Loss Of Natural Wetlands Research Articles

Natural versus artificial- wetlands and their waterbirds in Sri Lanka

As natural wetlands have disappeared around the world, artificial wetlands have increased. We found interesting differences in waterbird communities of two natural (Bundala Ramsar site) and seven artificial wetlands (irrigation tanks, salt ponds, rice paddies) in south-east Sri Lanka. Eight species exclusively used natural and one species artificial wetlands. Migratory species (shorebirds 64%, terns 47%) dominated species’ richness of natural lagoons, with densities of shorebirds 3–6 times greater than on artificial wetlands. Contrastingly, resident species (dabbling ducks, gallinules) contributed most to the diversity (59%) and density of waterbirds on artificial irrigation tanks. Cattle egrets dominated waterbird density (>70%) of rice paddies. Waterbird communities reflected physical and chemical character of wetlands: natural wetlands were shallow (<2 m) and saline (EC > 1000 msm −1) compared to deep (>2 m) and freshwater (EC < 110 msm −1) artificial wetlands. Artificial inputs of water drained into the natural Embilikala lagoon changing its physico-chemical profile and disrupting the natural seasonal drying. Consequently its waterbird community was similar to artificial irrigation tanks, with shorebird species particularly impacted: densities half that of the other natural lagoon. Artificial salt ponds had similar physico-chemical properties to the natural Bundala lagoon and a similar waterbird community. Even though artificial wetlands supported waterbirds, they were not adequate replacements for loss of natural wetlands, favouring some species. Imposed hydrological stability degraded habitat quality for migratory shorebirds on one of our Ramsar site lagoons.

Wetlands Mitigation Banking and the Problem of Consolidation

A mitigation bank is a large wetland or wetland complex that is restored or created for the sake of selling credits to private developers or government agencies to compensate for the loss of natural wetlands. Mitigation banking is now emphasized within federal environmental policy. Proponents of banking claim that banking is beneficial to the environment, but studies have shown that this practice threatens biodiversity. The problem is consolidation. With banking, wetlands in a broad geographical area are collapsed into a relatively small area. Wetlands within banks tend to be larger and they are less diverse in type than the wetlands that are lost. Studies have shown that consolidation threatens the diversity and abundance of amphibians and wetland birds. Mitigation banking actually rests, not on arguments concerning its environmental benefits, but on arguments concerning the benefits it provides to humans.

Identifying new buffer areas for conserving waterbirds in the Mediterranean basin: the importance of the rice fields in Extremadura, Spain

The impact of wetland loss on migratory waterbirds can be mitigated by the presence of anthropogenic habitats such as rice fields. In the Mediterranean basin, wetlands have been drained and altered to such a degree that their very existence is threatened. It is, therefore, essential to identify key buffer areas in the basin to develop conservation strategies for migratory waterbirds. In Extremadura, continental SW Spain, 30,000 ha of new rice fields have created since the 1960s. The present study describes for the first time the waterbird community associated with these inland rice fields, and addresses the question of the potential value of this area in buffering the loss of natural wetlands for populations of waterbirds using the East Atlantic Flyway (EAF). The waterbird community studied consisted of 45 species, with population levels reaching values of international importance (>1% of the biogeographical population using EAF) for the Common Crane Grus grus (19%), Black-tailed Godwit Limosa limosa (1.2%), Black-winged Stilt Himantopus himantopus (1.2%), and Cattle Egret Bubulcus ibis (1%). The presence of these rice fields may be modifying the wintering and/or feeding sites of some waterbird species such as the Common Crane and Black-tailed Godwit. Unfortunately, there is no legal protection for this area. We propose the designation of these rice fields as a Special Protection Area for birds.

