Impacts of invasive plants on resident animals across ecosystems, taxa, and feeding types: a global assessment

Parasitoid-host association in invaded communities

In nature, most parasitoids attack more than one host species, and nearly all hosts are attacked by several species of parasitoids. This opens many potential opportunities for interactions of invasive species with native parasitoid-host association networks in invaded communities. Despite this, few studies have examined the direct and indirect impacts of biological invasion on parasitoid-host associations. This review examines what is known of these relationships from the most recent literature and suggests future research priorities. We conclude that parasitoid-host association networks in invaded communities are complex, dynamic, and subject to trophic intrusions from invasive plants, herbivores, plant pathogens, parasitoids, and hyperparasitoids. Future studies should take a holistic systems approach to understanding the impact of biological invasion and its consequences in shaping community structure through altering existing native, coevolved parasitoid-host association networks.

An Invasion Risk Assessment of Alien Woody Species in Potential National Park Sites in Xinjiang, China, Under Climate Change

The invasion of alien woody species may have broad ecological, economic, and health impacts on ecosystems and biodiversity under climate change. Previous studies showed that disrupting the biodiversity conservation mechanisms in protected areas can seriously threaten natural ecosystems and the protection of rare and endangered species in such protected areas. However, there is currently no standard for evaluating the invasion risk of woody plants under climate change when establishing national parks in China. Therefore, we used a species distribution model to evaluate the invasion risk of 250 invasive alien woody species in potential national park sites in Xinjiang under climate change. The results indicated that the probability of forest invasion in the potential Altai Kanas National Park was determined to be significantly higher than that of the average level in Xinjiang nature reserves, both under current and future climate conditions. At the same time, the probability of invasive woody species invading coniferous forests, broad-leaved forests, and grassland ecosystems is higher in the Altai Kanas and Tianshan potential national parks. We found that Acer negundo, Robinia pseudoacacia, and Amorpha fruticose in potential parks in Xinjiang have higher invasion potential and thus require heightened vigilance to stop their spread. This study contributes to the monitoring and management of national parks and provides an actionable foundation for protecting ecosystem functions and minimizing the potential risk of invasive alien species under climate change.

Consequences of Spiraea tomentosa invasion in Uropodina mite (Acari: Mesostigmata) communities in wet meadows

Vegetation cover has been consistently reported to be a factor influencing soil biota. Massive spreading of invasive plants may transform native plant communities, changing the quality of habitats as a result of modification of soil properties, most often having a directional effect on soil microorganisms and soil fauna. One of the most numerous microarthropods in the litter and soil is Acari. It has been shown that invasive plants usually have a negative effect on mites. We hypothesized that invasive Spiraea tomentosa affects the structure of the Uropodina community and that the abundance and species richness of Uropodina are lower in stands monodominated by S. tomentosa than in wet meadows free of this alien species. The research was carried out in wet meadows, where permanent plots were established in an invaded and uninvaded area of each meadow, soil samples were collected, soil moisture was determined and the mites were extracted. We found that Uropodina mite communities differed in the abundance of individual species but that the abundance and richness of species in their communities were similar. S. tomentosa invasion led primarily to changes in the quality of Uropodina communities, due to an increase in the shares of species from forest and hygrophilous habitats. Our results suggest that alien plant invasion does not always induce directional changes in mite assemblages, and conclude that the impact of an alien species on Uropodina may cause significant changes in the abundance and richness of individual species without causing significant changes in the abundance and diversity of their community.

Ecological and anthropogenic factors influencing the Summer habitat use of Bos gaurus and its conservation threats in Chitwan National Park, Nepal

Background

Gaur (Bos gaurus) is listed as a vulnerable species in the IUCN Red List of threatened species due to the rapid population decline caused by human pressures in their habitats. To develop successful conservation plans, it is essential to understand the relationship between Gaur and their habitats. This study aimed to investigate the factors influencing Gaur habitat use and identify and rank conservation threats in Chitwan National Park, Nepal.

Methods

Using line transect surveys, we recorded Gaur's presence via direct sightings and indirect signs (dung, footprints, horns) over an area of 176 km2 in July and August 2022. We used binary logistic regression models to determine the collected ecological and anthropogenic factors influencing the occurrence of Gaur and the relative whole-site threat ranking method to rank conservation threats.

Results

The results revealed that the probability of Gaur occurrence increases with moderate to high canopy cover, riverine and Shorea robusta dominated forests, and nearest distance to road/path/firelines, while decreasing with the presence of predators. Uncontrolled fire, invasive species, human disturbances, and climate change were ranked as the most prevailing threats to Gaur in our study area. Conservation managers should implement effective habitat management interventions, such as construction of waterhole, firelines maintenance, grassland management, and control of invasive species in the potential habitats, to safeguard and maintain the sustainability of Gaur populations and associated herbivores. Future studies should consider larger geographical settings and multiple seasons, and habitat suitability assessments should be conducted to determine current and future suitable habitat refugia for Gaur and other threatened wildlife species at the landscape level.

Rural Households' Demand Status for Mitigation of Prosopis juliflora (Sw.) DC Invasion and Its Determinant Factors in Ethiopia: Empirical Evidence from Afar National Regional State

Ethiopia is among the world's poorest nations, and its economy is growing extremely slowly; thus, the government's budget to manage environmental amenities is not always sufficient. Thus, for the provision of environmental management services such as the eradication of Prosopis juliflora, the participation of local households and other stakeholders is crucial. This study is therefore initiated with the objective of assessing rural households' demands for mitigating Prosopis juliflora invasion in the Afar Region of Ethiopia. A multistage sampling technique was employed to obtain the 313 sample rural households that were used in the analysis, and those sample households were selected randomly and independently from the Amibara and Awash Fentale districts of Afar National Regional State, Ethiopia. In doing this, a seemingly unrelated bivariate probit model was used to determine factors affecting rural households' demands for mitigating Prosopis juliflora invasion. Consequently, as per the inferential statistical results, there was a significant mean/percentage difference between willing and nonwilling households for the hypothesized variables, except for some variables such as farm experience; years lived in the area, distance from the market, and dependency ratio. Furthermore, the seemingly unrelated bivariate probit model result indicates that sex, family size, tenure security, livestock holding, frequency of extension contact, and years lived in the area were important factors influencing the willingness to participate in Prosopis juliflora management practices positively, whereas age, off-farm/nonincome, and bid value affected willingness to pay negatively and significantly. Hence, to improve the participation level of households, policymakers should target these variables.

