THE MANGROVE
For a long time, I wanted to do an article on this forest that has fascinated me for a long time and it is by watching this report on the SUNDARBANS* that I am launching today to share with you the richness of mangroves and to raise the alarm signal on this forest in danger.
Some pointers to start:
Globally, mangroves occupy 75 of the tropical and subtropical coasts with a surface area of 180 000 Km2, ie 1 area covered by all tropical forests.
What is the mangrove? Mangrove is an amphibious coastal forest capable of developing and living on both land and water, which can therefore live in the air or water, from coastal, tropical to subtropical, characterized by the presence of mangroves.
The mangrove tree is the emblematic tree of mangroves, there are different kinds but all have in common to anchor deep in the soil, thus preserving the coastline erosion and thus mitigating the impacts of climate events. Red mangrove is found in seaside mangroves, deep water, black mangrove in shallow mangrove shrubs, and gray or white mangrove in dry areas.
But these vernacular names may correspond to different botanical species such as: Avicennia germinans, Avicennia vitida, Avicennia schaueriana, Conocarpus erectus, Clusia mangle, Laguncularia racemosa or Rhizophora mangle ...
The mangrove is therefore the king tree of the mangrove, fragile ecosystem that you will understand, typical of the tropical littorals. Located at the border between the sea and the land, the mangrove species undergo strong environmental constraints:
- a soft, unstable and oxygen-poor soil
- temporary and repeated submersion by salt water during tides Mangroves are the only trees capable of growing in these difficult conditions.
To achieve this, they have developed ingenious strategies such as their ability to remove salt and their aerial roots.
Some like the red mangrove have an aerial root system (rhizophore) that allows them to breathe and be stable on the mud. These are trees "on stilts". Others, such as white and gray mangroves, have pneumatophores (outgrowths of their roots) that rise vertically above the ground and water like tubas to ensure the respiration of the plant even when its roots are submerged by water tides.
Mangroves are the only trees to have climbing roots instead of going down.
To survive and reproduce in the mangrove, mangroves have also adopted a very special germination mode, which is a vegetal form of viviparity. Rather than risking drowning or asphyxiation, the seeds of red and white mangroves germinate when they are still on the parent tree. When they have developed sufficient roots, the young mangrove seedlings are detached from the mother tree to settle directly in the mud (at low tide) or be driven by the current (at high tide). This is how the mangrove extends by flotation ...
These trees are able to support both water and salt. They grow in the mud, or on the beaches.
Mangroves and their mangroves make us multiple ecological and economic services.
They promote the practice of coastal fishing and even sometimes the development of ecotourism! Some tourist operators propose to visit this typical landscape by kayak or canoe to try to observe the fauna.
Around the world, they promote the development of different types of fisheries:
artisanal, commercial, recreational around the world.
On the branches of a mangrove are oysters, sponges, mussels, molluscs, and in their roots, small fish and crabs. Fish, crabs and other marine species are harvested. In Guyana in 2001, fishing accounted for 18.4 million euros in exports.
It has been calculated that one hectare of mangroves in the Philippines "generates" 400 kg of fish, shrimps, crabs and molluscs each year plus an equivalent production of the same origin but growing elsewhere.
In Malaysia, 400 km2 of mangroves support a fishery of 100 million dollars a year.
Les usages de la mangrove et les activités qui s'y déploient sont nombreux et parfois conflictuels : pêche, cueillette, ramassage du sel sur les lignes arrières et sursalées, saliculture, agriculture (riziculture), aquaculture (crevetticulture), sylviculture, tourisme aujourd'hui.
Cette dernière activité s'est par exemple développée dans les Antilles françaises, en même temps que la protection de ce milieu s'est imposée : en Martinique, entre 1951 et 1998, 15% des surfaces de mangrove ont disparu dans la baie de Fortde-France et les travaux portuaires gagnent encore aujourd'hui sur la mangrove à l'est de la ville ;
Mangrove uses and activities are numerous and sometimes conflicting:
fishing, gathering, salt picking on back and supersaled lines, salt farming, agriculture (rice growing), aquaculture (shrimp farming), forestry, tourism today. hui.
This last activity developed for example in the French West Indies, at the same time that the protection of this environment was imposed: in Martinique, between 1951 and 1998, 15% of the mangrove areas disappeared in the Bay of Fortde- France and port works are still gaining ground on the mangrove to the east of the city;
Today only 1,500 hectares of mangroves remain on the island's shores.
