MANGROVES

DISTRIBUTION OF MANGROVES

Found on the coasts of countries.
These countries are mostly located between the Tropic of Cancer and the Tropic of Capricorn. However, there are also patches of mangroves further north and south of these tropics. Mangroves are most abundant on tropical coastlines such as the Malay peninsula.

ENVIRONMENTAL CONDITIONS AFFECTING GROWTH

Mangroves are a type of halophyte, which is a plant that grows naturally in a saline environment. They are typically found along sheltered coasts and river estuaries with muddy and waterlogged land. Coasts with Low energy waves allow mud and plant litter to accumulate and mangroves to thrive. Such environments are subjected to strong effects of the tides and sediment changes.

Some species such as Rhizophora, have prop roots to anchor the trees firmly in the soft, muddy ground. The roots Ensure that the trees will not be uprooted or swept away by the strong waves. Other species such as Bruguiera, have kneed roots that help to trap soil between their roots which is essential for plant growth.

Mangroves also adapt to their environment in other ways. Some mangrove fruits are javelin-shaped so they can pierce the soft mud to germinate and grow into a sapling immediately. Some fruits are buoyant, allowing them to float away and germinate in other coastal areas. These characteristics of the mangrove fruit increase their chances of survival.

Mangroves are also salt-tolerant and have developed ways to secrete excess salt. Some species do that through the underside of their leaves

VALUE OF MANGROVES

(Acronym: Stable Mangroves Protect & Improve Water)

1. Stabilising shorelines

• Their dense network of roots can absorb the energy of waves, thus slowing the flow of water. This network of roots allows the sediments that are washed down by rivers and washed up on coasts to build up amongst mangrove roots.

2. Breeding Ground and habitat for Marine Creatures

• Barnacles, oysters and sponges anchor on the hard surfaces of the aerial roots. Shrimps, lobsters, and crabs forage for food in the muddy sediments between mangrove roots and a variety of fish breed in the nearby waters.

3. Protect coastal areas

• Their dense network of roots and the build-up of sediments can help protect coastal areas from erosion by tides, storm waves and tsunamis.
• For example, a number of coastal sites in the Indian ocean region affected by the devastating tsunami in 2004 have been replanted with mangroves to protect the coast from future tsunamis

4. Improve water quality

5. Wood for fuel / provide building materials

PRESSURES ON MANGROVES

The world has lost 3.6 million hectares of mangroves.

1. DEMAND FOR FUEL WOOD AND CHARCOAL

Mangroves are cleared for fuel and charcoal, particularly in regions with Low technology and Low-income economies.
IMPACTS: Fish breeding grounds are reduced. Also, coasts become more open to storm waves
Eg. In Indonesia

2. CONVERSION TO OTHER LAND USES

Thousands of hectares of the flat, well-watered mangroves are converted into paddy fields and shrimp farms.
IMPACTS: Mangroves are cleared and coasts become more vulnerable
Eg. Thailand

3. LAND RECLAMATION

The land is reclaimed for housing, industry, and recreational uses.
IMPACTS: Mangroves largely disappear from the environment. Moreover, coastal waters are polluted as a result of human activities
Eg. Caribbean islands

4. WATER POLLUTION

Urban and manufacturing activities result in untreated or partly treated urban and manufacturing wastes being dumped into coastal waters.
IMPACTS: The pollution of coastal waters can overwhelm the delicate balance of mangrove ecosystems

5. RISING SEA LEVEL

Rising sea levels, together with extreme storm activity, are likely to occur in the future if climate change accelerates.
IMPACTS: Mangroves will have trouble colonising areas further inland despite sea-level rise as they will be in competition with human activities such as farming and the construction of sea defences.
Eg. Gulf of Thailand