Ecological values of mangroves

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.

Mangroves in Puerto Rico
Mangroves in Puerto Rico

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.[1]

Marine Fisheries

Mangroves provide nursery habitat for many wildlife species, including commercial fish and crustaceans, and thus contribute to sustaining the local abundance of fish and shellfish populations.[2] 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,[3] 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.[4] Seventy-five percent of the game fish and ninety percent of the commercial species in South Florida are dependent on mangrove ecosystems.[5] 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.[6]

Wildlife Habitat

Mangrove systems support a range of wildlife species including crocodiles, birds, tigers, deers, monkeys and honey bees.[7] 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.[8]

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 seagrass habitats.[9] 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.[7]

Mangroves are functionally linked to neighbouring coastal ecosystems.[3] 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.[10] Mangroves supply nutrients to adjacent coral reef and seagrass communities, sustaining these habitats’ primary production and general health.

Endangered Mangrove Coastlines and Human 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.[11] In addition, mangroves protect intertidal sediment along coastlines from eroding away in harsh weather year-round. As new cities are developed, mangrove forests around the world have felt a great impact not only on their ecosystems health, but also their wave-attenuating capacity.[12] Wave energy may be reduced by 75 per cent in the wave's passage through 200 meters of mangrove forests, a very substantial amount once the mangrove has been removed.[13] Mangrove covered shorelines are less likely to erode, or will erode significantly more slowly, than unvegetated shorelines during periods of high wave energy.[14] Other factors mangroves have an influence on, include coastal profile, water depth and bottom configuration. The mangrove population has felt both direct and indirect effects due to coastal engineering and human development, resulting in a devastating decline in population. This decline has led to a negative chain of effects in other ecosystems that are dependent on mangrove forest for survival.[15] In just the last decade, at least 35 percent of the world's mangroves have been destroyed, exceeding the rate of the disappearance of tropical rainforests.[16] Mangroves provide a number of essentials for many different ecosystems, including food and shelter for a diverse animal community, living both below and above sea level.[17] Maintaining a healthy mangrove forest 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 due to coastal currents. Unless ecosystems have the space to adjust their location or elevation in the intertidal zone to the sea-level rise, they will be stressed by changed inundation periods.[18] The Global Mean Sea Level (GMSL) has risen 4 to 8 inches over the past century, almost twice the average rate of 80 years prior.[19] It appears that as the sea-level is slowly rising, mangroves are a better alternative to protecting coastlines from eroding than other man made structures, such as seawalls.

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 [20] This study proves that mangroves provide a natural wall, which is necessary in high impact natural disasters areas such as this one.

World map mangrove distribution
Mangrove forests of the world in 2000

The role of mangroves in New Zealand

Comparisons of the productivity of mangroves from different latitudes worldwide suggest that productivity and plant biomass 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 inadequately understood. 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 fauna of New Zealand’s mangroves forests appear to be modest in both abundances and species diversity compared to other estuarine habitats.[21]

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 mullet (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.[21] It seems unlikely that New Zealand mangroves are important as spawning grounds for coastal fish 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 dependent 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 heron, 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.[21]> Remains of rows of mangroves planted to stabilize the coast by early generations of Maoris can still be seen in New Zealand.[22]

Mangrove management

The next section briefly discusses how mangrove has been managed today at the international and national level. Mangrove biodiversity, 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. Mangrove Restoration practices have also greatly improved over the past several years.

International level

At the International Level, the common approach to major environmental policy issues has been to formulate conventions, 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.[23] Of the approximately 100 countries that have mangrove vegetation, around 20 have undertaken rehabilitation initiatives [24] establishing nurseries and attempting afforestation and re-planting in degraded areas.[25] More than half a dozen international agreements and various regional agreements are directly relevant to the conservation of mangrove biodiversity.

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 Convention, 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[26]).

