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THE EXCEPTIONALLY HIGH CARBON STOCKS OF MANGROVES AND THEIR POTENTIAL FOR THE GLOBAL MARKET OF CARBON - A REVIEW OF RECENTLY PUBLISHED INFORMATION AND THE RESPONSE OF THE AQUACULTURE INDUSTRY

Iris J. C. Hernandez*, Acacia Alcivar-Warren

UNA SALUD/ONE HEALTH Genomics & Epigenetics Program, Fundacipara la Conservacide Biodiversidad Acuy Terrestre (FUCOBI), Quito, Ecuador; E-mail: fucobi@gmail.com
The role of land forests as a source and sink of greenhouse gases (GHG) is well known.1-4 Recent evidence indicates that another major source of GHG release is through the conversion of land use, from carbon (C) stored in the biomass and in deep sediments of marine ecosystems such as mangroves (Fig 1).2 In regions of Latin America and Asia large tracts of coastal mangrove forests have been cut down and destroyed for agricultural and/or aquaculture purposes, coastal development, and other uses. C emissions resulting from the conversion of mangroves to other uses are exceptionally high due to the large deposits of C in mangroves and the high vulnerability of these due to the conversion. This deforestation has resulted in the destruction of habitats for local fauna and the release of a large amount of C stored in the mangrove sediment/soil.

The range of C stocks found in the mangrove ecosystems in Asia Pacific is 500-1200 megagram (Mg) of C/ha, which is equivalent to 1603 a 8023 Mg/ha of carbon dioxide (CO2).1 The biomass carbon map of Ecuador (Fig 2)4 will be used to discuss C emissions in coastal provinces where mangrove forests were converted to shrimp farms (Fig. 3). Viglizzo (2010)5 described the Ecological Footprint (EF) as an accounting tool to estimate the requirements of consumption and waste assimilation of a population or country in relation to the amount of productive land available. There are countries whose biological production capacity exceeds what they actually consume, like other nations who have a pattern of consuming more than their biological capacity to produce goods. So much so that in recent years there has been a tendency to differentiate other tracks such as Carbon Footprint (CF), which is important because of its direct relationship with GHGs, and its impact on the current global warming. It consists of a measure that attempts to quantify the amount of GHG emissions, expressed in CO2 equivalents, which are released into the atmosphere as a result of human activities. The importance of the CF is that this is a large part of the EF total. Coastal ecosystems such as mangroves, commonly reside on sediments rich in organic matter, they can be several meters deep and hold C efficiently, thanks to low oxygen conditions and other factors that inhibit the decomposition in depth. When mangroves are destroyed or converted to other uses, these C sediments are destabilized or exposed to oxygen, increase microbial activity, which causes the release of GHG, mainly C stored in undisturbed mangroves released into the atmosphere as CO2, CH4 and other species of C. The resulting impact of GHG emissions include not only environmental consequences such as rising sea level, and the frequency of extreme weather events, but the potentially high emissions of C resulting from the degradation of marine ecosystems, such as mangroves, can also be a new untapped opportunity of C mitigation, such as the program for "Reduction of C Emissions caused by Deforestation and Forest Degradation (REDD)" of the UN, in which economic incentives are taken into account to maintain forests that are C deposits.

A presentation by ecologist Dr. J. Boone Kauffman of Oregon State University at the 2012 meeting of The American Association for the Advancement of Science has caused a series of sensational and misleading assumptions about the impact of shrimp farming, according to the Global Aquaculture Alliance (GAA).6 Kauffman and colleagues tried to determine the amount of CO2 that is represented in the shrimp, and estimated, based on typical shrimp aquaculture in Southeast Asia, that 401 metric tons of C are emitted into the atmosphere when one hectare of mangrove is converted to a shrimp farm. This amounts to 1472 tonnes of CO2. It was estimated that during the 5-year duration of a shrimp farm, 1,659 kg of shrimp are harvested. Thus, 100 grams of a shrimp cocktail represents 198 kg of CO2 footprint derived from mangrove loss. The GAA does not refute Dr. Kauffman concerns about the consequences inherent in the CF from the conversion of mangroves to other uses, and they stated their support for mangroves conservation. However, they question his calculations about shrimp farming, and pointed to inaccuracies about the lifespan of shrimp ponds and other issues. The GAA highlighted the importance of understanding how far off from reality such calculations are, and concluded that the data used by Dr. Kauffman "bear little relation to today's shrimp farming industry which has long moved away from the mangrove zone. It's akin to calculating soil erosion for U.S. agriculture based on the Dust Bowl practices of the 1930s".6

Coastal ecosystems have been lost due to market forces. Perhaps governments have been unwilling or unable to enforce the law to help ensure long-term sustainability of these ecosystems. There are currently only a few mechanisms in place to protect the stored C in coastal ecosystems. We do not know the exact amount of C stored in these ecosystems, and we must continue investigating to establish sound evidence according to the reality of each country. Here we will review the first C map, biodiversity, and ecosystem services in Ecuador, and highlight ongoing research by the Ministry of the Environment, the shrimp industry, and non-governmental organizations of Ecuador.

References:
1Pendleton L, Donato DC, Murray BC, Crooks S, Jenkins WA, Sifleet S, Craft C, Fourqurean JW, Kauffman JB et al. 2012. Estimating global "blue carbon" emissions from conversion and degradation of vegetated coastal ecosystems. PLoS One. 7(9): e43542. doi:10.1371/journal.pone.0043542
2Donato DC, Kauffman JB, Murdiyarso D, Kumianto S, Stidham M, Kanninen M. 2011. Nature Geoscience 4:293-297.
3Van Lavieren H, M Spalding, D M Alongi, M Kainuma, M ClZ Adeel. 2012. Securing the Future of Mangroves. A Policy Brief. United Nations University-Institute for Water, Environment and Health (UNU-INWEH), UNESCO-MAB with ISME, ITTO, FAO, UNEP-WCMC and TNC. 53 pp.
4UNEP-WCMC and MAE. Carbon, biodiversity and ecosystem services: exploring co-benefits. Ecuador. Technical Report. UNEP-WCMC, Cambridge, UK.
5Viglizzo E. 2010. Huella de carbono, ambiente y agricultura en el Cono Sur de SuramIICA. http://books.google.com.ec/books?id=TIyUlyosD1sC&pg=PA4&dq=viglizzo&hl=en&sa=X&ei=VbKnUNjyGpTu8ASA3oGwBA&ved=0CDsQ6AEwBg. Consultado el 17 de Noviembre 2012.
6GAA, Global Aquaculture Alliance. 2012. Dated, Erroneous Assumptions Yield Misleading 'Carbon Footprint' For Farmed Shrimp; http://www.gaalliance.org/newsroom/news.php?Dated-Erroneous-Assumptions-Yield-Misleading-Carbon-Footprint-For-Farmed-Shrimp-59; March 12, 2012; accessed October 6, 2012.




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