Philippine mangrove forests play a highly specialized and intricate role in tropical coastal ecosystems. Mangroves are characterized by a species of tree that have adapted to grow in tidal flats, bordering the ocean. Mangroves thrive in the salty coastal water, where other plant species would die. Aquaculture practices in the Philippines have had negative impacts on mangrove tracts, resulting in more than 337 000 hectares lost since 1925 (Samson and Rollon, 2008). The removal of mangroves for aquaculture creates exponential environmental backlash, as the role of mangroves is replaced with polluting aquaculture. The purpose of this paper is to compare the benefits of aquaculture to the negative effects on mangrove ecosystems. When considering the negative aspects of aquaculture it is also important to provide solutions to help mitigate mangrove damage and destruction. This paper has been organized to first provide a background on mangroves and Philippine aquaculture, specifically brackish water ponds. The second portion of this paper is to provide information on the damages caused by aquaculture unto mangrove ecosystems and the environment. The third portion provides solutions to the problems facing mangrove ecosystems because of aquaculture. This paper looks to inspire and educate on the relationship between aquaculture and mangrove ecosystems in the Philippines.

The Benefits of Mangroves

Mangroves provide countless benefits to coastal and inland ecosystems.
Acting as a boundary between ocean and land, mangroves help to buffer and dissipate wave energy. As sea levels rise, coastal erosion is degrading the shores and depositing sediment into the ocean. Mangroves work against erosion by providing a layer of protection against ocean waters. The physical nature of mangrove trunks buffers the force of waves, preventing the full strength of the wave from reaching the coast. Also, the roots of mangrove trees help stabilize shoreline sediments, holding soil and preventing erosion. Loss of mangrove vegetation leads to loss of coastal shore and total land area, as land is washed into the ocean.
The biodiversity of mangroves provides one of the most unique and specialized ecosystems in the world. The unique characteristic of rhizophora, mangrove trees, is that they thrive in salty water, creating a spawning and maturing area for countless fish species. Besides offering a physical enclave for fish habitat, the fallen leaves and dead plant material of mangroves provide rich sustenance for fish populations. Without the protection of mangroves infant fish would be easy prey and therefore be unable to reproduce.
The intense biodiversity of mangroves also helps to process wastes and pollution form the surrounding environment, especially aquaculture. Mangrove filters have been recommended as a solution for processing excess nitrogen waste from shrimp farms (Primavera, 2000; Baliao and Tookwinas, 2002).

The Benefits of Aquaculture

In 1994, the Philippines accounted for 2% of global aquaculture production (FAO, 1996), and in 2004 Philippine aquaculture contributed 1.8 percent of the GDP. Along with providing capitol to the Philippine economy, aquaculture employs over 1 million Philippinos (Rafael D. Guerrero III, 2008). Based on the growing contributions of aquaculture, the Philippine government has given it high priority in the Medium-Term Philippine Development Plan (2004-2010), as it is expected to produce 842 674 metric tons annually by 2010. Aquaculture is invaluable to the Philippine economy, as 40% of the country lives in abject poverty (Mark Doyle, 2008).
A starving population that experiences food shortages and rising prices on a regular basis compounds Low GDP. Aquaculture helps remedy the problems of a food crisis, by providing access to an inexpensive and nutritious source of food. In 2003 aquaculture products provided 56% of the animal protein consumed by Philippinos (Rafael D. Guerrero III, 2008). In a third world country, aquaculture has a positive influence providing economic and nutritional benefits.

