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Title: Analysis of the Responses of Mangrove Ecosystems to Climate Change

Abstract:

Despite the warnings against climate change since the early century, recent human activities are still geared towards enhancing them. Because of climate change coupled by other human activities, natural ecosystems such as mangroves are facing difficulties in coping with the impacts of climate change. Their natural ecological functions, which could provide benefits to human and other species of organisms, are disrupted. The impacts of climate change to the mangrove ecosystem can be analyzed based on the different environmental factors related to climate change such as sea-level rise, wind patterns and hydrodynamic shifts, storminess, temperature change, and availability of water from precipitation and runoff. Responses of mangrove ecosystems to such factors and recommendations for mangrove protection in relevance to climate change are discussed.

I. Introduction
A. Global Climate Change

Rapid rate of emissions of greenhouse gases such as carbon dioxide, methane, nitrous oxide, ozone and chlorofluorocarbons from anthropogenic sources such as burning of fossil fuels, tropical deforestation and other human activities resulted to increase in global temperature, otherwise known as global warming. Increased amount of solar energy has been trapped by these gases raising the Earth s surface temperature (Curry, 2005; Boesch, 2002; NRDC, 2006). Global average temperature records since 1860 showed a continuous increasing trend (Figure 1). Since 1990, eleven of the warmest years have occurred with the five warmest during the last seven years namely in decreasing intensity: 2002, 1998, 2003, 2001 and 1997. Due to the recent trends, the rate of global temperature increase accelerated from +0.6oC over the past century to an equivalent rate of +1.0oC per century in the past two decades.

Figure 1. Recorded global rise in temperature since 1860. (Source: Boesch, 2002) B. Threats from Global warming

The environmental factors with the greatest direct effects on estuarine and marine ecosystems in terms of global climate change are sea-level rise, wind patterns and hydrodynamic shifts, storminess, temperature change, and availability of water from precipitation and runoff. According to the report by the Third Assessment Report of Working Group I of the Intergovernmental Panel on Climate Change (IPCC), there is less uncertainty about predicted changes in temperature and sea levels than about predicted changes in precipitation, winds, and storminess (Kennedy et.al., 2002). However, the actual impacts of these factors will depend on the frequency and intensity coupled with human-controlled factors such as coastal land use and management approaches (Nicholls, 2003).

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1. sea level rise

Sea-level rise as a consequence of global warming is caused by increase in seawater temperatures resulting to thermal expansion of water and melting of glacier and polar land ice (Kennedy et. al., 2002).

According to the report of the IPCC, the global sea-level rise in the 20th century was between 10 and 20 cm and predicted that a further accelerated rise of 9 to 88 cm will occur between 1990 and 2100 with a mid-estimate of 48 cm (Kennedy et.al., 2002; Nicholls, 2003).This faster rate of sea-level rise estimated at 1-2 mm per year (Boesch, 2002) is caused by human-induced global warming. However, the global mean sea-level rise will not be uniform around the world since local change in sea level at any coastal location depends on the sum of global, regional, and local factors, which is termed as relative sea-level change (Nicholls, 2003).

Sea-level rise leads to a range of impacts including increased flood risk and submergence, salinization of surface and ground waters, and morphological change, such as erosion and wetland loss.

The significant changes due to global warming particularly sea-level rise will likely continue into the next century and beyond despite successful efforts to curb emissions of greenhouse gases because of the longevity of greenhouse gases in the atmosphere and the lag in warming effects of the oceans (Boesch, 2002).

Figure 2. Sea-level rise in relation to carbon dioxide emissions and temperature. (Source: Boesch, 2002)

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2. Wind patterns and hydrodynamic shift

Modest changes in the climate cycle, particularly sea-level conditions, short- and long-term, can alter the hydrologic balance and tidal prism sufficient to alter habitat type and boundaries (Doyle et.al., 2003).

The winds, which are created by the unequal heating of the Earth s surface, will experience weakening as polar regions experience higher temperatures that will reduce the thermal gradient between the poles and equator. A consequence of this is the weakening of the overall wind-driven water circulation that could seriously affect the structure and function of open ocean and nearshore ecosystems (Kennedy et.al., 2002).