Importance of gravel pits for the conservation of waterbirds in the Garonne river floodplain (southwest France)

The loss of natural wetlands throughout the World has made created habitats such as gravel pits, reservoirs or rice fields potentially important for waterbird conservation. In southwest France, the increasing abundance of gravel pits has allowed several bird species to colonize the region. The avian community was studied from 1996 to 1998 in six gravel pits in the Garonne floodplain. A total of 39 species of waterbirds were recorded, with higher abundance during the winter and post-breeding periods. We analyzed habitat use to identify key environmental factors determining the temporal and spatial distribution of the avian community. The presence of submerged macrophytes was found to be the most important factor influencing the distribution of waterbirds. The presence of paths in the vicinity of the areas reduced both the total number of birds and species richness owing to human disturbance. Gravel pits have an increasingly important role in the conservation of bird biodiversity. By controlling disturbance and management of vegetation, managers can enhance this role.

Are artificial wetlands good alternatives to natural wetlands for waterbirds? – A case study on Chongming Island, China

Loss of natural wetlands is a global phenomenon that has been a serious threat to the wildlife. A common practice is to construct artificial wetlands to compensate for the loss of natural wetlands. To test whether artificial wetlands as habitats for waterbirds are good alternatives to natural wetlands, we compared species richness, abundance, and seasonal dynamics of waterbird communities of natural (here tidelands) and artificial wetlands (here aquacultural ponds) on Chongming Island, China. Our results indicate that habitat preference of waterbirds showed seasonal difference: most of the shorebirds were found on tidelands in spring, whereas most of the natatorial birds were recorded in aquacultural ponds in winter. Waterbirds preferred the tidelands rather than aquacultural ponds in both spring and autumn, whereas they showed no preference for either the tidelands or the ponds in summer and winter. It is concluded that natural wetlands are better habitats for waterbirds than artificial wetlands on Chongming Island, while the artificial ones are also suitable habitats for waterbirds in winter. The waterbirds might use artificial wetlands only when natural wetlands are unavailable or of poor quality. An over-emphasis that artificial wetlands are suitable habitats for waterbirds might encourage land managers to convert natural wetlands into the artificial ones, resulting in considerable loss of bird diversity. Therefore, for the purpose of bird conservation, it would be a better practice to conserve natural wetlands rather than to construct artificial ones after destruction of natural wetlands.

Land resource impact indicators of urban sprawl

Sprawl has been loosely defined as dispersed and inefficient urban growth. We propose a series of five indicators that examine the per capita consumption of land taken in new development in relation to several critical land resource impacts associated to sprawl including: (1) density of new urbanization; (2) loss of prime farmland; (3) loss of natural wetlands; (4) loss of core forest habitat; and (5) increase of impervious surface. These Land Resource Impact (LRI) indicators were measured for each of New Jersey’s 566 municipalities using a 1986 to 1995 land use/land cover digital database along with US Census population data. By integrating population growth with land resource loss a more nuanced interpretation of land use change is provided than in previous analyses of sprawl.

Status of ecological health of wetlands in Punjab, India

To identify important wetlands from ecological, socio-economic, hydro-biological, religious and recreational points of view, a study was undertaken in the state of Punjab with the aim of designing suitable conservation strategies and developing site-specific management plans for their timely implementation. The survey shows that in Punjab, all the natural and man-made wetlands cover an area of about 23000 ha. While most of the natural wetlands are under severe stress from reclamation for agriculture, the man-made wetlands which are primarily being maintained for the purpose of meeting water requirements of Punjab and other adjoining states are under threat of general ecological degradation. Though conservation and protection of wetlands in the state have attracted the attention of the government, the general attitude of the public towards these ecosystems is negative with efforts directed toward making alternate uses of the wetlands in the short-term. As a consequence, a large number of natural wetlands have vanished and the trend is continuing. Some of the very prominent wetlands that have totally lost their ecological character due to reclamation include Bhupinder Sagar, Chhangali Chhamb, and Rahon de Chhamb. Major reasons for their loss include drainage of low lands, reduced flow of water into natural wetlands, siltation and encroachments. Due to the continuous loss of natural wetlands in the state not only the local hydrological regime is changing rapidly but also the biological diversity has come under threatening pressure. This study has found that immediate conservation measures have to be implemented in some important wetlands in the state. The Punjab State Council for Science and Technology has identified five wetlands, Keshopur-Miani Jheel, Chhawarian Bhangar Chhamb, Jastarwal Jheel, Mand Bharthala and Dholbaha Reservoir, to be designated as wetlands of state significance. These are in addition to Harike, Kanjli and Ropar wetlands that have been included in the list of wetlands of national importance.

