Tim M Blackburn

University College London | UCL · Department of Genetics, Evolution and Environment (GEE)

The recent thematic Assessment Report on Invasive Alien Species and their Control of the Intergovernmental Science‐Policy Platform on Biodiversity and Ecosystem Services reaffirmed biological invasions as a major threat to biodiversity. Anticipating biological invasions is crucial for avoiding their ecological and socio‐economic impacts, particular...

The ecological impact of non‐native species arises from their establishment in local assemblages. However, the rates of non‐native spread in new regions and their determinants have not been comprehensively studied. Here, we combined global databases documenting the occurrence of non‐native species and residence of non‐native birds, mammals, and vas...

Seasonal migration is an underappreciated driver of animal diversification. Changes in migratory behaviour may favour the establishment of sedentary founder populations and promote speciation if there is sufficient reproductive isolation between sedentary and migratory populations. From a systematic literature review, we here quantify the role of m...

Birds are among the best-studied animal groups, but their prehistoric diversity is poorly known due to low fossilization potential. Hence, while many human-driven bird extinctions (i.e., extinctions caused directly by human activities such as hunting, as well as indirectly through human-associated impacts such as land use change, fire, and the intr...

The Environmental Impact Classification for Alien Taxa (EICAT) is an important tool for biological invasion policy and management and has been adopted as an International Union for Conservation of Nature (IUCN) standard to measure the severity of environmental impacts caused by organisms living outside their native ranges. EICAT has already been in...

While the regional distribution of non-native species is increasingly well documented for some taxa, global analyses of non-native species in local assemblages are still missing. Here, we use a worldwide collection of assemblages from five taxa - ants, birds, mammals, spiders and vascular plants - to assess whether the incidence, frequency and prop...

The global pet trade is a major pathway for the introduction of invasive alien species. The composition of species selected for transport is driven by market demands, which may be influenced by a combination of both historical and cultural factors. We compared Eastern (Taiwan) and Western (Australia and the Iberian Peninsula) bird markets to explor...

Human impacts reshape ecological communities through the extinction and introduction of species. The combined impact of these factors depends on whether non-native species fill the functional roles of extinct species, thus buffering the loss of functional diversity. This question has been difficult to address, because comprehensive information abou...

We developed the DAMA (Distribution of Alien Mammals) database, a comprehensive source reporting the global distribution of the 230 species of mammals that have established self‐sustaining and free‐ranging populations outside their native range due to direct or indirect human action. Every alien range is accompanied by information on its invasion s...

Aim The number of alien species has been increasing for centuries world-wide, but temporal changes in the dynamics of their inter-regional spread remain unclear. Here, we analyse changes in the rate and extent of inter-regional spread of alien species over time and how these dynamics vary among major taxonomic groups. Location Global. Time period...

The species–area relationship (SAR) describes a range of related phenomena that are fundamental to the study of biogeography, macroecology and community ecology. While the subject of ongoing debate for a century, surprisingly, no previous book has focused specifically on the SAR. This volume addresses this shortfall by providing a synthesis of the...

The unabating rise in the number of species introduced outside of their native range makes predicting the spread of alien species an urgent challenge. Most predictions use models of the ecological niche of a species to identify suitable areas for invasion, but these predictions may have limited accuracy. Here, using the global alien avifauna, we de...

Biodiversity impacts caused by alien species can be severe, including those caused by alien birds. In order to protect native birds, we aimed to identify factors that influence their vulnerability to the impacts of alien birds. We first reviewed the literature to identify native bird species sustaining such impacts. We then assigned impact severity...

Unprecedented rates of introduction and spread of non-native species pose burgeoning challenges to biodiversity, natural resource management, regional economies, and human health. Current biosecurity efforts are failing to keep pace with globalization, revealing critical gaps in our understanding and response to invasions. Here, we identify four pr...

Macroecology is the study of patterns, and the processes that determine those patterns, in the distribution and abundance of organisms at large scales, whether they be spatial (from hundreds of kilometres to global), temporal (from decades to centuries), and organismal (numbers of species or higher taxa). In the context of invasion ecology, macroec...

The Environmental Impact Classification for Alien Taxa (EICAT) classifies the impacts caused by alien species in their introduced range in standardised terms across taxa and recipient environments. Impacts are classified into one of five levels of severity, from Minimal Concern to Massive, via one of 12 impact mechanisms. Here, we explain revisions...

The Environmental Impact Classification for Alien Taxa (EICAT) can be used to classify alien taxa according to the magnitude and type of their environmental impacts. The EICAT protocol, classifications of alien taxa using the protocol (EICAT classification) and the data underpinning classifications (EICAT data) are increasingly used by scientists a...

We use a recently proposed framework, the SocioEconomic Impact Classification for Alien Taxa (SEI-CAT) to undertake the first global assessment of the impacts of alien birds on human well-being. A review of the published literature and online resources was undertaken to collate information on the reported socioeconomic impacts of 415 bird species w...

