Course:CONS200/2019/Mangroves in the Asia-Pacific region

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Rhizophoraceae, or Black Mangrove by Dinesh Valke via Wikipedia Commons Public Domain

Climate change is a process that involves alterations in the Earth’s climate system, often resulting in weather changes that may last for decades or potentially millions of years. As the Earth’s climate is determined primarily by the amount of energy received or leaving the planet, changes in this flow of energy will alter weather patterns, leading to climate change. While natural activities have an influence on climate change, human activities contribute as well[1]. Global atmospheric concentrations of CO2, N2O and CH4 have increased due to human activities since the 1750s[1], and the climate will need to change to maintain global input and output of energy. Increases in climate change can result in sea level rise and biodiversity loss, heavily affecting food web structures and ecosystem functionality[2]. One of the species that may potentially be heavily impacted are mangroves. Mangroves are groups of trees and shrubs with long roots that extend and submerge into open saline water sources. Mangroves occupy many of the world's tropical and subtropical coastlines, and are unique in their ability to thrive in salty, low-oxygen soil. While there are up to 80 different species of mangrove, they may not necessarily be closely related to one another[3]. Some species may not exceed the size of a shrub, while other can grow up to 40 meters tall, and can be categorized into five basic types dependent on their surrounding environment: mangrove fringes, overwash forests, riverine forests, basin forests, and dwarf mangrove forests[3].

Value of Mangroves

Mangroves are highly productive and provide a multitude of provisioning, regulating, as well as supporting services. They provide timber, charcoal, food, wax, honey and tannins[4], serving commercial interests while simultaneously supporting the ecological needs for biodiversity in the area by providing “food, habitats, [...] and reducing global warming by acting as a Carbon sink”[5]. If value were to be placed on the ecosystem services provided by mangroves, a 2014 report by the United Nations Environment Programme estimated that the ecosystem services provided by mangroves were worth up to $57,000 per hectare per year, sustaining over 100 million individuals[6]. In addition to this, mangroves are proven to be effective buffers for tsunamis and can heavily mitigate damages done by natural disasters. Mangroves can absorb 70 to 90 percent of the ocean's wave energy, potentially blocking the negative effects of rising ocean levels and increasing severity of storms caused by climate change[6]. Furthermore, mangroves are extremely important carbon sinks. As with many other plants, mangroves collect atmospheric CO2 in their leaves which they subsequently store in their leaves, roots, trunk and soil. However, what makes mangroves so effective is how they do not have maximum storage capacity[6]. Their ability to store carbon that can remain for millennia demonstrates the value of mangroves as a tool to mitigate the effects of climate change. Mangroves also play an important role in the life of various marine biota. Mangrove roots serve as a substrate for species such as oysters, macro-algae and barnacles, also providing habitat for various fish species that use the roots as a nursery habitat or for long-term living[7]. Outside of economic and natural benefits, mangrove also retain aesthetic, historical and cultural value in many areas.

Factors affecting mangroves & potential impacts

The primary natural factor affecting mangroves is climate change. The climate has a wide range of ecological impacts on organisms. With climate change rapidly increasing, its impacts on mangroves are becoming increasingly apparent as well. Of the many impacts that climate change is responsible for, the main factors affecting mangroves are changes in temperatures, changes in atmospheric carbon dioxide concentration, changes in precipitation, changes in wind and storm intensities and sea level rise.

Change in Temperature

One of the impacts of climate change is an increase in temperature. Although the increase in temperature is not uniform within different areas of Asia, it is important to note that the expected increase in temperature within any area of Asia is higher than the expected global increase in temperature. The world observatory of NASA noted that the mean global temperature increase between 1880 until 2018 was around 0.8°C. However, the increase in temperature in the different parts of Asia are significantly higher; at 3.3°C in South Asia, 3.7°C in central Asia and 2.5°C in southeast Asia[8]. The impacts of this increase is equally as extreme. At different temperatures, mangroves growth and livelihoods are impacted in different ways. According to Faridah-Hanum et al. the impacts of various temperatures are as follows:

-Greater than 25°C: some species show reduced leaf formation

-Greater than 35°C: the root structures and seedlings of ALL species are affected

-Greater than 38°C: photosynthesis is inhibited in nearly all species

Furthermore, as high temperatures are undesirable conditions to live in, mangroves will move pole-ward with increasing temperatures[8]. However, as the continent of Asia itself is diverse in topography, this migration mechanism may not be possible for every species of the plant.

