Human activities such as transport, trade and tourism are likely to influence the spatial distribution of non-native species and yet, Species Distribution Models (SDMs) that aim to predict the future ...broad scale distribution of invaders often rely on environmental (e.g. climatic) information only. This study investigates if and to what extent do human activities that directly or indirectly influence nature (hereafter the human footprint) affect the global distribution of invasive species in terrestrial, freshwater and marine ecosystems. We selected 72 species including terrestrial plants, terrestrial animals, freshwater and marine invasive species of concern in a focus area located in NW Europe (encompassing Great Britain, France, The Netherlands and Belgium). Species Distribution Models were calibrated with the global occurrence of species and a set of high-resolution (9×9 km) environmental (e.g. topography, climate, geology) layers and human footprint proxies (e.g. the human influence index, population density, road proximity). Our analyses suggest that the global occurrence of a wide range of invaders is primarily limited by climate. Temperature tolerance was the most important factor and explained on average 42% of species distribution. Nevertheless, factors related to the human footprint explained a substantial amount (23% on average) of species distributions. When global models were projected into the focus area, spatial predictions integrating the human footprint featured the highest cumulative risk scores close to transport networks (proxy for invasion pathways) and in habitats with a high human influence index (proxy for propagule pressure). We conclude that human related information-currently available in the form of easily accessible maps and databases-should be routinely implemented into predictive frameworks to inform upon policies to prevent and manage invasions. Otherwise we might be seriously underestimating the species and areas under highest risk of future invasions.
Plastic contamination is an increasing environmental problem in marine systems where it has spread globally to even the most remote habitats. Plastic pieces in smaller size scales, microplastics ...(particles <5 mm), have reached high densities (e.g., 100 000 items per m3) in waters and sediments, and are interacting with organisms and the environment in a variety of ways. Early investigations of freshwater systems suggest microplastic presence and interactions are equally as far reaching as are being observed in marine systems. Microplastics are being detected in freshwaters of Europe, North America, and Asia, and the first organismal studies are finding that freshwater fauna across a range of feeding guilds ingest microplastics.
Drawing from the marine literature and these initial freshwater studies, we review the issue of microplastics in freshwater systems to summarise current understanding, identify knowledge gaps and suggest future research priorities. Evidence suggests that freshwater systems may share similarities to marine systems in the types of forces that transport microplastics (e.g. surface currents); the prevalence of microplastics (e.g. numerically abundant and ubiquitous); the approaches used for detection, identification and quantification (e.g. density separation, filtration, sieving and infrared spectroscopy); and the potential impacts (e.g. physical damage to organisms that ingest them, chemical transfer of toxicants). Differences between freshwater and marine systems include the closer proximity to point sources in freshwaters, the typically smaller sizes of freshwater systems, and spatial and temporal differences in the mixing/transport of particles by physical forces. These differences between marine and freshwater systems may lead to differences in the type of microplastics present. For example, rivers may show a predictable pattern in microplastic characteristics (size, shape, relative abundance) based on waste sources (e.g. household vs. industrial) adjacent to the river, and distance downstream from a point source.
Given that the study of microplastics in freshwaters has only arisen in the last few years, we are still limited in our understanding of 1) their presence and distribution in the environment; 2) their transport pathways and factors that affect distributions; 3) methods for their accurate detection and quantification; 4) the extent and relevance of their impacts on aquatic life. We also do not know how microplastics might transfer from freshwater to terrestrial ecosystems, and we do not know if and how they may affect human health. This is concerning because human populations have a high dependency on freshwaters for drinking water and for food resources. Increasing the level of understanding in these areas is essential if we are to develop appropriate policy and management tools to address this emerging issue.
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•Microplastics are widely distributed in waters and sediments of rivers and lakes.•Human density and activities influence the types of microplastics present.•Physical forces (e.g., winds, currents) influence distributions.•Organismal impacts may be as wide ranging as those seen for marine taxa.•Future research might investigate whether microplastics will impact humans.