Marine Protected Areas (MPA)

[27] 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 Reserve in the Waitematā Harbour, 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 ([28]). 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 ecosystems hampers efforts to conserve and manage mangroves, leading to the unsustainable exploitation of this productive coastal resources. According to [29] 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.[30] 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.[21]

See also

References

Notes

  1. ^ UNEP-WCMC 2006
  2. ^ Lal 1990
  3. ^ a b Mumby et al. 2004
  4. ^ (Blaber and Milton, 1990
  5. ^ Law and Pywell FRC-43
  6. ^ Horst, 1998
  7. ^ a b Saenger 2013
  8. ^ (Environment Australia, 2000)
  9. ^ Ewel, 1997
  10. ^ Ellison, 2004)
  11. ^ Mazda et al. 1997
  12. ^ Bruma, Tjeerd; Belzen, Jim; Balke, Thorsten; Zhu, Zhenchang (May 2014). "Identifying knowledge gaps hampering application of intertidal habitats in coastal protection: Opportunities & steps to take". Coastal Engineering. 87: 147–157. doi:10.1016/j.coastaleng.2013.11.014. Retrieved 19 July 2014.
  13. ^ Massel 1999
  14. ^ Saenger, 2002
  15. ^ Bruma, Tjeerd; Belzen, Jim; Balke, Thorsten; Zhu, Zhenchang (2014). "Identifying knowledge gaps hampering application of intertidal habitats in coastal protection: Opportunities & steps to take". Coastal Engineering. 87: 147–157. doi:10.1016/j.coastaleng.2013.11.014. Retrieved 19 July 2014.
  16. ^ "Mangroves". ocean.si.edu. Retrieved 25 July 2014.
  17. ^ Schongalla, Malacolm. "Salt Management in Avicennia germinans and Rhizophora mangle". jrscience.wcp.muohio.edu. Retrieved 19 July 2014.
  18. ^ Burma, Tjeerd (2014). "Identifying knowledge gaps hampering application of intertidal habitats in coastal protection: Opportunities & steps to take". Coastal Engineering. 87: 147–157. doi:10.1016/j.coastaleng.2013.11.014. Retrieved 19 July 2014.
  19. ^ "Sea Level Rise". ocean.nationalgeographic.com. Retrieved 23 July 2014.
  20. ^ (IUCN 2005)
  21. ^ a b c d Morrisey et al. 2007
  22. ^ (Vannucci, 1997)
  23. ^ Spalding, 1997
  24. ^ (Field 1998),
  25. ^ Erftemeijer & Lewis 1999
  26. ^ http://mangroveactionproject.org/search_
  27. ^ Spalding (1997)
  28. ^ Brown, 1997
  29. ^ Macintosh and Ashton (2002)
  30. ^ (Macintosh & Ashton 2002).

Bibliography

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  • Ewel, K.C.; Bourgeois, J.; Cole, T.; Zheng, S. (1998). "Variation in environmental characteristics and vegetation in high-rainfall mangrove forests, Kosrae, Micronesia". Global Ecology and Biogeography Letters. 7 (1): 49–56. doi:10.1111/j.1466-8238.1998.00267.x (inactive 2019-02-11).
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Aquatic ecosystem

An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.

Aquatic toxicology

Aquatic toxicology is the study of the effects of manufactured chemicals and other anthropogenic and natural materials and activities on aquatic organisms at various levels of organization, from subcellular through individual organisms to communities and ecosystems. Aquatic toxicology is a multidisciplinary field which integrates toxicology, aquatic ecology and aquatic chemistry.This field of study includes freshwater, marine water and sediment environments. Common tests include standardized acute and chronic toxicity tests lasting 24–96 hours (acute test) to 7 days or more (chronic tests). These tests measure endpoints such as survival, growth, reproduction, that are measured at each concentration in a gradient, along with a control test. Typically using selected organisms with ecologically relevant sensitivity to toxicants and a well-established literature background. These organisms can be easily acquired or cultured in lab and are easy to handle.

Benthos

Benthos is the community of organisms that live on, in, or near the seabed, river, lake, or stream bottom, also known as the benthic zone. This community lives in or near marine or freshwater sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.

