Effects of Anthropogenic Influences on the Trophic State,Land Uses and Aquatic Vegetation in a Shallow Mediterranean Lake: Implications for Restoration

Lake Pamvotis, NW Greece is a shallow Mediterranean eutrophic lake that has changed drastically over the past 50 years. Strong effects, resulted mainly from anthropogenic causes, in the hydrological regime are shown for this area using long term hydrological data and a GIS system for extracting land cover/use changes. A set of aerial imagery acquired in 1945 through 2002 were used to monitor and assess the spatial and temporal changes in land cover/use, focused mainly on the lake’s surface area and its surrounding ecosystem (Natura 2000 area). The significance of the changes in land cover/use distribution within Pamvotis wetland is further discussed depicting the role of the anthropogenic influence on the fragile ecosystem that resulted in the shrinkage of lake’s habitats extent. The purpose of this analysis was to examine the long-term changes on macrophyte community composition, species occurrence and relative abundance with water quality and water level changes over the past century, using historical data, aerial photos and GIS techniques. The results showed that for the last 25 years annual water level fluctuation ranged from 70 to 159 cm. Water level starts decreasing in mid June and increasing again gradually from November until March–April. Intra annual water level fluctuation seems to be affected by land use for agricultural purpose through intensive irrigation and the summer drought as well. A dramatic decline of the submerged vegetation is apparent mainly attributed to anthropogenic pressures. Regarding the land cover/use changes, the most notable and significant alterations are concerning the urban development around the lake, the disappearance of wet meadows and the extension of reed beds. Finally it seems that water budget data as well as the response of the key eutrophication parameters are affected from both hydrological alterations and point/non-point pollution sources.     

近30a来白洋淀土地利用变化规律及驱动力分析

分析土地利用变化规律对提高土地开发利用效率和推动生态环境保护工作具有重要意义。针对白洋淀的土地利用演变,为探究其变化趋势,以白洋淀湿地为例,采用30 a来8期Landsat TM/OLI遥感影像为数据源,结合遥感和地理信息系统方法,分析白洋淀湿地土地利用的时空变化特征和驱动力。结果表明:(1)1986—2018年,主导的土地利用类型是耕地和水域。耕地变化最为明显,减少了60.3%,水域变化次之,增加了24.1%。水生植物面积大致呈"增多—减少—增多"的趋势,居民地面积持续增加。(2)分析土地利用动态度得出,1986—2018年间水生植物和水域面积的单一动态度较大,综合动态度(L_C)从0.267%下降到0.117%,呈现缓慢下降趋势,说明白洋淀土地利用到后期的变化速度变慢,土地利用状态趋于稳定。(3)白洋淀土地利用类型变化的驱动因子为气候、人类活动和国家宏观政策。研究成果有利于区域进行土地利用决策,也可作为土地可持续利用和生态环境保护的科学依据。     

Detecting land use/land cover changes in the Lake Hayq (Ethiopia) drainage basin, 1957–2007

Land use/land cover changes in a lake drainage basin reflect changes in the magnitude of the water balance components and rate of sediment deposition in a lake as a reflection of the fundamental linkage between what happens in a lake considered against what is happening in the drainage basin of the lake. The objective of this study was to quantify the spatio‐temporal land cover/land use changes across the Lake Hayq 1 1 Lake Hayq is also locally called Lego.
closed drainage basin in north‐east Ethiopia over a 50‐years period, using multitemporal remote sensing and geospatial data. Two historical occasions of aerial photographs (1957 and 1986) and one satellite image (2007) were examined with image analysis tools: Leica Photogrammetric Suite (LPS 9.2) Project Manager, ArcGIS10.0, and ERDAS EMAGINE 9.2. Seven aerial coverage of land use/land cover categories were identified and mapped for the past three historical times. The results indicated that farmlands/settlements and shrublands/degraded lands increased by 43.1% and 136.9%, at an annual rate of 27.4 and 13.5 ha year^?1, respectively, between 1957 and 2007. In contrast, bushlands, grasslands, forestlands and lake surface area were diminished by 68.8%, 62.7%, 90.5% and 7.6%, at a rate of 24.0, 7.6, 6.1 and 3.7 ha year^?1, respectively, over the past five decades. The basin had undergone significant transformation in land use/land cover over the past half century, affecting the lake's biophysical stability by accelerating soil erosion in the basin, sediment accumulation, and a reduced quantity and quality of cumulative stream flow into the lake.     