Coastal currents can be affected by climate change in a number of important ways, including increasing or decreasing the frequency and strength of coastal upwelling, changing the properties, including temperature and salinity, of coastal waters that are tidally advected into estuaries thus affecting conditions at least in the lower estuary, changing the set-up of water levels along the coast thereby affecting relative sea-level over seasons or several years, and changing the direction, strength or timing of long-shore advection (Boesch, 2002).

3. Storminess

More energy is pumped into tropical storms by the warmer waters, making them more intense. This has been partially validated by increase in the number of category 4 and 5 storms over the past 35 years along with ocean temperature (NRDC, 2006). The IPCC, on the other hand, was unable to find a consistent pattern of tropical and extra- tropical storminess (frequency or intensity) due to variability in the data but recent national and regional scenarios in Europe suggest an increase in storminess, which will interact unfavourably with sea-level rise and have major negative effects on coastal ecosystems (Doyle et.al., 2003; Nicholls, 2003). The IPCC, however, concludes that increases in the peak wind intensity of tropical cyclones are probable as well as both mean and peak precipitation intensities. Increased storminess may be a result of intense latitudinal temperature gradients and increased evaporation from tropical sea surfaces (Boesch, 2002).

4. Temperature change

An increase of 0.6oC to the average temperature near the surface of the earth has been estimated since 1861 with most of the warming occurring from 1910 to 1945 and from 1976 to 2000. This is predicted to increase by 1.4 to 5.8 oC from the 1990 levels causing an increase also in the sea-surface temperature with the greatest warming expected to occur at high latitudes in winter (Boesch, 2002; Kennedy et.al., 2002). The greatest ecological change in estuarine and marine ecosystems may result from the rapidity in the temperature change (Kennedy et.al., 2002).

5. Precipitation change

Over most of the mid- to high-latitude and tropical land areas of the Northern Hemisphere in the 20th century experienced increased precipitation intensity and frequency, while a decrease over sub-tropical (10o N to 30o N) land areas has been

observed. In low latitude areas, effects of climate change on precipitation may vary (Kennedy et.al., 2002). Some areas may experience increased precipitation while others the opposite.

C. Philippine Vulnerability

The Philippines is highly prone to storm surges and riverine flooding due to high frequency of tropical cyclones and other environmental degradation. An average of 20 tropical cyclones pass yearly through the Philippines and about nine of them cross land (Perez, no date). Heavy rains brought by monsoons frequently flood low-lying areas in the Philippines (Figure 3). The northeast monsoon season from November to February, brings heavy rains on the eastern side of the country, while the western side during the southwest monsoon season from May to September, which coincides with the typhoon season as well. Heavy economic losses result from the damages by tropical cyclones. Climate variability such as El Nino causing drought and floods for La Nina also affects variability of the amount of rainfall in the country. Rising sea level due to climate change could aggravate the situation, as many low-lying places in the country are usually flooded during the monsoon seasons and tropical cyclones occurrences. With the pressing problems of climate change, this situation is expected to be a severe problem in the future. Since the country is comprised of 7,108 islands, many of which are small islands, the impacts of climate change will be further aggravated.

Figure 3. Most low-lying areas in the Philippines are flooded during monsoon seasons or occurrence of tropical cyclones. (Source: Perez, no date)

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D. Description of mangroves

Mangrove forests, which occupy intertidal settings along the mouths of rivers or estuaries of tropical and subtropical regions worldwide, are universally composed of a single overstory strata of relatively few tree species tolerant of fluctuating salinity (Doyle et.al., 2003; Kennedy et.al., 2002). Mangroves can tolerate the added stress of water-logging and salinity conditions that prevail in low-lying coastal environments influenced by tides because of their halophytic nature (Doyle et.al., 2003). They require slow currents, no frost and plenty of fine sediment in which to set their roots. Areas with high rainfall and upstream runoff are associated with best-developed mangrove forests, however they grow best in moderately saline environments. They can also keep up with sea level rise of up to 12 cm per 100 years (Perez, no date).

E. Benefits of mangrove ecosystem

The benefits derived from the mangrove ecosystem can be divided into four categories namely, direct use values in terms of the goods and services they provide, indirect use values in terms of the ecological functions which indirectly support economic activity, optional use values or the options to directly or indirectly use these ecosystems in the future, and non-use values, which may arise because individuals derive satisfaction from knowing that the ecosystems exist, and will continue to exist for future generations (Chong, 2005).

