Ecological values of mangrove
Encyclopedia
Mangrove ecosystems represent natural capital
capable of producing a wide range of goods and services for coastal environments and communities and society as a whole. Some of these outputs, such as timber, are freely exchanged in formal markets. Value is determined in these markets through exchange and quantified in terms of price.
habitat for many wildlife species
, including commercial fish and crustaceans, and thus contribute to sustaining the local abundance of fish and shellfish populations. In Selangor, Malaysia 119 species were recorded as associated with mangrove ecosystems while 83 species were recorded in Kenya, 133 from Queensland Australia, 59 species in Puerto Rico and 128 from the Philippines.
While mangroves in the Caribbean have been demonstrated to support juvenile coral reef fish, mangrove ecosystems in Papua New Guinea
and the Solomon Islands
have been found to provide important nurseries for sandy and muddy-bottom demersal and surface feeding species. Seventy-five percent of the game fish and ninety percent of the commercial species in South Florida are dependent on mangrove ecosystems. An estimated seventy five percent of the commercially caught prawns and fish in Queensland, Australia, depend on mangroves for part of their life cycles and on nutrients exported from the mangroves to other ecosystems.
including crocodiles, birds, tigers, deer
, monkeys and honey bees. Many animals find shelter either in the roots or branches of mangroves. Mangroves serve as rookeries, or nesting areas, for coastal birds such as brown pelicans and roseate
spoonbills. Many migratory species depend on mangroves for part of their seasonal migrations. For instance, an estimated two million migratory shorebirds of the East Asian-Australasian Flyway, which annually migrate from the Arctic Circle through South-East Asia to Australia and New Zealand and back, stop to forage at numerous wetlands along this Flyway, include the wetlands of Oceania.
habitats. Mangrove root systems slow water flow, facilitating the deposition of sediment. Toxins and nutrients can be bound to sediment particles or within the molecular lattice of clay particles and are removed during sediment deposition. Compared with the expense of constructing a wastewater treatment plant
, mangroves are commonly selected as receiving areas of effluent. Increasingly the notion of specifically constructed mangrove wetlands is being adopted and used for treatment of aquaculture
and sewage effluents.
Mangroves are functionally linked to neighbouring coastal ecosystems. For instance, terrigenous sediments and nutrients carried by freshwater
runoff are first filtered by coastal forests, then by mangrove wetlands, and finally by seagrass beds before reaching coral reefs. The existence and health of coral reefs are dependent on the buffering capacity of these shoreward ecosystems, which support the oligotrophic conditions needed by coral reefs to limit overgrowth by algae
. Mangroves supply nutrients to adjacent coral reef
and seagrass
communities, sustaining these habitats’ primary production and general health.
The tsunami
has provided an opportunity to illustrate that healthy mangroves serve as a natural barrier
against massive waves – protecting infrastructure developments and saving lives. The World Conservation Union (IUCN) compared the death toll from two villages in Sri Lanka that were hit by the devastating tsunami giant waves. Two people died in the settlement with dense mangrove and scrub forest, while up to 6,000 people died in the village without similar vegetation
decreases with increasing latitude. From this global pattern it is expected that mangroves in New Zealand, near their southern geographical limit would have relatively low productivity compared to their tropical equivalents.
of New Zealand’s mangroves forests appear to be modest in both abundances and species diversity
compared to other estuarine habitats
(Aldrichetta forsteri), as well as juvenile grey mullet
(Mugil cephalus) in the west coast estuaries. Nineteen fish species are ‘confirmed’ to be associated with mangroves, of which three species are probably partially reliant on them as juvenile nurseries It seems unlikely that New Zealand mangroves are important as spawning grounds for coastal fish
or as habitat for their larvae.
, harriers, kingfishers, welcome swallow and pükeko.
, management and conservation
have received considerable attention in recent years since research has increased the understanding of the values, functions and attributes of mangrove ecosystems.
, treaties and agreements, which all concerned countries become signatories to. Mangroves are today a global issue because more than 100 countries worldwide have mangrove resources. Of the approximately 100 countries that have mangrove vegetation, around 20 have undertaken rehabilitation initiatives establishing nurseries and attempting afforestation and re-planting in degraded areas. More than half a dozen international agreements and various regional agreements are directly relevant to the conservation
of mangrove biodiversity
.
