Coastal Environmental Impacts Brought About by Alterations to Freshwater Flow in the Gulf of Mexico

/ Freshwater inflow is one of the most influential landscape processes affecting community structure and function in lagoons, estuaries, and deltas of the world; nevertheless there are few reviews of coastal impacts associated with altered freshwater inputs. A conceptual model of the possible influences of freshwater inflows on biogeochemical and trophic interactions was used to structure this review, evaluate dominant effects, and discuss tools for coastal management. Studies in the Gulf of Mexico were used to exemplify problems commonly encountered by coastal zone managers and scientists around the world. Landscape alteration, impacting the timing and volume of freshwater inflow, was found to be the most common stress on estuarine systems. Poorly planned upstream landscape alterations can impact wetland and open-water salinity patterns, nutrients, sediment fertility, bottom topography, dissolved oxygen, and concentrations of xenobiotics. These, in turn, influence productivity, structure, and behavior of coastal plant and animal populations. Common biogeochemical impacts include excessive stratification, eutrophication, sediment deprivation, hypoxia, and contamination. Common biological impacts include reduction in livable habitats, promotion of "exotic" species, and decreased diversity. New multiobjective statistical models and dynamic landscape simulations, used to conduct policy-relevant experiments and integrate a wide variety of coastal data for freshwater inflow management, assume that optimum estuarine productivity and diversity is found somewhere between the stress associated with altered freshwater flow and the subsidy associated with natural flow. These models attempt to maximize the area of spatial overlap where favorable dynamic substrates, such as salinity, coincide with favorable fixed substrates, such as bottom topography. Based upon this principle of spatial overlap, a statistical performance model demonstrates how population vitality measurements (growth, survival, and reproduction) can be used to define sediment, freshwater, and nutrient loading limits. Similarly, a spatially articulate landscape simulation model demonstrates how cumulative impacts and ecosystem processes can be predicted as a function of changes in freshwater, sediment, and nutrient inflows.KEY WORDS: Resource management; Landscape impacts; Freshwater discharge; Coastal, ecosystem models; Coastal wetlands     

视觉影响评价技术研究与应用

文章首先对于国内外出现的视觉影响评价与景观影响评价的概念进行了对比分析，提出“视觉影响评价”在功能表述上更为确切，并给出了视觉影响评价的基本概念，然后针对视觉影响评价的特点，介绍了视觉模拟用以预测影响的手段以及评价方法和减缓措施，并通过一具体实例进行了说明，最后针对我国视觉影响评价的现状提出了一些加强和改善的建议。     

Delayed colonisation of arable fields by spring breeding ground beetles (Coleoptera: Carabidae) in landscapes with a high availability of hibernation sites

The colonisation of winter barley fields by spring breeding carabids and its temporal modulation by the amount of potential hibernation sites was studied. Species richness of carabids was lower in landscapes with high length of boundaries and a high amount of non-cropped open habitats during early stages of the beetles’ colonisation of arable fields. Species number of beetles with high dispersal potential responded to this landscape features at coarse spatial scales whereas beetles with low dispersal potential responded to intermediate scales. However, the negative impact of potential hibernation sites on colonisation diminished in later sampling phases. The patterns observed may be explained by both overwintering in arable soils in less complex landscapes and delayed colonisation in more complex landscapes. The seasonal patterns of landscape control suggest a need to account for temporal dynamics in interactions between species or functional groups and landscape properties. A high temporal resolution is needed in studies that focus on ecosystem function and services in agricultural landscapes, as direction of effect (positive/negative) of management on animal communities may change across spatial scales and within short time periods.     

Grasshopper assemblage response to conservation ecological networks in a timber plantation matrix

Grasshopper assemblages are well known to be sensitive and responsive to changes occurring in habitats, enabling their application as bioindicators. Large-scale ecological networks (ENs) have been proposed as a conservation mitigation measure, and are used extensively in southern Africa to offset the impacts on biodiversity of commercial afforestation. Here, grasshopper response to an EN of 15 semi-natural grassland sites embedded in an exotic timber plantation matrix was investigated over two time periods, one year apart. The aim was to determine which environmental variables had a significant effect on grasshoppers, whether this response was robust among seasons, and the extent of phylogenetic variability in the response. The results showed that grasshopper species responded strongly and consistently to area of the site, time lapse since the last fire, and inconsistently to proportion of short grasses. Generalized least squares models with phylogenetic adjustment showed that there was a strong phylogenetic signal in species response to habitat quality, illustrating that site occupancy patterns were distinct for species from different subfamilies. Since grasshopper assemblages are more sensitive to internal patch-level environmental factors of ENs than to patch isolation, ENs may indeed be a suitable mitigation measure, although effectiveness is expected to vary among taxa.     

A simulation study of the medium-term effects of field patterns on cross-pollination rates in oilseed rape (Brassica napus L.)