Large quantities of food and fuel, building materials and medicines are derived from the mangrove forest. Four hundred kilos of fish, shrimps, crabmeat, molluscs and sea cucumbers can be derived from one hectare of mangroves in the Philippines annually. This can also feed a further 400 kilos of fish and 75 kilos of shrimps that mature elsewhere. The leaves of Nypa, a species of palm, that thrives abundantly in mangrove areas is used by Filipinos to thatch roofs while its fermented sap produces an annual 10,000 liters of alcohol per hectare of mangroves (Perez, no date).

The mangrove trees are also good sources of tan bark for tannin extract industry (FAO and UNEP, 1981). The Philippines is also deriving income from mangrove- related tourism activities such as walk-through-the-mangrove programs, where they set- up boardwalks for people to see the interior of the forest.

Nutrients from decaying leaves and wood are concentrated in the muddy waters, which are home to sponges, worms, crustaceans, molluscs and algae. Since mangrove communities are very highly productive systems and their root systems are very intricate, they provide valuable habitat for fisheries, shorebirds, marine mammals, snakes and crocodiles as well as provide the basis for the nearshore marine food web (Perez, no date). In fact, majority of the world s marine species, including most fish catches depend on coastal wetlands for part of their life cycle (Doyle et.al., 2003). They also serve as refuges from predators (Kennedy et.al., 2002). By harbouring large number of species, mangrove ecosystems also support biodiversity conservation and acts as a natural gene bank.

The root system of mangrove forests can stabilize marine and terrestrial sediments reducing coastal erosion and supporting clear offshore waters favourable to

coral growth. Extensive tracts of mangroves can protect the adjacent land and human populations from storm surges of water caused by high intensity coastal storms and hurricanes (Kennedy et.al., 2002; Chong, 2005). A healthy mangrove forest can also prevent salt water intrusion preventing damage of freshwater ecosystems and agricultural areas.

F. Mangrove Communities in the Philippines

Philippine mangrove forests feature at least 40 of around 54 species in the Indo- Pacific. The main tree species are Rhizophora apiculata, Rhizophora mucronata, Ceriops tagal, Ceriops roxburghiana, Bruguiera gymnorrhiza, Bruguiera parviflora, Bruguiera cylindrica and Bruguiera sexangula. Further upstream, where the water is not so brackish, nipa palm (Nypa fruticans) may form extensive and dense stands that are major sources of roofing materials in coastal areas (FAO and UNEP, 1981).

The mangrove forests in the Philippines have faced massive deforestation from about 450,000 hectares in 1918 to about 100,000 hectares at present (Primavera, 2002). This has resulted from the indiscriminate cutting, land clearing and habitat conversion of mangrove forests to give way to aquaculture activities largely shrimp ponds, salt beds and human settlements. Mangrove depletion rate of 3,700 hectares per year was observed from 1980 to 1991 mainly due to the Blue Revolution program of the government that promoted mangrove conversion for aquaculture in order to increase fish supply, provide livelihood and alleviate poverty. Around half of the 279,000 ha of Philippine mangroves that disappeared between 1951 and 1988 were converted into ponds mainly for milkfish, but also for shrimp (Primavera, 2005). Less than 20,000 hectares of mangrove forests is considered old growth.

II. Statement of problem and objectives

Given the forecasted trends of the different environmental factors accompanying climate change, mangrove ecosystems will be among the most immediately threatened. Its increased vulnerability is due to the fact that these mangrove forests are located along the land-sea interface where most human activities are concentrated.

The main objective of this paper is to understand the responses of mangrove ecosystems to the different factors resulting from global climate change.

It will specifically try to answer the following specific objectives:

To identify various scenarios that will happen under the different environmental

factors of climate change;

To identify human activities or interventions that aggravates the effects of

climate change; and

To provide recommendations for future mangrove conservation actions in the

Philippines.

III. Presentation of impacts of global warming factors to mangrove communities

The following scenarios present the different responses of mangrove under the varying conditions of global climate change.

A. Sea level rise

1. Encroachment upland by mangrove

Mangrove encroachment upland through freshwater marsh and swamp environments is a possible consequent of sea-level rise in pristine undeveloped areas with gentle slope, which could lead to increase mangrove expanse and reduce freshwater marsh coverage (Doyle et.al., 2003; Boesch, 2002). This is due to the fact that salinity tolerance of mangroves will reach saturation causing encroachment upslope (Doyle et.al., 2003).

