The velocity of spatial population expansion

We consider the velocity with which an invading population spreads over space. For a general linear model, originally due to Diekmann and Thieme, it is shown that the asymptotic velocity of population expansion can be calculated if information is available on: (i) the net-reproduction, R _o; i.e. the expected number of offspring produced by one individual throughout its life, and (ii) the (normalized) reproduction-and-dispersal kernel, (a, – ); i.e. the density of newborns produced per unit of time at position by an individual of age a born at By means of numerical examples we study the effect of the net-reproduction and the shape of the reproduction-and-dispersal kernel on the velocity of population expansion. The reproduction-and-dispersal kernel is difficult to measure in full. This leads us to derive approximation formulas in terms of easily measurable parameters. The relation between the velocity of population expansion calculated from the general model and that from the Fisher/Skellam diffusion model is discussed. As a final step we use the model to analyse some real-life examples, thus showing how it can be put to work.     

饭店生态足迹模型的构建与应用

构建了饭店生态足迹模型,给出了饭店占地、能源、水、食物、棉织品、纸制品、废弃物的生态足迹和平均生态足迹的计算方法;并构建了基于生态足迹的饭店生态效率模型。利用所建模型对青岛市5家中高档饭店生态足迹的计算结果表明,各饭店食物与能源的生态足迹之和占其生态足迹总量的94%以上,饭店的总生态足迹、各种平均生态足迹与饭店的星级呈正相关,饭店的生态效率亦随饭店星级的提高而提高;但同星级饭店的生态足迹及生态效率均有较大差别。说明通过一系列绿色管理措施降低饭店生态足迹、提高饭店生态效率,具有巨大空间。     

Cystic echinococcosis in Italy from the 1950s to present

In Italy the epidemiological pattern of cistic echinococcosis (CE) is incomplete and the information for most regions is out of date, contradictory, and almost exclusively limited to the intermediate hosts. The disease is found most frequently in particular social and economic conditions: widespread use of extensive or semi-extensive sheep farming, illegal slaughtering, and high numbers of sheepdogs and other types of dogs. The highest incidence in sheep is found in Sardinia (70.6-92.8%), Sicily (6.5-36.5%), Basilicata (5-28%), Abruzzo (22%) and Tuscany (47%). It North Italy, it is never higher than 0.5% in slaughtered sheep. No data are available on the biomolecular characterization of the strains of E. granulosus in Italy, apart from Sardinia and recently Lazio. G1 (Sheep strain), G7 (Pig strain) G2 (Tasmanian sheep strain) have been identified in Sardinia and G1 and G3 (Buffalo strain) have been recently isolated in Lazio. In Italy, CE has was also found in buffaloes (2.63-9.8%) and horses (<1%). However, further epidemiological surveys and genotyping study are necessary. The small quantity of up to date information on the diffusion of E. granulosus in dogs (Abruzzo 4%, Sardinia 6-10% and Sicily 19.3%) highlights the need for modern, fast, sensitive and low risk diagnostic methods which would provide a true picture of the pattern of the infection in this host.     

Characterizing fishing effort and spatial extent of coastal fisheries

Biodiverse coastal zones are often areas of intense fishing pressure due to the high relative density of fishing capacity in these nearshore regions. Although overcapacity is one of the central challenges to fisheries sustainability in coastal zones, accurate estimates of fishing pressure in coastal zones are limited, hampering the assessment of the direct and collateral impacts (e.g., habitat degradation, bycatch) of fishing. We compiled a comprehensive database of fishing effort metrics and the corresponding spatial limits of fisheries and used a spatial analysis program (FEET) to map fishing effort density (measured as boat-meters per km2) in the coastal zones of six ocean regions. We also considered the utility of a number of socioeconomic variables as indicators of fishing pressure at the national level; fishing density increased as a function of population size and decreased as a function of coastline length. Our mapping exercise points to intra and interregional 'hotspots' of coastal fishing pressure. The significant and intuitive relationships we found between fishing density and population size and coastline length may help with coarse regional characterizations of fishing pressure. However, spatially-delimited fishing effort data are needed to accurately map fishing hotspots, i.e., areas of intense fishing activity. We suggest that estimates of fishing effort, not just target catch or yield, serve as a necessary measure of fishing activity, which is a key link to evaluating sustainability and environmental impacts of coastal fisheries.     