基于MODIS时间序列数据的洞庭湖湿地动态监测

本文以洞庭湖湿地为研究对象,以2001—2014年MODIS时间序列数据产品MODIS_13Q1为主要数据源,利用一年内23景时间序列增强型植被指数(EVI)数据建立不同地表类型(包括各种湿地类型)的时间序列特征参考曲线;在此基础上采用波谱匹配的最小距离分类方法对研究区进行湿地分类和制图。研究结果表明:(1)2014年研究区总体分类精度和Kappa系数分别为87.87%和0.85,表征湿地动态性特征的季节性湿地分类精度为84.85%,具有较好的分类精度,说明基于时间序列遥感数据的分类方法可以满足湿地动态性特征监测的需要;(2)2001—2014年洞庭湖天然湿地(包括永久性水域、永久性沼泽和季节性沼泽、泥滩)呈现了波动减少的趋势,其中永久性水域减少约11%,永久性沼泽减少约22%,而季节性湿地减少约13%;同时,林地则呈现了持续增长的特征,到2014年成为保护区内面积最大的覆盖类型,增长了29%;而农田面积保持了相对的稳定;(3)洞庭湖湿地水域面积缩小、季节性湿地空间位置的变化及沼泽区人工林地的大面积种植改变了洞庭湖原有生态系统格局,进而对洞庭湖湿地的生态服务功能产生潜在影响。     

Influence of lake levels on water extent,interspersion, and marsh birds in Great Lakes coastal wetlands

Coastal wetlands in the Laurentian Great Lakes undergo frequent, sometimes dramatic, physical changes at varying spatial and temporal scales. Changes in lake levels and the juxtaposition of vegetation and open water greatly influence biota that use coastal wetlands. Several regional studies have shown that changes in vegetation and lake levels lead to predictable changes in the composition of coastal wetland bird communities. We report new findings of wetland bird community changes at a broader scale, covering the entire Great Lakes basin. Our results indicate that water extent and interspersion increased in coastal wetlands across the Great Lakes between low (2013) and high (2018) lake-level years, although variation in the magnitude of change occurred within and among lakes. Increases in water extent and interspersion resulted in a general increase in marsh-obligate and marsh-facultative bird species richness. Species like American bittern (Botaurus lentiginosus), common gallinule (Gallinula galeata), American coot (Fulica americana), sora (Porzana carolina), Virginia rail (Rallus limicola), and pied-billed grebe (Podilymbus podiceps) were significantly more abundant during high water years. Lakes Huron and Michigan showed the greatest increase in water extent and interspersion among the five Great Lakes while Lake Michigan showed the greatest increase in marsh-obligate bird species richness. These results reinforce the idea that effective management, restoration, and assessment of wetlands must account for fluctuations in lake levels. Although high lake levels generally provide the most favorable conditions for wetland bird species, variation in lake levels and bird species assemblages create ecosystems that are both spatially and temporally dynamic.     

Investigation of aquaculture dynamics at a Ramsar site,using earth observation systems in conjunction with a socio‐economic assessment

This study presents a comprehensive site‐scale analysis conducted within the global wetland inventory and mapping (GWIM) project. GWIM was developed and promoted by the International Water Management Institute (IWMI) through global partnerships to investigate wetland analyses at multiple scales. The present study investigates the complexity of an inland freshwater wetland system, presenting a conceptual framework for mapping and monitoring the dynamics of Lake Kolleru (a wetland of international importance, as defined by the Ramsar Convention), utilizing a geospatial platform. Illustrating the pace of land use changes leading to the progressive elimination of the wetland ecosystem of freshwater Lake Kolleru, this study also highlights the impacts of such changes on the socio‐economic system. A comprehensive temporal analysis (1977–2007) provided a structural base to schematically analyse the dynamics of biophysical and ecological changes to the wetland by effectively using a spectrum of remote sensing data. The present status and changing trends in ecological dimensions of Lake Kolleru were illustrated, utilizing information from spatial analyses, complimented with socio‐economic assessment. Attention is drawn to the potential of utilizing earth resources systems in exploring space–time interactions in freshwater ecosystems heavily modified through aquaculture interventions. Further, the spatial derivatives are meant as reference material for local authorities and decision‐makers to rehabilitate the economic livelihood activities to the social community dependent on the lake ecosystem. The disseminated message emphasizes the applicability of geospatial tools to enhance the efficacy of the decision‐making process by facilitating regular monitoring of ecosystem dynamics and providing updated information on wetland patterns and uses.     