This document presents the IUCN Standard for classifying alien species in terms of their environmental impact; the IUCN Environmental Impact Classification for Alien Taxa (EICAT) Categories and Criteria: First edition (the same as Version 3.3 adopted by IUCN Council). To ensure full understanding of the application of EICAT, it is very important to...

Biological invasions have steadily increased over recent centuries. However, we still lack a clear expectation about future trends in alien species numbers. In particular, we do not know whether alien species will continue to accumulate in regional floras and faunas, or whether the pace of accumulation will decrease due to the depletion of native s...

Land use change—for example, the conversion of natural habitats to agricultural or urban ecosystems—is widely recognized to influence the risk and emergence of zoonotic disease in humans1,2. However, whether such changes in risk are underpinned by predictable ecological changes remains unclear. It has been suggested that habitat disturbance might c...

Article impact statement: In an era of profound biodiversity crisis, invasion costs, invader impacts, and human agency should not be dismissed.

Biological invasions are a global consequence of an increasingly connected world and the rise in human population size. The numbers of invasive alien species – the subset of alien species that spread widely in areas where they are not native, affecting the environment or human livelihoods – are increasing. Synergies with other global changes are ex...

Understanding the causes of spatial variation in the distribution and richness of alien species is a key goal of invasion biology. Thanks to the increasing availability of geographical compendia of alien species it is also the subject of a burgeoning scientific literature. Here, we review elements of this literature to argue that understanding the...

A recent analysis by Moulton & Cropper (2019) of a global dataset on alien bird population introductions claims to find no evidence that establishment success is a function of the size of the founding population. Here, we re-analyse Moulton & Cropper’s data and show that this conclusion is based on flawed statistical methods—their data in fact conf...

Abstract Invasive alien species are a major threat to biodiversity and human activities, providing a strong incentive to understand the processes by which alien invasion occurs. While it is important to understand the determinants of success at each of several invasion stages—transport, introduction, establishment, and spread—few studies have explo...

Alien birds are widely distributed across the globe, but information on their environmental impacts is available for less than a quarter of the regions in which they are located. We test a series of hypotheses better to understand why impact data are available for some regions but not others. Information on factors hypothesised to influence spatial...

Aim To quantify global latitudinal patterns in the distributions of alien bird species to assess whether these species conform to Rapoport's rule (i.e. show a positive latitudinal gradient in latitudinal range extent), and to test whether where species are introduced, and where species fail to establish, may help to drive observed patterns. Locati...

A key question in invasion biology is why some regions have more alien species than others. Here, we provide a general framework to answer this. We model alien species richness as a function of the number of species introduced (colonization pressure) and the probability that each species establishes, which is a function of propagule pressure (the n...

Human-mediated translocation of species to areas beyond their natural distribution (which results in ‘alien’ populations¹) is a key signature of the Anthropocene², and is a primary global driver of biodiversity loss and environmental change³. Stemming the tide of invasions requires understanding why some species fail to establish alien populations,...

New Zealand is home to around 40 alien bird species, but about 80 more were introduced in the 19th century and failed to establish. As most of these introductions were deliberate and documented in detail by the acclimatisation societies responsible for them, New Zealand bird invasions are often used as a model system to unravel what determines the...

The European Union (EU) has recently published its first list of invasive alien species (IAS) of EU concern to which current legislation must apply. The list comprises species known to pose great threats to biodiversity and needs to be maintained and updated. Horizon scanning is seen as critical to identify the most threatening potential IAS that d...

Aim Accelerating rates of anthropogenic introductions are leading to a dramatic restructuring of species distributions globally. However, the extent to which invasions alter the imprint of evolutionary history in species geographical ranges remains unclear. Here, we provide a global assessment of how the introduction, establishment and spread of al...

Native bird species show latitudinal gradients in body size across species (Bergmann's rule), but whether or not such gradients are recapitulated in the alien distributions of bird species are unknown. Here, we test for the existence of Bergmann's rule in alien bird species worldwide, and investigate the causes of the observed patterns. Published d...

Background Environmental trade-offs associated with land use—for example, between food security and biodiversity conservation—are crucial dimensions of planetary health. Land use-driven biodiversity change might predictably affect disease risk if reservoir host species are consistently more likely to persist under human disturbance (ie, if ecologic...

This book, containing 18 chapters, combines the hierarchy-of-hypotheses (HoH) approach with hypothesis networks for invasion biology. This book aims to further develop the HoH approach by inviting critical comments (Part I), apply it to 12 major invasion hypotheses (Part II) and explore how it can be expanded to a hierarchically structured hypothes...

A consistent determinant of the establishment success of alien species appears to be the number of individuals that are introduced to found a population (propagule pressure), yet variation in the form of this relationship has been largely unexplored. Here, we present the first quantitative systematic review of this form, using Bayesian meta-analyti...