The change in temperature will significantly impact the existence of the mangroves. Ultimately, authors Faridah-Hanum et al. conclude that there are 4 main impacts that we can expect to entail the increase in temperature:

  1. Changes in species diversity or composition
  2. Variation in flowering and fruiting time
  3. increase in productivity of mangroves at temperature below the upper threshold
  4. migration of mangroves to higher latitudes towards more favourable physiographic conditions

Change in atmospheric CO2

One of the main factors influencing climate change has been the concentration of CO2. Since 1880-2000 the concentration of atmospheric CO2 increased from 280 ppm to 370 ppm. With an increase of CO2, the photosynthesis of the mangrove plant increases and as a result the growth rate of the plant increases as well[8].

Although the rise in CO2 is beneficial in the growth of mangroves, the negative impact is indirect to the mangroves. Increasing the concentration of CO2 within the atmosphere increases the acidity of the ocean as the ocean naturally absorbs CO2 acting as a large carbon sink. The increase in acidity of the ocean puts coral reefs in danger as high acidity causes mass bleaching of the reefs and significantly weakens this natural coastline protector. Coincidentally, mangroves are primarily coastal flora that rely on the coral reefs for protection against wave action. Thus, increasing CO2 concentrations do have adverse effects on mangroves[8].

Ultimately, increasing CO2 concentrations have variable impacts on different species of mangroves because CO2 concentrations alone do not significantly alter the existence of the species, instead for CO2 concentrations to impact mangroves, it would have to work in tandem with other factors such as salinity, temperature, nutrient availability and water cycle processes[8].

Change in precipitation

One of the factors that are influenced by climate change is precipitation. The amount of rainfall and the timing are both altered due to climate change. In the IPCC of 2001 it was noted that by 2050 precipitation was expected to increase by 25%. The increase in precipitation can be attributed to increases in to an increase in CO2 which in turn increases temperature, ultimately increasing evaporation of the ocean causing more precipitation.

The impacts of changing precipitation vary. Positive impacts are the effects of increased precipitation in an area. Within the area, the mangroves would have an increased growth rate and in areas of diverse mangrove species, the overall area coverage of the forest increases as well. However, if precipitation increases too much, flooding of the coastal areas would cause the mangroves recede further towards land.

Other negative impacts refer to areas in which evaporation removed water from the area. The decrease in water level causes an increase in salinity, resulting in the survival of more salt tolerant species. Furthermore, the increase in these species also increases competition between mangroves and salt marshes which may also prove to be an issue that would otherwise not exist given typical environmental conditions

Change in wind and storm intensities

Climate change also causes changes in wind intensities. This is due to the higher temperature resulting in more thermal energy for more powerful storms. Consequently wind intensities are said to increase by 5-10% as well (Faridah-Hanum et al. p. 243). Unsurprisingly, strong winds and storms may cause damage to entire mangrove forests at a time, easily causing mass mortality. Storms such as hurricanes can easily cause forests to collapse and ultimately reduces the recovery and regeneration of the mangrove species. Furthermore, storms are often followed by a process called inundation, which is flooding of the affected area. This process affects many parts of the plant, threatening it's livelihood in multiple ways. Some ways that inundation impacts mangrove forests are:

  • Reducing photosynthesis and water conductivity, this reduces how much oxygen the plant is receiving at its roots often resulting in the death of the plant[8].
  • Mass erosion of soil caused by flooding. Having the soil become loose and disturbed can easily be the cause of mass forest mortality[8].

