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1.
A morphometric analysis of the gills ofOreochromis alcalicus grahami has been carried out on specimens from ecologically distinct lagoons and a water-holding tank of Lake Magadi, a highly alkaline salt lake situated in a volcanically active region of the southern part of the Great Rift Valley in Kenya. The data were compared with those fromOreochromis niloticus, a close relative that lives in fresh water and with data from other fresh water and marine fish. Our primary goal was to identify the possible adaptive features which enable the fish to survive in an environment characterized by severely fluctuating levels of oxygen, a condition exacerbated by factors such as high temperature, alkalinity and osmolarity. The specimens ofO. a. grahami from the south-western lagoons of the lake had gills better adapted for gas exchange with a body mass specific diffusing capacity for oxygen which was about 2 times greater than that of the gills of the specimens from the fish spring lagoons and 2.5 times that of those from the water-holding tanks. Some parameters of the gills ofO. a. grahami, e.g. the gill filament length and number of gill filaments are significantly greater than those ofO. niloticus but the number of secondary lamellae, area of secondary lamellae and the diffusing capacity of the gills are similar in the two species. Compared with most other fish, the gills ofO. a. grahami appear to be particularly well adapted for gas exchange especially by having a thin water-blood barrier. Perhaps in no other extant fish have the gills had to be so exquisitely designed to meet environmental extremes and regulate complex and at times conflicting functions such as gas exchange, iono-regulation, acid-base balance and nitrogenous waste excretion as inO. a. grahami  相似文献   

2.
Classification of washover dynamics in barrier islands   总被引：1，自引：0，他引：1  
This study systematically classifies washover dynamics with reference to coastal changes along the Ria Formosa barrier islands (Southern Portugal). Identification of washovers using a sequence of 11 sets of aerial photographs dated between 1947 and 2001 allowed a classification to be developed based on: (1) overwash evolution (increasing, decreasing, or constant overwash processes); (2) the mechanisms promoting washover formation (exceptional to infrequent oceanographic conditions, washout processes, structural erosion, inlet dynamics, and human interventions); and (3) the mechanisms promoting washover cessation (berm development, structural erosion, dune development, inlet dynamics, and human interventions). A total of 369 different washovers were observed along the Ria Formosa barriers during the study period, with 209 washovers being formed in various types of dune morphology and 303 being obliterated. The number of washovers was relatively stable from 1947 to 1972, and increased dramatically between 1972 and 1976 probably as a result of the development of immature inlet margins and downdrift starvation. From 1976 to 2001, washover occurrences declined and their spatial dimensions decreased, leading to a decrease in overwash activity over this time. Overall, the dominant formation mechanisms of washovers in the Ria Formosa were inlet dynamics (accounting for 57% of washovers formed) and structural erosion (20%), with human intervention mechanisms accounting for 12%. The cessation of washovers was dominated by dune development (33% of the washovers obliterated) followed by inlet dynamics (24%) and structural erosion (19%), while human intervention mechanisms accounted for 13%. The classification should be of use for the coastal management of barrier systems including the definition of overwash-prone areas and the determination of the relative importance of the mechanisms contributing to washover formation and cessation.  相似文献   

3.
A survey of the modern physical setting of Lake El’gygytgyn, northeastern Siberia, is presented here to facilitate interpretation of a 250,000-year climate record derived from sediment cores from the lake bottom. The lake lies inside a meteorite impact crater that is approximately 18 km in diameter, with a total watershed area of 293 km2, 110 km2 of which is lake surface. The only surface water entering the lake comes from the approximately 50 streams draining from within the crater rim; a numbering system for these inlet streams is adopted to facilitate scientific discussion. We created a digital elevation model for the watershed and used it to create hypsometries, channel networks, and drainage area statistics for each of the inlet streams. Many of the streams enter shallow lagoons dammed by gravel berms at the lakeshore; these lagoons may play a significant role in the thermal and biological dynamics of the lake due to their higher water temperatures (>6°C). The lake itself is approximately 12 km wide and 175 m deep, with a volume of 14.1 km3. Water temperature within a column of water near the center of this oligotrophic, monomictic lake never exceeded 4°C over a 2.5 year record, though the shallow shelves (<10 m) surrounding the lake can reach 5°C in summer. Though thermally stratified in winter, the water appears completely mixed shortly after lake ice breakup in July. Mean annual air temperature measured about 200 m from the lake was −10.3°C in 2002, and an unshielded rain gage there recorded 70 mm of rain in summer of 2002. End of winter snow water equivalent on the lake was approximately 110 mm in May 2002. Analysis of NCEP reanalysis air temperatures (1948–2002) reveals that the 8 warmest years and 10 warmest winters have occurred since 1989, with the number of days below −30°C dropping from a pre-1989 mean of 35 to near 0 in recent years. The crater region is windy as well as cold, with hourly wind speeds exceeding 13.4 m s−1 (30 mph) typically at least once each month and 17.8 m s−1 (40 mph) in winter months, with only a few calm days per month; wind may also play an important role in controlling the modern shape of the lake. Numerous lines of evidence suggest that the physical hydrology and limnology of the lake has changed substantially over the past 3.6 million years, and some of the implications of these changes on paleoclimate reconstructions are discussed. This is the second in a series of eleven papers published in this special issue dedicated to initial studies of El'gygytgyn Crater Lake and its catchment in NE Russia. Julie Brigham-Grette, Martin Melles, Pavel Minyuk were guest editors of this special issue.  相似文献   