What Is the Impact of Accidentally Transporting Terrestrial Alien Species? A New Life Cycle Impact Assessment Model

Alien species form one of the main threats to global biodiversity. Although Life Cycle Assessment attempts to holistically assess environmental impacts of products and services across value chains, ecological impacts of the introduction of alien species are so far not assessed in Life Cycle Impact Assessment. Here, we developed country-to-country-specific characterization factors, expressed as the time-integrated potentially disappeared fraction (PDF; regional and global) of native terrestrial species due to alien species introductions per unit of goods transported [kg] between two countries. The characterization factors were generated by analyzing global data on first records of alien species, native species distributions, and their threat status, as well as bilateral trade partnerships from 1870-2019. The resulting characterization factors vary over several orders of magnitude, indicating that impact greatly varies per transportation route and trading partner. We showcase the applicability and relevance of the characterization factors for transporting 1 metric ton of freight to France from China, South Africa, and Madagascar. The results suggest that the introduction of alien species can be more damaging for terrestrial biodiversity as climate change impacts during the international transport of commodities.

A synthesis of anthropogenic stress effects on emergence-mediated aquatic-terrestrial linkages and riparian food webs

Anthropogenic stress alters the linkage between aquatic and terrestrial ecosystems in various ways. Here, we review the contemporary literature on how alterations in aquatic systems through environmental pollution, invasive species and hydromorphological changes carry-over to terrestrial ecosystems and the food webs therein. We consider both the aquatic insect emergence and flooding as pathways through which stressors can propagate from the aquatic to the terrestrial system. We specifically synthesize and contextualize results on the roles of pollutants in the emergence pathway and their top-down consequences. Our review revealed that the emergence and flooding pathway are only considered in isolation and that the overall effects of invasive species or pollutants on food webs at the water-land interface require further attention. While very few recent studies looked at invasive species, a larger number of studies focused on metal transfer compared to pesticides, pharmaceuticals or PCBs, and multiple stress studies up to now left aquatic-terrestrial linkages unconsidered. Recent research on pollutants and emergence used aquatic-terrestrial mesocosms to elucidate the effects of aquatic stressors such as the mosquito control agent Bti, metals or pesticides to understand the effects on riparian spiders. Quality parameters, such as the structural and functional composition of emergent insect communities, the fatty acid profiles, yet also the composition of pollutants transferred to land prove to be important for the effects on riparian spiders. Process-based models including quality of emergence are useful to predict the resulting top-down directed food web effects in the terrestrial recipient ecosystem. In conclusion, we present and recommend a combination of empirical and modelling approaches in order to understand the complexity of aquatic-terrestrial stressor propagation and its spatial and temporal variation.

Opposite effects of nutrient enrichment and an invasive snail on the growth of invasive and native macrophytes

Many ecosystems are now co-invaded by alien plant and herbivore species. The evolutionary naivety of native plants to alien herbivores can make the plants more susceptible to the detrimental effects of herbivory than co-occurring invasive plants, in accordance with the apparent competition hypothesis. Moreover, the invasional meltdown hypothesis predicts that in multiply invaded ecosystems, invasive species can facilitate each other's impacts on native communities. Although there is growing empirical support for these hypotheses, facilitative interactions between invasive plants and herbivores remain underexplored in aquatic ecosystems. Many freshwater ecosystems are co-invaded by aquatic macrophytes and mollusks and simultaneously experience nutrient enrichment. However, the interactive effects of these ecological processes on native macrophyte communities remain an underexplored area. To test these effects, we performed a freshwater mesocosm experiment in which we grew a synthetic native community of three macrophyte species under two levels of invasion by an alien macrophyte Myriophyllum aquaticum (invasion vs. no invasion) and fully crossed with two levels of nutrient enrichment (enrichment vs. no enrichment) and herbivory by an invasive snail Pomacea canaliculata (herbivory vs. no herbivory). In line with the invasional meltdown and apparent competition hypotheses, we found that the proportional aboveground biomass yield of the invasive macrophyte, relative to that of the native macrophyte community, was significantly greater in the presence of the invasive herbivore. Evidence of a reciprocal facilitative effect of the invasive macrophyte on the invasive herbivore is provided by results showing that the herbivore produced greater egg biomass in the presence versus in the absence of M. aquaticum. However, nutrient enrichment reduced the mean proportional aboveground biomass yield of the invasive macrophyte. Our results suggested that herbivory by invader P. canaliculata may enhance the invasiveness of M. aquaticum. However, nutrient enrichment of habitats that already harbor M. aquaticum may slow down the invasive spread of the macrophyte. Broadly, our study underscores the significance of considering several factors and their interactions when assessing the impact of invasive species, especially considering that many habitats experience co-invasion by plants and herbivores and simultaneously undergo various other disturbances, including nutrient enrichment.

The native reed-specific bird, reed parrotbill, has been detected in exotic smooth cordgrass

After the smooth cordgrass Spartina alterniflora invaded coastal China, native birds started avoiding the green desert, and bird diversity declined. After many years, a few passerine birds began to enter and use smooth cordgrass, but only birds with a nonspecialised habitat. In this study, we found that a native reed-specific bird, the parrotbill Calamornis heudei, flocked and sang in a smooth cordgrass habitat throughout the overwintering period near Sheyang Port in Yancheng, Jiangsu Province. This observation suggests that native obligate birds may be forced to adapt to exotic smooth cordgrass habitats after long-term coexistence, which would, obviously, affect the distribution, feeding and reproduction of birds. The concern is that this could be an ecological trap, leading to unknown consequences. More research is required to examine the process occurring along the Chinese coast.

