Agricultural Encroachment Research Articles

Conversions between natural wetlands and farmland in China: A multiscale geospatial analysis

Agricultural activity is widely recognized as a leading driver of natural wetland loss in many parts of the world. However, little is known about the spatiotemporal patterns of conversion between natural wetlands and farmland in China. This information deficiency has limited decision-making for the sustainable management of natural wetland ecosystems. In this study, we explicitly quantified bidirectional natural wetland-farmland conversions during the periods of 1990–2000 and 2000–2010 at multiple spatiotemporal scales. Our results revealed that about 60% (15,765km2) of China's lost natural wetlands were due to agricultural encroachment for grain production, 74.7% (11,778km2) of which occurred from 1990 to 2000. Natural wetland conversion to farmland was highest in Northeast China (13,467km2 or 85.4%), whereas the natural wetlands in Northwest China demand extra attention because of a notable increase of agricultural encroachment. Natural wetlands in the humid zone experienced tremendous agricultural encroachment, leading to a loss of 10,649km2, accounting for 67.5% of the total agriculture-induced natural wetland loss in China. On the other hand, a total of 1369km2 of natural wetlands were restored from farmland, with 66.3% of this restoration occurring between 2000 and 2010, primarily in Northeast China and the humid zone. Although a series of national policies and population pressure resulted in agricultural encroachment into natural wetlands, there are also policies and management measures protecting and restoring natural wetlands in China. The spatial differences in natural wetland-farmland conversions among different geographic regions and climatic zones suggest that China must develop place-based sustainable management policies and plans for natural wetlands. This study provides important scientific information necessary for developing such policies and implementation plans.

Toxicity of Neonicotinoid Pesticide Imidacloprid and Impediment of Ecosystem Services

In agro-ecosystems, pollinators perform a variety of ecological services. The ecological role of pollinators and their ecosystem services are critical to the health of many ecosystems. Pollination by birds and bees are recognized as an important ecosystem function maintaining the dynamics of agro-ecosystems. As agriculture covers a significant portion of the globe, it necessitates the evaluation of their ecosystem services. There are overwhelming evidence that pollinators are experiencing tremendous population decline. Global agricultural encroachment, agriculture intensification, changes in cropped pasture, urban development and extensive use of pesticides are the major threats to farmland birds. Despite ecological importance and global awareness, farmland birds and bees are often considered as species of low conservation value. The worldwide use of neonicotinoid insecticides has raised concern over the decline of pollinators in the farmlands globally. Neonicotinoids are neurotoxins, applied to variety of agricultural crops to control sucking and biting pests and are readily incorporated into plant cells, inclusive of pollen and nectar. Among neonicotinoids, imidacloprid is found to have startling effects, disrupting several ecosystem services, inhibiting pollination and threatening global food security. The study focuses on imidacloprid and its wider risk to the environment with effects on non-target pollinators especially birds and bees. Some of the effects on bees include disrupting social behavior, foraging and altered navigation and in birds reduced reproduction and offspring immunity. Though the scientific community is intently examining the potential effects of imidacloprid on pollinators, the research warrants further investigations with field-realistic concentrations and at relevant exposure levels. This would facilitate the functioning of pollinators and promote sustainable agriculture by reducing the impact of neonicotinoids. This review summarizes the potential lethal and sublethal effects of neonicotinoid pesticide imidacloprid on pollinators and other invertebrate groups and also helps us to better understand the extent of their toxicity.

Effects of anthropogenic disturbance on bird diversity in Ethiopian montane forests

ABSTRACT The Afromontane forests of Ethiopia are global biodiversity hotspots, known for their high biological diversity and endemism. However, conservation of these areas is challenging due to increasing human threats, including encroachment of agriculture and settlements, overgrazing of livestock, and selective logging. We examined the effects of forest disturbances on birds, and highlights the potential conservation value of unprotected tropical montane forests for birds in the dry evergreen Afromontane forests of the Bale Mountains, Ethiopia. We sampled birds across 2 yr in both protected forests (characterized by low levels of cultivation, overgrazing, and logging) and unprotected forests (higher levels of disturbance). Using functional traits of birds related to habitat type, diet, and foraging stratum, we characterized the differences between protected and unprotected forests in terms of avian species richness, abundance, and assemblage composition. Overall, species richness was 27% higher and bird...