4.
Lake Balkhash,Kazakhstan   总被引：2，自引：0，他引：2  
Lake Balkhash is a large (18,000 km3), closed, and slightly saline lake in the south-west of Kazakhstan. It is divided into two basins, a south-western and an eastern basin. These have somewhat different limnological conditions, but the most obvious one is that the south-western basin has a salinity of <2 g L−1 whereas the salinity of the eastern basin is ∼4 g L−1. Numerous fish and invertebrate introductions, many successful, have been made. In 1969, a dam impounding the Kapchagay reservoir was constructed on the River Ili, the major river flowing into the lake. The impoundment of water in this reservoir caused a fall of some 1.5 m in the water-level of the lake. This fall, together with other events on the catchment, caused considerable damage to reedswamps in the lake, to the fishery and to conservation values. A number of suggestions has been made on how to prevent further damage. Some, particularly those involving a moratorium on further filling of Kapchagay reservoir and irrigation, have been implemented, at least in part. This has caused some remission in environmental damage and provides for cautious optimism with regard to the lake’s future. Even so, the environmental status of the lake remains vulnerable and many dangers persist.  相似文献   

5.
Although the Laguna de Mar Chiquita is among the largest saline lakes of the world (2,000–6,000 km2 area), knowledge about it is scarce. Like other large salt lakes, Mar Chiquita undergoes strong inter-annual changes in water level that are primarily linked to the variable expression of three different types of climate throughout its extensive catchment area. Water-level fluctuations and their overall environmental influence, especially on salinity (25–360 g L–1) and biota, have significant results. Comparison of Mar Chiquita with other fluctuating large salt lakes shows an independent long-term pattern of water-level (and salinity) changes. Primary determinants of its limnology are (1) its extensive catchment, (2) the occurrence of three different types of climate on the catchment, (3) the shallowness of the basin and (4) the effects of strong wind, water circulation within the lake, and sediment inputs from rivers. The effects of fluctuation on the lake biota are more evident at the level of dominant organisms at every fluctuation stage and their functions than in overall biodiversity and food-web complexity.  相似文献   

6.
The main limnological features of Lake Issyk-kul are described. The lake is a large (6,236 km2), deep (zm, 668 m), closed lake in eastern Kirgizia. It lies at ∼1,607 m above sea level, but water-levels have been dropping since the last century. It is slightly saline (salinity, ∼6g L−1), with Na+, Mg2+, Cl− and SO 4 2− the dominant ions. Nutrient levels are low and the lake is considered ultra-oligotrophic. Characeae dominate the macrophytes. About 300 and 117 taxa of, respectively, phytoplankton and zooplankton have been identified, withArctodiaptomus salinus the most numerous in the zooplankton. Chironomids dominate the benthos. Several endemic taxa of fish occur, of whichLeuciscus bergi was dominant until the 1970s. The fish fauna has been supplemented by many introduced species. Three mysids were introduced in 1965–8 and are now a significant part of the ecosystem. The present annual fish catch permitted is 320 t. The most important value of the lake is as a recreational resource. To promote and sustain this value requires careful, ongoing management. The most significant threats to the lake are local pollution, visitor pressure, and declining water-levels.  相似文献   