The Negative Effects of Brackish Water Ponds on Mangroves

Despite the beneficial economic aspects of aquaculture, there are many externalities associated with its operation. Aquaculture takes a heavy toll on mangrove ecosystems, as large swathes are deforested in order to create aquaculture environments. The proximity to the ocean is desirable for fish and shrimp farming, because of a large water supply. Effluent from aquaculture is also diluted in the ocean, during heavy rains. Mangrove areas provide perfect inlets for the construction of brackish and fresh water ponds, and marine pens.
Figure 1.shows brackish water ponds as the predominant source of aquaculture fish (Philippine Bureau of Fisheries and Aquatic Resources, 2005) It is estimated brackish water ponds are responsible for 50% or 141 000 hectares of mangrove loss in the Philippines (Primavera and Agbayani, 1996). The environmental problems associated with brackish water ponds have ramifications on inland and coastal ecosystems. To maximize profit and economic viability, brackish water ponds can be stocked with Figure 1: Fish Production from Aquaculture by Culture System in the Philippines (Philippine Bureau of Fisheries and Aquatic Resources, 2005) upwards of 1 400 fish per hectare (Rafael D. Guerrero III, 2008). The high density of marine life poses many health and environmental problems, as it is a breeding ground for disease and pathogens. The 1990’s saw unprecedented shrimp farm decimation due to self-pollution. The island of Negros Occidental saw decline in shrimp production, due to viruses, resulting in 20% of total shrimp ponds being operational (Rafael D. Guerrero III, 2008). A single bacteria, Vibrio Harveyi, was responsible for the economic decline of an entire island’s shrimp farm production. Yellow Head Baculovirus and White Spot Disease are also responsible for the decline in brackish pond productivity. As brackish water shrimp and fish farming intensify, the effluent and waste buildup increases the breeding of bacteria and pathogens. The waste from brackish water shrimp ponds has ramifications for inland and coastal ecosystems far away. Non-sustainable shrimp farming results in the eutrophication of fecal matter and nutrients. Intensive brackish water shrimp farming creates acid sulphate soils (NJ Stevenson). The high concentration of acid sulphate renders the aquaculture farm useless, as it becomes unbearable for any species. Mangroves cannot reclaim areas with high acid sulphate levels because the soil is too poisonous. Rehabilitation is an extensive process requiring the area to be flushed by the ocean. Flushing the unused ponds is a labour intensive process, as upwards of 150 flushes maybe required in order to remove the salts (NJ Stevenson). Flushing brackish ponds is a spatial displacement of the waste, diluting it in the ocean. Calatagan, a small town south of Manila, has been devastated by its mangrove loss. A wealthy lawyer and fish farm owner skirted the law against mangrove removal by damning off water to the thriving mangrove ecosystems. The mangroves died and were subsequently replaced by brackish water fishponds. As a result of the removal of mangroves for aquaculture purposes, the community suffered; their ground water became contaminated with salts, and their access to fishing areas was denied. The socioeconomic externalities associated with mangrove removal are often felt by the periphery of society, those without a voice. This case exposes one of the main reasons for mangrove loss, despite laws against mangrove removal, there is little enforcement. Government incentives for aquaculture and lax enforcement of environmental laws promote aquaculture as a means a survival for a country facing extreme poverty.

Solutions to Mitigate Damage

Despite the severe loss of the total mangrove area in the Philippines, there are many solutions to mitigate further damage. As awareness and understanding of mangrove ecosystems increases, there has been greater effort for their protection at every level. From grassroots initiatives to national policy changes, progress is being made.
Local grassroots initiatives are, collectively, making a national difference. The local communities around mangroves are quickly realizing their benefits and are making an effort to protect them. As seen in Figure 2: Initiatives of Mangrove Reforestation, the predominant driving factor behind replanting is local government and community based initiative. Local governments are funding the rehabilitation and planting of rhizophora, with mixed success. Planting mangroves species in a non-native area, or converting fishponds has limited success. Seedlings are exposed to wind and wave stress, which results in high plant mortality. The root systems of seedlings cannot negate wave erosion and the root systems are exposed. When flooding occurs on mangrove plantations, the entire canopy of the mangrove seedling is submerged, suffocating the plant. Although mangrove replanting can be very successful, it often results in monoculture, lacking the original biodiversity. Replanted mangrove stands are also less efficient at trapping sediment and preventing erosion (Samson and Rollon, 2008).
The National government has both positive and negative effects on the protection of mangrove ecosystems. The Philippine Fisheries Code of 1998, calls for the protection and conservation of aquatic resources, specifically it bans mangrove destruction for aquaculture development. While mangrove removal is now illegal this law is not regularly enforced. The Fisheries Administrative Order of 2001 called for a Code of Practice for Aquaculture. It guidelines “aquaculture must be of environmentally sound design and operation, for sustainable development”. While the specific guidelines are vague, it is another step toward better environmental practices.