Understanding the Role of Agriculture Encroachment in Pastoral Resources Degradation in Western Himalaya of Northern Pakistan

Understanding the Role of Agriculture Encroachment in Pastoral Resources Degradation in Western Himalaya of Northern Pakistan

Forest cover loss in Paraguay and perception of ecosystem services: A case study of the Upper Parana Forest

The Upper Parana Atlantic Forest (BAAPA) in Paraguay is one of the most threatened tropical forests in the world. Relentless agricultural encroachment has left less than 10% of its original cover intact. Many strategies and programs have been initiated, such as Payment for Ecosystem Services (PES) schemes, to halt forest cover loss. While the approach of ecosystem services (ES) has been continuously applied by policy makers, it has not been perceived strongly by the direct users of the forest. This study provides a comprehensive understanding on how landowners in the BAAPA perceive and benefits from ES derived from the forest and examines the influence of farmers on forest conservation. The results were obtained from an extensive household survey performed in the BAAPA region. An understanding of the high ecological value of the forest is common to all farmers. A strong dependency on forest-related products was observed for small and medium landowners whereas large-scale farmers considered the forest’s main value to be mostly recreational and cultural. PES appears to be well accepted by forest owners, but it must receive stronger promotion. Understanding the importance of ecosystem services is a valuable contribution toward to conserving natural resources.

Monitoring Agricultural Expansion in Burkina Faso over 14 Years with 30 m Resolution Time Series: The Role of Population Growth and Implications for the Environment

Burkina Faso ranges amongst the fastest growing countries in the world with an annual population growth rate of more than three percent. This trend has consequences for food security since agricultural productivity is still on a comparatively low level in Burkina Faso. In order to compensate for the low productivity, the agricultural areas are expanding quickly. The mapping and monitoring of this expansion is difficult, even on the basis of remote sensing imagery, since the extensive farming practices and frequent cloud coverage in the area make the delineation of cultivated land from other land cover and land use types a challenging task. However, as the rapidly increasing population could have considerable effects on the natural resources and on the regional development of the country, methods for improved mapping of LULCC (land use and land cover change) are needed. For this study, we applied the newly developed ESTARFM (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model) framework to generate high temporal (8-day) and high spatial (30 m) resolution NDVI time series for all of Burkina Faso for the years 2001, 2007, and 2014. For this purpose, more than 500 Landsat scenes and 3000 MODIS scenes were processed with this automated framework. The generated ESTARFM NDVI time series enabled extraction of per-pixel phenological features that all together served as input for the delineation of agricultural areas via random forest classification at 30 m spatial resolution for entire Burkina Faso and the three years. For training and validation, a randomly sampled reference dataset was generated from Google Earth images and based on expert knowledge. The overall accuracies of 92% (2001), 91% (2007), and 91% (2014) indicate the well-functioning of the applied methodology. The results show an expansion of agricultural area of 91% between 2001 and 2014 to a total of 116,900 km². While rainfed agricultural areas account for the major part of this trend, irrigated areas and plantations also increased considerably, primarily promoted by specific development projects. This expansion goes in line with the rapid population growth in most provinces of Burkina Faso where land was still available for an expansion of agricultural area. The analysis of agricultural encroachment into protected areas and their surroundings highlights the increased human pressure on these areas and the challenges of environmental protection for the future.