查干湖湿地的环境变化与保护

查干湖湿地是吉林省面积较大的重要湿地之一,随时间的位移,保护区周边人口不断增加,气候条件发生变化,时湿地的环境产生较大影响,为此,利用不同时期航片及卫片等遥感影像进行时比解译,并结合实地调查,查清了湿地保护区若干环境重耍因子变化情况,并有钟对地提出查干湖湿地保护区生态环境改善及保护性建议.     

Selective use and spatial distribution of native and non‐native fish in wetland habitats

Wetland habitats are crucial for many fish species as spawning, feeding or nursery areas, but the major factors that govern their use by fish are poorly identified. In the present study, we aim to investigate the selective use and the spatial distribution of native and non‐native fish species in different types of wetland habitats (grasslands and reed beds) in a large freshwater marsh (North Western France). The selective use was measured by comparing the community that uses wetland habitats to the total community of the marsh (sampled in the permanent aquatic habitats (canals) during the low water period). The spatial distribution was studied by analyzing the presence probability of fish in wetland habitats as a function of the distance from adjacent canals. All sampled wetland habitats were occupied by fish, and the fish community in wetland habitats was dominated by three native (Abramis brama, Scardinius erythrophthalmus and Anguilla anguilla) and three non‐native (Ameiurus melas, Gambusia holbrooki and Lepomis gibbosus) species. Species richness and total fish abundance differed between canals and wetland habitats as a consequence of a variable propensity to use wetland habitats by native (avoidance and preference) and non‐native (no preference) species. Non‐native species were also more abundant in reed beds than in grassland while no differences were observed for native species. Universally, the presence probability of fish always decreased in wetland habitats as the distance from the canals increased and only a narrow area, close to canals (50–80 m), was well used by fish. However, non‐native fish species used over greater distances in reed beds than in grasslands while no differences were observed for native species. Variable interpretations related to species tolerance, reproductive guilds or diet are proposed to understand the mechanisms that might explain the widespread success of non‐native species in this spatially varying environment. Copyright © 2008 John Wiley & Sons, Ltd.     

Temporal and spatial dynamics of surface run‐off from Lake Basaka catchment (Ethiopia) using SCS‐CN model coupled with remote sensing and GIS

The Lake Basaka catchment (Ethiopia) has undergone a significant land use–land cover (LULC) change and lake level rise over the past five decades. Significant quantities of water and sediment flow annually into the lake through erosion processes. An appropriate method of estimating the surface run‐off from such ungauged and dynamic catchment is extremely important for delineating sensitive areas (based on run‐off responses) to be protected and for development of suitable measures to reduce run‐off and associated soil loss. Reliable prediction of run‐off, however, is very difficult and time‐consuming for catchments such as that of Lake Basaka. The present study estimated the dynamics of surface (direct) run‐off using the NRCS‐CN model in ArcGIS, assisted by remote sensing and ancillary data. The results indicated the Lake Basaka catchment experienced significant temporal and spatial variability in its run‐off responses, depending on the rainfall (amount and distribution) pattern and LULC changes. A significant run‐off increase occurred after 1973, consistent with significant LULC changes and lake level increments occurring after that period. A reduced vegetation cover also resulted in increased run‐off coefficient of the lake catchment from 0.11 in the 1970s to 0.23 in the 2000s, indicating the important need to consider possible future LULC evolution when forecasting the lake catchment run‐off behaviour.     