Many organisms adapted to deep-water pressure cannot survive in the upperparts of the water column. The pressure difference can be very significant (approximately one atmosphere for each 10 metres of water depth).Because light is absorbed before it can reach deep ocean-water, the energy source for deep benthic ecosystems is often organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain; most organisms in the benthic zone are scavengers or detritivores.

The term benthos, coined by Haeckel in 1891, comes from the Greek noun βένθος "depth of the sea". Benthos is used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as lakes, rivers, and streams. There is also a redundant synonym, benthon.

Bioluminescence

Bioluminescence is the production and emission of light by a living organism. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some bioluminescent bacteria and terrestrial invertebrates such as fireflies. In some animals, the light is bacteriogenic, produced by symbiotic organisms such as Vibrio bacteria; in others, it is autogenic, produced by the animals themselves.

In a general sense, the principal chemical reaction in bioluminescence involves some light-emitting molecule and an enzyme, generally called the luciferin and the luciferase, respectively. Because these are generic names, the luciferins and luciferases are often distinguished by including the species or group, i.e. Firefly luciferin. In all characterized cases, the enzyme catalyzes the oxidation of the luciferin.

In some species, the luciferase requires other cofactors, such as calcium or magnesium ions, and sometimes also the energy-carrying molecule adenosine triphosphate (ATP). In evolution, luciferins vary little: one in particular, coelenterazine, is found in eleven different animal (phyla), though in some of these, the animals obtain it through their diet. Conversely, luciferases vary widely between different species, and consequently bioluminescence has arisen over forty times in evolutionary history.

Both Aristotle and Pliny the Elder mentioned that damp wood sometimes gives off a glow and many centuries later Robert Boyle showed that oxygen was involved in the process, both in wood and in glow-worms. It was not until the late nineteenth century that bioluminescence was properly investigated. The phenomenon is widely distributed among animal groups, especially in marine environments where dinoflagellates cause phosphorescence in the surface layers of water. On land it occurs in fungi, bacteria and some groups of invertebrates, including insects.

The uses of bioluminescence by animals include counter-illumination camouflage, mimicry of other animals, for example to lure prey, and signalling to other individuals of the same species, such as to attract mates. In the laboratory, luciferase-based systems are used in genetic engineering and for biomedical research. Other researchers are investigating the possibility of using bioluminescent systems for street and decorative lighting, and a bioluminescent plant has been created.

Dead zone (ecology)

Dead zones are hypoxic (low-oxygen) areas in the world's oceans and large lakes, caused by "excessive nutrient pollution from human activities coupled with other factors that deplete the oxygen required to support most marine life in bottom and near-bottom water. (NOAA)". Historically, many of these sites were naturally occurring. However, in the 1970s, oceanographers began noting increased instances and expanses of dead zones. These occur near inhabited coastlines, where aquatic life is most concentrated. (The vast middle portions of the oceans, which naturally have little life, are not considered "dead zones".)

In March 2004, when the recently established UN Environment Programme published its first Global Environment Outlook Year Book (GEO Year Book 2003), it reported 146 dead zones in the world's oceans where marine life could not be supported due to depleted oxygen levels. Some of these were as small as a square kilometre (0.4 mi²), but the largest dead zone covered 70,000 square kilometres (27,000 mi²). A 2008 study counted 405 dead zones worldwide.

Ecosystem of the North Pacific Subtropical Gyre

The North Pacific Subtropical Gyre (NPSG) is the largest contiguous ecosystem on earth. In oceanography, a subtropical gyre is a ring-like system of ocean currents rotating clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere caused by the Coriolis Effect. They generally form in large open ocean areas that lie between land masses.

The NPSG is the largest of the gyres as well as the largest ecosystem on our planet. Like other subtropical gyres, it has a high-pressure zone in its center. Circulation around the center is clockwise around this high-pressure zone. Subtropical gyres make up 40% of the Earth’s surface and play critical roles in carbon fixation and nutrient cycling. This particular gyre covers most of the Pacific Ocean and comprises four prevailing ocean currents: the North Pacific Current to the north, the California Current to the east, the North Equatorial Current to the south, and the Kuroshio Current to the west. Its large size and distance from shore has caused the NPSG to be poorly sampled and thus poorly understood.

