Alien species: to remove or not to remove? That is the question

Invasive alien species (IAS) are universally known for being a controversial management issue. What makes IAS management a particularly thorny question is that although numerous studies document the negative effects of IAS, the potential benefits of IAS are generally underreported. This may result in wrong assessments on the real socio-economic and environmental impact of IAS. This study aimed to provide new insights to support the decision making of IAS management. In particular, the biased approach to IAS management seems to be a likely consequence of the lack of appropriate metrics able to assess the real IAS impact. A basic aspect of IAS management is to decide whether and when IAS removal is a suitable action. Specifically, this study supported the idea that IAS removal may be considered as a possible solution only after establishing a tipping point relying on economic, cultural and pragmatic evaluations. This analysis should include the identification of the ecosystem services damaged and provided by IAS, the attribution of an economic value to such ecosystem services, and when expressing the interaction between IAS and culture is not possible in monetary terms, then social values and cultural traditions should be incorporated in any management plan. Novel ecosystems are now a fact worldwide that should prompt to be realistic about the extent of efforts required for IAS removal. A significant step towards well-pondered decisions should consider that a change in host communities does not imply necessarily harm, and that the functional roles of a species matter more than its origins.     

Some Trends in Research on the Biosphere

The current state of research on the biosphere is analyzed. Various approaches to determining the boundaries and estimating the chemical composition of the biosphere are reviewed. The concept of ecological space as a structural unit of the biosphere is proposed. It is shown that cartography as a methodological approach to biospheric research may be used for describing the specificity of terrestrial ecosystems in terms of ecological standardization.     

Relations between Urban Bird and Plant Communities and Human Well‐Being and Connection to Nature

Abstract: By 2050, 70% of the world's population will live in urban areas. In many cases urbanization reduces the richness and abundance of native species. Living in highly modified environments with fewer opportunities to interact directly with a diversity of native species may adversely affect residents’ personal well‐being and emotional connection to nature. We assessed the personal well‐being, neighborhood well‐being (a measure of a person's satisfaction with their neighborhood), and level of connection to nature of over 1000 residents in 36 residential neighborhoods in southeastern Australia. We modeled these response variables as a function of natural features of each neighborhood (e.g., species richness and abundance of birds, density of plants, and amount of vegetation cover) and demographic characteristics of surveyed residents. Vegetation cover had the strongest positive relations with personal well‐being, whereas residents’ level of connection to nature was weakly related to variation in species richness and abundance of birds and density of plants. Demographic characteristics such as age and level of activity explained the greatest proportion of variance in well‐being and connection to nature. Nevertheless, when controlling for variation in demographic characteristics (examples were provided above), neighborhood well‐being was positively related to a range of natural features, including species richness and abundance of birds, and vegetation cover. Demographic characteristics and how well‐being was quantified strongly influenced our results, and we suggest demography and metrics of well‐being must be considered when attempting to determine relations between the urban environment and human well‐being.     

Isolating the impact of sediment toxicity in urban streams

Several factors can contribute to the ecological degradation of stream catchments following urbanization, but it is often difficult to separate their relative importance. We isolated the impact of polluted sediment on the condition of an urban stream in Melbourne, Australia, using two complementary approaches. Using a rapid bioassessment approach, indices of stream condition were calculated based on macroinvertebrate field surveys. Urban stream reaches supported impoverished macroinvertebrate communities, and contained potentially toxic concentrations of heavy metals and hydrocarbons. Using a field microcosm approach, a bioassay was carried out to assess sediment pollution effects on native macroinvertebrates. Sediment from urban sites substantially altered the microcosm macroinvertebrate community, most likely due to elevated heavy metal and hydrocarbon concentrations. Macroinvertebrate surveys combined with a bioassay approach based on field microcosms can help isolate the effect of stream pollutants in degraded ecosystems.     

Estimating High Latitude Carbon Fluxes With Inversions Of Atmospheric CO2

Atmospheric inversions have proven to be useful tools, showing for example the likely existence of a large terrestrial carbon sink in the northern mid-latitudes. However, as we go to smaller spatial scales the uncertainties in the inversions increase rapidly, and the task of finding the distribution of the sink between North America, Europe and Asia has been shown to be very difficult. The uncertainty in the fluxes due to network selection, transport model error and inversion set up tends to be too high for studying either net annual fluxes or interannual variability on spatial scales such as the North American Boreal or Eurasian Boreal regions. We discuss the path forward; to couple together the atmospheric inversions with process based terrestrial carbon models, creating carbon data assimilation systems. Such systems are being developed now and could prove to be very powerful. The multi-disciplinary nature of the data assimilation system requires information from flux towers, soil and above ground biomass inventories, remote sensed fields, atmospheric CO₂ concentrations and climate data as well as model development and will need a massive community effort if it will succeed.     

