Abstract
Human activities such as transport, trade and tourism are likely to influence the spatial distribution of non-native species and yet, Species Distribution Models (SDMs) that aim to predict the future broad scale distribution of invaders often rely on environmental (e.g. climatic) information only. This study investigates if and to what extent do human activities that directly or indirectly influence nature (hereafter the human footprint) affect the global distribution of invasive species in terrestrial, freshwater and marine ecosystems. We selected 72 species including terrestrial plants, terrestrial animals, freshwater and marine invasive species of concern in a focus area located in NW Europe (encompassing Great Britain, France, The Netherlands and Belgium). Species Distribution Models were calibrated with the global occurrence of species and a set of high-resolution (9×9 km) environmental (e.g. topography, climate, geology) layers and human footprint proxies (e.g. the human influence index, population density, road proximity). Our analyses suggest that the global occurrence of a wide range of invaders is primarily limited by climate. Temperature tolerance was the most important factor and explained on average 42% of species distribution. Nevertheless, factors related to the human footprint explained a substantial amount (23% on average) of species distributions. When global models were projected into the focus area, spatial predictions integrating the human footprint featured the highest cumulative risk scores close to transport networks (proxy for invasion pathways) and in habitats with a high human influence index (proxy for propagule pressure). We conclude that human related information–currently available in the form of easily accessible maps and databases—should be routinely implemented into predictive frameworks to inform upon policies to prevent and manage invasions. Otherwise we might be seriously underestimating the species and areas under highest risk of future invasions.
Highlights
Species Distribution Models (SDMs) are increasingly used to investigate spatial patterns in the distribution of species [1], including invasive ones [2]
SDMs correlate the occurrence of a given species with the environmental conditions of the sites it inhabits in order to locate areas that are most similar to its current distribution, and likely to be the most susceptible to invasion in the future [3]
Using SDM, we modelled the distribution of 72 invasive species covering a broad spectrum of life forms and habitats: terrestrial plants, terrestrial animals, freshwater and marine organisms
Summary
Species Distribution Models (SDMs) are increasingly used to investigate spatial patterns in the distribution of species [1], including invasive ones [2]. SDMs correlate the occurrence of a given species with the environmental conditions of the sites it inhabits in order to locate areas that are most similar to its current distribution, and likely to be the most susceptible to invasion in the future [3]. Predictive SDMs have traditionally been calibrated with bioclimatic factors that are known to constrain species distribution at regional to global scales [4]. Temperature affects body size, reproduction, growth and survival, and is a key factor in determining the success of non-native species during different stages of the invasion process [5]. Non-native species often exhibit an extraordinary ability for adaptation and expand their distribution towards new climates [6]. Climatic factors alone may be insufficient for accurate prediction of the potential distribution of invasive species [7,8,9]
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