基于RS与GIS的杞麓湖流域土地利用变化分析

通过遥感(RS)技术获得的土地利用时间序列信息,分析杞麓湖流域土地利用的动态变化以及未来发展趋势。以杞麓湖流域1988年、1996年、2006年、2016年4期Landsat遥感数据为基础,在遥感与地理信息系统(GIS)技术支持下,遥感解译获取4个时段土地利用类型图,结合空间格局、转移矩阵、动态度、利用程度、空间重心,分析了该区域1988—2016年期间土地利用变化特征及其驱动机制。结果表明:空间格局上,林地变化最多,耕地次之,并且大部分耕地转化为建筑用地,其他用地不断向耕地、林地转化;土地利用重心不断向北发展,说明北部经济及其城镇化发展比南部快;方位变化表明该区域西部发展前期大于东部。最后通过驱动机制分析,发现社会经济因素是该区域土地利用变化的主要驱动因素,并且驱动作用不断扩张。研究成果可为该区土地利用可持续发展提供科学依据。     

Impacts and Implications of Major Changes Caused by the Three Gorges Dam in the Middle Reaches of the Yangtze River, China

The impoundment of the Three Gorges Dam (TGD) has disturbed the hydrological regime downstream and has directly affected the relationship between the Yangtze River and Dongting Lake. To trace the realistic and potential impacts, this paper examined the changes of the channel morphology and sedimentology caused by the TGD through a field survey on the channel cross-sections and then analyzed the impact on lake water level through BP neural networks. The possible impacts on inundation patterns in lake wetlands were studied based on the lake basin DEM. The results indicate that drastic sediment decline and severe channel erosion are putting considerable pressure on the river and lake. Changing river channels are evident in some monitoring cross-sections. Dongting Lake, for the first time, changed from trapping to supplying net sediment to the Yangtze River. During the water storage periods of the TGD, the water level decreased 2.03?m in 2006 and 2.11?m in 2009 at the outlet of the lake, with extreme decreases up to 3.30?m and 3.02?m, respectively. These changes have inevitably induced alterations in the inundation patterns of the lake wetlands, which in turn have disturbed the ecological function of lake wetlands as habitats for both migratory birds and aquatic fish. The serious droughts in Dongting Lake recent years were largely connected with the above changes. Therefore, proper attention should be paid to this occurrence.     

Fish Habitat Use Within and Across Wetland Classes in Coastal Wetlands of the Five Great Lakes: Development of a Fish-based Index of Biotic Integrity

The relative importance of Great Lake, ecoregion, wetland type, and plant zonation in structuring fish community composition was determined for 61 Great Lakes coastal wetlands sampled in 2002. These wetlands, from all five Great Lakes, spanned nine ecoregions and four wetland types (open lacustrine, protected lacustrine, barrier-beach, and drowned river mouth). Fish were sampled with fyke nets, and physical and chemical parameters were determined for inundated plant zones in each wetland. Land use/cover was calculated for 1- and 20-km buffers from digitized imagery. Fish community composition within and among wetlands was compared using correspondence analyses, detrended correspondence analyses, and non-metric multidimensional scaling. Within-site plant zonation was the single most important variable structuring fish communities regardless of lake, ecoregion, or wetland type. Fish community composition correlated with chemical/physical and land use/cover variables. Fish community composition shifted with nutrients and adjacent agriculture within vegetation zone. Fish community composition was ordinated from Scirpus, Eleocharis, and Zizania, to Nuphar/Nymphaea, and Pontederia/Sagittaria/Peltandra to Spargainium to Typha. Once the underlying driver in fish community composition was determined to be plant zonation, data were stratified by vegetation type and an IBI was developed for coastal wetlands of the entire Great Lakes basin.     

Remote sensing and GIS integration for land cover analysis, a case study: Bozcaada Island.

In this study, remote sensing and geographic information system (GIS) techniques were used in order to accomplish land cover change of Bozcaada Island, Turkey, by using multitemporal Landsat Thematic Mapper data. Digital image processing techniques were conducted for the processes of image enhancement, manipulation, registration and classification for land cover change analysis. The land cover changes between two different dates were visualized and analyzed by using Geographic Information System techniques. The results showed that remotely sensed data and GIS are effective and powerful tools for carrying out changes on land cover of the island and monitoring of its impact on the environment.     