, a country had to designate at least one such site and guarantee its protection. Around 110 countries have become signatories to the treaty. Some 850 "Ramsar sites" have been designated by these countries covering over 53 million hectares. About a third of these contain mangroves (e.g. Mangrove Action Project ).
in the Waitemata Harbour
, and Te Matuku Bay Marine Reserve, Waiheke Island; both managed by the Department of Conservation.
Sectoral management has inevitably resulted in prejudices regarding their objectives, leading to conflicts of interest, to unsustainable resource use, and to poor and less powerful groups becoming more disadvantaged and disenfranchised . These limitations are now recognised as a major constraint to achieving sustainable development of mangrove resources.
Economic arguments carry the greatest weight in conservation and management of
mangroves . However, the true economic value of mangrove diversity
and natural resources
is difficult to measure and important ecological processes and functions undervalued. All development plans and policies should include economic valuations that fully reflect the sociological, ecological and environmental costs of resource use, physical developments and pollution
.
In New Zealand for example much of the basic information required to address concerns and manage mangrove is lacking. Research has established that, regardless of which approach is decided upon, sustainable management can only be achieved if evaluation of mangrove areas is undertaken on a site-by-site basis.
Natural capital
Natural capital is the extension of the economic notion of capital to goods and services relating to the natural environment. Natural capital is thus the stock of natural ecosystems that yields a flow of valuable ecosystem goods or services into the future...
capable of producing a wide range of goods and services for coastal environments and communities and society as a whole. Some of these outputs, such as timber, are freely exchanged in formal markets. Value is determined in these markets through exchange and quantified in terms of price.
Ecological Values
The ecological values of mangroves in most tropical countries have been qualitatively well documented and recognised. However there is little quantitative scientific data to back this up. Most of the evidence is observational and anecdotal.Marine Fisheries
Mangroves provide nurseryNursery habitats
In marine environments, a nursery habitat is a subset of all habitats where juveniles of a species occur, having a greater level of productivity per unit area than other juvenile habitats . Mangroves, salt marshes and seagrass are typical nursery habitats for a range of marine species...
habitat for many wildlife species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, including commercial fish and crustaceans, and thus contribute to sustaining the local abundance of fish and shellfish populations. In Selangor, Malaysia 119 species were recorded as associated with mangrove ecosystems while 83 species were recorded in Kenya, 133 from Queensland Australia, 59 species in Puerto Rico and 128 from the Philippines.
While mangroves in the Caribbean have been demonstrated to support juvenile coral reef fish, mangrove ecosystems in Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
and the Solomon Islands
Solomon Islands
Solomon Islands is a sovereign state in Oceania, east of Papua New Guinea, consisting of nearly one thousand islands. It covers a land mass of . The capital, Honiara, is located on the island of Guadalcanal...
have been found to provide important nurseries for sandy and muddy-bottom demersal and surface feeding species. Seventy-five percent of the game fish and ninety percent of the commercial species in South Florida are dependent on mangrove ecosystems. An estimated seventy five percent of the commercially caught prawns and fish in Queensland, Australia, depend on mangroves for part of their life cycles and on nutrients exported from the mangroves to other ecosystems.
Wildlife Habitat
Mangrove systems support a range of wildlife speciesWildlife species
Wildlife species may refer to:*A taxonomic species found in the wild*Evolutionary Significant Unit, a grouping used in conservation which may refer to species, subspecies, or other groups...
including crocodiles, birds, tigers, deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...
, monkeys and honey bees. Many animals find shelter either in the roots or branches of mangroves. Mangroves serve as rookeries, or nesting areas, for coastal birds such as brown pelicans and roseate
Roseate
Roseate, literally rose-colored, rosy, is used in the names of the following animals:* Roseate Cockatoo* Roseate Frog* Roseate Skimmer* Roseate Spoonbill* Roseate Tern...
spoonbills. Many migratory species depend on mangroves for part of their seasonal migrations. For instance, an estimated two million migratory shorebirds of the East Asian-Australasian Flyway, which annually migrate from the Arctic Circle through South-East Asia to Australia and New Zealand and back, stop to forage at numerous wetlands along this Flyway, include the wetlands of Oceania.