Examples of events causing inundation:

  • Tsunamis
    • In the 26th of December 2004, an earthquake in the Indian Ocean resulted in tsunamis ranging from the coast of India extending to the Aceh province of Sumatra, Indonesia. The tsunami that ravaged the coast resulted in an estimated destruction of 3,825 - 10,200 ha of mangrove forest. While the impact in Sumatra, our area of research, reportedly had around 300 - 750 ha of mangrove forest destruction[8].
  • Hurricanes
    • Post-tsunami effects in all the affected regions showed increasing susceptibility to hurricane effects. These areas, already weakened, showed forests of lower canopy size, smaller diameter, and forests of lower diversity and complexity due to frequent hurricane events. Constant stripping of leaves, wearing of branches and uprooting of mangroves are the main consequence of hurricane events.
    • Typhoon Haiyan, which impacted the Philippines and numerous other countries in the region was responsible for mass mangrove loss. Total mangrove area initially impacted by Haiyan was 8568 ha, about 3.5% of the Philippines' total mangrove area or 20.4% of the region's total mangrove area. Nearly 870 ha of mangrove were severely damaged, 1820 ha were moderately damaged, and 5900 ha were minimally damaged during this time period[9].

Sea level rise

Sea level rise is an obvious consequence of climate change. Melting of glaciers and Antarctic ice sheets as a consequence of global warming results in a rising sea level. This factor is understood to be the factor that is most threatening to existing mangroves. Being flora that are able to take advantage of coastal conditions, mangroves can cope with sea level rises of around 1 mm per year[8]. The IPCC fourth assessment report of 2007 estimated average sea level rise from 1990-2090 to be 18-59 cm; in other words at a rate of 1.8-5.8 mm per annum. Evidently, this rate exceeds the threshold of 1 mm per year. This sea level rise that exceeds the rate at which mangroves can tolerate, is very consequential to the existence of mangroves as sea level rise is global meaning that all mangroves in existence will eventually be threatened by this process.

The implications of sea level rise include:

  • excess flooding,
  • erosion of sediments (resulting in uprooting and also erosion of the nutrients within the soil),
  • inhibition of nutrient cycling and gaseous exchange,
  • water logging, which is the process where soil becomes saturated or nearly saturated with water limiting the amount of air the roots of plants can receive through the soil, causing the death of not only the mangroves but flora habituated in similar conditions[8].

Categories of Actors

Affected Actors

In Asia-Pacific area, many countries are facing adverse effects by the loss of mangroves. The increased deforestation due to the conversion of mangroves into agricultural or aquacultural area has had significantly impact on the local inhabitants. The actors affected by mangrove loss in Asia-Pacific, are most commonly villagers who rely on the mangrove forests for their livelihoods. It is important to consider integrating local communities to management plan to avoid detrimental harm to those who rely on mangrove resources[10].

Interested Actors

Within the Asia-Pacific area, there are many countries cooperating with Non-Governmental Organisation to protect sensitive areas. NGOs such as World Wide Fund for Nature, The Nature Conservancy, the International Union for the Conservation of Nature (IUCN), and Conservation International teamed up to institute Global Mangrove Alliance. This alliance strives to acquire $10 billion in investments to expand the range of mangrove habitat by 20% globally by 2030. Additionally, the alliance seeks to improve the coastal communities through restoration and conservation projects[11]. Moreover, Blue Carbon Initiative is another global program that aims to mitigate climate change through conserving and restoring coastal and marine ecosystem. Currently, Blue Carbon Initiative focuses on protecting and restoring mangroves, tidal marshes and sea-grasses which sequester and store large amount of carbon[12]

Anthropogenic Causes for Mangrove Destruction

While the primary focus of this Wikipedia revolves around the effects of climate change on mangroves, there are human-driven actions that have also had substantial effects on mangrove numbers.