The relationship between landward slope and elevation in relation to tide range and extent, and an understanding of relative sea-level rise are important in predicting landward transgression of mangroves. In the modelling simulation of the mangrove communities of the Everglades, South Florida, faster or more extensive encroachment of mangroves into the Everglades slope result from greater rate of sea-level rise, however, inland penetration of saltwater conversely mangrove vegetation into upslope marsh will occur at any rate of sea-level rise (Figure 4). A negative impact of this is the increase loss of freshwater marsh and swamp habitats as tidal prism increases over time as it moves upslope (Doyle et.al., 2003). Over the next century under climate change conditions, mangrove habitats in the Everglades will increase while freshwater marsh/swamp will decrease.

Figure 4. Modelling simulation of mangrove Migration in South Florida, USA under different sea-level rise scenarios. (Source: Doyle et.al., 2003)

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A consequence of this landward encroachment of mangrove forest is enhancement of local fisheries as spawning and habitat area is increased. However, this might be in the short term only as other factors will have impacts on the fishery and will compromise other wildlife benefits dependent on freshwater habitat (Doyle et.al., 2003).

2. Mangrove loss due to coastal squeeze

The rate of sea-level rise rather than the total rise drives more mangrove losses as they have the capacity to respond to inundation (Nicholls, 2003). However, in areas with seaside human development, inland migration of mangrove forests will be prevented causing permanent submersion of the mangrove trees under high salinity water and plant death due to salt stress (Kennedy et.al., 2002). Presence of flood- control, navigational or other anthropogenic structures decreases sediment inputs to the mangrove communities preventing it from coping with sea-level rise through normal accretion or vertical accumulation of sediment (Figure 5). More frequent inundation stresses root metabolism due to low oxygen concentration and sulphide, which dramatically affects the production of organic matter needed for sufficient aggradations of soils (Boesch, 2002). However, in some estuary catchments prone to future increased sediment supply, inundation will be slower as sediment build-up around the estuary margins could act to counteract sea-level rise.

Figure 5. The figures depict changes in a mangrove forest that inhabits a depositional terrace that is over 6000 years old (A). In (B), sea level rises at a rate that erodes the foreshore yet allows the forest to retrogress inland. In the presence of human attempts to prevent sea level from inundating the land by building a seawall, the mangrove forest will be eroded away (C and D) and the seawall may have to be strengthened against wave action that is no longer buffered by the mangroves. BP= before present; MSL= mean sea level. (Source: Kennedy et.al., 2002)

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Another human-activity that will increase the negative effect of sea-level rise is too much extraction of groundwater leading to land subsidence. Accelerated rates of subsidence and sea-level rise may alter the depth and width of shallow estuaries, which may increase the bottom friction of wind-driven water circulation, thereby altering the hydrodynamics. Change in the patterns of water movement might affect significantly the dynamics of the mangrove ecosystem (Kennedy et.al., 2002).

B. Wind patterns and hydrodynamic shift

Coastal currents can be affected by climate change in a number of important ways, including, increasing or decreasing the frequency and strength of coastal upwelling, changing the properties including temperature and salinity of coastal waters that are tidally advected into estuaries thus affecting conditions at least in the lower estuary, changing the set-up of water levels along the coast thereby affecting relative sea-level over seasons or several years, and changing the direction, strength or timing of long-shore advection (Boesch, 2002).

Nearshore current changes may significantly affect migration of individuals to and from the mangrove ecosystem. Such is the case of larvae of species that spawn on the inner shelf and recruits back into estuarine nurseries (Boesch, 2002). Alongshore wind stress and differences in the densities and buoyancies of fresher and saltier waters in the U.S. East Coast help produce water movements that transport larval blue crabs, menhaden, and bluefish in the Middle and South Atlantic Bights. Transport of these species within estuaries and along the coast will be hindered by change in water circulation patterns, thus lowering abundances (Kennedy et.al., 2002; Doyle et.al., 2003).

Weakening of upwelling regions resulting from decrease of wind speeds affects the vertical mixing of food particles and larvae patches, thereby decreasing food supply to the larvae and increasing mortality. At wind speeds of roughly 5 to 6 meters per second, recruitment is maximized but lower than this poses lower survival (Kennedy et.al., 2002).