Improving Coastal Water Quality
Mangroves maintain coastal water quality by abiotic and biotic retention, removal, and cycling of nutrients, pollutants, and particulate matter from land-based sources, filtering these materials from water before they reach seaward coral reef and seagrassSeagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
habitats. Mangrove root systems slow water flow, facilitating the deposition of sediment. Toxins and nutrients can be bound to sediment particles or within the molecular lattice of clay particles and are removed during sediment deposition. Compared with the expense of constructing a wastewater treatment plant
Sewage treatment
Sewage treatment, or domestic wastewater treatment, is the process of removing contaminants from wastewater and household sewage, both runoff and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants...
, mangroves are commonly selected as receiving areas of effluent. Increasingly the notion of specifically constructed mangrove wetlands is being adopted and used for treatment of aquaculture
Aquaculture
Aquaculture, also known as aquafarming, is the farming of aquatic organisms such as fish, crustaceans, molluscs and aquatic plants. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
and sewage effluents.
Mangroves are functionally linked to neighbouring coastal ecosystems. For instance, terrigenous sediments and nutrients carried by freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
runoff are first filtered by coastal forests, then by mangrove wetlands, and finally by seagrass beds before reaching coral reefs. The existence and health of coral reefs are dependent on the buffering capacity of these shoreward ecosystems, which support the oligotrophic conditions needed by coral reefs to limit overgrowth by algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
. Mangroves supply nutrients to adjacent coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
and seagrass
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
communities, sustaining these habitats’ primary production and general health.
Protection of coastlines and Development
As a result of their intricately entangled above-ground root systems, mangrove communities protect shorelines during storm events by absorbing wave energy and reducing the velocity of water passing through the root barrier. Wave energy may be reduced by 75 per cent in the wave's passage through 200 metres of mangrove. but other factors also have an influence, including coastal profile, water depth and bottom configuration. Mangrove covered shorelines are less likely to erode, or will erode significantly more slowly, than unvegetated shorelines during periods of high wave energy. Protecting mangroves sustains natural protection, and is less expensive than seawalls and similar erosion control structures, which can increase erosion in front of the structure and at adjacent properties.The tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...
has provided an opportunity to illustrate that healthy mangroves serve as a natural barrier
Natural barrier
The most common use of the term "natural barrier" is in geography, where it refers to a naturally occurring obstacle to movement, especially of people and especially at modest technological levels....
against massive waves – protecting infrastructure developments and saving lives. The World Conservation Union (IUCN) compared the death toll from two villages in Sri Lanka that were hit by the devastating tsunami giant waves. Two people died in the settlement with dense mangrove and scrub forest, while up to 6,000 people died in the village without similar vegetation
The role of mangroves in New Zealand
Comparisons of the productivity of mangroves from different latitudes worldwide suggest that productivity and plant biomassBiomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
decreases with increasing latitude. From this global pattern it is expected that mangroves in New Zealand, near their southern geographical limit would have relatively low productivity compared to their tropical equivalents.
Intrinsic and unique values
Many aspects of New Zealand mangrove systems have not yet been sufficiently studied; therefore their importance in relation to marine and estuarine species and their role in terms of ecosystem structure and function is inadequate. The role played by mangroves in New Zealand estuarine foodwebs is, however, probably significant.Benthic fauna of mangroves
Relatively few studies have been undertaken on the benthic assemblages and species of mangrove forests in New Zealand. The benthic invertebrate faunaFauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
of New Zealand’s mangroves forests appear to be modest in both abundances and species diversity
Species diversity
Species diversity is an index that incorporates the number of species in an area and also their relative abundance. It is a more comprehensive value than species richness....
compared to other estuarine habitats
Fish fauna of mangrove ecosystems
Recent studies have shown that the temperate mangrove forests of northern New Zealand support high abundances of small fishes, but that New Zealand support high abundances of small fishes compared to other estuarine habitats, with most of the small fish assemblage dominated by juveniles of the ubiquitous yellow-eyed mulletMullet (fish)
The mullets or grey mullets are a family and order of ray-finned fish found worldwide in coastal temperate and tropical waters, and in some species in fresh water. Mullets have served as an important source of food in Mediterranean Europe since Roman times...