7.
Sandbars are of vital ecological and environmental significance, which however, have been intensively influenced by human activities. Morphodynamic processes of sandbars along the Yichang-Chenglingji Reach of the Changjiang River, the channel immediately downstream of the Three Gorges Dam (TGD), are assessed based on remote sensing images between 2000 and 2016. It can be found that the entire area of sandbars reduces drastically by 19.23% from 149.04 km2 in 2003 to 120.38 km2 in 2016, accompanied with an increase in water surface width. Owing to differences in sediment grain size and anti-erosion capacity, sandbar area in the upstream sandy gravel reach (Yichang-Dabujie) and downstream sandy reach (Dabujie-Chenglingji) respectively decreases by 45.94% (from 20.79 km2 to 11.24 km2) and 14.93% (from 128.30 km2 to 109.14 km2). Furtherly, morphological evolutions of sandbars are affected by channel type: in straight-microbend channel, mid-channel sandbars exhibit downstream moving while maintaining the basic profile; in meandering channel, point sandbars show erosion and deposition in convex and concave bank respectively, with mid-channel sandbars distributing sporadically; in bending-branching channel, point sandbars experience erosion and move downstream while mid-channel sandbars show erosion in the head part along with retreating outline. We document that the primary mechanism of sandbars shrinkages along the Yichang-Chenglingji Reach can be attributed to TGD induced suspended sediment concentration decreasing and increasing in unsaturation of sediment carrying capacity. Additionally, channel type can affect the morphological evolution of sandbars. Along the Yichang-Chenglingji Reach, sandbars in straight-microbend channel are more affected by water flow than that in bending-branching channel.  相似文献   

8.
The contemporary distribution of benthic diatoms and their use as ecological indicators were examined in a coastal wetland, the Ebro Delta, as a representative of environmental conditions in Mediterranean coastal wetlands. A total of 424 diatom taxa were identified across 24 sites encompassing a wide range of wetland habitat types (coastal lagoons, salt and brackish marshes, shallow bays, microbial mats and nearshore marine waters) and conductivities. Canonical correspondence analysis showed that water conductivity and water depth were the main factors structuring the diatom assemblages. Cluster analysis identified five habitat types according to the similarity in diatom species composition: salt marshes, brackish marshes, brackish coastal lagoons and bays, coastal lagoons with fresher conditions, and nearshore open sea. For each wetland habitat, diatom indicator species were identified. Partial canonical correspondence analysis showed that water conductivity, a proxy for salinity, was the most statistically significant and independent variable for explaining the distribution of benthic diatoms in the study area. A transfer function, using a weighted average regression model, was developed for conductivity and displayed reasonable performance (r 2 = 0.64; RMSEP = 0.302 log10 mS/cm). Our study in the Ebro Delta provides a basis for using diatom assemblages to make quantitative conductivity inferences, and for using diatom indicator species to identify wetland habitats. These approaches are complementary and may be valuable for paleoenvironmental studies of (1) effects of large-scale, natural changes in the Delta (e.g. sea-level fluctuations), and (2) impacts of short-term anthropogenic changes, such as the introduction and development of rice agriculture.  相似文献   

9.
Variations of chlorophylla and Margalef's pigment diversity index were studied in two solar salt ponds at Aveiro (Esmolas and Tanoeiras). Portugal. In the Esmolas ponds, mean chlorophyll a values varied between 2.49 and 13.33 mg m−3 in the non-growing season, and between 5.43 and 40.55 mg m−3 in the growing season. In the Tanoeiras ponds, mean chlorophylla values were between 8.12 and 14.85 mg m−3 in the non-growing season, and 8.65 and 21.19 mg m−3 in the growing season. Fluctuations of Margalef's pigment diversity index were more irregular.  相似文献   

10.
Using Landsat TM data, this article examines the environmental impact of the East Port Said harbour project on the surrounding landscape. The optimum three-band combination and the most appropriate multispectral bands were selected to enhance the images and monitor land cover changes for the periods of 1984–1991 and 1991–2003. The results indicate that wetland areas declined from 103 km2 in 1984 to 30 km2 in 2003. In addition, the surface area of El-Malha Lake has shrunk from 27 km2 to 18 km2 over the same period. In contrast, the area covered by salt crust has increased from 11 km2 in 1984 to 19 km2 in 2003. Urban land use and designed cultivated lands were also significant in 2003, covering 49 km2 and 71 km2, respectively. The rate of shoreline change between 1984 and 2003, the period when the East Port Said harbour was constructed, was calculated. Vector data indicate that the rate of shoreline loss was ?13 m/year from 1984 to 1991 and ?15 m/year from 1991 to 2003. Despite the fact that construction of the East Port Said harbour caused significant changes in the study area, there are several factors controlling coastline and land cover changes including industrial development and fish cultivation farms.  相似文献   