Indonesian palm oil production by Achmad Rabin Taim via Wikipedia Commons Public Domain

Palm Oil Production

Large-scale palm oil production has led to the conversion of large areas of mangrove swamps into oil palm groves, primarily in the Indonesian region. During 2000–2010, oil palm development accounted for the loss of approximately 4,744 ha of mangrove of the total 58,413 ha growing in the country[13]. This number pales in comparison to overall forest loss in the region, but mangrove losses total nearly 10% over the course of 10 years. This number is steadily increasing as oil palm plantations expand. The responsibility for inter-tidal habitats, such as mangroves, commonly falls between marine and terrestrial government agencies, which can lead to neglect of monitoring and management. Thus, in the past, conversion of mangrove forest to oil palm plantations might have been unnoticed or under-reported, because oil palm expansion is generally considered a terrestrial issue, and because plantations that replace mangrove forests may look similar to those that replace terrestrial and freshwater peat swamp forests[14].


Deforestation has been a large factor in the decline of mangrove growth in South-East Asia. Deforestation of mangroves is not a new impact, and is an activity done by humans for generations as mangroves serve useful for provisioning services. Often deforestation is due to increases in agricultural land use, and South-East Asian countries have been heavily affected, accounting for 5 out of the 10 most deforested mangrove areas in terms of absolute loss between 2000 and 2012[15]. Though data regarding the numbers vary, it is estimated that 35% of original mangrove forests had already been lost by the 20th century (Feller et al.). Average annual rates of mangrove loss due to deforestation ranged from 0.2%-0.7% between 2000 and 2012, depending on the area of study. One of the countries that has been heavily affected by deforestation has been Myanmar. In a study by Estoque et al. analyzing mangroves in Myanmar between 2000-2014, they noted that Myanmar has lost 191,122 hectares of forest since the beginning of the study, at a rate of 14,619 hectares annually[16]. Mangrove loss however has decreased in the early 21st century from the mid to late 20th century, likely as a result of increased sustainable forest management laws and community-based conservation mechanisms.

Ecological Implications

While mangroves may be heavily affected by climate change, the loss of mangroves would also affect the natural environment as well. The mangroves are extremely valuable parts of the South-Asian ecosystem, and affect both the natural and human environments extensively.

Carbon Sinks

Mangroves serve as a large carbon sink, helping protect the atmosphere from increasing climate change. Destruction of mangroves, as of present calculations, is approximately 150,000 hectares per year globally: resulting in a loss over this duration of “225,000 tons of carbon sequestration potential and a release of approximately 11 million tons of carbon from disturbed mangrove soil” [17]. The loss of mangroves would likely result in a vicious cycle: climate change and deforestation reduces the amount of mangrove vegetation, releasing stored carbon which in turn increases the negative effect of climate change.

Furthermore, when analyzing the carbon storing components of the mangrove, namely the above-ground and below-ground biomass, results show that on average, the combined carbon stored within mangroves per hectare is approximately 466.5 tonnes [4]. Globally, carbon stock of mangroves is at an estimated 6.5 Pg C (1 pentagram of carbon is equal to one billion metric tonnes)[4].

About 75% of carbon within biomass is emitted with land conversion. The carbon released following land conversion is within a range of 27.25-90% of soil carbon. When this range is calculated with global emissions due to mangrove loss, the estimates of high, central and low amounts of carbon released is 159 million, 122 million and 84 million tons of CO2 respectively.

Loss of Biomass and Increased Food Competition

Many animals, especially smaller fish, use mangroves as a place of refuge in addition to being a feeding ground. The loss of mangroves, while not the only source of nutrients, would place additional pressures on alternative seagrass beds, leading to increased food competition and a general loss in biomass[18]. In a study by Bologna, they noted that smaller fish tended to use mangroves during the day, while moving to seagrass beds during later hours of the evening[18]. The loss of mangroves however led to a hyperutilization of adjacent seagrass beds, and while this does may not directly translate in a loss in fish populations, the stress placed on seagrass beds to maintain the population is not as sustainable as having mangroves would be.

Options for Remedial Actions

Community-Based Conservation

The idea of community-based mangrove management (CBMM) has become increasingly important in the last fifty years[19]. CBMM relies heavily on local community involvement in the preservation and management of mangroves, placing emphasis on the community to complete resource identification, priority development, and making decisions regarding the choice and effectiveness of different technologies to manage mangrove populations. However, CBMM techniques can be distinct from other community-based conservation strategies. As mangroves management is often at odds with commercial aquaculture practices it may be difficult for communities to regain the right to manage mangroves as they choose. Additionally, mangroves often stretch beyond transnational borders leading to disputes and require high initial capital to protect. Consequently, incentive to implement CBMM has not been very popular until recently[19].

