Mangrove forests going missing to feed us fish
Mangroves are an important and diverse habitat that have a number of important functions from providing fish nursery grounds to slowing down coastal abrasion. However mangrove forests are being destroyed five times faster than landlocked forests. The Food and Agriculture Organisation of the UN claims this is due to high population pressure in coastal areas. However, research from Indonesia, which has the highest rate of mangrove loss, suggests aquaculture development and intensive logging are the main culprits.
Indonesia contains a fifth of the world’s mangroves totaling a massive 3.2 million hectares and the highest level of mangrove biodiversity. 79% of mangrove losses here are attributed to conversion into aquacultures ponds despite laws protecting them. The ecosystem services the mangroves provide should give them more than enough value to warrant their protection however more often than not politics determine their future.
1800 hectares of protected mangrove in the Kapuas estuary in Indonesia have been converted into brackish aquaculture ponds, this has mainly been driven by nonlocal aquaculture operators. As the land becomes privatised local residents are often not benefitting and are being deprived of resources such as firewood and crabs/mussels. Although locals are often employed to help with the initial setup after this period there is minimal labour required and little or no chance for the residents to profit.
Initially most aquaculture ponds in Indonesia cultivated milkfish ( Chanos chanos) for local consumption now they are mostly used for giant tiger shrimp (Penaeus monodon) which are produced for export. This shrimp overtake shows the change of focus from domestic protein to foreign exchange. Although farming shrimp is high income at first this rapidly declines after a few years and ponds are often abandoned after 5-10 years.
The ponds often fail due to the development of acid sulfate soils caused by sulfur reducing bacteria found in the soil of mangrove forests. To overcome this problem chemicals are applied to the aquaculture ponds. These chemicals promote algal growth and can lead to eutrophication. As well as this, wastewater is flushed out into coastal waters where it can be toxic and cause depletion of wild fish stocks reducing the yield of the traditional catch fisheries used by locals.
Aquaculture development is argued to boost economic development and food production as well as improving livelihoods. But does this justify the loss of wetland habitats that are so vital to wild fish stocks. The destruction and degradation has several knock on effects as well as the initial loss of habitat, it promotes the spread of disease in wild fish and can encourage invasive species to move in and monopolise. The effects on coastal erosion and sedimentation processes could be detrimental too.
The argument of land conversion has caused conflict between departments of the Indonesian government. The Ministry of Forestry declares vast areas of mangrove forest as protected only for them to be converted into aquaculture ponds. The conversion is controlled farmers who are fully aware of the laws protecting these areas but continue anyway because of their alliance with the Ministry of Marine Affairs and Fisheries, which fully supports aquaculture development and even proposes that a further 2.96 million hectares is converted. It has been said that the government grants permits for aquaculture development based on self-interest.
With government bodies in disagreement and local residents regularly protesting, it is unclear of the future for the remaining mangrove forests. With these environments being so key to local residents and for the health of wild fish by providing safe nursery grounds it is vital they are not only safeguarded but that any legislation put in place is enforced.
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