How do Typhoons Impact Tropical Coasts when the Mangrove Forests Have Gone?

By Jessie Shier.

This material is copyrighted,©️JShier, 2012, all rights reserved. All sources are referenced – see list.

This article investigates how the impacts of typhoons in the coastal regions of parts of the tropics have been affected by the removal of the mangrove forests that were once abundant. Particular interest is paid to the impact on people living in the regions and how their homes and livelihoods have fared since the forests’ removal.

Case studies are used to illustrate individual experiences.  Climatic data is presented to compare extreme weather impacts on the regions both with and without the mangroves.

The aims of the article:-

  • To find out why the mangroves were removed.
  • To discover the impacts of typhoons on vulnerable regions before and after the mangroves’ removal.
  • To investigate the effects of the storms’ impacts on individuals’ lives in the regions.
  • To find out what reforestation projects are currently underway and whether they are expected to be effective.
  • To discover the length of time it will take for the re-planted mangroves to reach maturity and whether they will provide protection in the meantime.

This article is authored by Jessie Shier. It presents experiences of various individuals, as shown on documentaries such as ‘Heads Above Water’, (CCTV News, 2013), and ‘Mayomi’, (Rock Salt Films, 2008), climatic data taken from the Proceedings of the National Academy of Science of USA (PNAS) and the Natural Coastal Protection Series, (wetlands.org, 1 October 2013) and the personal opinion of the author.

The article presents the sometimes disastrous impacts of typhoons experienced by regions once their mangrove forests have been removed. Often the forests are taken away to make room for a profit-making venture. This article presents the opinion that the decisions to remove the mangroves were counter-productive for the development and safety of the regions.

The author supports the projects currently in place to re-plant the forests and hopes that this article can help to convince others that natural defences, such as mangroves, are better left intact.

Introduction

Many years ago, much of the tropical coastlines were covered with deep mangrove forests. The forests provided the necessary protection from the typhoons and storm-surges that the regions regularly experience.

Mangroves absorb some of the impact of typhoons.  Their dense root system traps sediment, helping to stabilize the shoreline and therefore holding back soil erosion.  They act as a wind break, dissipating the waves’ energy as it travels through the dense forests, hence protecting the shores from sea-water inundation.

During the 1970s, at the endorsement of the World Bank and the Asian Development Bank, (Shanahan, 2003), the mangroves were removed to make way for shrimp farming and other fish farming that would be financially lucrative.  Communities in Indonesia had been shrimp farming since the 15th century on a small scale, but global demand industrialised the practice, resulting in high levels of two species of shrimp being farmed intensively.  Around 75% of shrimp farming takes place in Asia and it is an extremely lucrative business.

Unfortunately, these types of farms proved to be damaging.  Shrimp farms require a large amount of water and chemical pesticide.  The pesticide is hazardous to human health and the heavy use of water decreased that available for human and ecosystem consumption.  The most damaging aspect of these farms has been the removal of the mangrove forests, (Wikipedia).

Shrimp farms provided a lot of people with the means to make a living and so this idea was embraced by communities and the mangroves discarded without a thought.

 Once the mangroves had been removed, the natural defences for the land that the Earth had provided were gone.  When typhoons arrived, or any natural phenomenon that caused tidal flooding or bores, the coastal edges of the land were wide open to the sea-water, which met no resistance.  The dykes that some communities erected, lacking the complex nature of mangrove forests, were unable to stand up to the force of the water.

Over the last two decades it has become apparent that these coastal regions are extremely vulnerable to typhoons, other extreme weather events and, of course, climate change without the mangroves in place to absorb the effects of these phenomena.

Mangroves

Mangroves grow in low-oxygen, saline habitats along coastlines, where they help sediment to accumulate.  Mostly pollinated by animals, they are extremely slow growing.  One of the few studies conducted into mangrove ages determined that it could take 150-170 years for forest replacement to become established.  The young trees are vulnerable to disease and predation by fungi, crustaceans and animals.  Mangroves have dense root systems, through which tides flood, depositing sediment and mitigating wave energy before it reaches land.  The mangroves root systems help to stabilize the coast-line, reducing erosion and are an attractive ecosystem for many different species of fish and plants to take refuge in.

The mangrove has two main roots.  One root digs deep into the soil, where it takes up nutrients and water.  The second root takes oxygen for breathing from the air, but when sea-water rises above the level of that root, it is able to extract oxygen from the sea-water.