The conservation status of Moroccan wetlands with particular reference to waterbirds and to changes since 1978

Morgan made detailed descriptions of 24 major Moroccan wetlands visited in 1978, with a total area of 4529 ha (Morgan, N.C., 1982a. An ecological survey of standing waters in North West Africa: III. Site descriptions for Morocco. Biological Conservation, 24, 161–182.). We revisited these sites, and found that 25% of the wetland area had been destroyed by 1999. This loss was concentrated in wetland types of low salinity (<5 g/l NaCl), with a 98% loss of seasonal mesohaline sites, 41% loss of mountain lakes and 33% loss of seasonal Phragmites/Scirpus lacustris marshes. Surviving mountain lakes showed increased conductivities, suggesting reduced inflow. No loss of area of other wetland types was recorded, although degradation has occurred at all sites due to hydrological impacts, overgrazing or excessive reed-cutting, sedimentation, urban development, pollution, introduction of exotic fish and other causes. Similar threats face another 23 major Moroccan wetlands reviewed in this study. Of the 47 wetlands studied in total, only 10 have some kind of protection status. We assess the importance of these wetlands for waterbirds and aquatic submerged or floating plants. The number of plant species recorded is strongly correlated with the number of threatened waterbird species (but not the total number of waterbird species). Natural, freshwater wetlands most affected by wetland loss hold more species of aquatic plants and invertebrates, and are of great value for threatened waterbirds such as marbled teal ( Marmaronetta angustrirostris), ferruginous duck ( Aythya nyroca), ruddy shelduck ( Tadorna ferruginea) and especially the crested coot ( Fulica cristata). Most surviving natural, fresh wetlands are unprotected, and measures to conserve them are urgently required. Human-made wetlands such as reservoirs have some value for threatened waterbirds (especially ruddy shelduck and marbled teal), but hold much lower densities of waterbirds than natural wetlands, and support fewer plant species. Thus, they do not compensate for the continuing loss of natural wetlands.

Wild Populations of the Chinese alligator approach extinction

The Chinese alligator, Alligator sinensis, is on the verge of becoming extinct in the wild as a result of loss of natural wetlands in the lower Changjiang valley. Chinese alligators are only known from a small region in southeastern Anhui province, a fraction of its former distribution. Within this area, a 433 km 2 reserve has been declared that contains 13 designated habitat sites totaling 41 ha. The sites consist of small ponds located within or adjacent to villages, are completely surrounded by rice fields, or are biologically marginal oligotrophic ponds set in low hills. Alligators are only present at 10 of the 13 designated sites, with the largest groups containing a maximum of 10–11 animals and one adult female. In recent years nesting is known from only four areas, but the eggs are routinely collected and hatchlings retained in the Anhui alligator breeding center. The total population of wild Chinese alligators is probably <130 and is declining at an annual rate of 4–6%. If present trends continue, the Chinese alligator will be the first species of crocodilian to become extinct in the wild in historical times. Conservation efforts need to focus on protection of remaining wetlands and wetland restoration, and the inclusion of Chinese alligators in the active management of protected wetlands sites throughout the species' historic distribution.