An urban university's ecological footprint and the effect of climate change

Ecological footprint analysis (EFA) has been used since the early 1990s as a measure of sustainability for geographical regions, products, and activities. EFA is used as a measure of land and water ecosystems needed to provide the resources for a given population and process the waste that it produces in a globalized metric (global hectares), generally on an annual basis. As institutions seek ways to become more sustainable they have used a variety of metrics, ranking systems, and indicators to evaluate their baseline and progress towards those goals. An EFA for a large urban public university, the University of Illinois at Chicago (UIC), was calculated as 97,601 global hectares (2.66 global hectares per total faculty, staff and students). The breakdown of sources is energy for the built environment (73%), transportation and commuting (13%), materials and waste (12%), and food (3%). UIC's ecological footprint to actual landprint ratio has a value of 1005 which is 1–2 orders of magnitude higher than the other campuses that have performed EFAs. This is an indicator of the urban nature of the campus since the land resources in an urban environment are limited and the activities tend to be denser. A sensitivity analysis to examine the effect of climate change events on the footprint indicated that, if all other factors are held constant, climate change will increase the ecological footprint of UIC.     

Stochastic ecological network occupancy (SENO) models: a new tool for modeling ecological networks across spatial scales

Stochastic ecological network occupancy (SENO) models predict the probability that species will occur in a sample of an ecological network. In this review, we introduce SENO models as a means to fill a gap in the theoretical toolkit of ecologists. As input, SENO models use a topological interaction network and rates of colonization and extinction (including consumer effects) for each species. A SENO model then simulates the ecological network over time, resulting in a series of sub-networks that can be used to identify commonly encountered community modules. The proportion of time a species is present in a patch gives its expected probability of occurrence, whose sum across species gives expected species richness. To illustrate their utility, we provide simple examples of how SENO models can be used to investigate how topological complexity, species interactions, species traits, and spatial scale affect communities in space and time. They can categorize species as biodiversity facilitators, contributors, or inhibitors, making this approach promising for ecosystem-based management of invasive, threatened, or exploited species.     

Investigating the environmental Kuznets curve (EKC) hypothesis by utilizing the ecological footprint as an indicator of environmental degradation

This study investigates the environmental Kuznets curve (EKC) hypothesis using a country’s ecological footprint as an indicator of environmental degradation. Ninety-three countries were examined, categorized by income. The fixed effects and the generalized method of moments results clearly showed an inverted U-shaped relationship between the ecological footprint and GDP growth, which represents the EKC hypothesis in upper middle- and high-income countries but not in low- and lower middle-income countries. This relationship only occurs in a stage of economic development in which technologies are available that improve energy efficiency, energy saving and renewable energy, which are not accessible for countries with low income due to their high cost. Moreover, energy consumption, urbanization, and trade openness increase environmental damage through their positive effect on the ecological footprint of most countries across all income groups. However, financial development reduces environmental degradation in lower middle-, upper middle- and high-income countries. This relationship confirms that loans from banks are primarily given to firms that establish investments in projects that are mostly environmentally friendly. From the results of this study, a number of recommendations can be provided for the investigated countries.     

The impact of subsidies on the ecological sustainability and future profits from North Sea fisheries

Background

This study examines the impact of subsidies on the profitability and ecological stability of the North Sea fisheries over the past 20 years. It shows the negative impact that subsidies can have on both the biomass of important fish species and the possible profit from fisheries. The study includes subsidies in an ecosystem model of the North Sea and examines the possible effects of eliminating fishery subsidies.

Methodology/Principal Findings

Hindcast analysis between 1991 and 2003 indicates that subsidies reduced the profitability of the fishery even though gross revenue might have been high for specific fisheries sectors. Simulations seeking to maximise the total revenue between 2004 and 2010 suggest that this can be achieved by increasing the effort of Nephrops trawlers, beam trawlers, and the pelagic trawl-and-seine fleet, while reducing the effort of demersal trawlers. Simulations show that ecological stability can be realised by reducing the effort of the beam trawlers, Nephrops trawlers, pelagic- and demersal trawl-and-seine fleets. This analysis also shows that when subsidies are included, effort will always be higher for all fleets, because it effectively reduces the cost of fishing.