The Petit Cul-de-Sac Marin in Guadeloupe, on which the facilities of the autonomous port of Guadeloupe and the industrial area of Jarry have been developed, has also been largely filled in. On the other hand, the Grand Cul-de-Sac Marin mangroves cover nearly 3,000 hectares.
n Guyana, mangroves offer significant economic benefits because they condition the practice of coastal fishing in particular but the uses have been and remain restricted: harvest of mantou crab or beard crab, collection of stilt roots of red mangrove to make bows, ropes or basketry, hunt for ibis and small waders. .
Elsewhere on the planet, they also provide environmental benefits as a protective barrier to the shoreline against swell and ocean currents.
An attractive site for tourism
While mangroves are not traditionally perceived as recreational sites, this is changing rapidly.
People realize that this ecosystem can provide an extraordinary educational experience from the unusual species that can be easily observed.
Mangroves have promoted the creation of educational trails that contribute to the development of ecotourism. A mangrove stilt course was created in the Salines de Rémire-Montjoly in French Guiana Some tourist operators offer the opportunity to visit the mangroves by kayak or canoe.
Resources for pharmacopoeia
A study in Indonesia estimated that mangroves provide a net benefit of US $ 1,500 per square kilometer due to the medicinal plants they shelter.
In Guyana, mangle liana (or ihipkwatriyene in Palikur) is associated in creole medicine, white mangrove and tobacco to treat venomous sting bites. The roots of Zimmortelle or Mitiku * (a tree that grows in the flooded forests of the back - mangrove) are prepared in a decoction that drunk fever or malaria patients drink.
The mangrove of Martinique covers an area of about 1800 hectares and represents about 6% of the forest area of the island. It is located mainly in the center (Robert, Francis, Bay of the English, the Peninsula of Caravelle) and south of the island (Cul-de-Sack Marin, Diamond).
The largest area is located in Génipa Bay, at the bottom of Fort de France Bay (nearly 1000 ha).
The species that grow closer to the sea in clay soil are Red Mangrove, Mangrove or Black Mangroves, Mangrove or White Mango. Further back from the coast, the mangrove soil becomes clayey-sandy. There are mainly Gray Mangles, Gray Mangroves and more still inland, large golden ferns.
On the Trinity site flooded with fresh water, there are also Mangles Medals. Although the mangrove of Martinique is partially protected today, over the last few years, the men have enormously dehorned the still planted area of littoral forest. The biggest damage was done during the construction of the Port of Fort-de-France, the Lamentin airport and many houses and resorts "feet in the water"
THE ROLES OF THE MANGROVE
The mangrove has many advantages:
- Naturally filter pollutants (heavy metals and other toxic) contained in seawater:
The different root systems of mangroves contribute to the filtration and retention of pollutants (heavy metals and other toxicants) in the water, as well as the retention of nutrients and suspended solids.
- Trapping greenhouse gases like all other forests on the planet:
The data collected made it possible to determine that the sedimentary surface of the mangrove, consisting of plant microorganisms, had a capacity to sequester carbon from 10 to 100 times higher than that of mangroves. Carbon dioxide emissions from burning fossil fuels and changes in land use are the main causes of the increase in greenhouse gases in the atmosphere. Forests, crops, soils and organic matter trap carbon and thus help reduce the speed of climate change. Mangroves fix significant amounts of carbon, it is estimated today that mangroves could trap 25.5 million tons of carbon per year.
- To serve as a shelter and nursery for important fauna:
The water in and around mangroves is usually rich in nutrients. This results from the abundant organic matter produced by mangroves and sediments trapped between the roots of the latter. Mangroves produce about 1 kg of litter / m2 annually, which forms the basis of a complex food web and some of which is exported with the tide. As a result, mangroves promote fabulous marine life and often serve as a nursery, (the fry deposited can grow away from predators that have difficulty moving through the roots in stilt mangroves.) Once these juveniles become large, they go back to the coral reefs located a little further out to sea).
- Protect naturally against tsunamis and storms & protect the coastline against erosion due to swell and sea currents. In tropical countries hit by hurricanes, storms and hurricanes are very useful because they limit the damage caused by wind and wave strength, even in case of tsunami! The mangrove is an effective bulwark against erosion, cyclones or tsunamis.
A mangrove forest is a real protective barrier for the population in the event of a tsunami. The wave is micro-diffused by the aerial roots of mangroves. She loses her energy very quickly "; The energy of a wave can be reduced by 75% when it passes through 200 meters of mangrove if the latter is in good condition.