(Aldrichetta forsteri), as well as juvenile grey mullet
Mullet (fish)
The mullets or grey mullets are a family and order of ray-finned fish found worldwide in coastal temperate and tropical waters, and in some species in fresh water. Mullets have served as an important source of food in Mediterranean Europe since Roman times...
(Mugil cephalus) in the west coast estuaries. Nineteen fish species are ‘confirmed’ to be associated with mangroves, of which three species are probably partially reliant on them as juvenile nurseries It seems unlikely that New Zealand mangroves are important as spawning grounds for coastal fish
Coastal fish
Coastal fish, also called offshore fish or neritic fish, are fish that inhabit the sea between the shoreline and the edge of the continental shelf. Since the continental shelf is usually less than 200 metres deep, it follows that pelagic coastal fish are generally epipelagic fish, inhabiting the...
or as habitat for their larvae.
Use of mangroves by birds
While many species make extensive use of mangroves for roosting, feeding and breeding, no bird species is totally dependant on mangroves in New Zealand. The range of bird species that are found regularly in New Zealand mangroves includes several native species, such as banded rail, white-faced heronWhite-faced Heron
The White-faced Heron, Egretta novaehollandiae, also known as the White-fronted Heron, and incorrectly as the Grey Heron, or Blue Crane, is a common bird throughout most of Australasia, including New Guinea, the islands of Torres Strait, Indonesia, New Zealand, the islands of the Subantarctic, and...
, harriers, kingfishers, welcome swallow and pükeko.
Role of mangroves in sediment trapping and erosion prevention
This question has not been fully addressed in relation to New Zealand mangroves. However, previous and ongoing research, is extending the understanding of the role of mangrove contribution to habitat change. Remains of rows of mangroves planted to stabilize the coast by early generations of Maoris can still be seen in New ZealandMangrove management
The next section briefly discusses how mangrove has been managed today at the international and national level. Mangrove biodiversityBiodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
, management and conservation
Conservation biology
Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction...
have received considerable attention in recent years since research has increased the understanding of the values, functions and attributes of mangrove ecosystems.
International level
At the International Level, the common approach to major environmental policy issues has been to formulate conventionsConvention (norm)
A convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom....
, treaties and agreements, which all concerned countries become signatories to. Mangroves are today a global issue because more than 100 countries worldwide have mangrove resources. Of the approximately 100 countries that have mangrove vegetation, around 20 have undertaken rehabilitation initiatives establishing nurseries and attempting afforestation and re-planting in degraded areas. More than half a dozen international agreements and various regional agreements are directly relevant to the conservation
Conservation biology
Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction...
of mangrove biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
.
Ramsar Convention
In 1971, a convention to protect "Wetlands of International Importance" was adopted in the Iranian city of Ramsar. To become a signatory to the Ramsar ConventionRamsar Convention
The Ramsar Convention is an international treaty for the conservation and sustainable utilization of wetlands, i.e., to stem the progressive encroachment on and loss of wetlands now and in the future, recognizing the fundamental ecological functions of wetlands and their economic, cultural,...
, a country had to designate at least one such site and guarantee its protection. Around 110 countries have become signatories to the treaty. Some 850 "Ramsar sites" have been designated by these countries covering over 53 million hectares. About a third of these contain mangroves (e.g. Mangrove Action Project ).
Marine Protected Areas (MPA)
reviewed the global status for mangrove conservation: “There are 685 protected areas containing mangroves globally, distributed between 73 countries and territories. Countries with very large areas of mangroves have a significant number of protected areas notably Australia (180), Indonesia (64) and Brazil (63). Examples of marine reserves in New Zealand where mangrove form an important component of the protected foreshore vegetation are Motu Manawa (Pollen Island) Marine ReserveMotu Manawa (Pollen Island) Marine Reserve
Motu Manawa Marine Reserve is a protected area in the Waitemata Harbour in New Zealand. It is intersected by State Highway 16 and contains Pollen and Traherne Islands. The marine reserve was established in 1995.-External links:...
in the Waitemata Harbour
Waitemata Harbour
The quite famous Waitemata Harbour is the main access by sea to Auckland, New Zealand. For this reason it is often referred to as Auckland Harbour, despite the fact that it is only one of two harbours surrounding the city, and is crossed by the Auckland Harbour Bridge. The Waitemata forms the north...