The Amphibians of Mount Oku, Cameroon: an updated species inventory and conservation review

Amphibians are a disproportionately threatened group of vertebrates, the status of which in Sub-Saharan Africa is still uncertain, with heterogeneous fauna punctuated by mountains. Mount Oku, Cameroon is one such mountain, which holds many endemic and restricted-range species. The history of amphibian research on Mt Oku, current knowledge on biogeography and conservation biology is reviewed, including recent findings. This updated inventory adds 25 further species, with 50 species of amphibian so far recorded to the Oku Massif (c. 900 to 3,011 m). This includes 5 endemic to Mt Oku, 7 endemic to the Bamenda Highlands, 18 restricted to the highlands of Cameroon and Nigeria, and 20 with broader ranges across Africa. This includes a new mountain locality for the Critically Endangered Leptodactylodon axillaris. Among others, the first record of Phrynobatrachus schioetzi and Ptychadena taenioscelis from Cameroon are presented. The uncertainty of habitat affinities and elevational ranges are discussed. The proportion of threatened species on Mt Oku is 44.2%, but projected to increase to 47.9% due to new species descriptions and recent dramatic declines. The natural habitats of Mt Oku are irreplaceable refuges for its endemic and restricted-range amphibian populations under severe pressure elsewhere in their range. Threats to this important amphibian fauna are increasing, including agricultural encroachment, expanding aquaculture, livestock grazing, pollution, invasive species, forest loss and degradation. Past, present and desired conservation interventions to address these threats are discussed.

A Review on Causes of Climate Change: Challenges and Opportunities for Livestock Production in the Tropics

The growth in demand for livestock products will probably still play a dominant role over the next decades and lead to a net increase in the area dedicated to livestock, despite the intensification trend. It is estimated that the world food requirement by the year 2050 will be double that of 2010. A significant part of this requirement will emanate from the developing countries, on account of increased human populations, disposable incomes and urbanization. To the contrary, climate change poses the threat of serious social upheaval, population displacement; economic hardships and environmental degradation were it has been caused both by natural phenomenon and man-made activities. Livestock established their current geographic ranges through long-term adaptation to seasonal climate patterns. Anthropogenic climate change is likely to alter those seasonal patterns on a timescale far more rapid than has occurred naturally over past millennia. It is this rapid rate of climate change which challenges the natural adaptive capacity of livestock. The faster the changes, the greater will be the risk of damage exceeding ability to cope with the consequences. Significant negative consequences including loss of livestock through heat stress, loss of land to agricultural encroachment, an increase in frequency of flooding and the spread of human and livestock diseases were some the problems. Since, livestock are an irreplaceable source of livelihoods for the poor community and there is a chance to give attention for the sector. Because, it is the fastest growing sector and in some countries accounts for 80% of the GDP, in particular in dry lands. As to livestock products, about two-thirds of the increased demand needs to be met by improving the production efficiency of feeds (forages and concentrates). Balanced nutrition contributes to improve animal output as well as to reduce both the cost of production and the emission of greenhouse gases per animal. Ultimately large scale implementation of such programs can help to improve the productivity of livestock in developing countries. Therefore, livestock management system-efficient and affordable adaptation practices have to be developed for producers not able to buy expensive adaptation technologies.

Human population and socioeconomic modulators of conservation performance in 788 Amazonian and Atlantic Forest reserves.

Protected areas form a quintessential component of the global strategy to perpetuate tropical biodiversity within relatively undisturbed wildlands, but they are becoming increasingly isolated by rapid agricultural encroachment. Here we consider a network of 788 forest protected areas (PAs) in the world’s largest tropical country to examine the degree to which they remain intact, and their responses to multiple biophysical and socioeconomic variables potentially affecting natural habitat loss under varying contexts of rural development. PAs within the complex Brazilian National System of Conservation Units (SNUC) are broken down into two main classes—strictly protected and sustainable use. Collectively, these account for 22.6% of the forest biomes within Brazil’s national territory, primarily within the Amazon and the Atlantic Forest, but are widely variable in size, ecoregional representation, management strategy, and the degree to which they are threatened by human activities both within and outside reserve boundaries. In particular, we examine the variation in habitat conversion rates in both strictly protected and sustainable use reserves as a function of the internal and external human population density, and levels of land-use revenue in adjacent human-dominated landscapes. Our results show that PAs surrounded by heavily settled agro-pastoral landscapes face much greater challenges in retaining their natural vegetation, and that strictly protected areas are considerably less degraded than sustainable use reserves, which can rival levels of habitat degradation within adjacent 10-km buffer areas outside.