Annual variation in fishery recruitment may also be affected by the timing and extent of high water conditions in the mangrove ecosystem, since many fishes make regular movements onto flooded marsh to feed and marsh access is apparently important to the growth and survival of individuals. Climate change also affects recruitment in terms of the species preference to high or low intertidal habitats as nurseries. Sea level rise may thus act in favour of species preferring high water level (Boesch, 2002).

C. Storminess

Estuaries are affected by storms in a number of ways including sediment resuspension, and shoreline erosion due to high winds, storm surges that flood wetlands and cause salinity intrusion, and large freshets produced by intense rainfall on the watershed (Boesch, 2002). Storm damage from wind and surge forces such as devastating blow downs to intact but defoliated canopies are sufficient to alter structure

and recovery of mangrove forests (Doyle et.al., 2003) In a model projections of mangrove forests in South Florida USA, it was suggested that as hurricane intensity increases over the next century, average height of mangroves will be diminished and a certain species of red mangroves will dominate. It was also inferred based on hindcast simulation that structural composition of modern day mangrove forests across south Florida is accounted for by major storms with periodicity of every 30 years and with tracks that subtended larger distribution of mangrove habitat.

Increase in hurricane intensities is projected over the next century as a result of global climate change, which could further alter the structure and composition of mangrove landscapes (Doyle et.al., 2003). This can also act synergistically with sea- level rise causing higher storm surges resulting to more destruction of the mangrove forests. Forest elevation cannot keep pace with sea level rise due to failure of mangrove to produce peat as a result of excessive wind damage stresses resulting to additional plant mortality and irreversible loss of habitat (Kennedy et.al., 2002).

Figure 6. Modelling simulation of mangrove forest damage in South Florida, USA from three intensities of hurricanes. (Source: Doyle et.al., 2003)

D. Temperature change

1. Biological effects

Temperature at sub-lethal levels governs animal behaviour and distribution patterns of organisms, influences growth and metabolism, timing or reproduction, and controls rates of egg and larval development. It also acts in concert with other environmental variables such as dissolved oxygen. (Kennedy et.al., 2002).

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a. Physiological changes in organisms

Slight increases in temperature can cause appreciable impacts to many species. A study has shown that in short-term (days) temperature-tolerance experiments on estuarine invertebrates in the laboratory, a temperature increase of 1oC often raised mortalities from ~0 percent at the lower temperature to ~100 percent at the increased temperature. However, higher than 1oC temperature increases are expected in the coming century.

Warmer waters can cause decrease egg survival and larval hatching and development as evidenced by the recent declines in the abundance of winter flounder in New England. Increase in water temperature tends to increase the metabolism of organisms, however warm waters have less capacity to hold oxygen, which is a primary reactant for metabolism. This imbalance of oxygen supply and demand will cause stress to the organisms (Kennedy et.al., 2002).

b. Effects on the abundance and distribution of organisms

Population abundances and distribution of organisms are directly or indirectly influenced by temperature changes. Higher temperatures may result to elimination of highly mobile species from part of its range since they can migrate to other more suitable environments. Migration and colonization to new habitats depend on many factors such as the number of adults available in the original habitat and their ability to produce young, an adequate number of potential colonizers (seeds, spores, larvae, migrating juveniles or adults), the ability of potential colonizers to move into the new habitat including their ability to cross barriers, and the survival of adequate numbers of individuals in the new habitat to ensure genetic diversity to meet environmental challenges and to produce succeeding generations. Given such factors are met, environmental corridor is another determining factor for successful colonization, which link a region where a species is at risk and a more suitable region. However, these corridors may not be present for mangrove species that cannot survive the high salinity marine conditions that occur between mangrove communities resulting to the decrease in the population of the species that have low or no dispersal capabilities such as clams and oysters.

c. Effects on species interactions

Changes in the population of species in the mangrove communities due to temperature change will also lead to changes in species interactions such as predator- prey relationship. Decrease in prey population will starve the predator population or force them to shift to other resources thereby increasing competition for those new resources. Another situation might be the change in the timing of physiological events by advancing or retarding the timing of reproduction for many species (Kennedy et.al., 2002).

d. Increase hypoxic or anoxic conditions

As stated earlier, warmer waters hold lesser amount of oxygen than cooler water. Water column stratification will occur as the upper layer of water is warmed

increasingly preventing oxygen from penetrating the deeper water resulting to hypoxic or anoxic deeper waters, a condition not suitable for benthic organisms.

e. Pathogens and Harmful Algal Bloom

Higher temperatures and salinities typically increase the incidence of infection. This will decrease the health of the mangrove forest and disrupts its ecological functions.