Comparison of soil and other environmental conditions in constructed and adjacent palustrine reference wetlands

Wetlands are created to compensate for the loss of natural wetlands as a result of human landuse activities. How well these constructed wetlands mimic natural wetlands is in debate. The goal of this study was to compare soil and other environmental conditions within constructed and adjacent reference wetlands to assess the progress of the constructed wetlands towards a functional wetland. Three constructed wetlands in Virginia, USA, 4 to 7 years old, were paired with adjacent palustrine forested and scrub-shrub reference wetlands to examine differences in topography, hydrology, soil properties, and other environment conditions such as soil temperature and redox potential. Degree of microrelief was greater in reference wetlands than in the associated constructed wetlands. Seasonal fluctuations in water-table levels were similar in both wetland types. Two of the paired wetlands showed considerable differences (15 to 20 cm) in the depth to the water table. Redox potentials were similar in reference and constructed wetlands. Paired wetlands with water-table levels at or near the soil surface throughout the year showed similar soil temperatures. At the site where the summer water levels were 80 to 100 cm below the soil surface, summer temperatures were substantially higher in the poorly shaded, constructed wetland. At the two sites with high water-table levels throughout the year, percent clay and silt, levels of organic C and N, and cation exchange capacity were significantly greater (p <0.05) in the reference wetlands. At the drier site, only 3 of the 16 soil parameters compared were significantly different. In this limited study, observed differences in soil and other environmental conditions between paired wetlands suggest that constructed wetlands may not function in the same capacity as adjacent reference wetlands.

Ecological issues related to wetland preservation, restoration, creation and assessment

A wide range of local, state, federal, and private programs are available to support the national (USA) policy of wetland ‘No Net Loss’. Implementation of programs, however, has resulted in the continued loss of natural wetlands on the premise that restored or created wetlands will replace the functions and values lost by destruction of natural wetlands. What are the ecological implications and consequences of these programs from a biodiversity and ecosystem perspective? From a biodiversity perspective, ongoing wetland protection policies may not be working because restored or created wetlands are often very different from natural wetlands. Wetland protection policies may also be inadequate to preserve and restore ecological processes such as nutrient cycling because they mostly focus on individual wetlands and ignore the fact that wetlands are integral parts of landscapes. Wetland mitigation projects, for example, often result in the exchange of one type of wetland for another and result in a loss of wetland functions at the landscape level. The most striking weakness in the current national wetlands policy is the lack of protection for ‘dry-end’ wetlands that are often the focus of debate for what is and what is not a wetland. From an ecological perspective, dry-end wetlands such as isolated seasonal wetlands and riparian wetlands associated with first order streams may be the most important landscape elements. They often support a high biodiversity and they are impacted by human activities more than other types of wetlands. The failings of current wetland protection and mitigation policies are also due, in part, to the lack of ecologically sound wetland assessment methods for guiding decision making processes. The ecologically based Hydrogeomorphic (HGM) approach to wetland assessment has the potential to be an effective tool in managing biodiversity and wetland ecosystem function in support of the national ‘No Net Loss’ policy.