A River Basin over the Course of Time: Multi-Temporal Analyses of Land Surface Dynamics in the Yellow River Basin (China) Based on Medium Resolution Remote Sensing Data

The Yellow River Basin is one of China’s most densely-populated, fastest growing and most dynamic regions, with abundant natural resources and intense agricultural production. Major land policies have recently resulted in remarkable landscape modifications throughout the basin. The availability of precise regional land cover change information is crucial to better understand the prevailing dynamics and underlying factors influencing the current processes in such a complex system and can additionally serve as a valuable component for modeling and decision making. Such comprehensive and detailed information is lacking for the Yellow River Basin so far. In this study, we derived land cover characteristics and dynamics from the complete last decade based on optical high-temporal MODIS Normalized Differenced Vegetation Index (NDVI) time series for the whole Yellow River Basin. After filtering and smoothing for noise reduction with the use of the adaptive Savitzky–Golay filter, the processed time series was used to derive a large variety of phenological and annual metrics. The final classifications for the basin (2003 and 2013) were based on a random forest classifier, trained by reference samples from very high-resolution imagery. The accuracy assessment for all 18 thematic classes, which was based on a 30% reference data split, yielded an overall accuracy of 87% and 84% for 2003 and 2013, respectively. Major land cover and land use changes during the last decade have occurred on the Loess Plateau, where land and conservation reforms triggered large-scale recovery of grassland and shrubland habitat that had been previously covered by agriculture or sparse vegetation. Agricultural encroachment and urban area expansion are other processes influencing the dynamics in the basin. The necessity for regionally-adapted land cover maps becomes obvious when our land cover products are compared to existing global products, where thematic accuracy remains low, particularly in a heterogeneous landscape, such as the Yellow River Basin. The basin-wide novel land cover and land use products of the Yellow River Basin hold a large potential for climate, hydrology and biodiversity modelers, as well as river basin and regional governmental authorities and will be shared upon request.

Land Use and Land Cover Changes in the Commercial Farming Region of Chiredzi District, Zimbabwe

This study analyses land use and land cover changes that occurred in the commercial farming region of Chiredzi district in Zimbabwe between 1989 and 2012. It analysed the current arrangement of land use and land cover and the changes in land use and land cover over the 23 years along with the extent of changes that have occurred as well as the causes and impacts of the changes detected. Land use and land cover changes were determined from maximum likelihood supervised classification and interpretation of 1989, 1999, 2007 and 2012 Landsat TM satellite imagery while the drivers and impacts were noted using observations and secondary data. The results showed that cultivated land had expanded at the expense of bushland. Cultivated fields and bush land areas generally concentrated in the same locality and this was assumed to be a result of the arid conditions within the district. These changes in land use pattern and spread were mainly attributed to encroachment and expansion of agriculture; bush land clearance for firewood collection and construction, population increase due to resettlement and to a lesser extent the general arid conditions associated with climate change. The study recommends that further studies be undertaken to establish the consequences of sugarcane production on natural carbon sequestration processes such that further bushland losses will not pose detrimental environmental effects.