11.
This is an updated study on the biogeographic distribution of the populations of the genusArtemia (Branchiopoda, Anostraca) in Spain, with special focus on populations inhabiting salt lagoons and inland salterns. The populations recorded (40) belong to the bisexual speciesA. tunisiana and to the asexual groupA. parthenogenetica (diploid and tetraploid strains). They usually appear in three different hypersaline ecosystems: solar salterns and lagoons filled with sea water, solar salterns and lagoons containing brines of diluted mineral salts, and lagoons filled with athalassic (endorheic) brines. The brines in salinas are chemically characterized by high Cl– concentrations, especially in inland salinas, whose brine sources are geologically associated with evaporitic formations developed in the Triassic and Lower Liassic of eastern Spain. Brines in athalassic lagoons, geologically associated with Mesozoic and Cenozoic periods, show higher levels of sulfate (up to 40–50%) as well as Mg2+. From a geographical point of view, bisexual and diploid asexual populations are mainly found in coastal and inland salinas or lagoons below 40° N, while asexual tetraploid populations are found in inland salinas and athalassic lagoons above that latitude. These populations have been biologically characterized by the morphology of their adults through multivariate analysis.  相似文献   

12.
近30年来藏北高原湖泊变化对气候波动的响应   总被引：7，自引：1，他引：6  
According to the analysis of the climate materials including the topographic map in 1975, the TM and CBERS satellite remote sensing materials from the 1980s to 2005 as well as the air temperature, precipitation, evaporation rate, maximum depth of snow and the biggest depth of frozen soil in the past 45 years, the water level area of four lakes at the southeast of Nagqu, Tibet including Bam Co, Pung Co, Dung Co and Nuripung Co show a distinct trend of expansion in the past 30 years. In 2005, the water level area of the above four lakes increased by 48.2 km2, 38.2 km2, 19.8 km2 and 26.0 km2 respectively compared to 1975, with the respective increase rate of 25.6%, 28.2%, 16.2% and 37.6%. That is closely related to the warming and humidified climate change in the recent years such as rise of the air temperature, increase of the precipitation, decrease of the evaporation rate and permafrost degradation. Foundation: National Natural Science Foundation of China, No.40761005 Author: Bian Duo (1966–), Professor, specialized in application of remote sensing and GIS on environment.  相似文献   

13.
We present 137Cs profiles for three low lying coastal lagoons in Southwest England that show a decline in activity with sediment depth. 137Cs inventories are lower than expected by comparison with local reference inventories despite the fact that sampling was undertaken in the deep-water zone of each lake where sediment and 137Cs focusing would be expected. At all three locations, lake sediment 7Be and unsupported 210Pb (210Pbun) inventories are not significantly lower than the local reference inventory. 137Cs inventories in the study cores range from 38 to 95% of local reference inventories. The standing water level and mud: water interface at two sites are below maximum tide level and, at all three sites, salinity increases significantly in the water columns between low and high tide and in the pore waters of the underlying sediments. We suggest that the difference in hydrostatic pressure between sea level and standing water levels in the lagoons forces salt water up through the sediment column and that monovalent cations (especially Na+ and K+) replace 137Cs on exchange sites leading to the upward migration and loss of 137Cs. Rising sea levels may therefore contribute to remobilisation and release of 137Cs to the aquatic environment from the sediments of coastal lagoons.  相似文献   