The application of geospatial analyses to support an integrated study into the ecological character and sustainable use of Lake Chilwa

Wetlands, which occupy a considerable proportion of Malawi, are an important resource for the rural-poor. In regions of low and erratic rainfall, they provide important opportunities for agriculture and fisheries and are often vital for food security. However, overutilization and some farming practices can result in environmental degradation and the loss of valuable ecosystem services. The Lake Chilwa wetland, a complex aquatic ecosystem comprising a shallow open water lake surrounded by marsh and floodplain grassland, is one of the most important wetlands in Malawi. Most of the 1 million people who live in the vicinity of the lake derive their livelihoods from the wetland. Increases in population in recent decades have increased the pressures on the wetland. In light of continued population growth, it is anticipated that some levels of resource use may be difficult to sustain in the long-term. Consequently, planning the use of wetland resources is a priority if the diverse benefits that local communities presently receive are to be sustained. Baseline wetland information is needed to determine appropriate sustainable management plans, as well as to identify limits to resilience. However, for many wetlands in southern and eastern Africa, these data are lacking, or not available to those who need them. This paper provides an overview of the distribution and characteristics of wetlands in Malawi. Using Lake Chilwa as an example, it illustrates how Earth Observation data, in combination with hydrometric and botanical data, can be used to provide information crucial for sustainable wetland management.     

基于GIS的抚仙湖流域土地利用时空变化研究

高原湖泊是流域内生产生活的重要水源地,维系着当地经济社会的发展,对于调节气候和美化环境起着不可替代的重要作用。由于城镇化的推进和旅游产业的发展,湖泊流域空间格局发生变化,高原湖泊环境污染加剧。以云南省抚仙湖流域为研究对象,运用GIS空间分析技术和数理统计方法,基于2005～2015年3期遥感影像从土地利用幅度变化、土地利用转移类型和土地利用动态度3个方面分析了流域10 a来土地利用时空变化特征。结果表明:①抚仙湖流域土地利用类型以湖泊水面、有林地、旱地、水田和草地为主,水田、有林地和建设用地面积增长,旱地、草地和灌木林地面积减少,园地、湖泊水面和未利用地面积先增后减,水库坑塘先减后增;②土地利用转换类型以农用地向建设用地转移、耕地内部转移和耕地向林地转移3类为主;③不同时期不同地类不同区域的土地利用动态度存在较大差异,2010～2015年与2005～2010年相比,变化更为剧烈,其他建设用地动态度最高,湖泊水面动态度最低,动态度较高的区域分布于湖泊北岸以及西岸中部,而流域北部边缘、西部边缘的动态度较低。研究成果可为该流域生态环境的保护和土地资源的可持续利用提供理论参考。     

Mapping of Conjunctive Water Use Productivity Pattern in an Irrigation Command Using Temporal IRS WiFS Data

Irrigated agriculture in many areas of the world is currently being practiced from multiple water sources such as precipitation, canal, wetlands, ground aquifer, etc. This study highlights the use of high temporal remote sensing data [IRS-1D; Wide Field Sensor (WiFS), 188-m resolution] to assess conjunctive water use pattern and its productivity in the 6 Main Canal command of Damodar Irrigation Project West Bengal, India. In this command three sources of water (canal water, groundwater and wetland) were used for the rice growing system during the summer season. A multi-date (ten dates, two bands) image stack was prepared. Using this image stack and an unsupervised classification (Fuzzy k-means) backed by space–time spiral curve (ST-SCs) technique, canal release and wetlands information was used to prepare irrigated classes (canal, groundwater or wetlands) map for summer 2000. ST-SCs have been used to analyze temporal WiFS data to continuously monitor class dynamics over time and space and to determine class separability (different types of irrigated-classes) at various time periods within the season. Results showed that the area under agriculture, non-agriculture and water were 81%, 18.5% and 0.5%, of the total area respectively. While, groundwater, canal water and wetland irrigated rice were 67.6%, 25.6% and 6.8%, respectively out of the total agriculture area. Classification results found to have more than 89.3% overall accuracy for broad land cover, while sub-classes of rice i.e. irrigated classes found have reasonably good accuracy of 85.7%. A productivity index (LAI/water-requirement) was also developed. Productivity index was high for the wetland and groundwater irrigated rice as compared to the rice irrigated through canal water. These results were weighed against the observed yield data.     