Fuelwood collection and its impacts on a protected tropical mountain forest in Uganda

Local communities who live close to protected tropical forests often depend on them for woodfuel, their main source of energy. The impacts of fuelwood extraction in humid forests are rarely studied, yet the extraction of wood for fuel can impact forest structure, function and biodiversity. We assessed the effects of fuelwood collection on the forest of Mt Elgon National Park (Uganda). We interviewed 192 households about fuelwood use and surveyed dead wood in 81 plots inside the park. Forest was the most important source of fuelwood. People collected on average between 1.1 and 2.0m3 of fuelwood per capita per year. Other activities involving wood fuel extraction from the forest included illegal commercial fuelwood harvesting and charcoal making. Quantities of dead wood were affected by fuelwood collection up to at least 1000m inside the boundary of the park. Depletion of dead wood inside the park was greater in the sites where the population was most dense. Nevertheless, people who planted more trees on their own land perceived land outside the park to be important and valued old growth forest less as a source of fuelwood. Highly-preferred tree species were most depleted, particularly when they were also valued timber trees, such as Prunus africana, Popocarpus milianjianus, Allophylus abyssinicus and Olea spp. Locally dominant species were less affected. Impacts varied among sites depending on the history of agricultural encroachment and locally-specific forest uses, e.g. harvesting of trees for poles or use of the forest land for grazing. Allowing the collection of dead wood in forests is double-edged as it creates opportunities for other activities that are more damaging. Demand for wood fuel from tropical forests is still likely to grow in the foreseeable future. Our results indicate that the forest may become more degraded as a result, with negative consequences for the people who depend on the forest and for conservation. Research into local ecological and cultural contexts and perceptions concerning costs and benefits can help devise more sustainable management options, including alternative sources of fuel.

An assessment on the nature of channel migration of River Diana of the sub-Himalayan West Bengal using field and GIS techniques

Lateral movement of river channel within its valley with time is a universal phenomenon. Various processes of fluvio-geomorphological environment such as rapid valley fill deposition due to very low channel gradient and resultant migration of active channel, bank failure and bankline migration, frequent occurrence of floods, capturing of lower courses of the tributaries by the trunk streams, and abandonment of tracks and avulsion are the most prominent factors behind channel dynamics in the sub-Himalayan part of West Bengal. Additionally, human interventions in the form of engineering constructions (bridges, flood embankments, etc.), tea plantation, mining and quarrying, and agricultural encroachment have emerged as another dominant issue which is pulverizing the ways of natural channel adjustment as well as also the channel behaviors. Both these processes are carrying significant messages of immense vulnerability for the study area known for its geomorphological instabilities. The dynamics of channel adjustment in terms of lateral migration can be lucidly illustrated through the application of modern tools of geoinformatics, i.e., the techniques of remote sensing and geographic information system (GIS) which is widely capable of detecting as well as representing the changes that took place over space and time. A meticulous endeavor has been made to assess the channel dynamics of the Diana River of this concerned region for an 85-year spanning period to unveil the nature of channel migration in terms of changes in historical bankline and centerline positions and alterations in meander geometries through numeric and graphical methods coupled with field observations to define the overall zone of channel migration for three subsequent reaches of the Diana River.

Modeling residential development in California from 2000 to 2050: Integrating wildfire risk, wildland and agricultural encroachment

Between 1940 and 2000, nearly 10 million housing units were constructed throughout California. This increased interaction between human and natural communities creates a number of significant socio-ecological challenges. Here we present a novel spatially explicit model that allows better characterization of the extent and intensity of future housing settlements using three development scenarios between 2000 and 2050. We estimate that California's exurban land classes will replace nearly 12 million acres of wild and agricultural lands. This will increase threats to ecosystems and those presented by wildfire, as the number of houses in ‘very high’ wildfire severity zones increases by nearly 1 million.

