Solutions to blue carbon emissions: Shrimp cultivation, mangrove deforestation, and climate change in coastal Bangladesh

  • January 1, 2016
Marine and Coastal Aquaculture Mangroves

Study Number

107

Author

Nesar Ahmed, William W.L. Cheung, Shirley Thompson, and Marion Glaser

Abstract

In Bangladesh, export-oriented shrimp farming is one of the most important sectors of the national economy. However, shrimp farming in coastal Bangladesh has devastating effects on mangrove forests. Mangroves are the most carbon-rich forests in the tropics, and blue carbon (i.e., carbon in coastal and marine ecosystems) emissions from mangrove deforestation due to shrimp cultivation are accumulating. These anthropogenic carbon emissions are the dominant cause of climate change, which in turn affect shrimp cultivation. Some adaptation strategies including Integrated Multi-Trophic Aquaculture (IMTA), mangrove restoration, and Reducing Emissions from Deforestation and forest Degradation (REDD+) could help to reduce blue carbon emissions. Translocation of shrimp culture from mangroves to open-water IMTA and restoration of habitats could reduce blue carbon emissions, which in turn would increase blue carbon sequestration. Mangrove restoration by the REDD+ program also has the potential to conserve mangroves for resilience to climate change. However, institutional support is needed to implement the proposed adaptation strategies.

Main Results and Conclusions

  • Expansion of shrimp farming has encouraged deforestation of mangroves in coastal ecosystems of the Sundarbans, Bangladesh.
    • “Overall, 10,000 ha of mangrove loss has resulted from shrimp culture in Bangladesh (Table 2)” (69).
  • Mangrove deforestation for shrimp aquaculture has a devastating impact on the economy.
    • “[…the annual economic value of mangroves in Bangladesh is over US $4.43 billion” (69).
    • “When mangroves are cleared for shrimp ponds, land values decrease by approximately US$10,000 per hectare [26]. At this rate, the annual economic value of mangrove loss to shrimp culture in Bangladesh is over US$100 million” (69).
  • Loss of mangrove ecosystems will increase global carbon concentrations.
    • “[… mangroves are the most carbon-rich forests in the tropics and blue carbon emissions have been seriously augmented due to devastating effects on mangroves” (68).
    • “Globally, blue carbon ecosystems are about 51 million ha that store 11.5 billion tons of carbon, of which the highest blue carbon pool is mangroves (6.5 billion tons)” (69).
    • “In the Bangladesh Sundarbans, about 55 and 36 million tons of blue carbon are stored in the below ground and above ground respectively, resulting in total blue carbon stock of 91 million tons [44]” (71).
    • “[…the loss of blue carbon stock from 10,000 ha of deforested mangroves to shrimp farms in Bangladesh is ranging from 6.61 to 11.35 million tons (Table 3)” (71).
  • An increase in blue carbon emissions from deforestation will expedite global climate change and negatively impact shrimp cultivation.
    • “Changes in […] climatic variables have detrimental effects on the ecosystem of shrimp farms, and thus, affect survival, growth, and production of shrimp” (71).
    • “Mangrove forests protect shrimp farms from tidal surges by providing an active barrier to cyclones and reduce wave energy” (71).
    • Expedited global climate change from deforestation will have adverse effects on fisheries.
    • “In 2014–2015, total annual fish catch in the Sundarbans was estimated at 17,580 t, with an average annual yield of 99 kg/ha [1]. Whereas, total annual fish catch in the Sundarbans was much higher at 22,451 t in 2010–2011, with an average annual yield of 126 kg/ha [21]” (72).
    • “According to MacKinnon and MacKinnon [65], deforestation of a hectare mangrove area nearby coastal fisheries may result in the loss of 480 kg of fish annually” (72).
  • Deforestation of mangroves increases economic and environmental vulnerability of coastal communities to the effects of climate change.
    • “Moreover, coastal communities are vulnerable to sea level rise as Bangladesh lies just less than 2 m above sea level [56]. A 45 cm rise in sea level would inundate 11% of Bangladesh, making millions of people homeless [68]” (72).
    • “The livelihoods of around 200,000 fishers are dependent on fisheries of the Sundarbans [28]. However, declining fish catch has severely affected livelihoods and income of coastal fishers [66]” (72).
  • Integrated Multi-Trophic Aquaculture (IMTA) is a feasible option to compensate for the loss of ecosystem services.
    • “Open-water IMTA in coastal Bangladesh can help to restore mangroves through plantation, regeneration, and avoiding deforestation. Seaweed cultivation in IMTA could also help to sequester blue carbon through photosynthesis [79]” (72).
    • “IMTA can increase biodiversity at aquaculture sites [81], which in turn enhances the resilience of coastal ecosystems [82,83]” (72).
  • Mangrove restoration is a strategy to encourage blue carbon sequestration following anthropogenic and natural disturbances.
    • “Blue carbon could be seen as an opportunity for restoration and conservation of mangroves to promote ecosystem-based mitigation and adaptation to climate change [86]” (73).
  • Reducing Emissions from Deforestation and forest Degradation (REDD+) is a mechanism for reforesting and afforesting coastal ecosystems.
    • “The REDD+ approach is suitable for mitigating greenhouse gas emissions by economic support for preventing mangrove deforestation and degradation [90]” (73).
    • “A Collaborative REDD/IFM (Improved Forest Management) Sundarbans Project (CRISP) in Bangladesh is aimed to conserve mangrove forests to reduce emissions of about 6.4 million tons of CO2 over a 30-year period [96]” (73).
  • Strategies to adapt to the loss of mangroves depend on public and government support.
    • “Social acceptability and economic viability of IMTA will need to be determined for its development in coastal Bangladesh. IMTA will also face environmental and technological problems due to its operation in open-water conditions [97]” (73).
    • “Mangrove restoration is also complicated and challenging in coastal Bangladesh because of the effects of intensive human intervention in the context of very poor socioeconomic conditions [87]” (73).
    • “[… a legal and institutional review and reform is needed for the successful implementation of REDD+ project [100]” (73).
  • Prolonged shrimp cultivation through mangrove deforestation will further the vulnerability of Bangladesh to the effects of climate change.
  • It is imperative to mitigate the effects of climate change from mangrove deforestation with sustainable shrimp cultivation and adaptive strategies.