Fallopia japonica and Impatiens glandulifera are colonized by species-poor root-associated fungal communities but have minor impacts on soil properties in riparian habitats

Fallopia japonica and Impatiens glandulifera are major plant invaders on a global scale that often become dominant in riparian areas. However, little is known about how these species affect interactions in soil–plant systems. The aim of this study was to investigate the impact of both species on abiotic and biotic soil properties, with a special focus on fungi. We investigated eight sites along small streams invaded by F. japonica and I. glandulifera, respectively, and compared each with nearby sites dominated by the native species Urtica dioica. Three different types of samples were collected: bulk soil, rhizosphere soil and roots from invasive and native stands at each site. Bulk soil samples were analysed for soil physicochemical, microbial properties (soil microbial respiration and ergosterol) and soil arthropod abundance (Acari and Collembola). Soil respiration was also evaluated in rhizosphere samples. The fungal community composition of both bulk soil and roots were analysed using a metabarcoding approach. Soil physicochemical properties as well as soil microbial activity, fungal biomass and soil fungal operational unit taxonomic unit (OTU) richness did not differ between invaded and native riparian habitats, indicating only minor belowground impacts of the two invasive plant species. Soil microbial activity, fungal biomass and soil fungal OTU richness were rather related to the soil physicochemical properties. In contrast, Acari abundance decreased by 68% in the presence of F. japonica, while Collembola abundance increased by 11% in I. glandulifera sites. Moreover, root-associated fungal communities differed between the invasive and native plants. In F. japonica roots, fungal OTU richness of all investigated ecological groups (mycorrhiza, endophytes, parasites, saprobes) were lower compared to U. dioica. However, in I. glandulifera roots only the OTU richness of mycorrhiza and saprobic fungi was lower. Overall, our findings show that F. japonica and I. glandulifera can influence the abundance of soil arthropods and are characterized by lower OTU richness of root-associated fungi.

Climate change adaptation measures conflicted with the recreational demands on city forests during COVID-19 pandemic

Recurrent droughts in southwest Germany threaten the city and community-owned forests (CCF). At the same time, the COVID-19 pandemic has increased the demand for recreation in CCF of southwest Germany. We interviewed stakeholders from different interest groups to critically analyze their opinion on how the high recreation demand on CCF due to the pandemic can be ensured along with implementing climate change adaptation measures in CCF in Karlsruhe, Germany. We found that stakeholders particularly highlighted the importance of the recreational function of the CCF during the pandemic. However, the behavior of visitors was criticized by the stakeholders. We showed that demand for the recreational use of CCF conflicted with climate change adaptation measures such as sanitary and forest restoration actions, creating a dilemma among stakeholders. Therefore, enhancing citizens' knowledge of forests' recreation functions and the need for climate change adaptation through communication and education should be prioritized.

Effects of the Density of Invasive Lantana camara Plants on the Biodiversity of Large and Small Mammals in the Groenkloof Nature Reserve (GNR) in South Africa

Multi-scale approaches have been used to determine scales at which mammal species are responding to habitat destruction due to invasion, but the impacts of weeds on mammals have not been extensively studied, especially in Africa. Inside the Groenkloof Nature Reserve (GNR), we assessed how mammals are affected by an invasive weed Lantana camara. A series of models were applied to determine the differences in species abundance as well as richness, separated for large and small mammals. When diversity indices were used, an Analysis of Variance (ANOVA) revealed no statistically significant difference between treatments (F₅ = 0.233, p = 0.945) for large mammals. The results of a Generalised Linear Mixed Model (GLMM) showed that vegetation type (Wald χ²₂ = 120.156; p < 0.01) and foraging guilds (Wald χ²₃ = 76.771; p < 0.01) were significant predictors of large mammal species richness. However, for small mammals, the results of a GLMM showed that only treatment type (Wald χ²₅ = 10.62; p = 0.050) was a significant predictor of the number of small mammals trapped. In addition, the ANOVA revealed statistically significant differences in species diversity between treatments (F₅ = 0.934; p < 0.001) and by season (F₁ = 9.122 p = 0.003) for small mammals. The presence of L. camara coupled with other predictors was associated with differences in large mammal abundances and diversity, and differences in how these large mammals were distributed across the landscape. Furthermore, the highest species diversity was found in the spring for small mammals. Therefore, for all the mammals studied, the presence of L. camara negatively affected species abundance, richness, and diversity, as well as how these species were distributed across the invaded and cleared areas.

Invasion by an ecosystem engineer changes biotic interactions between native and non-native taxa

Earth systems are nearing a global tipping point, beyond which the dynamics of biological communities will become unstable. One major driver of instability is species invasion, especially by organisms that act as "ecosystem engineers" through their modification of abiotic and biotic factors. To understand how native organisms respond to modified habitat, it is essential to examine biological communities within invaded and non-invaded habitat, identifying compositional shifts in native and non-native taxa as well as measuring how modification by ecosystem engineers has affected interactions among community members. Using dietary metabarcoding, our study examines the response of a native Hawaiian generalist predator (Araneae: Pagiopalus spp.) to habitat modification by comparing biotic interactions across metapopulations of spiders collected in native forest and sites invaded by kāhili ginger. Our study shows that, although there are shared components of the dietary community, spiders in invaded habitat are eating a less consistent and more diverse diet consisting of more non-native arthropods which are rarely or entirely undetected in spiders collected from native forest. Additionally, the frequency of novel interactions with parasites was significantly higher in invaded sites, reflected by the frequency and diversity of non-native Hymenoptera parasites and entomopathogenic fungi. The study highlights the role of habitat modification driven by an invasive plant in altering community structure and biotic interactions, threatening the stability of the ecosystem through significant changes to the biotic community.