Stream Communities Along a Catchment Land-Use Gradient: Subsidy-Stress Responses to Pastoral Development

When native grassland catchments are converted to pasture, the main effects on stream physicochemistry are usually related to increased nutrient concentrations and fine-sediment input. We predicted that increasing nutrient concentrations would produce a subsidy-stress response (where several ecological metrics first increase and then decrease at higher concentrations) and that increasing sediment cover of the streambed would produce a linear decline in stream health. We predicted that the net effect of agricultural development, estimated as percentage pastoral land cover, would have a nonlinear subsidy-stress or threshold pattern. In our suite of 21 New Zealand streams, epilithic algal biomass and invertebrate density and biomass were higher in catchments with a higher proportion of pastoral land cover, responding mainly to increased nutrient concentration. Invertebrate species richness had a linear, negative relationship with fine-sediment cover but was unrelated to nutrients or pastoral land cover. In accord with our predictions, several invertebrate stream health metrics (Ephemeroptera–Plecoptera–Trichoptera density and richness, New Zealand Macroinvertebrate Community Index, and percent abundance of noninsect taxa) had nonlinear relationships with pastoral land cover and nutrients. Most invertebrate health metrics usually had linear negative relationships with fine-sediment cover. In this region, stream health, as indicated by macroinvertebrates, primarily followed a subsidy-stress pattern with increasing pastoral development; management of these streams should focus on limiting development beyond the point where negative effects are seen.     

A Simple Stream Monitoring Technique Based on Measurements of Semiconservative Propertiesof Water

Correlative relationships exist among conductivity, alkalinity, and hardness in streams due to natural geological and climatological controls, but the relationships among these three water-quality factors can be altered strongly by inputs of ion-rich wastewaters. The degree of alteration can be monitored conveniently by use of a simple chemical perturbation index, computed by subtracting the sum of rank pairwise correlations among the conductivity, alkalinity, and hardness (for observations on each of these variables, measured through time) from 3.0. The chemical perturbation index can be used to document or characterize spatiotemporal changes in stream water quality. This study explains the development of the index's concept and provides examples of its application in an extensive stream monitoring program used to assess ecological conditions in streams on the Department of Energy's Oak Ridge Reservation in east Tennessee, USA. The chemical perturbation index technique may be particularly useful in community-based stream monitoring programs because to its simplicity and low cost.     

Respective influence of habitat conditions and management regimes on prealpine calcareous grasslands

The calcareous grasslands of the south-western French Alps have been poorly studied, although they provide suitable habitat for rare plant species and communities. The separate and combined effects on calcareous grassland communities of habitat conditions (lithology, soil moisture) and management regimes (grazing intensity, cutting regime) were studied using constrained ordination techniques (canonical correspondence analysis with variance partitioning). Among the explanatory variables considered, the most important factor determining floristic composition was lithology, which explained 11.9% of floristic variability, followed by grazing intensity (6.0%). Additive effects of management and lithology explained 23.9% of floristic variability. Species niche amplitude was measured by conditional variances of samples along main ordination axes, in order to define adequate conservation management for the rarest short-lived species with narrow niche breadth on both habitat and management gradients.     

Non-Point-Source Impacts on Stream Nutrient Concentrations Along a Forest to Urban Gradient

We conducted statistical analyses of a 10-year record of stream nutrient and sediment concentrations for 17 streams in the greater Seattle region to determine the impact of urban non-point-source pollutants on stream water quality. These catchments are dominated by either urban (22–87%) or forest (6–73%) land cover, with no major nutrient point sources. Stream water phosphorus concentrations were moderately strongly (r²=0.58) correlated with catchment land-cover type, whereas nitrogen concentrations were weakly (r²=0.19) and nonsignificantly (at < 0.05) correlated with land cover. The most urban streams had, on average, 95% higher total phosphorus (TP) and 122% higher soluble reactive phosphorus (SRP) and 71% higher turbidity than the most forested streams. Nitrate (NO₃), ammonium (NH₄), and total suspended solids (TSS) concentrations did not vary significantly with land cover. These results suggest that urbanization markedly increased stream phosphorus concentrations and modestly increased nitrogen concentrations. However, nutrient concentrations in Seattle region urban streams are significantly less than those previously reported for agricultural area streams.