Threats To Mangroves
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Threats To Mangroves

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  • 1. Threats to Mangroves
    A2 Geography
  • 2. Learning Objectives
    Understand the nature and extent of mangrove loss
    What are the drivers of change
    Understand the problems associated with Human activity within Mangroves, including exploitation
    Appreciate the consequences of climate change on Mangrove forests
  • 3. Mangrove Loss
    Over 50% of the world’s original mangroves have now been lost
    A size similar to 13 UK’s
    By 2007 less 15 million left hectares left
    Currently the rate of loss is 1% p.a. (Roughly the size of London)
  • 4. Rates of Loss
    Thailand has lost over half of its mangroves since 1961
    The Philippines 40% were lost to aquaculture between 1918 and 1988
    By 1993 123,000 hectares were left (70% loss in 70yrs)
    Ecuador – Mangrove loss is estimated to range between 20% to 50% of the 362,000 hectares of mangrove forested coast.
  • 5. Why?
    Think in groups why this might happen and write them down on the post it notes provided
    Think why do we deem this a palatable thing to do.
  • 6. Asia has lost 50% due to aquaculture (38% Shrimp. 14% fish) 25% due to deforestation. 11% to upstream freshwater diversion.
    Latin America – Mainly due to the expansion of agriculture and cattle rearing, as well as the cutting of fuelwood and building materials as well as the establishment of a shrimping industry.
  • 7. Drivers of Change
    What are the main threats to biodiversity:
    Habitat change
    Climate change
    Invasive species
    Habitat change
    Climate change
    Invasive Species
    Pollution (N, P)
    Coastal Wetlands
  • 8. Shrimp Farming in Thailand
    Case Study (LEDC)
  • 9. Shrimping
    Been done in Thailand for over 60 years
    Traditional method now known as ‘Extensive production’ Shrimp (Known as ‘fry’) are trapped in salt beds and padi-fields around estuaries and harvested when mature.
    Between 1970 -1990 the coastal shrimp industry expanded massively
    With help from the govt the shrimping industry became more intensive
  • 10. Why
    To help meet global demand
    Exported to USA (500,000 tonnes a year – 2003)
    Japan = 250,000 tonnes
    France, Spain, UK and Italy = 500,000 tonnes
    Since 1990’s amount consumed in Thailand has also increased – rising incomes due to improved economic conditions
    Increase in tourist industry.
  • 11. Production
  • 12. Land Conversion
  • 13. Shrimp farming area and Mangrove area
  • 14. Impacts of the Industry
    What are the positive impacts of the industry?
    Shrimp farming has had positive impacts such as increased wealth leading to improved infrastructure and reduction in migration to Bangkok many are negative
  • 15. Negatives
    Effluent from shrimp farms has to be removed before next crop cycle begins
    It is full of decaying food, shells and chemicals (Antibiotics)
  • 16. If chemicals get discharged into mangroves this can have a harmful effect on biodiversity
    Conflicts arise due to this discharge
    Constant threat of disease and infection
    Rice fields and channels suffer from salinisation
    Depletion of biodiversity in shrimp farms and surround areas
    Loss of mangrove forest or fertile land
    Degradation of the soil due to salinisation
    Deterioration of water quality
  • 17. Future?
    Marine shrimp culture along the coast is one of the main economic activities in the country
    It provides employment and earns national income
    Without management the environment maybe damaged beyond repair
    Governments should promote the development of marine shrimp culture along the coast but before implementation, a development plan should be formulated and good management practices should be specified
  • 18. Department of Fisheries, Bangkok advice on Shrimp farming
    A land use plan should be formulated which does not allow the utilisation of mangrove for shrimp culture. The most suitable area for shrimp farming is rice fields or unused low land beyond the mangrove. The level of such land will be not over 1–2 m above the high tide level.
    To provide infrastructure which supports the shrimp culture industry such as drainage canals, roads, electricity and other necessary services.
    Control and enforcement of farm practices will be done by the official agency.
    To provide education on farm and water management to farm owners and farm operators before they start farming.
    Monitoring of sea water quality along the coast will be routinely conducted and information on water quality transferred to the farmers.
    Shrimp pond wastes will not be discharged directly into natural water ways. The waste treatment pond will be attached to the farm system and waste must be treated before discharge.
    Research on farm management, disease and parasite problems must be conducted and findings regularly transferred to the farmers
  • 19. Climate Change
    Threats to Mangroves
  • 20. Links to AS
    I in 10 people live less than 10m above sea level near the coast
    Asia contains 75% of these people
    Global warming leads to:
    Increased Arctic ice cap melt
    Greenpeace predict sea levels to rise between 15 – 95cm this century
    This could cause some shorelines to retreat by upto 200m
  • 21. Carbon Sequestration
  • 22. Mangroves take up about 1.5million tonnes/hectare/year
    Current removal means we are losing 220,000 tonnes of sequestration potential
    High levels of carbon in the soils is dug up and also released
    Removal of mangroves means carbon release is often 50 times higher than rate of sequestration
    By converting 2% of mangroves it effectively means all advantages of sequestration are lost
  • 23. Mangrove time bomb
  • 24. Mangrove Benefits
    Healthy mangroves can act as a buffer zone between the coastal fringes and inland areas
    Increases are expected in hurricanes and cyclones and the mangrove can help protect land
    Protect against coastal erosion
  • 25. However
    Rising seas levels will swamp the forests nullifying their benefit
    Mangroves need a buffer zone themselves to develop and re-establish above the rising low tide – this too maybe lost
  • 26. Over- Harvesting
    Mangrove trees serve many purposes
    Construction material
    Wood Chip and pulp production
    Animal fodder
    Harvesting has been going on for centuries but it is no longer sustainable
  • 27. Over Exploitation of Marine Life
    Unregulated fishing is depleting fish stocks
    As stocks of one become uneconomic to exploit people are simply turning to another
    Decline in biodiversity, loss of income and jobs
    Over fishing alters the food chain and webs and mangroves communities can be altered as a result
  • 28. Other Threats
    Removal for golf courses
    Building of new cruise ship ports
    Hotels, apartments and restaurants
  • 29. Oil Exploration
    Changes in Soil pH
    Discharge of solids and liquid waste
  • 30. Other Threats
    Domestic and Industrial waste
    Waste from aquaculture
    Exploration of minerals
  • 31. Learning Objectives
    • Understand the nature and extent of mangrove loss
    • 32. What are the drivers of change
    • 33. Understand the problems associated with Human activity within Mangroves, including exploitation
    • 34. Appreciate the consequences of climate change on Mangrove forests
  • Homework
    Write a 500 word report
    Within which you must report on the threats to biodiversity in mangroves
    How far these are likely to change
    Whether these threats reflect people’s attitudes to mangroves and biodiversity
  • 35. Links
    Shrimp Culture in Thailand
    The Rise and Fall of the Blue Revolution
    The Impact of International fish trade on Food security in Thailand
    Manu Potaros, Department of Fisheries, Bangkok