Inter-basin Water Transfers (IBWT) are recognized as one of the major pathways of freshwater invasion. They provide a direct link between previously isolated catchments and may modify the habitat ...conditions of the receiving waters such that they become more favourable for the establishment of invasive species. Combined, IBWT and invasive species will intensify the stress upon native species and ecosystems. Using the Severn and Thames Rivers –two of the largest river systems in Great Britain—as a case study, here we assess the potential influence of IBWT on the expansion of invasive species and thus their impact on biodiversity conservation. The Thames Valley is subject to extensive water abstraction, and an increasing population means that supplemented flow from the River Severn is being considered. Multi-scale Suitability Models, based on climate and water chemistry respectively, provided novel evidence that there is serious risk for further spread of invasive species in the focus area, particularly of the quagga mussel, a recent invader of the Thames River. Native freshwater mussels are particularly vulnerable to changing environmental conditions, and may suffer the decrease in alkalinity and increase in sedimentation associated with an IBWT from the lower Severn to the upper Thames. Regional models suggest considerable overlap between the areas suitable for three vulnerable native freshwater mussels and the expansion of invasive species that negatively impact upon the native mussels. This study illustrates the use of novel spatially-explicit techniques to help managers make informed decisions about the risks associated with introducing aquatic invasive species under different engineering scenarios. Such information may be especially important under new legislation (e.g. EU Invasive Species Regulation No 1143/2014) which increases the responsibility of water managers to contain and not transfer invasive species into new locations.
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•Inter-basin Water Transfers promote the expansion of invasive species.•Quagga mussels show the highest invasion potential in the Thames and Severn Rivers.•Landscape Analysis of Connectivity identified least-cost corridors between rivers.•Regional suitability models allowed to narrow down river-segments at risk.•Native mussels will particularly suffer river engineering operations.
A pioneering, quantitative study published in Journal of Animal Ecology in 1966 on freshwater mussel populations in the River Thames, UK, continues to be cited extensively as evidence of the major ...contribution that mussels make to benthic biomass and ecosystem functioning in global river ecosystems.
Ecological alteration, as well as declines in freshwater mussel populations elsewhere, suggest that changes to mussel populations in the River Thames are likely to have occurred over the half century since this study.
We resurveyed the site reported in Negus (1966) and quantified the changes in mussel population density, species composition, growth patterns and productivity.
We found large declines in population density for all unionid species. The duck mussel Anodonta anatina decreased to 1.1% of 1964 density. The painter's mussel Unio pictorum fell to 3.2% of 1964 density. The swollen river mussel Unio tumidus showed statistically nonsignificant declines. In contrast to 1964, in 2020 we found no living specimens of the depressed river mussel Pseudanodonta complanata (classified as Vulnerable by the IUCN Red List) but found new records of the invasive, nonnative zebra mussel Dreissena polymorpha and Asian clam Corbicula fluminea. Additionally, we found strong decreases in size‐at‐age for all species, which now grow to 65–90% of maximum lengths in 1964. As a result of reduced density and size, estimated annual biomass production fell to 7.5% of 1964 levels.
Since mussels can be important to ecosystem functioning, providing key regulating and provisioning services, the declines we found imply substantial degradation of freshwater ecosystem services in the River Thames, one of the UK's largest rivers. Our study also highlights the importance to conservationists and ecologists of updating and validating assumptions and data about wild populations, which in the present era of anthropogenic ecosystem alteration are undergoing significant and rapid changes. Regular population surveys of key species are essential to maintain an accurate picture of ecosystem health and to guide management.
Freshwater mussels in the River Thames have declined by over 90% and are growing more slowly, compared with a study published in Journal of Animal Ecology 56 years ago. Drivers may include changing nutrient levels and the arrival of invasive species. The loss of these ecosystem engineers could have crucial impacts.
1. Aquatic invasive species are a growing concern to environmental managers because of their diverse impacts on aquatic biodiversity and high eradication costs, necessitating effective management ...policies. In this study, we evaluate the ability of environmental and socioeconomic factors to predict the risk of invasion in Great Britain and Ireland of 12 potential aquatic invaders covering all major aquatic groups. Despite their potential to inform risk assessments, this is the first time socio-economic factors related to propagule pressure have been specifically integrated in distribution modelling. 2. Species distribution models (SDM, MaxEnt algorithm) were calibrated with a set of environmental factors (e.g. bioclimatic, geographical and geological) and integrated with socioeconomic (e.g. human influence index, population density, closeness to ports) predictors. 3. The inclusion of socio-economic factors in SDM did not affect accuracy scores (AUC already >0·90), but their effects were more pronounced in spatial predictions, resulting in up to a sixfold amplification of the area predicted suitable for each species. Despite the inclusion of potential surrogates of water chemistry (e.g. geology) and propagule pressure (e.g. population density), temperature-related variables were most important predictors of aquatic species' distributions. 4. According to SDM, the environmental suitability for a suite of invaders belonging to different taxonomic groups and regions of origin is greatest in east and south-east England and decreases towards the north and west. Multiple invasions in this region are of special concern, as species are known to modify their habitat facilitating subsequent invasions, thereby potentially exacerbating their impacts. 5. Major management regions to be prioritized in monitoring programmes include the Humber, Thames and Anglian River Basin Districts. Species of special concern include a mysid (Hemimysis anomala), a gammarid (Dikerogammarus villosus), a plant (Ludwigia grandiflora) and two crayfishes (Procambarus clarkii and P. fallax). 6. Synthesis and Applications. The inclusion of socio-economic factors in species distribution models has the potential to improve predictions of areas under a highest risk of multiple invasions and to help disentangle the complex interplay between biological invasions and global environmental and socio-economic processes. Such understanding is pivotal to prioritize limited resources for the optimum prevention and control of biological invasions.