The life processes in open-ocean ecosystems are a sink for the atmosphere’s increasing CO2. Gyres make up a large proportion, approximately 75%, of what we refer to as the open ocean, or the area of the ocean that does not consist of coastal areas. They are considered oligotrophic, or nutrient poor because they are far from terrestrial runoff. These regions were once thought to be homogenous and static habitats. However, there is increasing evidence that the NPSG exhibits substantial physical, chemical, and biological variability on a variety of time scales. Specifically, the NPSG exhibits seasonal and interannual variations in primary productivity (simply defined as the production of new plant material), which is important for the uptake of CO2.

The NPSG is not only a sink for CO2 in the atmosphere, but also other pollutants. As a direct result of this circular pattern, gyres act like giant whirlpools and become traps for anthropogenic pollutants, such as marine debris. The NPSG has become recognized for the large quantity of plastic debris floating just below the surface in the center of the gyre. This area has recently received a lot of media attention and is commonly referred to as the Great Pacific Garbage Patch.

Floodplain restoration

Floodplain restoration is the process of fully or partially restoring a river's floodplain to its original conditions before having been affected by the construction of levees (dikes) and the draining of wetlands and marshes.

The objectives of restoring floodplains include the reduction of the incidence of floods, the provision of habitats for aquatic species, the improvement of water quality and the increased recharge of groundwater.

Florida mangroves

The Florida mangroves ecoregion, of the mangrove forest biome, comprise an ecosystem along the coasts of the Florida peninsula, and the Florida Keys.

GIS and aquatic science

Geographic Information Systems (GIS) has become an integral part of aquatic science and limnology. Water by its very nature is dynamic. Features associated with water are thus ever-changing. To be able to keep up with these changes, technological advancements have given scientists methods to enhance all aspects of scientific investigation, from satellite tracking of wildlife to computer mapping of habitats. Agencies like the US Geological Survey, US Fish and Wildlife Service as well as other federal and state agencies are utilizing GIS to aid in their conservation efforts.

GIS is being used in multiple fields of aquatic science from limnology, hydrology, aquatic botany, stream ecology, oceanography and marine biology. Applications include using satellite imagery to identify, monitor and mitigate habitat loss. Imagery can also show the condition of inaccessible areas. Scientists can track movements and develop a strategy to locate locations of concern. GIS can be used to track invasive species, endangered species, and population changes.

One of the advantages of the system is the availability for the information to be shared and updated at any time through the use of web-based data collection.

Lake ecosystem

A lake ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions.Lake ecosystems are a prime example of lentic ecosystems. Lentic refers to stationary or relatively still water, from the Latin lentus, which means sluggish. Lentic waters range from ponds to lakes to wetlands, and much of this article applies to lentic ecosystems in general. Lentic ecosystems can be compared with lotic ecosystems, which involve flowing terrestrial waters such as rivers and streams. Together, these two fields form the more general study area of freshwater or aquatic ecology.

Lentic systems are diverse, ranging from a small, temporary rainwater pool a few inches deep to Lake Baikal, which has a maximum depth of 1642 m. The general distinction between pools/ponds and lakes is vague, but Brown states that ponds and pools have their entire bottom surfaces exposed to light, while lakes do not. In addition, some lakes become seasonally stratified (discussed in more detail below.) Ponds and pools have two regions: the pelagic open water zone, and the benthic zone, which comprises the bottom and shore regions. Since lakes have deep bottom regions not exposed to light, these systems have an additional zone, the profundal. These three areas can have very different abiotic conditions and, hence, host species that are specifically adapted to live there.

Limnology

Limnology ( lim-NOL-ə-jee; from Greek λίμνη, limne, "lake" and λόγος, logos, "knowledge"), is the study of inland aquatic ecosystems.

