Impact Of Invasive Alien Species Research Articles

Biological Invasion Data Gaps in China: Examples of Distribution, Inventories, and Impact

The impact of invasive alien species (IAS) on nature and society is increasing globally. It is crucial to utilize information systems for evidence-based management, enabling the assessment and supporting survey and control actions. However, the lack of accessible and comprehensive baseline IAS data often impedes the ability to prioritize and allocate resources efficiently. Despite the increased public awareness of biological invasions in China over the past decades, the critical importance of data requirements has not been fully recognized, leading to gaps in available data. Here, we outline the key data demands for the management of biological invasions and highlight the current lack of high-quality data for invasion management in China, and critically assess data gaps in IAS distribution, inventory, and impact. Additionally, we propose a conceptual framework to illustrate the data requirements throughout the invasion management process, along with indicators to assess data quality within three dimensions: relevance, resolution, and reliability.

Invasive neophytes alter ecological functions and services of riparian hardwood forests

Riparian hardwood forests, now rare in Europe, occur in small patches within agricultural landscapes and are important biodiversity hotspots protected by the EU Habitats Directive and monitored. They play a vital ecological role and provide essential ecosystem services (ES). Recent studies indicate their unfavourable conservation status with a negative trend reported by EU Member States. One of the most visible symptoms of the degradation of riparian hardwood forest is the invasion of alien plant species which can radically change ecosystem functions. In this work, we use plant functional trait analysis to develop proxies and quantify an impact of invasive alien species, specifically invasive neophytes, on specific functions of riparian hardwood forests and their potential to provide five relevant regulating services. Data from 249 phytosociological relevés across 83 Natura 2000 habitat monitoring sites in Poland were analyzed.Our findings indicate that invasive neophytes negatively affect the potential for maintaining nursery populations and habitats, as well as regulation of the chemical condition of freshwaters by these forests. On the other hand, they do not significantly influence the local climate conditions and the forests’ potential to produce antimicrobial compounds. We recommend integrating an ES assessment based on plant functional traits into habitat monitoring. This approach is cost-effective, leveraging existing data, and its results could be used in some cases as a premise for initiating additional environmental monitoring based on direct field measurements.

Study of the Impact of Prosopis juliflora on Soil moisture and Humidity

This paper aims to present the impact of invasive alien species on soil moisture over the other native species. Prosopis juliflora is a majestic, non-native species that grows abundantly over the arid and semi-arid regions especially over the southern part of Indian sub-continent. These non-native, invasive species are modifying the native bio diversity, natural irrigation and local ecosystem by alternating the soil fertility measures such as soil moisture and relative humidity of the soil. In this study, the impact of the non-native species and native species on soil moisture and atmospheric humidity are considered for the analysis of the effect of the Prosopis juliflora and the variation in the conditions are visualized using the k- means clustering technique. The soil moisture at a depth of 2 meters and 1 meter and the air humidity is compared for regions in the presence of the nonnative species and in the absence of nonnative species. The results indicate that the non-native species has a negative impact on the cultivating land, spoiling its fertility measures by reducing its soil moisture content. The study provides evidence for the need to take necessary actions to eradicate species such as Prosopis juliflora and in turn to protect the native vegetation and develop management strategies to control the spread of the species.

Relatório temático sobre espécies exóticas invasoras no Brasil: sumário para tomadores de decisão