Figure 2: Initiatives of Mangrove Reforestation (Samson and Rollon, 2008)

The Philippine government also controls brackish water ponds through 25-year lease agreements. In the mid 80’s to 1990’s it provided several lease agreements to boost economic potential that cleared the way for mangrove deforestation. Owners of lease agreements are unlikely to revert their aquaculture farms back to mangroves due to loss of income (Samson and Rollon, 2008). The easiest and most effective solution to mitigate aquaculture damage on mangrove, takes place before the aquaculture infrastructure is built. Selecting the most appropriate type of aquaculture best suited for the environment, often results in decreasing environmental damage. Off shore marine pens are a way to raise and contain fish without mangrove destruction. Holding nets are placed off shore, where fish are raised in captivity. There is less convenience compared to fishponds, but no mangroves need to be deforested. Mangroves can also be integrated into aquaculture design as to produce more yield and profit. Mudcrabs have been successfully raised in mangrove pens. Stocked pens with 5-7 mudcrab / sq m. at a weight between 150-200g resulted in a higher yield. After 10-15 days the mudcrabs weighted between 200-250g at a net income of 80 cents per kilo (Guerrero, 2000). This lucrative business utilizes mangroves for protection of mudcrabs and as a fertile feeding ground.
Integrating agriculture and aquaculture is another solution to the environmental damage of brackish water ponds. In several cases rice paddies have been stocked with ammonia producing fish such as tilapia. Rice greatly benefits from the ammonia rich excrement of tilapia, which results in less pesticide and fertilizer use. The raising of tilapia and rice is a common practice in China and Vietnam that is now taking hold in the Philippines. Inland rice and tilapia operations require no destruction of mangrove ecosystems, as they are fresh water. Consumer awareness can play huge role in the export of aquaculture products, as consumers become more environmentally engaged. Labeling fish products with their environmental sustainability can force producers to re-examine their aquaculture practices. As demand for more ecologically conscious food rises, aquaculture would take on more sustainable development. Conclusion

Mangrove destruction in the Philippines due to aquaculture is a serious problem. Aquaculture plays a large role in the destruction of mangrove ecosystems, as thousands of hectares of mangroves are deforested to create space for ponds. The removal of such a delicate and specialized ecosystem poses many environmental problems. Mangroves help to anchor coasts against the powerful forces of the ocean and provide a unique habitat for countless fish species. Comparing the socioeconomic benefits of aquaculture with the removal of mangroves is a difficult balancing act. One must consider the externalities and environmental ramifications associated with losing a valuable ecosystem.
Improvements to aquaculture design and infrastructure along with rehabilitation efforts have helped reduce damage to Philippine mangrove ecosystems. The best solution to prevent mangrove destruction is to create an appreciation for the important role mangroves play. Figure 2 shows an increasing appreciation of local communities towards mangroves, which has resulted in communities taking an active role in mangrove rehabilitation. By re-analyzing aquaculture practices to best suit the environment, sustainability can be achieved. Sustainability is key, to ensure continually viable aquaculture production and everlasting mangrove ecosystems.
Hopefully future generations will be able to absorb the beauty and diversity contained within mangroves.

Works Citied

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Guerrero III, Rafael D. Eco-Friendly Fish Farm Management and Production of Safe Aquaculture Foods in the Philippines. Philippines. Philippine Council for Aquatic and Marine Research and Development. Laguna, 2008.

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Primavera, J.H., and Agbayani, R. F (1996) Comparative strategies in community based mangrove rehabilitation programs in the Philippines. Page 34 In Proceedings of the ECOTONE V Regional Seminar: Community Participation In Conservation, Sustainable Use and Rehabilitation of Mangroves In Southeast Asia, Ho Chi Minh City, Vietnam, 8-12 January,1996. Mangrove Ecosystem Research Centre (MERC), Vietnam National University, Vietnam

Samson, Maricar S., and Rene N. Rollon. "Growth Performance of Planted Mangroves in the Philippines: Revisiting Forest Management Strategies." Ambio 37 (2008): 234-40.

The State of World Fisheries and Aquaculture. PublicationNo. Food and Agriculture Organization of the United Nations (FAO), United Nations. Rome: FAO, 1996. 12-12.

Stevenson, N.J. "Disused Shrimp Ponds: Options for Redevelopment of Mangrove." Coastal Management 25: 423-25.