The study of limnology includes aspects of the biological, chemical, physical, and geological characteristics and functions of inland waters (running and standing waters, fresh and saline, natural or man-made). This includes the study of lakes, reservoirs, ponds, rivers, springs, streams, wetlands, and groundwater. A more recent sub-discipline of limnology, termed landscape limnology, studies, manages, and seeks to conserve these ecosystems using a landscape perspective, by explicitly examining connections between an aquatic ecosystem and its watershed. Recently, the need to understand global inland waters as part of the Earth System created a sub-discipline called global limnology. This approach considers processes in inland waters on a global scale, like the role of inland aquatic ecosystems in global biogeochemical cycles.Limnology is closely related to aquatic ecology and hydrobiology, which study aquatic organisms and their interactions with the abiotic (non-living) environment. While limnology has substantial overlap with freshwater-focused disciplines (e.g., freshwater biology), it also includes the study of inland salt lakes.

List of watershed topics

This list embraces topographical watersheds and drainage basins and other topics focused on them.

Mangrove tree distribution

Global 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). In the last 50 years, human activities have strongly affected mangrove distributions, resulting in declines or expansions of worldwide mangrove area. Mangroves provide several important ‘free services’ including coastal stabilization, juvenile fish habitats, and the filtration of sediment and nutrients). Mangrove loss has important implications for coastal ecological systems and human communities dependent on healthy mangrove ecosystems. This English Wikipedia page presents an overview of global Mangrove Forest biome trends in mangrove ecoregions distribution, as well as the cause of such changes.

As of 2012, mangroves are found in 105 nations globally. Although distributed across 105 nations, the top 10 mangrove holding nations contain approximately 52% of the global mangrove stock with Indonesia alone containing between 26% and 29% of the entire global mangrove stock. The largest continuous area of mangrove forest is likely in-and-around the Sundarbans National Park in India and the Sundarbans Mangrove Forests in Bangladesh, which are both recognized by UNESCO as World Heritage Sites. Although existing almost exclusively in the tropics and near-tropics, warm ocean currents support mangrove forests as far north as Walsingham Nature Reserve (Idwal Hughes Nature Reserve) in Bermuda and as far south as Snake Island, Australia.

Particle (ecology)

In marine and freshwater ecology, a particle is a small object. Particles can remain in suspension in the ocean or freshwater. However, they eventually settle (rate determined by Stokes' law) and accumulate as sediment. Some can enter the atmosphere through wave action where they can act as cloud condensation nuclei (CCN). Many organisms filter particles out of the water with unique filtration mechanisms (filter feeders). Particles are often associated with high loads of toxins which attach to the surface. As these toxins are passed up the food chain they accumulate in fatty tissue and become increasingly concentrated in predators (see bioaccumulation). Very little is known about the dynamics of particles, especially when they are re-suspended by dredging. They can remain floating in the water and drift over long distances. The decomposition of some particles by bacteria consumes a lot of oxygen and can cause the water to become hypoxic.

Photic zone

The photic zone, euphotic zone (Greek for "well lit": εὖ "well" + φῶς "light"), or sunlight (or sunlit) zone is the uppermost layer of water in a lake or ocean that is exposed to intense sunlight. It corresponds roughly to the layer above the compensation point, i.e. depth where the rate of carbon dioxide uptake, or equivalently, the rate of photosynthetic oxygen production, is equal to the rate of carbon dioxide production, equivalent to the rate of respiratory oxygen consumption, i.e. the depth where net carbon dioxide assimilation is zero.

It extends from the surface down to a depth where light intensity falls to one percent of that at the surface, called the euphotic depth. Accordingly, its thickness depends on the extent of light attenuation in the water column. Typical euphotic depths vary from only a few centimetres in highly turbid eutrophic lakes, to around 200 meters in the open ocean. It also varies with seasonal changes in turbidity.