Linear scaling – negative effects of invasive Spiraea tomentosa (Rosaceae) on wetland plants and pollinator communities

Invasive plants directly and indirectly disrupt the ecosystem functioning, of which indirect effects, for example, through trophic cascades, are particularly difficult to predict. It is frequently assumed that the impact of an invading species on the ecosystem is proportional (linearly related) to its density or abundance in a habitat, but this assumption has rarely been tested. We hypothesised that abundance and richness of plants and potentially pollinators of wet meadows change as a result of invasion of steeplebush Spiraea tomentosa and that these changes are proportional to the density of the shrub. We selected 27 sites amongst wet meadows habitats invaded by S. tomentosa with coverage ranging from 0% to 100% and examined the diversity of plants, as well as the abundance and diversity of flower visitors (bees, butterflies with moths and flies). Our results showed that the richness of plants, as well as the richness and number of individuals of flower visitors, decrease significantly and linearly with an increase of the S. tomentosa cover. This finding supports the hypothesis that the impact of an invasive species can be proportional to their population density, especially if this species is limiting the available resources without supplying others. Our study is the first to show such an unequivocal negative, linear effect of an invasive shrub on the abundance and richness of potential pollinators. It proves that the negative impact of S. tomentosa on the wetland ecosystem appears even with a minor coverage of the invader, which should be taken into account when planning activities aimed at controlling the population of this transformer species. The simultaneously detected linear dependence allows us to assume that the benefits of controlling secondary populations of the shrub can be proportional to the incurred effort.

A mini-review on the impact of common gorse in its introduced ranges

It is indisputable that invasive plant species strongly impact the ecosystems they invade. Many of such impacts can be negative and threaten the local species through competition, environmental change, or habitat loss. However, introduced plants may also have positive roles in the ecosystems they invade. This review extracted information from reports on common gorse (Ulex europaeus), one of the top 100 invasive plants on the earth, including its detrimental effects and potential beneficial roles in invaded ecosystems. The reduction of native fauna and flora are the main harmful effects of common gorse identified by the literature review. Soil impoverishment and fire hazards are other negative impacts reported for common gorse that could affect agricultural systems and local economies. Despite the negative impacts, reports of positive ecological services provided by common gorse also exist, e.g., as a nursery plant or habitat for endangered native animals. We also reviewed the known human uses of this plant that could support management strategies through harvest and benefit the local communities, including its use as biofuel, raw matter for xylan extraction, medicine, and food. Finally, our review identified the gaps in the literature regarding the understanding of the beneficial role of common gorse on native ecosystems and potential human uses, especially in the tropics.

Tangled in a Web: Management Type and Vegetation Shape the Occurrence of Web-Building Spiders in Protected Areas

Land management of parks and vegetation complexity can affect arthropod diversity and subsequently alter trophic interactions between predators and their prey. In this study, we examined spiders in five parks with varying management histories and intensities to determine whether certain spider species were associated with particular plants. We also determined whether web architecture influenced spider occurrence. Our results showed that humpbacked orb-weavers (Eustala anastera) were associated with an invasive plant, Chinese privet (Ligustrum sinense). This study revealed how invasive plants can potentially influence certain spider communities, as evidenced by this native spider species only occurring on invasive plants. Knowing more about spider populations-including species makeup and plants they populate-will give insights into how spider populations are dealing with various ecosystem changes. While we did not assess the effect of invasive plants on the behavior of spiders, it is possible that invasive species may not always be harmful to ecosystems; in the case of spiders, invasive plants may serve as a useful environment to live in. More studies are needed to ascertain whether invasive plants can have adverse effects on spider ecology in the long term.

Effect of freshwater on plant species diversity and interspecific associations in coastal wetlands invaded by Spartina alterniflora

Plant invasions in coastal wetlands lead to the degradation of native vegetation; the introduction of freshwater in coastal wetlands would prevent the spread of invasive plants and facilitate the restoration of native vegetation. In this study, we evaluated the effects of freshwater on plant communities in the coastal wetlands of Yancheng, China, invaded by Spartina alterniflora Loisel. Two field investigations were conducted in 2008 and 2018 before and after the introduction of freshwater (started in 2011). The characteristics of plant communities were subjected to hierarchical cluster analysis and compared using several diversity indices. In addition, differences in habitat community composition and interspecific relationships of dominant species were analyzed. The results showed that S. alterniflora reduced the overall species diversity in the region. Plant species diversity increased after freshwater was introduced into the study site when compared to the areas without freshwater introduction. The introduction of freshwater caused a shift often changes in the interspecific relationships between Suaeda salsa (L.) Pall. and other species. The intensified invasion of S. alterniflora changed the interspecific relationship of native halophytes from negative to positive. Although freshwater effectively inhibited further invasion of S. alterniflora, it also increased the risk of expansion of the glycophytes in the community. The results of this study highlight the need for early intervention for restoration of coastal wetlands, preservation of biodiversity, and management of plant resources.

Distribution and pathways of introduction of invasive alien plant species in Romania

Biological invasions are one of the main drivers of modern human-induced species losses. Research on the distribution of alien species and their pathways of introduction is essential for understanding and tackling the invasion process. A comprehensive overview on invasive alien plant (IAP) species in Romania is lacking. With this paper, we aim to contribute to filling this gap and to provide a visualization of national patterns regarding plant species invasions, geographical origins and pathways of introductions. Based on plant species occurrence records in the published literature and herbaria we compiled a national database of 102 invasive and potentially invasive alien plant species. We georeferenced 42776 IAP species occurrences and performed an analysis of their spatial patterns. The spatial analyses revealed a biased sampling, with clear hotspots of increased sampling efforts around urban areas. We used chord diagrams to visualize the pathway of introduction and geographical origins of the IAP species, which revealed that species in Romania originate mainly in North and Central America, while the dominant pathway of plant introduction was horticulture. Our results provide an important baseline in drafting management and action plans, as invasive alien plant species represent a priority for the European Union through the Biodiversity Strategy for 2030, and a good starting point for various analyses as the database is further developed and regularly updated.