Mangrove forests provide vital defences for the land against typhoons and storm surges, by breaking up the waves and dissipating the energy.

They can act as vital carbon dioxide emissions sequesters and filter the water around them, keeping their ecosystem clean and healthy.  

Personal Stories

Thana Phong, Vietnam

Thana Phong is a farmer in South Vietnam.  His farm is situated on the land side of a thin covering of mangroves.  During the last typhoon, Thana Phong reports that the sea was able to penetrate through the mangrove forest, break the dyke and flood the field beyond, destroying his crops and rendering the soil too saline for arability.  This happened because the mangrove forest was too thin.

Thana Phong explains what happened, “Mangroves act like a wind- break.  However, the forest is not very thick or high.  When the strong winds and high waves came, the waves forced through the trees.  Then sea-water reached this site, where we are planting our crops.”  

Twenty years previously, the area had been covered with a mature and extensive mangrove forest.  They were removed to make way for shrimp farms.  Ten years ago the people of South Vietnam began to replant the mangroves, including the area near Thana Phong’s farm, but the new plantings were not strong enough to withstand the storm.  The forests take many years to mature.  It will be many years before Thana Phong can farm on his land again because of the deluge.  

(‘Heads Above Water’, 2013)

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Mayomi, Sri Lanka

Mayomi lived on the island of Sri Lanka with her family before the 2004 tsunami came.  Sri Lanka’s coast used to be home to deep mangroves.  These lush forests would have protected the islands from the worst that events such as tsunamis and typhoons could muster.  Once the mangroves in some areas were replaced with shrimp farms, however, that protection was lost.  Mayomi and her family paid the price of the pursuit of profit.

Her mother was killed in the flood that inundated the land on the coastal regions without mangroves.  Their home was destroyed and all of their possessions were lost.  Thousands of people subsequently lived in emergency shelters until new homes could be erected.  Mayomi’s mother could not be replaced.  A few family photographs were the only items Mayomi had left after the tsunami.  The culture in that part of the world demands that Mayomi, the only girl in the family, take responsibility for her sick and ageing father and abandoned nephew, since her mother’s demise.

Mayomi states that she is too afraid to continue to live in the old family house once it is rebuilt.  She chooses to live further inland, isolated from her remaining family members.

Neighbouring regions along the coasts of Sri Lanka, with mangrove forests intact, did not experience the same devastating deluge of sea-water that Mayomi’s region did.

(‘Mayomi’, 2008)

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Pujiyo and Sulium, Java

Pujiyo, a construction worker, and his wife Sulium, have lived in a small village in Java since 1983.  For some time now, their house has been flooded by tides and rain for six months of every year as a direct result of the region’s mangrove forests having been removed and replaced by shrimp farms.  

Puiyo explains that he has tried to make his house habitable a number of times using local wood and concrete because he and his wife do not have enough money to move away from the area.  Puiyo and Sulium have installed planks of wood to serve as walkways throughout their house over the sea water.  Sulium keeps her shoes on a plank of wood as she wades, barefoot, around her bed to prepare her sleeping arrangements.  Their families live further inland, but are unable to help because they do not make enough money from their farms.  Puiyo works as a construction worker from job to job, but sometimes there is no work available, so they have no money.

Pujiyo uses a measuring stick to see how high the water is inside his house, “Sometimes, when the rain is heavy, the water reaches 40cm”.

They do what they can to survive.

(‘Heads Above Water’, 2013)

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Satibi, Java

Satibi used to live in a village near the coast of Java, but had to be relocated because of severe flooding.  As he tells his story, he explains that the flooding began in his village around four or five years ago.  He adds, “Sometimes the flood water came up to my bed, so I couldn’t be there anymore.”  

Satibi was able to relocate thanks to the help he received from Ir. Maryono, a government official for the Demak Marine and Fisheries Office.  Satibi took down his old house in his village and transported it, using a boat and a truck, to the relocation site, where he rebuilt his house using those same bricks and stones that he had transported from his village.  

Today Satibi goes back to his old village to earn a living as a fisherman in what used to be Main Street.

Ir. Maryono states that since 2006, approximately 200 families have been relocated, but that many more still need to be moved and the flooding will increase.

(‘Heads Above Water’, 2013)

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Supardiwarno, Vietnam

Supardiwarno is a retired railroad worker in South Vietnam.  He has shown entrepreneurial spirit by taking advantage of the flooded railroad that he used to work in.  