Abstract Biological invasions are one of the major threats to biodiversity and good quality of life, resulting from the translocation of species by human action. There are more than 500 alien species currently invading ecosystems in Brazil, particularly plants and fishes, while little is known about invasive microorganisms. Although invasive alien species are present in all ecosystems in the country, most have been recorded in habitats with greater human interference, such as urban and peri-urban areas, farmland, dams, reservoirs, ports, and canals. Historically, the southern and southeastern regions of Brazil have had more invasive alien species, but there has been an increase in the number of invasive alien species in the central-western and northern regions in recent decades. The ornamental trade of plants and fishes as well as the illegal pet trade of wild mammals and reptiles are some of the main pathways for invasive species introduction and spread in Brazil. Breeding and cultivation systems that allow escape to natural areas are a relevant route of species introductions in freshwater ecosystems, while unintentional introductions from shipping and infrastructure are of extreme concern in marine ecosystems. The negative impacts of invasive alien species on the biota mainly include changes in community structure and local decrease in native species richness, mediated by predation, competition, and ecosystem changes. Most negative impacts are recorded for intentionally introduced species, such as fishes and plants, but unintentional introductions have led to impacts on good quality of life, with associated costs and impacts on human health. The management of biological invasions faces challenges that need to be overcome, such as the lack of public knowledge about the impact of invasive alien species, the popular appeal of charismatic invasive species or those used by humans, and the use of controversial control techniques. However, successful experiences of eradication and control in terrestrial and marine ecosystems have been recorded, some of them involving public engagement in management actions. Recognizing the issue as a cross-cutting public policy and developing ongoing governance experiences are fundamental goals for the management of invasive alien species in Brazil.

Analysis of the Potential Level of Threat of Invasive Alien Species Regenerating Tree Poles in Laweyan Village

Plants play an important role in producing organic substances and oxygen needed by other living things, but plants can potentially threaten and disrupt the diversity of other plants, causing the quality of biodiversity to decline. Plants that develop in Indonesia can come from various parts of the world, and then these foreign plants can become invasive and have a negative impact on the ecosystem. The aim of this research is to determine the potential level of threat from invasive alien species to tree regeneration in Laweyan Village and the impact of invasive alien species on the environment. The method used is sampling using satellite imagery to determine observation points and methods purposive sampling by making a 10×10 m plot. The results obtained were four plant species that were classified as invasive foreign plants in Laweyan Village, namely Leucaena leucocephala, Cnidoscolus aconitifolius, Sandoricum koetjape, Bougainvillea glabra with different levels of risk. The highest risk category is Leucaena leucocephala with a risk index of 115.2, and the second highest is Bougainvillea glabra with a risk index of 112.8. The risk level is medium, namely Cnidoscolus aconitifolius with a risk index of 100.8 and Sandoricum koetjape with a risk index of 56.28.

New interactive functional indicator approach for river health assessment in an Asian temperate river: Comprehensive analysis of water chemistry, physical habitat, land use, and the biological disturbance of invasive alien species

Elucidating the responses of aquatic communities to environmental (e.g., chemical, habitat, and flow regime) and biological disturbances is essential to the maintenance and restoration of healthy ecosystems. This study investigated the interactions between environmental and biological disturbance factors and functional indicators of ecological health in 99 sampling sites along a temperate river. Variance tests and multivariate statistical tools, such as non-metric multidimensional scaling (NMDS) and generalized linear models (GLMs), were employed to evaluate the responses of functional indicator guilds and ecological river health to various in-stream chemical, physical, habitat, and land-use pattern factors along with the biological impact of invasive alien species (IAS). Variance testing revealed significant variation (χ2 > 6.2 and p < 0.05) in common species abundance and ecological functional guilds among spatial groups according to chemical pollution levels, land-use intensity, and land-use patterns. NMDS analysis and GLMs based on trophic, habitat, and tolerance guilds, and the results of the multi-metric index of biological integrity for fish, indicated statistically significant patterns in response to environmental disturbance, particularly chemical degradation associated with nutrient (nitrogen and phosphorus) enrichment and organic pollution, loss of gravel and cobble substrates, and intensified agricultural land use. The spatial pattern of IAS abundance was also significantly correlated with the alteration in fish community structures. This study underscores the often-unnoticed impact of high IAS abundance on river health, and its interactions with chemical and physical degradation resulting from agricultural and urban land uses. In summary, this study highlights the importance of addressing multiple environmental and biological disturbances to maintain and conserve the health of river systems.