Increasing water temperature also facilitates eutrophication usually resulting to proliferation of harmful algal species in a process known as Harmful Algal Blooms. These algal species usually contain small amount of toxins that when concentrated by shellfishes and fishes become toxic to higher trophic organisms in the mangrove ecosystem (Kennedy et.al., 2002).

2. Hydrodynamic change

Productivity of estuarine and marine systems is influenced by nutrients carried from deeper waters through upwelling process. Increases in temperature can act in two opposite ways. The first scenario is that upwelling events will be weakened as stratification of warm-surface water and cold-deeper water intensifies preventing nutrients for primary production. The second scenario expects strengthening of upwelling because there will be more warming over land than in ocean, which will increase low-pressure cells that typically occur over land adjacent to offshore high- pressure cells. This will in turn enhance alongshore winds promoting upwelling.

Coastal currents and offshore-inshore transport corridors, which are expected to change as a result of temperature change, has considerable effects to the distribution, recruitment, and survival of coastal marine fish and invertebrate communities of mangrove ecosystems (Kennedy et.al., 2002).

E. Precipitation change

Global climate change can either increase or decrease the intensity and frequency of precipitation in coastal areas. A wide variety of consequences results from changes in the amount and timing of freshwater inputs to mangrove ecosystems including shifting of the estuarine gradient up or down the estuary thereby affecting the distribution of organisms, alteration of the flushing rates, strengthening density stratification under higher flows and weakening under lower flows, changes in the delivery of sediments, nutrients, and contaminants, and modifications in the seasonal pattern of freshwater delivery to which the life history of migrating estuarine and anadramous organisms may be programmed (Boesch, 2002; Doyle et.al., 2003).

1. Extreme precipitation

Extreme precipitation events, which when impounded, can cause acute rise of water level and result to massive dieoffs. The sudden decrease in salinity can cause severe stress to mangrove trees such as root zone decomposition, which can further

result to rapid substrate collapse or subsidence. This has high probability of prohibiting recolonization and promotes coastal erosion (Doyle et.al., 2003).

Shrinking of the mangrove forest is also expected if increased rainfall is coupled with sea-level rise because the mangrove forest will have to compensate for the advancing high salinity water from the sea and freshwater run-off from the land.

Water run-off is also expected to bring high amounts of nutrients, which may lead to eutrophication of the mangrove waters. Decomposition of plant materials will use up much of oxygen thereby increasing water-column stratification with high nutrient freshwater above and saline hypoxic or anoxic water at the bottom layer (Kennedy et.al., 2002).

Catastrophic deposition of sediments can happen after extreme rainfall causing high water turbidity, which has profound effects to the structure and function of benthic communities.

2. Decreased rainfall

Decreased supply of freshwater from precipitation coupled with sea-level rise would promote salinity encroachment into the tidal freshwater reaches of the estuary. This would affect lower-salinity communities of organisms as well as alter the food webs in estuaries and change the residence time of nutrients and contaminants. Increases in drought intensity or frequency would increase the incidence of coastal hypersalinity that can lead to reduction of valuable habitats such as mangrove forests.

Loss in productivity in the mangrove forests can be expected as nutrient input from upstream is reduced by less water run-off.

IV. Human interventions

It is recognized that environmentally-degrading activities of human beings have caused the rapid climate change, and further activities are perceived to enhance the effects of these changes. The present aggressive mitigation measures will only buy time for highly vulnerable areas because such effects are highly probable to occur.

A. Increased human population

With the high birth rate of the Philippines, more people are expected to encroach into the coastal ecosystems since most of the inner land areas are already owned and occupied. This means higher investments will be put into building new houses and other infrastructures in the coastal zone, which could also mean further reduction of mangrove forests. However, present environmental laws in the Philippines prohibit further removal of mangrove vegetation. Thus, most planners would set aside the mangrove areas while building constructions are allowed after the mangrove forests. If we consider the possibility of landward encroachment of mangrove forest in the face of sea-level rise, this measure may not be appropriate for coastal planning.