Antarctica is experiencing significant ecological and environmental change, which may facilitate the establishment of non‐native marine species. Non‐native marine species will interact with other ...anthropogenic stressors affecting Antarctic ecosystems, such as climate change (warming, ocean acidification) and pollution, with irreversible ramifications for biodiversity and ecosystem services. We review current knowledge of non‐native marine species in the Antarctic region, the physical and physiological factors that resist establishment of non‐native marine species, changes to resistance under climate change, the role of legislation in limiting marine introductions, and the effect of increasing human activity on vectors and pathways of introduction. Evidence of non‐native marine species is limited: just four marine non‐native and one cryptogenic species that were likely introduced anthropogenically have been reported freely living in Antarctic or sub‐Antarctic waters, but no established populations have been reported; an additional six species have been observed in pathways to Antarctica that are potentially at risk of becoming invasive. We present estimates of the intensity of ship activity across fishing, tourism and research sectors: there may be approximately 180 vessels and 500+ voyages in Antarctic waters annually. However, these estimates are necessarily speculative because relevant data are scarce. To facilitate well‐informed policy and management, we make recommendations for future research into the likelihood of marine biological invasions in the Antarctic region.
Are there non‐native marine species in Antarctica? With over 500 visits from more than 180 vessels annually and rapidly changing environmental conditions, Antarctica appears to be increasingly vulnerable to impacts from non‐native marine species. We explore factors that influence the likelihood of non‐native marine species establishing in the Antarctic region, present new estimates for human activity, and make recommendations to researchers, environmental managers and policy makers.
Abstract
Plastic debris widely pollutes freshwaters. Abiotic and biotic degradation of plastics releases carbon-based substrates that are available for heterotrophic growth, but little is known about ...how these novel organic compounds influence microbial metabolism. Here we found leachate from plastic shopping bags was chemically distinct and more bioavailable than natural organic matter from 29 Scandinavian lakes. Consequently, plastic leachate increased bacterial biomass acquisition by 2.29-times when added at an environmentally-relevant concentration to lake surface waters. These results were not solely attributable to the amount of dissolved organic carbon provided by the leachate. Bacterial growth was 1.72-times more efficient with plastic leachate because the added carbon was more accessible than natural organic matter. These effects varied with both the availability of alternate, especially labile, carbon sources and bacterial diversity. Together, our results suggest that plastic pollution may stimulate aquatic food webs and highlight where pollution mitigation strategies could be most effective.
► Ensemble Species Distribution Models (SDM) are used to anticipate joint changes in native and invasive species distribution. ► SDM confirm that invasive species like Dreissena polymorpha may ...benefit from climate changes (15-20% expansion). ► Native Pseudanodonta complanata may face a notable contraction (14-36%), its overlap with the invader increasing by 25%. ► In contrast, both the native and invasive crayfishes showed a contraction in their potential range. ► SDM allowed identifying areas of shared bioclimatic suitability as well as potential refugia for native species conservation.