Impact of Species Invasiveness on Biodiversity: A Study in the Indian Context

Over the past few decades, anthropogenic activities have emerged as a significant contributor to the decline of indigenous species in their natural habitats. This paper presents an overview of the impact of Invasive Alien Species (IAS) and BT cotton cultivation on biodiversity in India. The methodology employed is rooted in secondary data sources, drawing from various government publications, reports, and BT cotton production records spanning 2002 to 2021. These data sources were carefully analyzed and compared with relevant research reports to fulfill the study's objectives. The findings reveal pronounced invasiveness of species across diverse ecosystems, disrupting ecosystem functions and services, ultimately leading to biodiversity loss with economic implications and health risks. Moreover, BT cotton, introduced as a tool in the agricultural sector, acts as a form of biological invasion. However, it has shown negative repercussions on the environment by affecting non-target organisms and degrading soil health. This study underscores the need to comprehend and address the consequences of these anthropogenic activities for effective conservation and sustainable practices.

Advancing terrestrial biodiversity monitoring with satellite remote sensing in the context of the Kunming-Montreal global biodiversity framework

Satellite remote sensing (SRS) provides huge potential for tracking progress towards conservation targets and goals, but SRS products need to be tailored towards the requirements of ecological users and policymakers. In this viewpoint article, we propose to advance SRS products with a terrestrial biodiversity focus for tracking the goals and targets of the Kunming-Montreal global biodiversity framework (GBF). Of 371 GBF biodiversity indicators, we identified 58 unique indicators for tracking the state of terrestrial biodiversity, spanning 2 goals and 8 targets. Thirty-six shared enough information to analyse their underlying workflows and spatial information products. We used the concept of Essential Biodiversity Variables (EBV) to connect spatial information products to different dimensions of biodiversity (e.g. species populations, species traits, and ecosystem structure), and then counted EBV usage across GBF goals and targets. Combined with published scores on feasibility, accuracy, and immaturity of SRS products, we identified a priority list of terrestrial SRS products representing opportunities for scientific development in the next decade. From this list, we suggest two key directions for advancing SRS products and workflows in the GBF context using current instruments and technologies. First, existing terrestrial ecosystem distributions and live cover fraction SRS products (of above-ground biomass, ecosystem fragmentation, ecosystem structural variance, fraction of vegetation cover, plant area index profile, and land cover) need to be refined using a co-design approach to achieve harmonized ecosystem taxonomies, reference states and improved thematic detail. Second, new SRS products related to plant physiology and primary productivity (e.g. leaf area index, chlorophyll content & flux, foliar N/P/K content, and carbon cycle) need to be developed to better estimate plant functional traits, especially with deep learning techniques, radiative transfer models and multi-sensor frameworks. Advancements along these two routes could greatly improve the tracking of GBF target 2 (‘improve connectivity of priority terrestrial ecosystems), target 3 (‘ensure management of protected areas’), target 6 (‘control the introduction and impact of invasive alien species’), target 8 (‘minimize impact of climate change on biodiversity’), target 10 (‘increase sustainable productivity of agricultural and forested ecosystems’) and target 12 (‘increase public urban green/blue spaces’). Such improvements can have secondary benefits for other EBVs, e.g. as predictor variables for modelling species distributions and population abundances (i.e. data that are required in several GBF indicators). We hope that our viewpoint stimulates the advancement of biodiversity monitoring from space and a stronger collaboration among ecologists, SRS scientists and policy experts.

Cumulative Negative Impacts of Invasive Alien Species on Marine Ecosystems of the Aegean Sea.