Another impact of increased human population is the increased demand for freshwater for drinking and other purposes. Most of the places in the Philippines previously promote the use of deep-well and artesian wells as cheap source of freshwater. This aggravates the problems of land subsidence and salt water intrusion. Since mangrove forests require constant supply of freshwater to compensate the high salinity seawater, increase consumption of freshwater upstream will enhance hypersalinity condition causing stress to mangrove species.

B. Increased nutrient sources

Agricultural activities have increased inputs of fertilizers to enhance yields of agricultural lands. With the expected increase in the intensity of precipitation due to climate change, these nutrients are easily carried downstream by surface run-off towards the mangrove forests causing the series of negative impacts for the ecosystem. Other sources of nutrients are untreated industrial wastes, urban sewage and increased aquaculture activities in mangrove forests.

C. Non-ecologically based mitigation measures

Several actions by human to counteract sea-level rise and other climate change factors may cause added harm to mangrove ecosystem rather than conserving it. Such measures may include armouring of wetlands with berms or dikes that will prevent biological systems from adjusting naturally. These structures may also decrease sediment supply to the mangrove forests preventing them from vertical accretion (Kennedy et.al., 2002) as well as impede the landward migration of mangrove forests (Boesch, 2002).

After the recent Indian Ocean tsunami in 2004, most affected governments have realized the importance of mangrove forests in counteracting the effects of tsunami and perhaps climate change related factors as well. Thus, massive mangrove reforestations have been undertaken. However, conservation organizations have raised warning concerning the non-ecologically planned mangrove forest restoration. Experts say that ill-planned mangrove plantations could damage coastal ecosystems since they might displace other marine communities near them such as turtle nesting grounds and seagrass beds. They also offer little protection from storms or flooding because not suitable mangrove tree species with low stature or thin trunks might be used. According to a Food and Agriculture Organization s mangrove expert, the protective effects of mangroves against tsunamis mainly depend on the scale of the tsunami and the width of the forest and, to a lesser extent, the height, density and species composition. Mangrove strips with narrow, thinly-planted mangrove trees are more likely to be uprooted or snapped off at mid-trunk by heavy storms (Arborvitae, 2005).

V. Conclusions and recommendations

The loss or further decline and perhaps migration of mangrove ecosystems due to climate change and other human activities will lead to considerable disruption of values derived directly and indirectly from this ecosystem. Ecosystem functions will be disrupted such as the role of mangrove forests as natural habitats, and spawning and nursing grounds for organisms. Other adjacent ecosystems will also be affected since some species derive their recruits from the mangrove communities and water circulation that offers migration corridors. Transport of nutrients and energy flow within the mangrove ecosystem and other systems will also be disrupted. Protective functions of the mangrove will also be minimized or lost causing loss of human properties and lives. Aquaculture activities in mangrove ecosystem, which is an increasingly important source for seafood products in the Philippines, might also decline. Loss of mangrove species also means loss of potential important genetic resources, which are valuable for the present and future generations.

The delay of the impacts of the current mitigation measures for climate change assures that effects of climate change will continue for hundreds or thousands of years given a stable climate. Thus, planning for the conservation of the mangrove ecosystem must consider the potential effects of the different factors related to climate change. A combination of adaptation and mitigation measures is seen as the most appropriate response to climate change for mangrove ecosystems.

Planned adaptation options to climate change are considered under three approaches namely planned retreat, accommodation, and protection. In planned retreat, all natural system effects are allowed to occur and human impacts are minimized by pulling back from the coast. In the accommodation approach, all natural system effects are allowed to occur and human impacts are minimized by adjusting human use of the coastal zone. With protection approach, natural system effects are controlled by soft or hard engineering, reducing human impacts in the zone that would be impacted without protection (Nicholls, 2003)

If mangrove protection and conservation will not consider the impacts of climate-change, these efforts may just be wasted in the long-run. It is also recommended that further studies be conducted to assess other potential impacts of climate change to the mangrove ecosystem.

