Swathes of Australia's mangroves died in a month, shows survey
Jul 26, 2016
According to the scientist, with climate change the likely cause, thousands of hectares of mangroves in Australia’s remote north have died.
Details of the study:
- Some 7,000 hectares (17,300 acres), or nine per cent of the mangroves in the Gulf of Carpentaria, perished in just one month
- The so-called dieback — where mangroves are either dead or defoliated — was confirmed by aerial and satellite surveys and was likely to have been the result of an extended drought period
What are Mangroves:
Mangroves are Salt tolerant plant community found in tropical and sub-tropical intertidal region of the word receiving rainfall between 1,000 to 3,000 mm and temperature ranging between 26-35 C. hey exhibits a variety adaptation in morphology, anatomy and physiology to survive in a hostile environment which is marked with water logged soils and high salinity regime frequented by storm and tidal surge.Prominent among these adaptations are presence of pneumatophores, buttress, stilt roots viviparyetc
Where are they found:
About one third of the world’s mangroves are found in Asia (39%), followed by Africa (21%) and North and Central America (15%) (FAO, 2007). The world map below shows where mangrove forests are located.
Importance of Mangroves
a. Buffer Zone between the land and sea.
b. Protect the land from erosion.
c. Play an invaluable role as nature's shield against cyclones, ecological disasters and as protector of shorelines.
d. Breeding and nursery grounds for a variety of marine animals.
e. Harbour a variety of lifeforms like invertebrates, fish, amphibians, reptiles, birds and even mammals like tigers.
f. Good source of timber, fuel and fodder.
g. Main source of income generation for shoreline communities like fisherfolk.
h. Save the marine diversity, which is fast diminishing.
i. Purify the water by absorbing impurities and harmful heavy metals and help us to breathe a clean air by absorbing pollutants in the air.
j. Potential source for recreation and tourism.
Threat to Mangroves
- Biotic pressures and natural calamities are the enemies of mangrove ecosystems. Growing industrial areas along the coastlines and discharge of domestic and industrial sewage are polluting these areas. Many studies have highlighted these problems and intensive conservation efforts are needed to conserve the sensitive ecosystem of Mangroves. Some threat in detail:
- Clearing: Mangrove forests have often been seen as unproductive and smelly, and so cleared to make room for agricultural land, human settlements and infrastructure (such as harbours), and industrial areas. More recently, clearing for tourist developments, shrimp aquaculture, and salt farms has also taken place. This clearing is a major factor behind mangrove loss around the word.
- Overharvesting: Mangrove trees are used for firewood, construction wood, wood chip and pulp production, charcoal production, and animal fodder. While harvesting has taken place for centuries, in some parts of the world it is no longer sustainable, threatening the future of the forests.
- River changes: Dams and irrigation reduce the amount of water reaching mangrove forests, changing the salinity level of water in the forest. If salinity becomes too high, the mangroves cannot survive. Freshwater diversions can also lead to mangroves drying out. In addition, increased erosion due to land deforestation can massively increase the amount of sediment in rivers. This can overcome the mangrove forest’s filtering ability, leading to the forest being smothered.
- Overfishing: The global overfishing crisis facing the world’s oceans has effects far beyond the directly overfished population. The ecological balance of food chains and mangrove fish communities can also be altered.
- Destruction of coral reefs: Coral reefs provide the first barrier against currents and strong waves. When they are destroyed, the stronger-than-normal waves and currents reaching the coast can undermine the fine sediment in which the mangroves grow. This can prevent seedlings from taking root and wash away nutrients essential for mangrove ecosystems.
- Pollution: Fertilizers, pesticides, and other toxic man-made chemicals carried by river systems from sources upstream can kill animals living in mangrove forests, while oil pollution can smother mangrove roots and suffocate the trees.
- Climate change: Mangrove forests require stable sea levels for long-term survival. They are therefore extremely sensitive to current rising sea levels caused by global warming and climate change.