Biological invasions are a human-induced environmental disturbance that can cause major changes in ecosystem structure and functioning. Located in the northeastern Mediterranean basin, the Aegean Sea is a hotspot of biological invasions. Although the presence of alien species in the Aegean has been studied and monitored, no assessment has been conducted on their cumulative impacts on native biodiversity. To address this gap, we applied the CIMPAL index, a framework developed for mapping the cumulative impacts of invasive species, to identify the most affected areas and habitat types and determine the most invasive species in the region. Coastal areas showed stronger impacts than the open sea. The highest CIMPAL scores were four times more frequent in the South than in the North Aegean. Shallow (0-60 m) hard substrates were the most heavily impacted habitat type, followed by shallow soft substrates and seagrass meadows. We identified Caulerpa cylindracea, Lophocladia lallemandii, Siganus luridus, Siganus rivulatus, and Womersleyella setacea as the most impactful species across their range of occurrence in the Aegean but rankings varied depending on the habitat type and impact indicator applied. Our assessment can support marine managers in prioritizing decisions and actions to control biological invasions and mitigate their impacts.

Nagoya Protocol and Africa’s willingness to share biological control agents, are we deterred by barriers instead of using opportunities to work together?

Amongst members of the biological control community there is a range of perceptions regarding the Nagoya Protocol, at best it will hinder access to natural enemies of pests and invasive plants and at worst implementation of the Protocol will prevent access to these resources. In this preliminary study of Africa’s preparedness to implement the Nagoya Protocol and control access to potential biological control agents, we found that several countries have not yet established procedures and policies in this regard. Several factors including lack of awareness, insufficient relevant information and lack of capacity may cause delay in countries implementing access and benefit sharing legislation and processes. The lack of preparedness provides an opportunity for the research community to work with government officials to facilitate future access to natural enemies to act as biological control agents on invasive plants and agricultural pests. Collaboration between researchers, managers and bureaucrats in support of African countries could lead to collective action that develops policies and implements processes to foster exploration of African biodiversity. This collaboration could also foster the sharing of biological control agents that will benefit Africa through integrated pest management in agriculture, protection of human lives and livelihoods, and reduction of the impact of invasive alien species on biodiversity and environmental infrastructure.

Impacts of invasive alien species on riparian plant communities in South African savanna

Abstract Biological invasions are a threat to protected areas globally; however, the relative lack of studies quantifying the ecological impacts impairs informed decision-making. We selected three annual alien plants, widespread in the riparian habitats of the Kruger National Park, South Africa: Datura innoxia, Parthenium hysterophorus, and Xanthium strumarium, to examine their potential impacts on riparian plant communities. We identified 12–13 populations for each and placed a pair of invaded and uninvaded plots in each population. Species richness, Shannon diversity, and Pielou evenness were compared between the invaded and uninvaded plots using LMM models, and species composition was compared using ordination. The invaded vegetation showed lower species richness compared to the uninvaded, with the strongest effect observed for P. hysterophorus. The invaded plots also showed lower Shannon diversity and Pielou evenness due to the presence of alien dominants. For all three invaders, the invasion resulted in changes in the composition of native vegetation. Some native plants were more frequent and abundant in the invaded vegetation, possibly due to the habitats created in sandy river beds. The native species richness decreased with increasing invader cover, but the species richness of aliens accompanying the invasive dominants was not negatively affected by their cover. Our results confirmed the negative impact of invasive aliens on native plant diversity, with the most pronounced effect by Parthenium hysterophorus invasions.

Knowledge needs in economic costs of invasive species facilitated by canalisation

Canals provide wide-ranging economic benefits, while also serving as corridors for the introduction and spread of aquatic alien species, potentially leading to negative ecological and economic impacts. However, to date, no comprehensive quantifications of the reported economic costs of these species have been done. Here, we used the InvaCost database on the monetary impact of invasive alien species to identify the costs of those facilitated by three major canal systems: the European Inland Canals, Suez Canal, and Panama Canal. While we identified a staggering number of species having spread via these systems, monetary costs have been reported only for a few. A total of $33.6 million in costs have been reported from species linked to European Inland Canals (the fishhook waterflea Cercopagis pengoi and the zebra mussel Dreissena polymorpha) and $8.6 million linked to the Suez Canal (the silver-cheeked toadfish Lagocephalus sceleratus, the lionfish Pterois miles, and the nomad jellyfish Rhopilema nomadica), but no recorded costs were found for species facilitated by the Panama Canal. We thus identified a pervasive lack of information on the monetary costs of invasions facilitated by canals and highlighted the uneven distribution of costs.

