Mangroves

(10/03/25)

Mangrove Conditions

Distrubuted near/in bodies of water, at the coastlines of different continents. No distrubution in the far north, but only below. Tropical & sub-tropical areas.

Found between 30 degrees north and south, where minimum sea surface temperatures are 16 degrees celcius.

Coral reefs and mangroves grow well together (mangroves catch a lot of the sediment)

They need brakish water (mixed fresh and salt)
Often found in intertidal zones (zone between high and low tide)
Found in estuaries, saltmarshes, and bays. Prefer sheltered and protected areas.
Mangroves are flowering trees that can grow in salt water.
Mangroves are found where salinity ranges from 0-90PPT. (parts per thousand)
Water is not a requirment for mangrove growth (faculative halophytes), but in freshwater areas other species compete with mangroves for space.

Prop Roots
Sread far and wide, acting as an anchor.

Can withstand high wave energy. (because there are so many of them)

Support tree on soft, silty soils.

Provides large surface for oxygen absorbing lenticels.

Lenticels (they are like stomatas)

Small pores present on the roots.

Oxygen enters a mangrove through lenticels, thousands of cell-sized breathing pores.

Lenticels close tightly during high tide, thus preventing mangroves from drowning.

Pneumatophores

Breathing roots
Commonly found in mangrove species that grow in saline mud flats.
Lateral roots that grow upwards out of the mud and water to function as the site of oxygen intake for the submerged primary root system (underground).

Propagules

Elongated, dart-shape seedlings.
Develops from a seed that germinates while still attatched to the parent tree.
The parent supplies the seedling with nutrients and water until it becomes heavy and drops off into the mud like a dart to start growing.
It can’t just drop as a seed, as it would be washed away, it has to have started growing before reaching the ground.

Leaves

Leaves have adapted glands that secrete (sweat out) salt.
Waxy covering keeps water from being lost.
Sacrificial (older) leaves take in any excess salt.

Red Mangroves

Right at the land’s ege, into the water.
Maximum water depth of 0.4 metres.
Has propt roots to help it stay up in water and soft mud.
Sap is red in colour.

Black Mangroves

Grows on land, in muddy wet areas.
Predominent in high tide areas.
Has air roots to help it breathe in soil without much air.
Fruits and seeds are black.

White Mangroves

Grows on dry, salty land above the high tide line.
Salt is sent out of the plant through the leaves, , making the underside of leaves white.

Why are Mangroves Important?

They protect the coastines
They slow down erosion
They are carbon sinks
Support fisheries
Provide habitat
- Mangroves provide a nursery habitat for many commercial fish (that we eat) and crustaceans, sustaining local fish and shellfish population abundancy and fishing industries.
- Examples: South Florida and Queensland, Australia.
Support for locals
Water filtration
- Tangled root systems slow down water, increasing deposition of sediment.
- Pollution coming from the land can be bound into the mud, filtering them out of the water before they can escape into the sea and harm coral reefs.
- Existence and health of coral reefs depends on the buffering capacity of shore-based mangrove systems.
Recreation

(17/03/25)

Threats to Mangroves

Coastal developments
Unsustainable tourism
Climate change
Agricultural expansion
Aquaculture: The cultivation of fish and other marine life for food. (fish farming)
- Mariculture: A growing fish products only in seawater.

Aquaculture

The shrimp mariculture (marine farming of shrimps) is one of the greatest threats to the remaining mangrove forests, specifically in Southeast Asia and Nicuragua.

Rising Sea Levels

Primarily due to loss of land ice and thermal expansion of oceans.

Mangroves ability to adapt depends on:

Sediment availability for accretion to occur.
Extent of future human development & infrastructure.
Localised landward surface gradient.
Localised natural competition.

To protect mangroves: Formulate international conventions, treaties and agreements.

1971 ‘Wetlands of International Importance’ Conventions signed by 110 countries (Ramsar, Iran), that had to choose an important wetland and gaurantee its protection.
Around 850 Ramsar sites exist.

Initiatives:

Mangrove Alliance for Climate (MAC)

Launched in UAE with Indonesia to rpomote mangrove as a natural solution to climate change. 17 member countries, including India.

Mangroves for Future Initiative (MFF)

Aims to promote investment in coastal ecosystem conservation for sustainable development.

Mangrove Initiative for Shoreline Habitats and Tangible Incomes (MISHTI)

Aims to explore the possible areas for development of Mangrove development.

QUESTIONS

(some answers in p59 of book)

In what way are mangroves a transitional zone?
Mangroves need brakish water (mixed fresh and salt) and are often found in intertidal zones between sea and land.
How can mangroves live in salt water when other plant life cannot?
Because mangroves have leaves that secrete salt and sacrificial, older leaves that absorb any excess salt water.
What % of all tropical fish are born in the sheltered waters of mangrove forests?
75%.
How much of the world’s mangroves have been destroyed in the past 50 years?
Over 25%.
How much remain?
147,000km2 (size of Bangladesh)
How much is being lost per year?
0.6% annually.
What proportion of mangrove species are endangered?
Eleven out of seventy, 16% at elevated extinction threat.
40% of mangroves species present are threatened with extinction.
What are the main threats to the mangrove ecosystem?
- Climate change (rising sea levels)
  - erosion
  - weakening of root structures
  - increased salinity'
  - will eventually flood and kill many coastal mangrove trees
- Aquaculture
  - loss of important ecological and socio-economic functions of mangrove ecosystems
  - changes in hydrology and salinisation
  - introduction of non-native species and diseases
  - lack of wild fish for feed
- Unsustainable tourism
- Human development and infrastucture
  clearing land for buildings.
What rapidly expanding industry poses one of the greatest threats to the world’s remaining mangrove forests (particularly in Southeast Asia)?
Aquaculture— Shrimp farming.
What range of benefits do mangroves offer local communities?
- Coastal protection.
- Money from tourism.
- Food security.
- Clean water.
- Biodiversity.
In addition to their huge importance to tropical fish species, what other terrestrial (land-based) and marine (water-based) fauna and flora (animals & plants) are the mangroves a major habitat for? Many of which are highly endangered.
- Snails, shrimps, crabs, turtles, crocodiles.
Given the global problem of overfishing, and fishing at an accelerated rate what is the increasing importance of Mangroves?
- Mangroves increase fish abundance in nearby coral reefs.
- Mangroves serve as feeding grounds for fish.
- Mangroves decrease predation risk for fish species.
How could mangroves be an important solution to addressing (managing) the problem of global warming?
- Mangroves can store five times more carbon than tropical forests. (carbon sink)
- Reducing global warming and greenhouse gases.
How can mangrove forests act as coastal protection?
They reduce wave energy and slow water action, preventing/slowing coastal erosion.
How can mangroves reduce the problems of pollution and protect coastal reefs?

Pollution is trapped by mangroves slowing down water flow, so the sediments and pollutants do not reach the coral reefs.
Mangroves absorb gases like carbon dioxide from the atmosphere.