The flooding at the railroad started to increase in 1985 and, in response, the company began removing the trains, making Supardiwarno redundant.  He decided to use part of the flooded railroad as a fish pond to supply his family, but discovered that there were so many fish in the water that he decided to turn to commercial use.  He opens his ponds to people for recreation and fishing purposes and makes approximately 40-50,000 rupees per day doing so.  He uses some of that income to fund a pre-school centre for his community.

Supardiwarno is an example of personal adaptation and is setting the seeds for community- level adaptation.

(‘Heads Above Water’, 2013)

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Impact Comparisons

The Proceedings of the National Academy of Sciences of the United States of America (PNAS) has conducted research into mangroves’ ability to mitigate the effects of storm surges, (Das and Vincent, 2008).  They collated data from several hundred villages to test the impact of the presence of mangrove forests on human deaths during the super-cyclone, Orissa, that struck India in 1999.

The PNAS states that studies conducted after the 2004 Asian tsunami suggested that mangrove forests ‘acted as bio-shields, with villages located behind them suffering less damage than ones directly exposed to the coast’, (Das and Vincent, 2008).  

For their study, the PNAS study took various population and topography variables into account as well as the fact that some regions received a government warning in advance of the storms’ arrival.  Their findings indicated that villages with wider mangrove forests between them and the coast experienced fewer deaths than those villages with fewer or no mangroves.  

They plotted a graph demonstrating how mangrove width affected human deaths during the 1999 super-cyclone.  The graph shows that the areas with the wider mangroves recorded fewer deaths.

Graph by Das and Vincent Showing Correlation Between Mangrove Width and Human Deaths.

Map of the Study Site Undertaken by PNAS to Investigate the Impacts of the Super-Cyclone, Orissa.

Zhang et al (2012), (McIvor et al, 2012), explored the effects of different widths of mangroves and they found that the largest reduction in storm-surge height occurred at the closest point to the coast, (Page22, McIvor et al, 2012).  PNAS’s study also confirms that regions within 10km were the most affected by the presence of mangroves during storms.

 Tran Quang Bao of the Vietnam Forestry University undertook a study to examine the possibility of a correlation between wave attenuation and the presence of mangroves.  His study found such a correlation, as demonstrated by his scatter graph, (Page5, Bao, 2011).

Solutions

There are many projects currently in place to reforest the coast lines of parts of the tropics with mangroves.  A number of NGOs, (Mangrove Action Project, 1 October 2013), work alongside local governments and communities to re-forest wetlands and coastlines.

In Vietnam, the International Development Association supported Coastal Wetlands Protection in the development of a long-term project to re-forest several provinces at the same time as tackling the causes for the forest’s destruction.  More than 4,500 hectares of mangrove forest were planted in the Buffer Zone settlements, (World Bank, 2009).  

In one of the regions, coastal erosion has decreased by 40% in the period between 2000 and 2007.  Training and social support is also in place to ensure the forests will be maintained.

The United Nations Development Programme has completed a project to replant the depleted mangrove forest in Setiu, Malaysia.  They have worked with local groups and have successfully replanted the forest as well as conducted awareness and training workshops, (UN, 2008).

The Mangrove Environmental Rehabilitation Network (MERN), which is a co-operative of sixteen environmental groups has begun a project to replant mangroves in Rakhine.  They also wish to educate local people to care for and value the mangroves and the protection they can provide, (Lwin, 2011).

In Vietnam, Dr. Kuan Phuong of the Forest Science Sub-institute of South Vietnam, has been planting mangrove forests for more than ten years along South Vietnam’s coast.  He says, “…the mangrove forest can help us minimize the effects of strong typhoons and strong waves… it can also help to sequester carbon dioxide emissions… and it can protect our dykes and agriculture crops behind the mangrove forest.”  The Vietnamese government has set a target to plant 250,000 hectares of mangroves along its entire coastline, (‘Heads Above Water’, 2012).

Local groups plant the mangrove plants 1.5-3 metres apart, tying the seedlings to sticks for support, on the wetlands along the coasts.  The seedlings are young and it will take some time for the roots to penetrate into the ground, but this is an important step towards sustainability.

In this region of Vietnam, people who used to farm shrimp and prawns have turned to farming mudskippers instead.  Mudskippers live in mangroves and are more profitable than shrimp, so these people can continue to make a living while replanting and protecting their mangrove forests and feeling more secure when typhoons come. 