Interspecific Aggression and Food Competition between the Global Invader Palaemon macrodactylus and the Native Palaemon elegans

The impact of invasive alien species on native communities can act at different levels both by affecting the ecosystem’s structure (i.e., mainly in the case of vegetation) and through direct interactions (i.e., competition for food or space). Behavioral studies under controlled conditions can provide relevant information on both the invasive potential of alien species and the potential impact of the invaders on the local native species. In the laboratory, the competition for food resources between the invasive oriental shrimp Palaemon macrodactylus, Rathbun, 1902, and the Mediterranean native shrimp Palaemon elegans, Rathke, 1836, was analyzed. These species are typical residents of coastal transitional and estuarine waters, so the experiments were carried out using two salinity conditions that characterize the coastal lagoon of Venice. Although at both salinity treatments the alien species tended to be more aggressive than the native one, significant differences between the two species were mainly observed at a salinity of 30. In particular, at a salinity of 30, P. macrodactylus spent more time attending to the food source than the native species. The results are discussed in light of the potential inter-specific competition between the two species within the conditions of the Venice lagoon.

Significance of Soil Seed Bank in Forest Vegetation—A Review

Seed banks present in soils provide information on past/existing standing vegetation and the probable future vegetation of the area. We reviewed 187 articles related to seed banks that were published worldwide from 1859 to 2022 to understand the dynamics of soil seed banks. The heterogeneity and biodiversity of most ecosystems appear vulnerable due to the over-exploitation of soil over the years. The studies on seeds present in soil provide knowledge on species cover, which supports the restoration of degraded areas. An interesting feature observed in most references was that species identified in seed banks do not necessarily represent or reflect the standing vegetation—this is attributed to the varied dispersal mechanisms of different species. The most significant contributions of a seed bank are conservation and the provision of propagules to the ecosystem. These banks are critical for identifying the composition and spatial organisation of understorey plant communities in degraded forests following soil disturbances, such as wildfire, harvesting, and/or logging. Regeneration from soil seed banks enables biodiversity recovery in tropical forests. There has been little understanding of the function soil seed banks play in forest restoration, which is critical to the natural regeneration of forest reserves. The impact of invasive alien species and the associated soil seed banks on vegetation dynamics is poorly researched. With landscape restoration gaining significance in the present decade, it becomes exceedingly important to maintain existing vegetation. It is relevant to India, which has international commitments to restore 26 mha of degraded and deforested land by 2030. This review reveals the importance of soil seed banks and their role in the future maintenance of forest cover.

Economic impact of invasive alien species in Argentina: a first national synthesis

Invasive alien species (IAS) affect natural ecosystems and services fundamental to human well-being, human health and economies. However, the economic costs associated with IAS have been less studied than other impacts. This information can be particularly important for developing countries such as Argentina, where monetary resources for invasion management are scarce and economic costs are more impactful. The present study provides the first analysis of the economic cost of IAS in Argentina at the national level, using the InvaCost database (expanded with new data sources in Spanish), the first global compilation of the reported economic costs of invasions. We analyzed the temporal development of invasions costs, distinguishing costs according to the method reliability (i.e. reproducibility of the estimation methodology) and describing the economic costs of invasions by invaded environment, cost type, activity sector affected and taxonomic group of IAS. The total economic cost of IAS in Argentina between 1995 and 2019 was estimated at US$ 6,908 million. All costs were incurred and 93% were highly reliable. The recorded costs were mainly related to terrestrial environments and the agricultural sector, with lack of costs in other sectors, making it difficult to discuss the actual distribution of invasion costs in Argentina. Nevertheless, the reported costs of IAS in this country are very high and yet likely much underestimated due to important data gaps and biases in the literature. Considering that Argentina has an underdeveloped economy, costs associated with biological invasions should be taken into consideration for preventing invasions, and to achieve a more effective use of available resources.