Agricultural encroachment and lack of enforcement threaten connectivity of range-wide jaguar (Panthera onca) corridor

The purpose of protected areas is to safeguard natural habitats and their biodiversity. However, few protected areas are large enough for the long-term conservation of resident species, making the landscapes surrounding protected areas equally important for species conservation. This is especially true for wide-ranging carnivores such as the jaguar (Panthera onca), for which conservation strategies stress the maintenance of range-wide habitat connectivity via protected areas and dispersal corridors. We used 587 interviews with local people in 441 36-km2 sampling units to assess the presence of jaguar and six prey species in a critical corridor in Central America, linking Bosawas Biosphere Reserve and Wawashan Nature Reserve in Nicaragua. We analyzed these data using single-season false-positive detection models in a site occupancy framework. We found that agricultural encroachment, particularly pervasive within a protected area, was the main factor limiting the presence of jaguar and three large-bodied prey species: white-lipped peccary (Tayassu pecari), collared peccary (Pecari tajacu), and red brocket deer (Mazama americana). We suggest that improperly-managed protected areas can suffer the loss of apex predators and their prey, thereby jeopardizing range-wide conservation strategies for threatened species.

Water quality, habitat, land use, waterfowl, and fish community data from wetlands in the Boreal Transition Zone, Alberta

Water quality, environment, agricultural land use, waterfowl, and fish community data were collected from wetlands in four landscapes (West Peace Lowlands, East Peace Lowlands, West Central, and East Central) in the Boreal Transition Zone (BTZ) of Alberta (AB) and with one landscape in British Columbia (East Peace Lowlands, BC) during May and August over three years (2005–2007). This data set is unique in that it provides comprehensive water quality sampling, habitat conditions, and associated breeding and molting waterfowl data over a three‐year period, which includes a drought year. Land use in the BTZ has rapidly changed with at least 73% of the BTZ, particularly in Saskatchewan, AB, being converted from forest to agriculture since the early 20th century. The BTZ has experienced a drying trend over the past 60 years with the lowest cumulative effective precipitation since 1943 with a −2323‐mm precipitation deficit recorded in 2006. A total of 723 and 489 wetlands were surveyed for waterfowl abundance during the breeding and molting seasons, respectively. A subset of 214 and 213 wetlands in May and August, respectively, was further sampled for habitat, limnology, and agricultural encroachment surrounding the wetland. A subset of 25 wetlands was sampled in 2006 for fish abundance data. This data set has been used in several papers in assessing the impact of drought and agricultural impact on water quality and wetland conditions, as well as drought and land use impacts on habitat associations between breeding and molting waterfowl and wetland condition.

Habitat characterization of western hoolock gibbons Hoolock hoolock by examining home range microhabitat use

Conserving a species depends on an understanding of its habitat requirements. Primatologists often characterize the habitat requirements of primates using macroscale population-based approaches relying on correlations between habitat attributes and population abundances between sites with varying levels of disturbance. This approach only works for species spread between several populations. The populations of some primates do not fulfill these criteria, forcing researchers to rely on individual-based (microscale) rather than population-based approaches for habitat characterization. We examined the reliability of using micro-scale habitat characterizations by studying the microhabitat preferences of a group of wild western hoolock gibbons (Hoolock hoolock) in order to compare our results to the habitat preferences of western hoolock gibbons identified during a macroscale study of populations across Bangladesh. We used stepwise discriminant analysis to differentiate between the areas of low, medium, and high usage based on microhabitat characteristics (tree species availability, altitude, canopy connection, distance from forest edge, and levels of human disturbance). The gibbons used interior forest habitat with low food tree availability most frequently for sleeping and socializing, and used edge habitat containing high food tree availability for medium periods for feeding. These results indicate that the gibbons prefer interior forest but are frequently forced to visit the forest edge to feed. Therefore, the optimal habitat would be interior forest away from human disturbance with high sleeping-tree and feeding-tree availability. These habitat preferences are consistent with the habitat attributes of Bangladesh's largest remaining western hoolock gibbon populations, which live in areas containing low agricultural encroachment and high food-tree availability. Microhabitat use studies can be used to characterize the habitat requirements of a species, but should include multiple scales of analysis wherever possible.