Since the photic zone is where almost all of the photosynthesis occurs, the depth of the photic zone is generally proportional to the level of primary production that occurs in that area of the ocean. About 90% of all marine life lives in the photic zone. A small amount of primary production is generated deep in the abyssal zone around the hydrothermal vents which exist along some mid-oceanic ridges.

The zone which extends from the base of the euphotic zone to about 200 metres is sometimes called the disphotic zone. While there is some light, it is insufficient for photosynthesis, or at least insufficient for photosynthesis at a rate greater than respiration. The euphotic zone together with the disphotic zone coincides with the epipelagic zone. The bottommost zone, below the euphotic zone, is called the aphotic zone. Most deep ocean waters belong to this zone.

The transparency of the water, which determines the depth of the photic zone, is measured simply with a Secchi disk. It may also be measured with a photometer lowered into the water.

Ramsar Convention

The Ramsar Convention on Wetlands of International Importance especially as Waterfowl Habitat is an international treaty for the conservation and sustainable use of wetlands. It is also known as the Convention on Wetlands. It is named after the city of Ramsar in Iran, where the Convention was signed in 1971.

Every three years, representatives of the Contracting Parties meet as the Conference of the Contracting Parties (COP), the policy-making organ of the Convention which adopts decisions (Resolutions and Recommendations) to administer the work of the Convention and improve the way in which the Parties are able to implement its objectives. COP12 was held in Punta del Este, Uruguay, in 2015. COP13 was held in Dubai, United Arab Emirates, in October 2018.

Ramsar site

A Ramsar site is a wetland site designated to be of international importance under the Ramsar Convention.The Convention on Wetlands, known as the Ramsar Convention, is an intergovernmental environmental treaty established in 1971 by UNESCO, which came into force in 1975. It provides for national action and international cooperation regarding the conservation of wetlands, and wise sustainable use of their resources.Ramsar identifies wetlands of international importance, especially those providing waterfowl habitat.

As of 2016, there were 2,231 Ramsar sites, protecting 214,936,005 hectares (531,118,440 acres), and 169 national governments are currently participating.

Sustainable gardening

Sustainable gardening includes the more specific sustainable landscapes, sustainable landscape design, sustainable landscaping, sustainable landscape architecture, resulting in sustainable sites. It comprises a disparate group of horticultural interests that can share the aims and objectives associated with the international post-1980s sustainable development and sustainability programs developed to address the fact that humans are now using natural biophysical resources faster than they can be replenished by nature.Included within this compass are those home gardeners, and members of the landscape and nursery industries, and municipal authorities, that integrate environmental, social, and economic factors to create a more sustainable future.

Organic gardening and the use of native plants are integral to sustainable gardening.

Value of Earth

The Value of Earth, i.e. the net worth of our planet, is a debated concept both in terms of the definition of value, as well as the scope of "earth".

Since most of the planet's substance is not available as a resource, "earth" has been equalled with the sum of all ecosystem services as evaluated in ecosystem valuation or full-cost accounting.

The price on the services that the world's ecosystems provide to humans has been estimated in 1997 to be $33 trillion per annum, with a confidence interval of from $16 trillion to $54 trillion. Compared with the combined gross national product (GNP) of all the countries at about the same time ($18 trillion) ecosystems would appear to be providing 1.8 times as much economic value as people are creating. The result details have been questioned, in particular the GNP, which is believed to be closer to $28 trillion (which makes ecosystem services only 1.2 times as precious), while the basic approach was readily acknowledged. The World Bank gives the total gross domestic product (GDP) in 1997 as $31.435 trillion, which would about equal the biosystem value.

Criticisms were addressed in a later publication, which gave an estimate of $125 trillion/yr for ecosystem services in 2011, which would make them twice as valuable as the GDP, with a yearly loss of 4.3–20.2 trillion/yr.The BBC has published a website that lists various types of resources on various scales together with their current estimated values from different sources, among them BBC Earth, and Tony Juniper in collaboration with The United Nations Environment Programme World Conservation Monitoring Centre (UNEP-WCMC). The value of freshwater alone has been given as $73.48 trillion.

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