Populations of Heracleum sosnowskyi and H. mantegazzianum (Apiaceae) in Kyiv (Ukraine)

Abstract In connection with the increasing negative impact of invasive alien species on biodiversity and the environment in general, their research, as well as throughout the world, is relevant. The distribution of the Heracleum sosnowskyi and H. mantegazzianum of the secondary range on the example of the Kyiv agglomeration is investigated in the work. In our study we aimed to evaluate the possibility of spontaneous spread of giant hogweeds in the secondary range, adaptation of the species to the new conditions of the environment that favor to control of these species’ expansion and reduce the threat to the urban ecosystems and citizens’ health. We hypothesise that in the secondary range H. sosnowskyi and H. mantegazzianum settle sites with relatively high temperature (Tr), lightening (Lc), and soil moisture conditions similar to that in their natural range. 17 populations and four localities (sites) of H. sosnowskyi and H. mantegazzianum were studied. They were found within forest, meadow, riverine and ruderal plant communities. It is indicated that the advent species fully adapted to the conditions of the environment. The difference by ecological indicators Lc2 and Tm1 is pointed out. According to the results of our research, for the area of Kyiv urban agglomeration the growth of H. sosnowskyi and H. mantegazzianum is indicated in the plants communities of six classes. They spread most in ruderal plant communities of the: Robinietea, Artemisietea, Epilobietea classes. The studied species belong to invasive plant species in Ukraine and are characterized by extremely high effect on the environment and high invasive potential.

Mapping spatial distribution of invasive alien species through satellite remote sensing in Karachi, Pakistan: an urban ecological perspective

The exponential population growth of Karachi city has taken a very heavy toll on the indigenous environment of this South Asian megacity. In this context, the unlikely roadsides plantation of nonnative species by the city decision-makers was a short-term solution to cultivate green belts, ultimately, to improve city environment. However, this has backfired and become a very serious ecological crisis as the species become invasive alien species and destroyed the native ecological environment of the city significantly. This study provided an accurate spatial extent of invasive alien species and evaluated the intensity of the problem using remote sensing technology. Firstly, the importance value index was developed to highlight the intensity of invasive alien species in native plant communities. Afterwards, the hot spots were sampled to develop training areas for Object Based Image Analysis to map the extent of invasive alien species in the city using high-resolution GeoEye satellite imagery. The overall accuracy of mapping was 93.17% with Kappa coefficient value of 0.904. In addition, to explore hyperspectral remote sensing analysis, two techniques—Derivative Vegetation Index and Spectral Angle Mapper—were employed on EO-I hyperspectral imagery to map invasive alien species using spectral signatures. The analysis revealed 99.94% correlation between the two mapping techniques. Finally, to identify the impact of invasive alien species on the microclimate of the city, a spatiotemporal analysis (1992–2016) at selected sites was performed on Landsat thermal images. The study ruled out the concept of invasive alien species influence on the microclimate of the city as both vegetation growth and ambient air temperature change were not interdependent.

Effects of invasive alien species on riparian vegetation over a 20-year time-lapse: a case study from the Tiber river in Central Italy