References for the experimental analysis in Fig 3. (DOCX)

Supplementary methods and results. (DOCX)

References for S1 Data. (DOCX)

Full data file for analysis. (CSV)

Nest predation is a primary cause of nest failure in open-cup nesting woodland birds and low reproductive success is a common reason why reintroduced species fail to establish in the wild. We used video monitoring to record the breeding outcomes and identify the causes of nest failure in a reintroduced population of the Critically Endangered Regent...

Aim: To identify traits related to the severity and type of environmental impacts generated by alien bird species, in order to improve our ability to predict which species may have the most damaging impacts. Location: Global. Methods: Information on traits hypothesized to influence the severity and type of alien bird impacts was collated for 113...

Significance Our ability to predict the identity of future invasive alien species is largely based upon knowledge of prior invasion history. Emerging alien species—those never before encountered as aliens—therefore pose a significant challenge to biosecurity interventions worldwide. Using a global database of the first regional records of alien spe...

1. Many alien taxa are known to cause socio-economic impacts by affecting the different constituents of human well-being (security; material and non-material assets; health; social, spiritual and cultural relations; freedom of choice and action). Attempts to quantify socio-economic impacts in monetary terms are unlikely to provide a useful basis fo...

To identify the factors that influence the availability of data on the negative impacts of alien bird species, in order to understand why more than 70% are currently classified as Data Deficient (DD) by the Environmental Impact Classification of Alien Taxa (EICAT) protocol. Information on factors hypothesised to influence the availability of impact...

Statistical approaches for inferring the spatial distribution of taxa (Species Distribution Models, SDMs) commonly rely on available occurrence data, which is often clumped and geographically restricted. Although available SDM methods address some of these factors, they could be more directly and accurately modelled using a spatially-explicit appro...

Predictive accuracy of boosted regression trees (BRT) species distribution modelling method when varying the complexity of the underlying regression trees during inference. Points represent mean AUC score over a set of 5000 simulated species where a prediction of the true range is attempted using a set of simulated sampling points, with whiskers sh...

Options tested for four different species distribution model methods (for details see text). Letters in ‘Setting’ columns indicate abbreviations used and numbers previous analyses from the literature. (DOCX)

Predictive accuracy of the MAXENT species distribution modelling method when varying the complexity of the inference models using the beta, or “regularisation”, coefficient. Points represent mean AUC score over a set of 5000 simulated species where a prediction of the true range is attempted using a set of simulated sampling points, with whiskers s...

Predictive accuracy of boosted regression trees (BRT) species distribution modelling method when varying the bag fraction used to hold-back parts of data for internal validation. Points represent mean AUC score over a set of 5000 simulated species where a prediction of the true range is attempted using a set of simulated sampling points, with whisk...

Predictive accuracy of three species distribution modelling methods to infer 5000 simulated species’ ranges that were generated using either (a) just additive or (b) additive and interaction terms in formula used to determine the relationship between species’ presence and a set of simulated covariates. A repeated set of comparisons (c-d) is made fo...

Predictive accuracy of the MAXENT species distribution modelling method when varying what class of terms are included in the inference model. Letter labels on x-axis represent model terms (Hinge—H, Product—P, Quadratic—Q, Threshold—T, Linear—L, Auto Feature—AF). Points represent mean AUC score over a set of 5000 simulated species where a prediction...

Predictive accuracy of boosted regression trees (BRT) species distribution modelling method when varying the learning rate of tree inference algorithm. Points represent mean AUC score over a set of 5000 simulated species where a prediction of the true range is attempted using a set of simulated sampling points, with whiskers showing the 95% confide...

Predictive accuracy of boosted regression trees (BRT) species distribution modelling method when varying the number of regression trees retained in the final modelling set. Points represent mean AUC score over a set of 5000 simulated species where a prediction of the true range is attempted using a set of simulated sampling points, with whiskers sh...

R code used to run analysis. (ZIP)

Using horizon scanning techniques, we identified 14 emerging issues, not yet widely recognized or understood, that are likely to affect how biological invasions are studied and managed on a global scale [1]. Zenni et al. [2] do not comment on the major issues identified in our study. Instead, they draw attention to the nationalities of our authorsh...

Effective prevention and control of invasive species generally relies on a comprehensive, coherent and representative list of species that enables resources to be used optimally. European Union (EU) Regulation 1143/2014 on invasive alien species (IAS) aims to control or eradicate priority species, and to manage pathways to prevent the introduction...

Managing biological invasions relies on good global coverage of species distributions. Accurate information on alien species distributions, obtained from international policy and cross-border cooperation , is required to evaluate trans-boundary and trading partnership risks. However, a standardized approach for systematically monitoring alien speci...

Human-mediated transport beyond biogeographic barriers has led to the introduction and establishment of alien species in new regions worldwide. However, we lack a global picture of established alien species richness for multiple taxonomic groups. Here, we assess global patterns and potential drivers of established alien species richness across eigh...