With its ability to break waves, the mangrove protects human lives and buildings on the shoreline. In India, in the district of Chidambaran, the role of coastal protection by mangroves is well known.
A 113 km2 mangrove is considered a sacred forest; it is also called Alaithi Kadukal, which means in Tamil, "the forest that controls the waves". It has been documented that the tsunami damage in South Asia in December 2004 would have been greater in some areas had the wave force not been absorbed by mangrove areas. Conversely, the destruction of mangroves entails expenditures to set up facilities that protect the coastline against marine erosion. The Republic of Maldives (Indian Ocean) has invested $ 10 million per kilometer in an artificial breakwater to protect its beaches.
Guiana, because of its position away from cyclonic trajectories, is immune to these types of damage.
The mangrove protects the coastline by trapping the sediments coming from the continent and avoiding their too fast dispersion by the marine currents.
THREATS OF THE MANGROVE
In some parts of the world, removals and degradations have gone so far, that there are now in Asia, Florida and Africa, mangrove restoration projects.
The causes of this rapid disappearance are many, because of the exploitation of wood for construction, for charcoal, for the extraction of salt but especially because of deforestation for the creation of shrimp ponds ...
The construction of roads and infrastructure can also cause the disappearance of the mangrove and promote erosion.
In Guyana, mangrove trees are cut systematically in some areas of Cayenne and Kourou, because they constitute the main nourishing plants of the caterpillars of the "butterfly ash".
The latter is feared for the itching caused by stinging hairs.
Mangroves are also little appreciated because they are favorite places for mosquitoes. However, these localized cuts do not put the Guyanese mangrove in danger.
Industrial and domestic pollution
More than 77% of the pollutants arriving at sea come from the mainland and 44% of these pollutants come from untreated waste and the phenomenon of runoff. Waste and wastewater discharged into ecosystems adjacent to mangroves such as rivers, marshes and rivers can eventually reach the mangrove through currents and tides.
Rejected directly in the mangrove, they pose as many problems. Visual pollution first, bad smells, deterioration of the quality of the water ... by the sewage laden with various chemical products resulting from the domestic and industrial activities. The most risky mangrove areas are those downstream of commercial ports (heavy pollution by hydrocarbons: storage in these areas, and significant river traffic ...).
In Asia, mangroves can also be destroyed to make way for paddy fields, farms or salt marshes. In very arid regions, the mangrove is cut more than the surface necessary for salt marshes because it takes wood to boil salty water to recover salt. In Guyana, the most risky mangrove areas are those near the rice fields of Mana (threat by phytosanitary used in large quantities).
Natural barrier against tsunamis, immense reservoir in terms of biodiversity, natural "super-market" for certain populations, the mangrove is in danger.
A true link between the land and the sea, the mangrove is one of the first ecosystems to undergo this climate change, particularly the warming and the rising of the oceans. In the case however it would disappear, it is of course an entire ecosystem that would be damaged. An ecosystem whose role is crucial from both an economic and an environmental point of view. Many people have already borne the brunt of the destruction of mangrove forests
These can be exploited on a large scale as was the case in Nigeria where they were used for coal mines. Although the demand for coal has subsequently declined, the wood is still exploited for various purposes, particularly for the construction of frames.
IN SUMMARY
An awareness of the importance of protecting this ecosystem, which is developing mainly in the intertropical zones, has made it possible to set up concrete projects. the NGO Mangrove Action Project (MAP) * is present in nine countries, in Asia, Africa and Latin America. La Map supports reforestation and education programs. Children from schools located in mangrove areas are invited each year to participate in a contest "Mangrove Art Calendar" whose goal is to make the voices of children living in this environment heard.
* http://mangroveactionproject.org/english
In terms of restoration and reforestation, the NGO implements programs in partnership with fishermen to promote sustainable development. Many actions are currently taking place, notably in Ecuador, Brazil, Guatemala, Thailand, Sri Lanka and Malaysia. The Sundarbans, in India and Bangladesh, have been skimmed since 1892-1893, when the first forest management plan was implemented. The system has been excellent for the sustainable management of this ecosystem. In the SUNDARBANS separate annual cuttings are established for the extraction of lumber, firewood and pulpwood.
Aujourd’hui, cette mangrove est l’une des plus grandes. Elle est classée au patrimoine mondial de l’UNESCO depuis 1987 et est connue pour la richesse de sa faune, qui comprend 260 espèces d’oiseaux, le tigre du Bengale et d’autres espèces menacées comme le crocodile marin et le python indien.
PLANTES, SENS & ESSENCES