The Role of Migratory Waterfowl as Nutrient Vectors in a Managed Wetland

Dense aggregations of waterfowl, often caused by loss of native wetlands and increased waterfowl numbers, can result in the destruction of wetland vegetation and agricultural crops, increase the risk of infectious disease outbreaks, and decrease water quality. Problems related to water quality may be particularly severe in arid regions of the southwestern United States, where water quality and quantity are contentious issues. Over 40,000 Lesser Snow Geese (Chen caerulescens caerulescens) and Ross’ Geese (Chen rossii) winter annually at Bosque del Apache National Wildlife Refuge, New Mexico. Daily feeding bouts by geese move large quantities of nutrients from farm fields where they feed to managed wetlands where they roost. Using energy and mass balance models, population estimates, daily and seasonal migration patterns, and feeding behaviors, we estimated the mass and ratio of nitrogen to phosphorus of nutrients loaded by geese into the wetlands of the Bosque del Apache National Wildlife Refuge. Loading rates peaked in late November 1995 at more than 300 kg nitrogen per day and over 30 kg phosphorus per day. As feeding behaviors changed through the winter and bird densities declined, loading rates fell. Our estimates suggest that in the winter of 1995–1996, bird‐borne nutrients supplied nearly 40% of the nitrogen and 75% of the phosphorus entering the primary wetland used for geese roosting. High loading rates by geese are a consequence of their colonial roosting behavior; over 90% of the geese roost on 10% of the wetland area. The effects of nutrient loading could be reduced by increasing flushing rates or dispersal of roosting waterfowl. The loss of natural wetlands, however, limits options for expanding wetland area available to waterfowl, and it may be difficult to increase flushing rates in this arid region. Thus, management of waterfowl and the nutrients they move will continue to be an important issue for wetlands of wildlife refuges. El Papel de las Aves Acuáticas como Vectores de Nutrientes en un Humedal Manejado Densas agregaciones de aves acuáticas causadas frecuentemente por la pérdida de humedales nativos y el incremento en el número de ave acuáticas, puede resultar en la destrucción de la vegetación de humedales y cultivos, un incremento en el riesgo de dispersión de enfermedades infecciosas y una disminución en la calidad del agua. Los problemas relacionados con la calidad del agua pueden ser particularmente problemáticos en regiones áridas del suroeste de los Estados Unidos, en donde la calidad y cantidad del agua son temas polémicos. Cerca de 40,000 ganzos Lesser snow (Chen caerulescens caerulescens) y ganzos Ross (Chen rosii) invernan anualmente en el Refugio de vida silvestre Bosque del Apache, en Nuevo Mexico. Diariamente grandes cantidades de nutrientes son trasladadas de las granjas donde los ganzos se alimentan an los humedales donde descansan. Mediante el uso de modelos de energía y balance de masas, estimaciones de la población, patrones de migración diaria y estacional y conductas alimenticias, estimamos la masa y proporción nitrógeno:fósforo de los nutrientes descargados por los ganzos en los humedales del Bosque del Apache. Las tasas de descarga tuvieron picos al final de Noviembre de 1995 de&gt; 300 kg de nitrógeno y&gt; 30 kg de fósforo por dia. Como la conducta alimenticia cambió a lo largo del invierno y las densidades de aves disminuyeron, las tasas de descarga cayeron. Nuestras estimaciones sugieren que en el invierno de 1995–1996 los nutrientes de origen avícola aportaron cerca del 40% del nitrógeno y 75% del fósforo que entró al humedal mayormente utilizado por los ganzos para descanso. Altas tasas de descarga por ganzos son consecuencia de su conducta de descanso en colonias;&gt; 90% de los ganzos descanzó en solo 10% del área del humedal. Los efectos de descarga de nutrientes podrían ser reducidos incrementando las tasas de flujo o la dispersión de las aves en descanzo. La pérdida de humedales naturales limita de cualquier manera las opciones para expander el área de humedal disponible para las aves, además de que un incremento de las tasas de flujo puede ser dificil en esta árida región. Por lo tanto, el manejo de las aves y los nutrientes que mueven continuará siendo un problema importante para los humedales en refugios de vida silvestre.

Mine-associated wetlands as avian habitat

Surveys for interior wetland birds at mine-associated emergent wetlands on coal surface mines in southern Illinois detected one state threatened and two state endangered species. Breeding by least bittern (Ixobrychus exilis) and common moorhen (Gallinula chloropus) was confirmed. Regional assessment of potential wetland bird habitat south of Illinois Interstate 64 identified a total of 8,109 ha of emergent stable water wetlands; 10% were associated with mining. Mine-associated wetlands with persistent hydrology and large expanses of emergent vegetation provide habitat that could potentially compensate for loss of natural wetlands in Illinois. We encourage identification and management of such areas and reclamation of mine areas to wetlands where possible.