Conclusions/Significance

The study found that while removing subsidies might reduce the total catch and revenue, it increases the overall profitability of the fishery and the total biomass of commercially important species. For example, cod, haddock, herring and plaice biomass increased over the simulation when optimising for profit, and when optimising for ecological stability, the biomass for cod, plaice and sole also increased. When subsidies are eliminated, the study shows that rather than forcing those involved in the fishery into the red, fisheries become more profitable, despite a decrease in total revenue due to a loss of subsidies from the government.     

Range expansion of an exotic ungulate (Ammotragus lervia) in southern Spain: ecological and conservation concerns

Evidence of aoudad Ammotragus lervia expansion in the southeastern quarter of the Iberian Peninsula is provided based on recent field surveys. Aoudad has become common in a limited region of the southeast of Spain since its introduction as a game species in Sierra Espuña Natural Park in 1970. Its adaptability enabled it to colonise nearby areas in a short period. Apart from this source of expansion, the increasing number of aoudads in Spanish private game reserves provided other centres of dispersion. In addition, aoudads were introduced on La Palma Island (Canary Islands), becoming a serious threat to endemic flora. Of great conservation concern is the species' potential as a competitor against native ungulates inhabiting the peninsula. Surveys conducted in southern Spain documented rapid colonization of new areas and established viable populations, consisting of adult males and females and the unequivocal presence of nursery groups, in the provinces of Alicante, Almería, Granada and Murcia. Also, aoudads have spread throughout the north and centre of La Palma. There are two main conservational concerns: the necessity of conducting detailed and reliable surveys in all potential regions where the species might expand, and the urgent need of changing current game policies in order to establish reliable controls on big game reserves to prevent animals from escaping.     

The spatial pattern of Enchytraeidae (Oligochaeta)

Summary Spatial pattern of enchytraeids (Oligochaeta: Enchytraeidae) was studied in an experimental plot in an apple orchard near Bavorov, South Bohemia, Czechoslovakia. A total of 450 soil cores were taken in 1982, all individuals were determined (juveniles to genus, mature individuals to species) and counted. In total, 17 species of 4 genera were found. Both juveniles and mature individuals exhibited a distinctly aggregated spatial pattern. The distribution of the number of individuals in a sampling unit may be effectively fitted by the negative binomial distribution. The fit of Neyman type A distribution was considerably poorer. Comparing juveniles and mature individuals of the same genus using Lloyd's index of patchiness we found mature individuals to be slightly more aggregated than juveniles. Comparing the observed distribution of species number with that expected under the assumption of independence we may conclude that individuals appear in multispecies aggregation centres. These two conclusions support the hypothesis that aggregations are environmentally conditioned (abiotic factors and/or food availability) rather than caused by the type of reproduction.     

The environmental impact of salmonid cage culture on inland fisheries: present status and future trends

This paper briefly reviews the environmental impact of the cage culture of salmonids in fresh waters, and evaluates the effects of this fish farming practice on the growth, behaviour and diseases of inland fish populations, concentrating on relationships between rainbow trout cage culture and indigenous brown trout populations. Possible future developments in salmonid cage culture are also discussed and the implications of this development for inland fisheries evaluated. The paper argues that the development of models should enable improved prediction of eutrophication from cage culture, to the benefit of the fish farmer, inland fisheries and other freshwater users, but also identifies a clear need for research in other areas of possible conflict.     

The ecological energetics of Amoeba proteus (Protozoa)

The consumption, production and respiration of Amoeba proteus were measured in the laboratory for cells cultured over a range of Tetrahymena pyriformis concentrations (125–4 000 cells/0.5 ml) at 10, 15 and 20 °C. Differences were attributed to both temperature and prey availability. A series of generation energy budgets were constructed for amoebae grown under the above conditions. The biological efficiencies linking the parameters of the budget equation were calculated. Assimilation efficiencies ranged from 22–59% regardless of temperature. Net production efficiencies were high at 15 and 20 °C (65–82%) but low at 10 °C (11–49%). Gross production efficiencies were also higher at 15 and 20 °C (16–47%) than at 10 °C (4–29%). The ecological implications of this investigation are discussed.     