ABSTRACT Invasive alien species (IAS) have a severe impact on indigenous vegetation globally, including in riparian ecosystems, which are already subject to severe natural and anthropogenic modifications. This paper presents a case study of the long-term impact of IAS that was carried out on the banks of the Tiber River near Lake Alviano in Central Italy. We compared the vegetation composition from 1998 and 2020, to record IAS invasion after a time-lapse of 22 years. We performed 48 phytosociological relevés in 2020, using the same method that had been used in 1998 (with 46 relevés). The importance of IAS in determining the changes in floristic composition and vegetation dynamics was quantified using chorology, life forms and Ellenberg’s ecological indicator values. Results of our multivariate analysis revealed that Paspalum distichum L. and Amorpha fruticosa L. are the most impactful species, due to their ecological traits that make them highly competitive in disturbed environments. Ellenberg’s indicator values show that the habitat has shifted towards increased eutrophication and warming. The multivariate analysis confirmed a change in species composition and therefore in vegetation, leading to a more monotonous habitat with completely different vegetation types than before. Finally, the consequences for Natura 2000 habitats were assessed. Key policy insights IAS drastically changed and reduced the cover of native vegetation species between 1998 and 2020, changing the environment from an herbaceous marshy vegetation type to a more homogeneous shrubland. The analysed habitat increased in eutrophication driven by 22 years of overgrazing and by the establishment of a nitrogen-fixing IAS (Amorpha fruticosa L.). The most impactful IAS were Paspalum distichum L. and Amorpha fruticosa L. Some IAS (e.g. Paspalum distichum L.) are currently considered characteristic species of some N2000 habitats (e.g. 3280 and 3290), presenting a paradox of the negative effects of invasions and evidencing a gap in the inclusion of important native communities in the EU Habitats Directive worthy and in need of protection.

Behavioral Responses of Invasive and Nuisance Vertebrates to Harvesting: A Mechanistic Framework

Wildlife species are harvested for a variety of purposes. This is known to drive phenotypic change, particularly in the context of exploitative harvesting. As the impact of invasive alien species grows, and new conflicts with nuisance species arise, management of these problematic species has emerged as a key topic. Yet there is little to no attention directed to whether and how species are changing as a consequence of lethal control, particularly in terms of their behavior. In this synthesis, we draw attention to the fact that nuisance and invasive species undergoing control are likely to exhibit behavioral change. First, we highlight the potential consequences of behavioral responses to control on species’ management and ecological impact. Second, we provide a framework of mechanisms that can lead to behavioral responses to lethal control. Three categories are described: evolutionary mechanisms, cognitive mechanisms and stress mechanisms. Understanding which mechanism underlies a behavioral response is paramount as it allows to predict how prevalent the response will be in the population. We argue for increased monitoring of behavior by managers and more research efforts into the mechanisms of behavioral responses to novel threats in order to better predict and mitigate unforeseen and unwanted behavioral change.

A diagnosis-based approach to assess specific risks of river degradation in a multiple pressure context: Insights from fish communities

In the context of increasing pressure on water bodies, many fish-based indices have been developed to evaluate the ecological status of rivers. However, most of these indices suffer from several limitations, which hamper the capacity of water managers to select the most appropriate measures of restoration. Those limitations include: (i) being dependent on reference conditions, (ii) not satisfactorily handling complex and non-linear biological responses to pressure gradients, and (iii) being unable to identify specific risks of stream degradation in a multi-pressure context. To tackle those issues, we developed a diagnosis-based approach using Random Forest models to predict the impairment probabilities of river fish communities by 28 pressure categories (chemical, hydromorphological and biological). In addition, the database includes the abundances of 72 fish species collected from 1527 sites in France, sampled between 2005 and 2015; and fish taxonomic and biological information. Twenty random forest models provided at least good performances when evaluating impairment probabilities of fish communities by those pressures. The best performing models indicated that fish communities were impacted, on average, by 7.34 ± 0.03 abiotic pressure categories (mean ± SE), and that hydromorphological alterations (5.27 ± 0.02) were more often detected than chemical ones (2.06 ± 0.02). These models showed that alterations in longitudinal continuity, and contaminations by Polycyclic Aromatic Hydrocarbons were respectively the most frequent hydromorphological and chemical pressure categories in French rivers. This approach has also efficiently detected the functional impact of invasive alien species. Identifying and ranking the impacts of multiple anthropogenic pressures that trigger functional shifts in river biological communities is essential for managers to prioritize actions and to implement appropriate restoration programmes. Actually implemented in an R package, this approach has the capacity to detect a variety of impairments, resulting in an efficient assessment of ecological risks across various spatial and temporal scales.