长江大保护视角下鄱阳湖湿地保护的研究思考

鄱阳湖是长江流域的典型通江湖泊,也是我国面积最大的浅水湖泊和国际重要湿地.2003年来,受长江与鄱阳湖之间"江湖关系"变化影响,加之流域区域人类活动干扰,鄱阳湖湿地退化特征明显.以习近平总书记关于"长江大保护"的重要论述为根本遵循,综述国内外研究文献并统计分析相关数据,梳理了鄱阳湖湿地保护研究的关键问题及研究思路.从确...     

Experiences and lessons learned from interventions in the Lake Victoria Basin: The Lake Victoria Environmental Management Project

The Lake Victoria basin has experienced a myriad of environmental changes leading to its degradation, and necessitating various interventions to be implemented. The purpose of this study was to review early development initiatives, past and ongoing interventions in order to document experiences and lessons learned from them. The methods used in this study include review of published articles, project reports, and personal opinions of experts and project implementers in the lake basin. There are numerous threats to the lake basin, the major ones being poor land use and agricultural practices, catchment deforestation, destruction of wetlands, pollution loading, fishing malpractices and invasion by exotic aquatic weeds. These threats have resulted in rampant land and wetland degradation, leading to poor water quality and consequent water loss, a decline in the diversity of the commercial fisheries, and the lake’s biodiversity in general, unsustainable use of natural resources, increased poor human health and food insecurity, with high levels of poverty among the riparian communities. Initiatives for socio‐economic development within the lake basin began as early as the turn of the 20th century, while intervention studies started as early as the 1920s. Current lake management intervention projects, such as the Lake Victoria Environmental Management Project (LVEMP), undertaken by the riparian states of the East African Community, have invested heavily in the lake basin, with the goal of addressing the above‐noted threats to the lake. Some pilot projects undertaken through the LVEMP include: (i) water quality and quantity monitoring; (ii) industrial and municipal management; (iii) fisheries studies; (iv) water hyacinth control; (v) wetlands; (vi) land use; (vii) catchment afforestation; and (viii) micro‐projects to alleviate poverty, to cite a few examples. Phase 1 of the LVEMP was a major effort in the history of the lake basin; hence, its critical examination. To this end, this study highlights, in chronological order, the experiences, achievements, challenges and lessons learned with regard to Phase 1 of the LVEMP.     

基于输出系数模型的洞庭湖流域面源污染分析

为分析洞庭湖流域面源污染情况,在分析统计洞庭湖流域土地分类利用情况的基础上,借助GIS平台和遥感技术,采用输出系数模型,计算了洞庭湖流域2008年面源污染负荷量,并将流域内农药、化肥的使用折算成面源污染负荷与模型结果进行对比验证。计算结果表明,模型模拟结果与折算分析成果较一致,湘江流域和环湖区对洞庭湖面源污染负荷的贡献最大,污染负荷强度最高。     

Spatial-temporal changes of wetlands and its driving factors in Guangdong-Hong Kong-Macao Greater Bay Area from 2010 to 2020EI北大核心CSCD

基于高分遥感影像提取2010年、2015年和2020年湿地数据,使用探索性空间数据分析和地理探测器,定量解析了粤港澳大湾区2010—2020年湿地时空变化及其驱动因素。结果表明:2010—2020年粤港澳大湾区湿地面积不断减少,其中,人工湿地减少更明显(305.33 km^(2)),自然湿地减少90.17 km^(2),湿地向建设用地、草地转移是湿地损失的主要形式;2010—2015年湿地损失的主要区域为大湾区中部核心区和沿海城镇带,2015—2020年湿地损失区域在新区、新建产业基地等局部区域聚集;人工湿地变化主要受GDP、渔业产量、第二产业产值等社会经济发展因素驱动,常住人口的影响力逐渐增强;气温、第一产业产值和道路密度对自然湿地变化起重要作用,其余因子影响较弱。