Gene flow between cultivars within a landscape may lead to impurities that reduce harvest value. In OSR, as for most crops, impurity rates are expected to depend on the spatial distribution of crops over the landscape. However, in contrast to other well-studied crops such as maize, OSR crops generate seed banks in European agro-ecosystems. Gene flow is thus a spatio-temporal process which depends on cropping systems. We therefore aimed at identifying spatial variables that have an effect on regional or local harvest impurities, taking account of the time since the introduction of OSR crops in the regions and of cropping system. Gene flow was simulated over 36 field patterns cultivated with either 15% or 30% of OSR fields, among which 10% or 50% were GM, for three contrasted cropping systems, with the GeneSys software already used for EU co-existence studies. Through regression analyses, we determined spatial and agronomic factors that most affected harvest impurity rates of non-GM OSR after one or seven years of OSR cultivation. The cropping system was the main factor explaining regional harvest impurity rates. Its importance increased after six years of OSR cultivation. For a given cropping system, the regional impurity rate after one year increased linearly with the current proportion of GM crop. In contrast, impurity rates after six years largely depended on the proportions of OSR crop (GM or not) in the two preceding years. During the first year of OSR cultivation, local impurity rates were mostly explained by the distance to the closest GM field. After six years, these rates were mostly explained by the density of GM volunteers in the analysed field and, to a lesser degree, to that of volunteers in neighbour non-OSR fields. Cropping systems were most important in determining impurity rates and the way impurity rates related to regional or local factors. Determination of isolation distances to ensure harvest purity should thus consider past history of OSR cultivation in the area and, in particular, how current or future cropping systems will manage volunteers. Regression quantiles were fitted to the simulated data to determine regional rules (i.e. the maximum regional area of GM OSR and isolation distances between GM and non-GM crops) as a function of the risk accepted by the decision-maker (i.e. the % of situations exceeding harvest impurity thresholds), the cropping system and the volunteer infestation.     

Governance structures for social-ecological systems: Assessing institutional options against a social residual claimant

Rural areas face increasing pressures to deliver both private and public goods from land management. Multiple stakeholders seek different outcomes and there is substantial heterogeneity in values. Trade-offs, synergies and complementarities exist between different services and alternative bundles of goods. The resulting complex social-ecological systems (SES) therefore require adaptive co-management. In a governance context, no single organisation has oversight across the variety of interests involved, but the challenge remains as to how these interests can best be balanced and negotiated, to deliver socially beneficial outcomes. This paper analyses how this might be achieved by considering the perspective of a ‘social residual claimant’ (SRC). The SRC, as an ideal type, represents the ultimate ‘owner’ or steward of an ecosystem which sets the criteria to assess alternative outcomes, identifying best approaches and addressing uncertainty through adaptive management. A SRC cannot be a static construct, but must interact with and influence private land-holders and other stakeholders, adjusting actions as circumstances change. We identify the criteria that would be required in order for an SRC to act in the best interests of society. We then make a comparison of these criteria against the conditions applying in three contrasting approaches currently operating in the UK: National Parks, Landscape Partnerships and Nature Improvement Areas. This enables us to identify the differences between approaches and to suggest changes that could enhance capabilities, as well as ideas for further research. We suggest that the ideal of an SRC offers a simple method of benchmarking that has potential application across a wider range of different local contexts, beyond the UK.     

The role of water in the development of The Netherlands— a historical perspective

In this paper an overview is presented of the landscape development of the low-lying parts of The Netherlands. It is shown that water has played an important role in this development. Since prehistoric times, but especially since about 800 AD, man has gradually occupied the low lands along the sea and the main rivers. Through these settlements a chain of actions and reactions of man and his physical environment was set into motion. This chain of events is briefly outlined. It is stated and also illustrated that not only the characteristics of the landscape of the western part of The Netherlands, but also the organization of the Dutch society has been influenced strongly by manÕs need to cope with the omnipresence of water and the threats and opportunities posed by that. It is concluded that the outlined events can only be understood properly if interdisciplinary research takes a more prominent role than it does now.     

Landscape fires as social disasters: An overview of ‘the bushfire problem’

The ‘landscape’, ‘bushfire’ or ‘forest-fire’ problem is exemplified by the destruction of homes and human lives by landscape fires raging out of control. The ‘problem’ involves a series of landscapes (e.g. wildland and suburb), a series of systems (e.g. biophysical system and environmental-effects system), and a series of time phases (e.g. planning phase). It is a multi-stakeholder, multi-variable, multi-scale problem. Land uses, like ‘farmland’, imply a set of specific assets and, therefore, particular perceptions of losses. In all land-use designations, at any one point, fire-proneness may be seen as a function of exposure to ignition sources (embers, burning brands or flame radiation and flame contact) and the ease of ignition. The landscape-fire problem has multiple partial ‘solutions’, not just one overall solution, and these involve social governance, land management (public and private), suppression capacity and personal preparedness. The problem needs to be addressed at multiple temporal and spatial scales in an integrated fashion for the outcome to be of maximal benefit. There will always be a residual risk of severe fire occurrence. Minimisation of residual risk requires effective land management, recurrent funding and the perpetual vigilance of all parties.     

Urban forest landscape patterns in Ma'anshan City,China

The landscape pattern of Ma'anshan City was analyzed based on theories and methodologies of landscape ecology, remote sensing, global positioning, and a geographic information system (GIS). The study area encompassed the entire built-up area of 63.88 km²; a north–south transect 3-km wide and 13-km long was established along the long axis of the city. Five major landscape elements were assessed: urban land, urban forest, agriculture, water, and grass. Urban land was the dominant land cover type, and occupied 67% of total land area; while patches of urban forest occupied 16%, with a landscape element dominance of 0.42. Urban forest was classified according to land-use category and location into six types: scenic forest, yard forest, recreational forest, roadside forest, shelter forest, and nurseries. There were 2464 urban forest patches, the largest being 185.1 ha, with an average of 0.43 ha. The low nearest neighbor index and high patch density indicated that urban forest patches tend to be aggregated and have a high degree of fragmentation. This study also demonstrated that the spatial pattern of urbanization could be quantified using a combination of landscape metrics and gradient analysis. Urban forest has distinct spatial characters that are dependent on specific landscape metrics along the urbanization gradient.