Climate change and invasive species are two major biodiversity threats expected to provoke extinctions of many species in the future. This study evaluates the joint threat posed by climate change and two invasive species: the zebra mussel (Dreissena polymorpha) and the signal crayfish (Pacifastacus leniusculus), on the distribution of two endangered freshwater species: the depressed river mussel (Pseudanodonta complanata) and the white-clawed crayfish (Austropotamobius pallipes), at the scale of Europe. We expected the native species to experience a gradual contraction over time in their geographic range size, while the invasive species would maintain or increase their spread; therefore, their overlap would increase, further threatening the conservation of the native species. To test these three hypotheses, ensemble species distribution models (SDMs) were calibrated with current distributions and projected onto present and 2050 future climatic scenarios. In agreement with our expectations, the 2050 scenarios suggested D. polymorpha may strongly benefit from climate changes (increase of 15–20% in range size), while the depressed river mussel would experience a considerable loss (14–36%), the overlap between both mussels increasing up to 24%. Although both crayfishes were predicted to be negatively affected by climate changes, the contraction was more severe for the invasive P. leniusculus (up to 32% decrease in range size). Moreover, the overlap between both crayfishes decreased by 13–16%, which may reduce the pressure upon the native A. pallipes. This study illustrates how SDMs can assist in management of endangered species over large spatial and temporal scales by identifying current and future areas of shared bioclimatic suitability and potential refugia.
Protected areas (PAs) are intended to provide native biodiversity and habitats with a refuge against the impacts of global change, particularly acting as natural filters against biological invasions. ...In practice, however, it is unknown how effective PAs will be in shielding native species from invasions under projected climate change. Here, we investigate the current and future potential distributions of 100 of the most invasive terrestrial, freshwater, and marine species in Europe. We use this information to evaluate the combined threat posed by climate change and invasions to existing PAs and the most susceptible species they shelter. We found that only a quarter of Europe's marine and terrestrial areas protected over the last 100 years have been colonized by any of the invaders investigated, despite offering climatically suitable conditions for invasion. In addition, hotspots of invasive species and the most susceptible native species to their establishment do not match at large continental scales. Furthermore, the predicted richness of invaders is 11%–18% significantly lower inside PAs than outside them. Invasive species are rare in long‐established national parks and nature reserves, which are actively protected and often located in remote and pristine regions with very low human density. In contrast, the richness of invasive species is high in the more recently designated Natura 2000 sites, which are subject to high human accessibility. This situation may change in the future, since our models anticipate important shifts in species ranges toward the north and east of Europe at unprecedented rates of 14–55 km/decade, depending on taxonomic group and scenario. This may seriously compromise the conservation of biodiversity and ecosystem services. This study is the first comprehensive assessment of the resistance that PAs provide against biological invasions and climate change on a continental scale and illustrates their strategic value in safeguarding native biodiversity.
Protected areas are championed as refugia for native biodiversity and habitats, but we do not know how effective they are in shielding native taxa from biological invasions under projected climate change.
Here, we found that only a quarter of Europe's marine and terrestrial areas protected over the last 100 years have been colonized by 100 of the worst terrestrial, freshwater, and marine invaders, with long‐established areas showing the lowest richness of invaders (A).
This situation may change in the future, as models anticipate a shift in species distribution toward the north and east of Europe in response to climate change (B).
The outcome of multiple invasions from a common origin may lead to facilitative interactions because the invaders have co‐evolved under similar environmental conditions. This outcome is often ...referred to as invasional meltdown, with a resultant increase in invasive species and a decline in native species richness and abundance. This study seeks to assess the full scope of the threat posed by a high‐risk group of 23 freshwater invaders originating from the Ponto–Caspian region (south‐east Europe) across Great Britain. Ponto–Caspian invaders constitute a group of special concern because they have recently caused a large‐scale invasion into western Europe. According to a literature review, 76% of reported interactions between Ponto–Caspian invaders are positive (mostly provision of food and commensalism) or neutral (habitat partitioning). Negative interactions (mostly predation) were rare, thus highlighting the ability of Ponto–Caspian invaders to coexist. At least 14 out of the 23 Ponto–Caspian organisms investigated are well‐established in the Rhine estuary and Dutch ports. Four of them (Hemimysis anomala, Dikerogammarus villosus, D. haemobaphes and Hypania invalida) have recently established in Great Britain. Regression models suggest the rest are under a critical risk of being transported, with four species predicted to have arrived already to Great Britain: Echinogammarus ischnus, Jaera istri, Limnomysis benedeni and D. bispinosus. According to species distribution models, the cumulative risk of invasion of multiple Ponto–Caspian species, thus invasional meltdown, is highest in the south‐east of England and decreases to the north and west. Great Britain might be on the brink of invasional meltdown, and as a consequence, confronting the problem of Ponto–Caspian invasive species is a vital element for national biosecurity. Synthesis and applications. The predictive models and maps developed in this study provide a means for an evidence‐based prioritization of species and habitats for the management of existing and future invasions of Ponto–Caspian species. This integrated approach can be easily applied to risk assess other groups of species and habitats.
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