An impact assessment of alien invasive plants in South Africa generally dispersed by native avian species

Invasive alien plant species have been identified as a major threat to biodiversity and the relationship with native avian dispersers may increase their invasion potential. The impact of invasive plant species needs to be quantified using comparable assessment tools across different habitats and species to allocate limited resources to high-priority species. Here, we used the Generic Impact Scoring System (GISS) to assess the impacts of 16 fleshy-fruited alien invasive plant species in South Africa generally dispersed by native avian species. The results showed that fleshy-fruited invasive species have both environmental and socio-economic impacts. The cumulated impact scores for lantana (Lantana camara) and the tree of heaven (Ailanthus altissima) were the highest, with scores of 42 and 32, respectively. Some species, such as white mulberry (Morus alba), camphor tree (Cinnamomum camphora), American bramble (Rubus cuneifolius) and Brazilian pepper tree (Schinus terebinthifolius), had low overall impact scores of 8, 18, 14 and 16, respectively, but scored the maximum impact of 5 for certain mechanisms. Environmental impacts of fleshy-fruited invasive plant species had a high impact magnitude through effects on the ecosystem and vegetation. Socio-economic impacts were mainly through effects on forest production, agriculture and human health. Species with large crop sizes, small seeds and fruit sizes had higher environmental and socio-economic impact magnitude. The information generated in this study is important for guiding resource allocation and preventing the uncontrolled introduction of invasive species in South Africa. The impact of the fleshy-fruited invasive species transcended sectors and, therefore, effective management of invasive species will require the collaboration of multiple and inter-sectoral stakeholders in South Africa.

Gunnera tinctoria invasions increase, not decrease, earthworm abundance and diversity

Invasive plants often modify soil biotic communities through changes in soil physicochemical characteristics or the amount and/or quality of litter inputs. We assessed the impacts of Gunnera tinctoria invasions on soil and the earthworm community, on Achill Island, Co. Mayo, Ireland. We compared replicated (n = 5) areas invaded by G. tinctoria with uninvaded semi-natural grasslands, as well as with areas subjected to mechanical removal or herbicide treatment. Modifications in physiochemical properties included lower soil temperatures and higher soil pH during the summer in invaded areas, yet little effect on C and N stocks, or soil moisture. Marked differences in litter were observed, however, with invaded areas having c. 20-fold higher (above-ground) litter input than uninvaded ones, as well as lower C:N ratio (17 vs. 29). This was associated with a significantly higher overall abundance and biomass of earthworms in invaded plots (375 individuals m–2, 115 g biomass m–2), compared to the uninvaded control (130 individuals m–2, 45 g biomass m–2), with removal treatments having intermediate values. Earthworm communities comprised 10 species, typical for Irish grasslands, dominated by the common endogeic species Allolobophora chlorotica, Aporrectodea caliginosa and Aporrectodea rosea. Both earthworm species richness and Shannon diversity were significantly higher in invaded areas, but only in spring samples. Based on this new information, plant invaders may increase the abundance and diversity of earthworms, mainly due to much larger litter inputs, increased soil pH and possibly lower soil temperatures in the summer.typical of Irish grasslands

Who can pass the urban filter? A multi-taxon approach to disentangle pollinator trait-environmental relationships

Cities are considered important refuges for insect pollinators. This has been shown repeatedly for wild bees, but may also be true for other diverse taxa such as hoverflies. However, our understanding of how urban environmental filters shape pollinator species communities and their traits is still limited. Here, we used wild bee and hoverfly species, communities and their functional traits to illustrate how environmental filters on the landscape and local scale shape urban species pools. The multi-taxon approach revealed that environmental filtering predominantly occurred at the landscape scale as urbanisation and 3D connectivity significantly structured the taxonomic and functional composition of wild bee (sociality, nesting, diet, body size) and hoverfly (larval food type, migratory status) communities. We identified urban winners and losers attributed to taxon-specific responses to urban filters. Our results suggest that insect pollinator conservation needs to take place primarily at the landscape level while considering species traits, especially by increasing habitat connectivity.

A Consideration of Wildlife in the Benefit-Costs of Hydraulic Fracturing: Expanding to an E3 Analysis

High-volume hydraulic fracturing (“fracking”) for natural gas in the Marcellus Shale (underlying about 24 mil ha in New York, Pennsylvania, Maryland, West Virginia, Ohio, and Virginia) has become a politically charged issue, primarily because of concerns about drinking water safety and human health. This paper examines fracking in the Marcellus region, and the tradeoffs between the energy and economic potential of natural gas extraction and the environmental impacts on wildlife. Therefore, we introduce a new E3 analysis that combines the costs and benefits as regards energy, economics, and the environment. The Marcellus Shale has the most proven reserves of natural gas of any basin in the United States, at 129 trillion cubic feet. Income from natural gas development comes primarily from direct and indirect jobs, and induced jobs (those created when direct workers spend their earnings in a community), taxes and fees, and royalty and lease payments to rights holders. Fracking, however, has detrimental effects on wildlife and wildlife habitats. Terrestrial habitat effects are primarily due to landscape fragmentation from the clearing of land for pipeline and well pad development, which often removes mature forest and creates open corridors and edge habitats. An increase in forest edge and open corridors is associated with shifts in the bird community, as generalist species that do well around people increase in abundance, while forest specialists decline. Invasive plants associated with disturbance further degrade forest habitats. Aquatic habitats are also affected, both directly and indirectly. Hydraulic fracturing requires up to 20 mil L of water per well fracture, most of which comes from surface water sources in the Marcellus region. The removal of water, especially in smaller headwaters, can increase sedimentation, alter water temperature and change its chemistry, resulting in reductions in aquatic biodiversity. Given the reality that hydraulic fracturing will continue, there is a need to develop practices that best minimize negative impacts on terrestrial and aquatic habitats, as well as policies and the resolve to enforce these practices. To achieve a more sustainable balance between economic, energy, and environmental costs and benefits, we recommend that industry, scientists, non-governmental organizations, mineral rights holders, landowners, and regulators work together to develop a set of best management practices that represent the best knowledge available.