, and Te Matuku Bay Marine Reserve, Waiheke Island; both managed by the Department of Conservation.
National level
Historically the responsibility of mangrove management at the national level in many tropical mangrove countries have been assigned on a sectoral basis to executing agencies of the government, institutions for example Forestry, Fishery or Agriculture Departments. The agencies responsible for administering mangroves differ between each country and even between states and districts within Countries.Sectoral management has inevitably resulted in prejudices regarding their objectives, leading to conflicts of interest, to unsustainable resource use, and to poor and less powerful groups becoming more disadvantaged and disenfranchised . These limitations are now recognised as a major constraint to achieving sustainable development of mangrove resources.
Limitations of management
Lack of knowledge of mangrove ecosystems, their extent, status and linkages to other ecosystemshampers efforts to conserve and manage mangroves, leading to the unsustainable exploitation of this productive coastal resources. According to a comprehensive information database of mangrove biodiversity in each country is necessary to monitor the status of mangrove biological diversity, realise its economic potential and areas of application. This is critical in planning an effective management of mangroves.Economic arguments carry the greatest weight in conservation and management of
mangroves . However, the true economic value of mangrove diversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
and natural resources
Natural Resources
Natural Resources is a soul album released by Motown girl group Martha Reeves and the Vandellas in 1970 on the Gordy label. The album is significant for the Vietnam War ballad "I Should Be Proud" and the slow jam, "Love Guess Who"...
is difficult to measure and important ecological processes and functions undervalued. All development plans and policies should include economic valuations that fully reflect the sociological, ecological and environmental costs of resource use, physical developments and pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
.
In New Zealand for example much of the basic information required to address concerns and manage mangrove is lacking. Research has established that, regardless of which approach is decided upon, sustainable management can only be achieved if evaluation of mangrove areas is undertaken on a site-by-site basis.
See also
- Ecological EconomicsEcological economicsImage:Sustainable development.svg|right|The three pillars of sustainability. Clickable.|275px|thumbpoly 138 194 148 219 164 240 182 257 219 277 263 291 261 311 264 331 272 351 283 366 300 383 316 394 287 408 261 417 224 424 182 426 154 423 119 415 87 403 58 385 40 368 24 347 17 328 13 309 16 286 26...
- MangroveMangroveMangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
- Changes in global mangrove distributionsChanges in global mangrove distributionsGlobal mangrove distributions have fluctuated throughout human and geological history. The area covered by mangroves is influenced by a complex interaction between land position, rainfall hydrology, sea level, sedimentation, subsidence, storms and pest-predator relationships)...
- Salt marshSalt marshA salt marsh is an environment in the upper coastal intertidal zone between land and salt water or brackish water, it is dominated by dense stands of halophytic plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh...
- Coastal biogeomorphologyCoastal biogeomorphologyOver the past two decades, biogeomorphology has developed as an established research field examining the interrelationship between organisms and geomorphic processes in a variety of environments, both marine, and terrestrial...
- Coastal erosionCoastal erosionCoastal erosion is the wearing away of land and the removal of beach or dune sediments by wave action, tidal currents, wave currents, or drainage...
- Coastal managementCoastal managementIn some jurisdictions the terms sea defense and coastal protection are used to mean, respectively, defense against flooding and erosion...
- Earth economicsEarth EconomicsEarth Economics, a 501c3 non-profit headquartered in Tacoma, Washington, United States, is dedicated to researching and applying the economic solutions of tomorrow today. Earth Economics provides robust, science-based, ecologically-sound, economic analysis, policy and tools to governments,...
(policy think tank) - Ramsar ConventionRamsar ConventionThe Ramsar Convention is an international treaty for the conservation and sustainable utilization of wetlands, i.e., to stem the progressive encroachment on and loss of wetlands now and in the future, recognizing the fundamental ecological functions of wetlands and their economic, cultural,...
- Coral reefsReefIn nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....