CBMM in South-East Asia

CBMM strategies have been implemented most heavily in South-East Asia, as the continent itself has the highest amount of mangrove area in the world[4]. While communities originally had control and authority over the use and harvesting of mangroves, government control due to colonization eventually led to mass amounts of commercial logging and shrimp farming in the region. As a result, communities have since been alienated from the forests and view them solely as a form of extra income[4]. However, since the 1980s there has been a resurgence in CBMM. Countries such as Indonesia, Vietnam, Thailand and the Philippines have all implemented CBMM, mostly with moderate success. While there are many issues surrounding the implementation of CBMMs -- whether ecological, social or economic -- they ultimately serve as a promising solution to help preserve mangroves, especially in South-East Asia where they are so prevalent.


Establishment of protected areas, regulated by official legislation, is one of the best methods to protect coastal mangroves. Unfortunately, many of these protected areas are poorly designed or poorly enforced and some fail to prevent mangrove loss and degradation within their boundaries. Also, there are still large gaps in protected area coverage. Matang Mangrove Forest Reserve in the State of Perak, Malaysia, is arguably the best example of a sustainably managed mangrove ecosystem and demonstrates that an effective balance can exist between the harvest of natural resources and conservation.The existing management plan regulates forestry, fishing, and aquaculture activities and only non-destructive practices are permitted[20].

Restorative Actions

- Human intervention- assisting natural mangrove colonization in sheltered coastal segments by providing or enhancing seedling fluxes to the area

-Government of Thailand approved a national mangrove management plan in 1987, designating remaining areas into a preservation/conservation zone (research, education, recreation and biodiversity, 42,678 ha), an economic zone A (sustained yield, 200,000 ha) and economic zone B (conversion to aqua/agriculture 130,000 ha). However, the goal of 8000 ha/yr of reforested areas has not been achieved since the start of the project in 1992 (approximately 5% of the target is achieved according to Dierberg and Woraphan, 1996)[21].


According to Baconguis, aquasilviculture is defined as a multiple use system that promotes a harmonious co-existence between fishery species and mangrove tree species in a semi-enclosed system while providing coastal protection and maintenance to the ecosystem[22]. The concept of aquasilviculture is that mangroves are planted in a shallow central area covering 70-80% of the selected site, and the remaining 20-30% is used to create a deeper pond along the dikes, which is devoted to brackish water aquaculture (fish, shrimp, or crab). The expected forestry (mangrove) development and the expected fisheries production over time are expected to provide profits, such that the first 5 years rely on fish production to repay construction costs and the main activities are the maintenance of dikes, fertilization for fish production, protection of plants from pests and diseases, control of predators, and replanting[23].


Mangroves are a vital part of the ecosystem in the Asia-Pacific region. Being the prominent source of multiple ecosystem services, in addition to being a massive carbon sink, mangroves serve as a critical actor in South-East Asian ecosystem. However, they are at risk at an alarming rate due to both ecological factors (main one being climate change) and anthropogenic factors. The issue of climate change is not one that only members of a particular government should address; this long lasting problem has been and will continue to affect our planet until everyone, including those in every level of government to the every day person takes part in making a change. There are obviously many ways to improve our situation but one way that should be prioritized would be to reduce the use of fossil fuels. Whether it be in the form of transportation or a mode of production such as factories and other industrialized process, cutting the use of fossil fuels greatly reduces the amount of emissions in our atmosphere and ultimately reduces climate change and its impacts. We must come to the realization that planet should come before profit, and thus, we should attempt to implement systems in which renewable energy use is reimbursed or rewarded whilst the use of fossil energy is heavily penalized. This way, it will perhaps be an incentive to use alternate energy sources as the benefit gained from its use would be greater than the use of fossil energies


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