Impact of Invasive Weeds on the Diversity and Dissimilarity of Bird Communities in Forested Areas

Caucasian hogweeds, mainly the Sosnowsky’s hogweed Heracleum sosnowskyi and the giant hogweed Heracleum mantegazzianum, create one of the most problematic plant invasions in the world. Due to their large size (weeds reaching 4–5 meters in height), they seem to be herbaceous plants that can threaten birds living in forest stands. This research quantified the structure and diversity of the forest birds’ community in forests with varying areas of invasive hogweeds located in south-eastern Poland. Changes in the accompanying non-forest birds’ community were also assessed. The study addressed the following questions: 1. How does the invaded area correlate with the abundance of forest birds? 2. How do communities and species respond to invaded vegetation? 3. How do the invading plants affect the various types of diversity of forest and non-forest birds? It turned out that both surveyed bird communities had a lower alpha diversity in invaded sites. Only forest birds, not able to change their location easily, formed a unique community (i.e., had a higher beta diversity) near invaders. Forest birds showed unchanged functional diversity based on the relative bird abundance and their connection, or lack of it, with the forest development phases. The effect of hogweeds on the abundance of forest birds was more negative in severely invaded areas with anthropogenic habitats. Non-forest birds showed higher species loss near the invasion, constant beta diversity and decreased functional diversity. This study is important as the forest is a climax community in the temperate zone, and unused open areas become spontaneously overgrown with young forests. Weeds disseminating after crop abandonment can highly and commonly affect forest and non-forest bird communities co-occurring in this type of overgrowing area.

Invasive Plants Differentially Impact Forest Invertebrates, Providing Taxon-Specific Benefits by Enhancing Structural Complexity

Exotic plant species often negatively affect native herbivores due to the lack of palatability of the invading plant. Although often unsuitable as food, certain invasive species may provide non-nutritional ecological benefits through increased habitat structural complexity. To understand the potential for common invasive forest plant species of the eastern United States to benefit invertebrate communities, we examined the functional and taxonomic community composition of forest insects and spiders in long-term monitoring plots that contained invasive plant species. The extent of invasive plant species ground cover significantly altered spider community composition as categorized by hunting guild. Areas with higher invasive herbaceous and grass cover contained a higher abundance of space web-weaving and hunting spiders, respectively. Spider species richness and total invertebrate abundance also increased with greater invasive grass cover. Still, these trends were driven by just two invasive plant species, garlic mustard and Japanese stiltgrass, both of which have previously been shown to provide structural benefits to native invertebrate taxa. While these two species may improve the structural component of understory forest habitat, many invertebrate groups were not significantly correlated with other prevalent invasive plants and one species, mock strawberry, negatively affected the abundance of certain insect taxa. Particularly in forests with reduced native plant structure, invasive plant management must be conducted with consideration for holistic habitat quality, including both plant palatability and structure.

Avian haemosporidia in native and invasive sparrows at an Afrotropical region

Bio-invasions are a major threat to biodiversity and ecosystems globally and may contribute to the proliferation of emerging infectious diseases. We examined the prevalence and phylogenetic diversity of avian haemosporidian parasites infecting the non-native house sparrows (Passer domesticus) and the native southern grey-headed sparrows (Passer diffusus). Blood samples from 104 sparrows (74 house sparrows and 30 southern grey-headed sparrows) mist-netted inside and around the Kruger National Park were used. Genomic DNA was extracted from each blood sample and subjected to nested PCR analyses, Sanger sequencing and phylogenetic analyses. Overall, 35.57% (37/104) of the birds sampled were infected with at least one haemosporidian parasites. Southern grey-headed sparrows had a higher parasite prevalence (60%) than house sparrows (24.3%). A total of 16 parasite lineages were identified, of which eight were novel lineages. Whereas Haemoproteus spp. showed the highest lineage diversity, Leucocytozoon spp. were the most prevalent parasites, albeit with significant differences between sparrow species. A single Plasmodium sp. infection was recorded in a southern grey-headed sparrow. In support of the enemy release hypothesis, we found that prevalence on non-native house sparrows was lower than prevalence recorded in their region of origin and also that they were infected only by indigenous parasites lineages.

Differing impacts of two major plant invaders on urban plant-dwelling spiders (Araneae) during flowering season

Plant invasions can have major impacts on ecosystems and influence global species diversity. In Central Europe, Himalayan balsam (Impatiens glandulifera) and American goldenrods (Solidago canadensis and S. gigantea) are important invaders often establishing dense and homogeneous stands, especially in urban and other disturbed habitats. We investigated their impacts on plant-dwelling spiders (abundance, family structure, guild structure) and potential spider prey items during flowering season within an urbanized landscape using a paired design comparing invaded and native reference vegetation plots. In general, flowering American goldenrods and Himalayan balsam had no significant impacts on the spider family composition. Invasion of American goldenrods further had no effect on total spider abundance and potential prey item abundance. In contrast, goldenrods showed a significantly increased crab spider (Thomisidae) abundance while being less inhabited by web builders. Himalayan balsam negatively influenced free hunters and running crab spider (Philodromidae) abundance, while we found no effects on other groups and total spider abundance. For Himalayan balsam, potential prey item abundance was higher than in native vegetation stands. Notwithstanding that our results only represent a snapshot of the system, they suggest that large-scale removal of urban goldenrod stands during flowering season might negatively influence local spider abundance, especially of crab spiders. Management efforts should therefore be accompanied by compensation measures to avoid disruptive effects on local plant-dwelling spider communities.