However, mangrove forests are extremely slow-growing and the immature trees do not provide adequate protection from storms, so people in vulnerable regions are also looking to other ways to adapt to new climates.  Sea walls and dykes may help somewhat, but relocation or adaptation, such as that seen by Supardiwarno and the communities farming mudskipper, may be necessary.  

Summary

Large areas of mangroves were removed over the past twenty years to make way for shrimp and prawn farms.  In India, spontaneous agricultural expansion, mostly for rice, was a major cause of mangrove destruction, (Das and Vincent, 2008).  The farming was expected to be financially lucrative to the regions concerned.

It has been found through studies that regions with mangrove forests intact experience fewer impacts from storm-surges than regions without mangroves.  The impacts are severe flooding, sometimes permanently as in the case of Java; tidal bores and inundation of the land by sea water; salinization of crop lands and destruction of both lives and property.

Typhoons’ impacts on people’s lives are intense.  Thousands of people have been displaced due to damage and flooding.  People’s livelihoods; their farms and houses, are often destroyed.  Thousands of people’s lives have been lost.

There are a number of restoration projects currently underway and some of them have been completed.  The UN is working alongside a number of NGOs and local groups and the work has been successful.  The forests that have been replanted are not effective against storms because they have not reached maturity.  They are expected to be effective once they are mature, if they are planted at the same volume as the forests that were removed.

The replanted forests will not provide protection until they are fully mature and thick enough to withstand strong waves.  Young mangrove forests have been found to be insufficient against strong waves.  It is suggested that mangroves can take up to 170 years to re-establish themselves at maturity.  Current generations must seek other ways to protect themselves and their communities from the impacts of typhoons. 

Conclusion

The Mangroves provided security from extreme weather events as well as being unique ecosystems themselves.  Their removal occurred largely for financial gain.  The cost to the ecosystems and the people has been total.

Attempts are being made to reforest the mangroves, but will it work in time to provide the regions with defences against climate change?

Their removal was a mistake that may have deadly, irreversible and long-lasting effects. 

References

Salter, C. (2008) Mayomi’s Story [online].  Available from: http://www.rocksaltfilms.com/aboutmayomi.html [accessed 2012].

Das, S. and Vincent, J.R. (2008) Mangroves Protected Villages and reduced Death Toll During Indian Super Cyclone[online].  Available from: http://www.pnas.org/content/106/18/7357.full [accessed September 2013].

Nature and Science, CCTV News (2013) Heads Above Water [online].  Available from: http://english.cntv.cn/program/natureandscience/20130511/103408.shtml [accessed September 2013].

Shanahan, M. (2003) Appetite for Destruction [online].  Available from: http://www.thirdworldtraveler.com/Environment/Appetite-Destruction.html [accessed September 2013].

Wikipedia (2012) Marine Shrimp Farming [online].  Available from: http://en.wikipedia.org/wiki/Marine_shrimp_farming [accessed September 2013].

McIvor, A., Spencer, T., Moller, I., Spalding, M. (2012) Storm Surge Reductin by Mangroves [online].  Available from: http://www.wetlands.org/LinkClick.aspx?fileticket=tUFNulbR0U0%3D&tabid=56 [accessed September 2013].

World Bank (2009) Renewing Mangrove Forest for More Secure Livelihoods [online].  Available from: http://web.worldbank.org/WBSITE/EXTERNAL/COUNTRIES/EASTASIAPACIFICEXT/VIETNAMEXTN/0,,contentMDK:22293193~menuPK:3949587~pagePK:1497618~piPK:217854~theSitePK:387565,00.html  [accessed September 2013].

Mangrove Action Project MAP Ecological Mangrove Restoration (EMR) Method [online].  Available from: http://mangroveactionproject.org/map-programs/restoration/ecological-mangrove-restoration-emr [accessed October 2013].

Quang Bao, T. (2011) Effect of Mangrove Forest Structures on wave Attenuation in Coastal Vietnam [online].  Available from: http://www.iopan.gda.pl/oceanologia/533baotr.pdf [accessed 1 October 2013].

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This project article is authored by Jessie Shier as part of a BSc in Environmental Studies with The Open University in ~2012. All the material is copyrighted, ©️JShier, 2012, all rights reserved.

All external sources are referenced and credited.