References

Arborvitae. 2005. The IUCN/WWF Forest Conservation Newsletter

Boesch, 2002. Summary of Climate Change Assessments: Implications for estuarine Biocomplexity. Estuarine Research Foundation

Chong, Jo. 2005. Protective Values of Mangrove and Coral Ecosystems: A Review of Methods and Evidence. The World Conservation Union, IUCN

Curry, William. 2005. Common Misconceptions about Abrupt Climate Change. Woodshole Oceanographic Institute

http://www.whoi.edu/institutes/occi/currenttopics/abruptclimate_15misconceptions.html

Doyle, T.W., G.F. Girod, and M.A. Books. 2003. Modelling Mangrove Forest Migration along the Southwest Coast of Florida Under Climate Change. U.S. Geological Survey, National Wetlands Research Center.

FAO, UNEP. 1981. Tropical Forest Resourcess Assesment Project, Forest Resources of Tropical Asia. FAO, UNEP, 475 pp.

Kennedy, V.S., R.R. Twilley, J.A. Kleypas, J.H. Cowan Jr., and S.R. Hare. 2002. Coastal and Marine Ecosystems: Potential Effects on U.S. Resources and Global Climate Change. Pew Center on Global Climate Change

Natural Resource Defense Council. 2006. Consequences of Global Warming. http://www.nrdc.org/globalWarming/fcons.asp

Nicholls, R.J. 2003. Case Study on Sea-Level Rise Impacts. Organisation for Economic Co-operation and Development, France

Perez, R.T. no date. Assessment of Vulnerability and Adaptation to Climate Change in the Philippines Coastal Resources Sector. Natural Disaster reduction Branch (NDRB). Philippine Atmospheric , Geophysical, and Astronomical Services

Primavera, J.H. 2002. Management and Conservation of Mangroves in the Philippines. Joint UNU-Iwate-UNESCO International Conference. Conserving Our Coastal Environment 8-10 July 2002

Primavera, J.H. 2005. Global Voices of Science: Mangroves, Fishponds, and the Quest for Sustainability. Science vol. 310 (5745): 57-59

HERE ARE THE QUESTIONS

Read the attached article entitled "Analysis of Responses of Mangrove Ecosystems to Climate Change" and then prepare a review of the article, including the following components:

Thesis: What are the main points of the article?

Analysis:

How different environmental factors related climate change such as sea level rise, wind pattern, temperature change and availability of water from precipitation and runoff.
Discuss the responses of mangrove ecosystems to such factors and recommendations for mangrove protection in relevance to climate change.

Conclusion:

Which point of view did you most agree with and why?
What made this point of view so convincing?
What made other points of view less convincing?

Explanation / Answer

Ans.) The current climate change situations point to temperature increment and an ascent in ocean level as the most imperative factors specifically influencing the dispersion of mangroves and firmly propose an extension of these woodlands. The available perceptions lead us to infer that the mangroves cannot just continue inside the new ecological conditions forced by environmental change additionally, will prosper. Seeing how human exercises and a changing atmosphere are probably going to collaborate and influence the conveyance of administrations by these biological community, is absolutely critical to the present basic leadership which influences the soundness of marine and beach front frameworks and their capacity to manage who and what is to come. With respect to worldwide environmental change, the investigations broke down in this audit demonstrated that in spite of the fact that there are regions where mangroves will endure because of ecological changes, for the most part in maritime islands and deltas of various substantial tropical waterways and those beach front destinations encased by soak inclines that are at danger of being suffocated by the propelling ocean, in many areas mangrove territory will build reacting to expanding ocean level, diminishing precipitation and saline interruption. Under such natural setting mangroves react to changing states of waves and saltiness by relocating to places more distant inland, regularly to the detriment of other plant species and their capacity to exploit states of hotter winters by extending their breaking points toward higher scopes.

In my opinion one of the most convincing assumption of this entire mangrove phenomenon is the human mediation including asset abuse, stream bowl procedures and designing works for shoreline insurance, principally expected to adjust to worldwide change, rather increment powerlessness of mangroves, decreasing relieving choices to address the unfavorable outcomes of environmental change.

The above made point is so convincing due to the fact that indeed adjustment choices to upgrade mangrove resistance and flexibility to environmental change recommends that it is the human-initiated debasement of mangroves that should be tended to. In this manner, territorial checking to enhance the comprehension of mangroves' reaction, preparing and limit building programs pointed towards the general population and chiefs, towards an expanded familiarity with the estimation of mangrove biological system products and ventures, will add to diminishing the danger of mangrove misfortune identified with environmental change. The fate of mangroves along these lines, to a great extent relies upon the level of human intercessions and their cooperation with atmosphere related changes.

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