14.
In this study, we combined grain size and geochemical analyses with radioisotope analysis of lead-210 (210Pb), caesium-137 (137Cs) and radiocarbon (14C) ages to reconstruct the sedimentation history of two urbanised coastal lagoons in south-east Australia. Towradgi and Fairy Lagoons were both found to exhibit slow initial sedimentation of less than 1 mm year−1 prior to anthropogenic influences. Land clearing in the catchments increased runoff and erosion in the creeks feeding into the estuaries, and has resulted in progradation of fluvial material into the estuarine systems with a marked increase in sedimentation to between 2 and 7 mm year−1. The upper 20–50 cm of the sediment column in both lagoons contained elevated concentrations of heavy metals such as Pb, Cu, Ni and Zn. This pollution trend was found to be consistent with the history of industrialisation and urbanisation in the region, which expanded rapidly post World War 2. The total metal concentrations were consistent with other urbanised/industrialised estuaries around the world. Despite the fairly disturbed nature of these coastal lagoons, the use of 210Pb, 137Cs and 14C dating in combination with bulk geochemical analyses allowed detailed reconstruction of sedimentation history.  相似文献   

15.
选择川中丘陵区和三峡地区四川盐亭、南充和重庆开县的4个小流域,采集塘库沉积泥沙137Cs样品,确定了1963年以来塘库淤沙量,并据此分析了流域输沙模数和侵蚀模数。研究表明,开县春秋沟的淤沙模数最高,为1869t.km-2.a-1;盐亭武家沟和集流沟分别为701t.km-2.a-1和710 t.km-2.a-1;南充天马湾沟为566 t.km-2.a-1。对小流域地貌特征的分析和谷地水田取样结果表明,除塘库淤积区外,各小流域谷地内基本无泥沙淤积。因此,除南充天马湾沟按现有水面面积作为淤积面积求算的淤沙模数明显偏小外,其他小流域的塘库淤沙模数基本可以表征各研究小流域的侵蚀模数。对研究小流域侵蚀产沙影响因素的分析表明,除降雨和土地利用状况外,地形起伏、土壤抗蚀性及岩层产状也是三地侵蚀程度差异的重要原因。  相似文献   

16.
新疆阿勒泰地区2002-2011年地表水资源变化趋势   总被引：1，自引：0，他引：1  
在RS技术支持下,应用气象数据（主要为气温、降水）、基础地理数据及2002-2011年时间序列的Landsat TM、ETM+、MODIS/Terra+Aqua MCD43A4遥感影像产品,对阿勒泰地区地表水资源时空变化特征进行了分析,探索气象因素影响下阿尔泰山冰川积雪和地表水资源之间的相互作用。结果表明：在研究时段内,阿尔泰山6月2日的冰川积雪面积呈波动增加趋势,8月21日的冰川积雪面积则呈波动减少趋势。从景观格局的特征来看,随着夏季冰雪融水量增加,水资源量总体呈上升趋势,在研究时段内水域总面积增加了57.91 km2,增加面积主要来源于湖泊和水库,2011年的湖泊和水库面积分别为1 044.33 km2和196.27 km2,比2002年分别增加了16.67 km2和101.79 km2;沼泽湿地和坑塘湿地的面积变化呈一定的起伏,2002-2011年间面积分别减少了35.91 km2和24.27 km2,湖泊和水库的破碎度较低,沼泽湿地、河流和坑塘湿地的破碎度高,表明沼泽湿地、河流和坑塘湿地对气象因素变化较敏感。  相似文献   

17.
The mass transport of nutrients by migratory animals can markedly alter the biogeochemistry and ecology of recipient ecosystems, particularly in nutrient-poor regions such as the Arctic. However, the role of biovectors in the global cycling of nutrients is often overlooked. Here we investigate nitrogen dynamics in two seabird-affected ponds in the Canadian High Arctic. The ponds lie at the base of a large seabird colony and have been greatly enriched in nutrients due to the input of guano and other wastes. Using sediment cores that span the last ~200 years, we measured stable isotopes of nitrogen (δ15N) in bulk sediments as well from the subfossil remains of chironomid (Diptera) head capsules and Daphnia ephippia. The bulk-sediment samples from our seabird-affected ponds had elevated δ15N values relative to seabird-free sites elsewhere in the Arctic. In general, the chironomid δ15N profiles roughly paralleled those of bulk sediments in both study ponds, while the Daphnia profile remained relatively stable in contrast to the considerable variation recorded in the bulk sediments and chironomids. Interestingly, no apparent pattern emerged among δ15N values recorded in the bulk sediments, chironomids, and Daphnia between the two study ponds. The stability recorded in the δ15N profiles from bulk sediments relative to the more variable invertebrate profiles point towards the complexity of nitrogen uptake by chironomids and Daphnia at these sites. These data suggest that the bulk sediments are integrating the different fractions of the overall δ15N pool and thus may be most appropriate for reconstructing overall trends in lake trophic status.  相似文献   