COVID-19 Pandemic Turns Life-Science Students into “Citizen Scientists”: Data Indicate Multiple Negative Effects of Urbanization on Biota

The COVID-19 pandemic and its restrictions strongly affect the higher education community and require diverse teaching strategies. We designed a course where we combined online teaching with independently conducted ecological data collections by students using a “citizen science” approach. The aim was to analyze the impact of urbanization on biota by comparing urban and rural grasslands. Seventy-five students successfully conducted the data collections and the results provide evidence for prevailing negative effects of urbanization. Individual numbers of ground-dwelling invertebrates (−25%) and pollinating insects (−33%) were generally lower in urban sites. Moreover, animal and seed predation were reduced in urban grasslands, indicating the potential of urbanization to alter ecosystem functions. Despite the general limitations of online teaching and citizen science approaches, outcomes of this course showed this combination can be a useful teaching strategy, which is why this approach could be used to more actively involve students in scientific research.

Dual threat of tidal flat loss and invasive Spartina alterniflora endanger important shorebird habitat in coastal mainland China

China's coastal wetlands are critically important to shorebirds. Substantial loss of tidal flats, shorebirds' primary foraging grounds, has occurred from land claim and other processes, and is driving population declines in multiple species. Smooth cordgrass Spartina alterniflora was intentionally introduced to the coast of China in 1979 to promote conversion of tidal flats into dry land and has since spread rapidly. The occurrence of S. alterniflora reduces the availability of foraging and roosting habitat for shorebirds, and may be particularly detrimental in places that have experienced other tidal flat loss. However, the extent to which S. alterniflora is encroaching upon important shorebird habitat throughout coastal mainland China, and its intersection with tidal flat loss, has not been quantified. Here, we i) estimate change in the spatial extent of tidal flats between 2000 and 2015 in coastal mainland China where internationally important numbers of shorebirds have been recorded; ii) map the extent of S. alterniflora coverage in 2015 at the same set of sites; and, iii) investigate where these two threats to important shorebird habitat intersect. Our analysis of remote sensing data indicated a 15% net loss in tidal flat area between 2000 and 2015 across all sites, including a net loss in tidal flat area in 39 of 53 individual sites (74%). Spartina alterniflora occurred at 28 of 53 sites (53%) in 2015, of which 22 sites (79%) also had a net loss in tidal flat area between 2000 and 2015. Combined pressures from tidal flat loss and S. alterniflora invasion were most severe in eastern coastal China. Species highly dependent on migrating through this region, which include the Critically Endangered Spoon-billed Sandpiper and Endangered Nordmann's Greenshank and Far Eastern Curlew, may be particularly impacted. Our results underscore the urgent need to arrest tidal flat declines and develop a comprehensive control program for S. alterniflora in coastal areas of mainland China that are important for shorebirds.

What drives private landowner decisions? Exploring non-native grass management in the eastern Great Plains

Non-native grasses used as forage for domestic livestock can negatively impact ecosystem services provided by grasslands. In the U.S., most grazed grasslands are privately owned so the introduction and reduction of non-native grasses are both driven by landowner behavior. Yet, the social factors that shape non-native grass management are rarely explored. To address this knowledge gap, we evaluated how decisions to reduce these grasses through practices such as herbicide application, prescribed fire, and physical removal are influenced by attitudes, norms, and perceived ability. We administered a mixed mode (mailback and online) survey in 2017 to landowners in the eastern Great Plains of the U.S., in a region where cattle production remains the predominant land-use. Using structural equation modeling with parceling, we tested hypotheses related to management decisions derived from a model integrating two theories - the Theory of Planned Behavior and the Norm Activation Model. In this analysis, we identified perceived ability (i.e., access to time, skills, or other necessary resources) as a barrier to adoption for landowners who were already willing to manage non-native grasses. Positive attitudes toward management and increased social norm pressures were both associated with increased sentiments of moral responsibility to reduce non-native grasses. These personal norms, together with attitudes, positively influenced willingness to control non-native grasses. Further, we observed that social norms related to expectations of neighbors had more influence on personal norms than the social norms from natural resource agencies. The power of norms to explain individual management decisions suggests that landowners could be engaged in landscape-scale initiatives by leveraging moral responsibility and influential social groups.

Evaluating the Effect of Prosopis juliflora, an Alien Invasive Species, on Land Cover Change Using Remote Sensing Approach

Invasive plant species (IPS) affect people’s livelihoods and well-being by providing both benefits and costs in different contexts. The objective of this study was to investigate the impact of Prosopis juliflora invasion on land cover change using ground survey and satellite sensor data derived from Landsat ETM+. The study was conducted at Sweimeh, Jordan Valley, between 1999 and 2017. The overall classification accuracy of remotely sensed data was 86% for 1999 and 80% for 2017. Accordingly, a remote sensing approach has the potential to assess land change/cover and aid in monitoring the IPS, specifically Prosopis invasion. Change detection analysis of Landsat classes (i.e., 1999 and 2017) showed that bare soil, urban, and water surface areas decreased by 6%, 11%, and 3%, respectively. Conversely, the vegetation class (i.e., IPS and native plants) increased by 20%. Ground surveys in 1999 and 2017 showed that the average vegetation area in Sweimeh invaded by Prosopis was approximately 60% in 1999 and 70% in 2017. Accordingly, the total estimated area invaded by P. juliflora at Sweimeh (2106 ha) in 1999 was approximately 92 ha, while Prosopis coverage in the same region was approximately 413 ha in 2017. The high emergence rate, the adaptation to high temperatures and low precipitation as well as governmental regulations which restrict the removal of trees, including IPS, were the main factors that prompted the extreme P. juliflora invasion in the Jordan Valley. The high invasion rate has led to a reduction in native species, including Tamarix spp., and dried up five natural water springs in the area. Overall, a monitoring plan should be applied to control the invasion problem by Prosopis in the valley. In addition, the conservation regulations that deal with IPS should be revised to mitigate the IPS risk.