A characterization of the drivers, pressures, ecosystem functions and services of Namatala wetland, Uganda

Abstract Namatala wetland near the town of Mbale in the Eastern region of Uganda is a papyrus wetland that is subject to conversion for agriculture (mainly rice farming) and pollution by wastewater. The main goal of this study was to analyze the ecosystem functions and services of Namatala wetland and their drivers of change, and to suggest directions for sustainable use. Data on climate, hydrology, water quality, population and land use were collected. Stakeholder workshops were organized at national and local levels to identify stakeholder interests in the wetland and conflicts. The institutional context for management of Namatala wetland was analyzed. A qualitative assessment of the ecosystem services was performed. All results were integrated into a DPSIR network showing the drivers of change, impact on ecosystem services and possible responses for management. Results show that the communities around Namatala wetland strongly depend on the wetland ecosystem for provisioning services. A spatial gradient in ecosystem services was observed. The upper, converted part of the wetland is more important for provisioning services while the lower, more intact wetland supports regulating and habitat ecosystem services. The institutional framework is complex due to the involvement of several ministries at the national level and several levels of decentralized, local government. Horizontal and vertical coordination of policy implementation is weak. There are diverging perceptions among stakeholders about the priority issues in wetland management. Resource users worry about water and land use conflicts, while local and national government agencies are more concerned about agricultural encroachment and biodiversity loss. There are also differences in interpretation of land ownership between the national wetland policy and local customary arrangements. For sustainable management of Namatala wetland, there is a need for more horizontal and vertical coordination in wetland policy implementation, application of sustainable agriculture and integrated water and nutrient management techniques, and continued monitoring, research and capacity building to support adaptive management.

A census and status review of the Endangered François' langur Trachypithecus francoisi in Chongqing, China

AbstractFrom September 2009 to September 2010 we undertook a survey of the Endangered François’ langur Trachypithecus francoisi in south-east Chongqing to compare the species' present status with historical records from the 1990s. Based on a literature review, interviews with local people and our survey we found François’ langurs in only three isolated sites, across four counties, with a total area of occurrence of c. 57 km2. The total population was estimated to be c. 200 individuals in 27 mixed sex groups. There were 21 groups (149 individuals) within a reserve (Jinfoshan), and four groups (36) in Furongjiang and two groups (13) in Heishangu were not within any reserve. The primary threat to the langur is habitat loss caused by traditional firewood use and agricultural encroachment but there is also increasing loss of forest to hydroelectric projects and construction of tourism infrastructure and facilities such as highways, hotels and telephone lines. The three sites in southern Chongqing province are adjacent to four areas in north-east Guizhou province that contain c. 60% of the wild population of the species in China. The seven sites combined are the main stronghold of this species and the geographical proximity of the sites raises the possibility of setting up ecological corridors between some of them.

Agricultural impact on the pelagic ecosystem of the small temporarily open/closed Seteni Estuary, South Africa

The encroachment of agriculture and human population is placing increasing levels of stress on estuarine ecosystems worldwide. The catchment of the Seteni Estuary, a small temporarily open/closed estuary in South Africa, has been under extensive sugar cultivation for over 60 years. The present study reports on the impact of agricultural practices on the structure and dynamics of its pelagic communities over a 1-year period, from April 2008 to March 2009. The physico-chemical characteristics of the system were strongly linked to seasonality, with the system exhibiting a distinct open- and closed-mouth phase in response to rainfall. Concentrations of dissolved inorganic nitrogen (DIN) were exceptionally high in comparison to concentrations of dissolved inorganic phosphorus (DIP), resulting in high DIN : DIP ratios. Despite this, microalgal biomass remained relatively low, exhibiting maximum values of 91.7 mg chl a m–2 and 18.0 mg chl a m–3 for microphytobenthos and phytoplankton, respectively. Zooplankton abundance and biomass were significantly higher during the dry phase, with Pseudodiaptomus hessei dominating the zooplankton community both in terms of abundance and biomass throughout the study period. The ichthyofaunal community was dominated by Ambassis ambassis and Myxus capensis in terms of abundance and biomass, respectively. Results suggest that the system remains functional, but there is potential for deterioration, should the catchment become more nutrient-rich through poor management or land-use changes.