climate responsibility.

There has been examples of successful projects, and showcasing that can spur on multiple endeavors elsewhere.

Another important thing for mangrove protection is calculation of financial value of their ecosystem services. When done properly, these forests can be part of payment for ecosystem services projects like REDD+.

This will show the value of forests to local communities and give them a real life incentive and impetus to conserve them. The proceeds accrued from involving these forests in carbon credit schemes can be used for the benefit of the locals or added to the national kitty and used for development projects such as building infrastructure. This will better the living conditions of the people.

Also, since mangroves provide a livelihood to so many, when destroyed, they lead to an increase in poverty and associated evils like crime and insecurity, early and child marriages, dropping out of school and generally lower quality of life.

So, encouraging mangrove conservation leads to more jobs in the ecotourism sector, in sustainable fisheries, and sustainable timber extraction and selling of forest products in an environmentally safe manner.

There have been efforts to conserve mangroves by encouraging non-destructive management approaches to forests. This includes farming of rare and endangered butterfly species, which both protects the biodiversity of these forests and earns income for the people.