A "plan bee" for cities: Pollinator diversity and plant-pollinator interactions in urban green spaces

Green infrastructure in cities is considered to serve as a refuge for insect pollinators, especially in the light of an ongoing global decline of insects in agricultural landscapes. The design and maintenance of urban green spaces as key components of green infrastructure play a crucial role in case of nesting opportunities and for foraging insects. However, only few research has explored the impact of urban green space design on flower visitor communities, plant-pollinator interaction and the provision of the ecosystem service of pollination in cities. We investigated the abundance and diversity of pollinator communities in different urban park types in designed, standardized vegetation units, linked the visitation rates to the structural composition of the park types and derived indices for implemented pollination performances. The study was performed in two different structural park elements, flower beds and insect-pollinating trees. To gain a comprehensive understanding of the interaction between plants and pollinators, we calculated a plant-pollinator network of the recorded community in the investigation area. Visitation rates at different park types clearly showed, that the urban community gardens in comparison to other urban park types had a significantly higher abundance of pollinator groups, comparable to results found on a rural reference site. Tilia trees contributed significantly to the ecosystem service of pollination in investigated green spaces with a high supply of nectar and pollen during their flowering period. Calculations of pollination performances showed that recreational parks had comparably low visitation rates of pollinators and a high potential to improve conditions for the ecosystem service of pollination. The results indicated the strong potential of cities to provide a habitat for different groups of pollinators. In order to access this refuge, it is necessary to rely on near-natural concepts in design and maintenance, to create a wide range of flower diversity and to use even small green patches. Based on the findings, we encourage an integrated management of urban free spaces to consider parks as key habitats for pollinators in anthropogenic dominated, urban environments.

Physiological indicators of habitat quality for a migratory songbird breeding in a forest invaded by non-native Japanese barberry (Berberis thunbergii)

Non-native, invasive plants can impact birds by altering food sources, nesting substrates and other critical resources. Japanese barberry (Berberis thunbergii) is one of the most invasive, non-native woody plants in in the northeastern USA, and yet almost nothing is known about its effects on birds or other wildlife. To investigate individual-level impacts of Japanese barberry on a forest-breeding bird, we compared food abundance (leaf-litter arthropod biomass) and the physiological condition of territorial male ovenbirds (Seiurus aurocapilla) between areas of a forest preserve in New York State that had high or low densities of Japanese barberry. We used haemoglobin and plasma triglyceride concentrations to indicate energetic condition, plasma uric acid and total plasma protein levels to indicate diet quality, and heterophil to lymphocyte ratios to indicate chronic stress. We found no difference in arthropod biomass between ovenbird territories that were heavily invaded by or relatively free of Japanese barberry. Perhaps largely as a result, we found no relationship between Japanese barberry density and any of our five haematological condition indices. There was also no difference in body mass, body size or age ratio between ovenbirds nesting in areas with low or high densities of Japanese barberry to suggest that relatively uninvaded forest patches were in greater demand and acquired by the most dominant individuals. Our results indicate that Japanese barberry does not reduce habitat quality for breeding male ovenbirds in a way that affects their prey abundance or physiological condition, but we caution that other species of birds and other aspects of habitat quality could be affected differently. We encourage future research on additional bird species and the effects of Japanese barberry on factors such as diet composition, pairing and nesting success and post-fledging survival to improve science-based decision-making about the extent to which conservation resources should be applied towards Japanese barberry control.

Setting the scene for achievable post-2020 convention on biological diversity targets: A review of the impacts of invasive alien species on ecosystem services in Africa

Invasive alien species (IAS) are known to pose a serious threat to biodiversity, and reduce the ability of ecosystems to provide benefits to humans. In recognition of this threat and to address the impacts of IAS, Parties to the Convention on Biological Diversity (CBD) adopted Aichi Biodiversity Target 9, which is dedicated to the control or eradication of priority IAS and the management of their introduction pathways by 2020. The achievement of Target 9 relies strongly on the commitment and ability of Parties to set ambitious national or regional targets and achive them, the availability of information and the requisite expertise on invasion biology. Now that the global community is gearing for the post-2020 Biodiversity Framework, it is time to take stock and identify opportunities to improve the performance of the African region beyond 2020. We approached this task by reviewing information on the impacts of IAS on ecosystem services in Africa, as a large proportion of Africans directly rely on ecosystem services, particularly in rural areas. Furthermore, we assessed the expertise on IAS in Africa. Our data sources were National Reports of African countries to the CBD, as well as peer-reviewed scientific literature. National Reports under the CBD provide information on measures taken to implement the Convention at country level, as well as progress towards the achievement of set targets. We found National Reports for 48 (about 90%) countries of which 73% provided feedback on IAS indicating commitment to fight IAS. However, there were few studies within peer-reviewed scientific literature looking at impacts of IAS on ecosystem services in Africa and almost half of the authors were non-Africans. This alludes to limited scientific expertise to inform and support IAS management on the continent. Both the National Reports and scientific literature showed that provisioning services were the most negatively affected by IAS. Also, more than 100 species were listed as problematic. More efforts and resources are needed to document IAS impacts across different realms (e.g. marine, terrestrial and freshwater) and for sub-regional bodies so that more integrated strategies and approaches can be developed. This information is also needed to support the development and implementation of national legislative and regulatory initiatives, as well as to report on international obligations such as the Aichi Biodiversity Targets.