The role of crustacean fisheries and aquaculture in global food security: past, present and future

The 1996 World Food Summit defined food security as "Food security exists when all people, at all times, have physical and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy life". This paper looks at the status of production from both shrimp capture fisheries and shrimp aquaculture, as well as trade, in order to understand the contribution of the crustacean sector to overall fish production and thus to global food security. This paper also examines some sustainability issues that will potentially affect the contribution of the crustacean sector (particularly shrimp) to food security. These include sustainable shrimp capture fisheries, sustainable shrimp trade and sustainable shrimp aquaculture. The paper concludes that crustaceans are an important source of aquatic food protein. Production (as food and ornamental) and trade are extremely important for developing countries. It provides both economic development and empowerment in terms of contribution to GDP, consumption, employment, catch value and exports. The crustacean sector generates high value export products which enables producers to buy lower value products in the world market - thus a positive contribution to food security in both producing and exporting countries.     

Socio-economic and ecological impacts of global protected area expansion plans

Several global strategies for protected area (PA) expansion have been proposed to achieve the Convention on Biological Diversity''s Aichi target 11 as a means to stem biodiversity loss, as required by the Aichi target 12. However, habitat loss outside PAs will continue to affect habitats and species, and PAs may displace human activities into areas that might be even more important for species persistence. Here we measure the expected contribution of PA expansion strategies to Aichi target 12 by estimating the extent of suitable habitat available for all terrestrial mammals, with and without additional protection (the latter giving the counterfactual outcome), under different socio-economic scenarios and consequent land-use change to 2020. We found that expanding PAs to achieve representation targets for ecoregions under a Business-as-usual socio-economic scenario will result in a worse prognosis than doing nothing for more than 50% of the world''s terrestrial mammals. By contrast, targeting protection towards threatened species can increase the suitable habitat available to over 60% of terrestrial mammals. Even in the absence of additional protection, an alternative socio-economic scenario, adopting progressive changes in human consumption, leads to positive outcomes for mammals globally and to the largest improvements for wide-ranging species.     

The rivers Rhine and Meuse in The Netherlands: present state and signs of ecological recovery

The ecosystems of the rivers Rhine and Meuse have suffered drastic environmental changes, for example because of the regulation of the stream bed and the construction of weirs and dams. Furthermore, discharges of industrial and municipal waste water have caused the water quality of these rivers to deteriorate; this problem became acute in the sixties and seventies. Recently some chemical parameters of water quality have improved in the Rhine, and as a consequence some aquatic communities are showing signs of recovery after decades of severe degradation. This paper describes the present state of the aquatic communities in the Dutch part of the rivers Rhine and Meuse, using published observations on plankton, macrophytes, invertebrates, and fish. The sparse information on the food chain in these rivers is summarized. The main channels of the Rhine and Meuse are characterized by a dense plankton that develops rapidly in the nutrient-rich river waters. The stream beds, now dominated by wave-exposed sand and gravel, have a sparse fauna and flora. The river banks, mostly consolidated by blocks of stone, offer a substratum for numerous benthic organisms, particularly now that the water quality has improved. The floodplain waters and old river channels harbour a flora and fauna rich in species. The degree of water exchange with the river is crucial for the ecological development of the river and its backwaters. Today the freshwater tidal reaches of the rivers occupy a very restricted area, and only remnants of the previously abundant vegetation of rushes are found. Losses in the numbers of animal and plant species, notably those specific to rivers, are evident, but over the last 15 years several species have returned. Allochthonous species (exotics), including crustaceans and molluscs, have also settled in the Rhine and Meuse. Fish species characteristic of these rivers, such as river lamprey, sea trout, barbel, and flounder, have recently been observed in appreciable numbers. The Rhine Action Programme provides a framework for the large-scale rehabilitation of the Rhine. Experiments on re-stocking the Rhine with Atlantic salmon and on the ecological rehabilitation of floodplains are being carried out on the assumption that there will be a further reduction of the pollution load. A similar programme is required for the Meuse.