18.
Artificial water sources have been used for decades to enhance and restore wildlife habitat but the benefits of their use have been subject to debate. During the past century, the number of natural springs in Joshua Tree National Park, California, USA, has declined. In response to concerns about the viability of the bighorn sheep (Ovis canadensis nelsoni) population, a number of water developments were constructed throughout the park. We modeled potential historical and present-day summer habitat of female bighorn sheep to evaluate the effectiveness of the artificial and remaining natural water sources in maintaining habitat and to determine how loss of artificial sources might affect future habitat availability. Prior to 1950, 583.5 km2 of summer habitat was potentially available. Presently, only 170.6 km2 of habitat is available around natural water sources and 153.5 km2 is available around guzzlers. When all perennial water sources are included in the habitat model (minus overlap), 302.3 km2 of summer habitat is potentially available. This represents only 51.7% of summer habitat available prior to 1950. Without artificial water developments, 47.7% of present-day summer habitat would be lost, which raises important management questions regarding the debate about what is natural or artificial within otherwise protected areas.  相似文献   

19.
Sheep were originally brought to Brazil approximately 500 years ago from Europe and Northern Africa; they adapted quickly to their new environments and developed unique traits. The objective of this study was to correlate environmental variables with sheep production in Brazil to promote the development of this activity. Brazil has several distinct environments as shown in this paper. These variables included vegetation cover (NDVI), precipitation, temperature, altitude, relative humidity (RH), solar radiation and the temperature humidity index (THI). Correlation analyses were performed with environmental variables and production levels at national and regional level. A factor analysis was performed to characterize the covariance between variables. We formed groups (clusters) due to productivity levels and performed canonical discriminant analyses to determine which variables were associated with different levels of production. The municipalities with the highest levels of sheep production were selected to define the intervals of each environmental variable. A map was drafted in ArcGis 9.3 to illustrate the landscape features where the highest levels of production are located. The results showed that, nationally, production is influenced by a great diversity of environments, thus masking possible correlations. When the correlation analysis was carried out by region, significant correlations were observed. Cluster analysis identified two dominant, clearly separated producing regions (northeast and south). The canonical analysis indicated that the most important variables delineating the clusters were precipitation, THI, temperature and RH. The map showing the landscape features where the highest production levels are located indicated that the breeds in the northeast are reared on an area of approximately 900,000 km2, while those from the south are reared on an area of approximately 1,100 million km2. This study showed that it is important to consider the environmental characteristics of different regions of Brazil when proposing public policies related to sheep production.  相似文献   

20.
This study aimed at characterizing land cover dynamics for four decades in Eastern Mau forest and Lake Nakuru basin, Kenya. The specific objectives were to: (i) identify and map the major land cover types in 1973, 1985, 2000 and 2011; (ii) detect and determine the magnitude, rates and nature of the land cover changes that had occurred between these dates, and; (iii) establish the spatial and temporal distribution of these changes. Land cover types were discriminated through partitioning, hybrid classification and spatial reclassification of multi-temporal Landsat imagery. The land cover products were then validated and overlaid in post-classification comparison to detect the changes between 1973 and 2011. The accuracies of the land cover maps for 1973, 1985, 2000 and 2011 were 88%, 95%, 80% and 89% respectively. Six land cover classes, namely forests-shrublands, grasslands, croplands, built-up lands, bare lands and water bodies, were mapped. Forests-shrublands dominated in 1973, 1985 and 2000 covering about 1067 km2, 893 km2 and 797 km2 respectively, but were surpassed by croplands (953 km2) in 2011. Bare lands occupied the least area that varied between 2 km2 and 7 km2 during this period. Overall, forests-shrublands and grasslands decreased by 428 km2 and 258 km2 at the annual average rates of 1% each, whereas croplands and built-up lands expanded by 660 km2 and 24 km2 at the annual rates of 6% and 16% respectively. The key hotspots of these changes were distributed in all directions of the study area, but at different times. Therefore, policies that integrate restoration and conservation of natural ecosystems with enhancement of agricultural productivity are strongly recommended. This will ensure environmental sustainability and socio-economic well-being in the area. Future research needs to assess the impacts of the land cover changes on ecosystem services and to project the future patterns of land cover changes.  相似文献   

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