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The 100th of the world's worst invasive alien species

DOI:10.1007/s10530-013-0561-5
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Gloria M. Luque at Université Paris-Sud 11
Gloria M. Luque
Céline Bellard at Center for biodiversity and environment research, University College of London
Céline Bellard
  • Center for biodiversity and environment research, University College of London
Cleo Bertelsmeier at University of Lausanne
Cleo Bertelsmeier
Elsa Bonnaud at Université Paris-Sud 11
Elsa Bonnaud
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Biological invasions are among the greatest threats to global biodiversity, but in contrast to most other global threats, they suffer from specific communication issues. Our paper presents the first new addition to the widely cited IUCN list of ''100 of the world's worst invasive species'', a list created a decade ago in response to these communication issues. We briefly present this list, the recent removal of one species from that list, and the rationale to include a novel, 100th species to replace it. The new species of this list, giant salvinia (Salvinia molesta), was chosen by the community of invasion biologists (over 650 experts from over 60 countries). This new addition to the list will draw public attention to the damage caused by invasive alien species and it will help stimulate the necessary discussion of this critical issue in science and policy circles.
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INVASION NOTE
The 100th of the world’s worst invasive alien species
Gloria M. Luque •Ce
´line Bellard •Cleo Bertelsmeier •
Elsa Bonnaud •Piero Genovesi •Daniel Simberloff •
Franck Courchamp
Received: 14 May 2013 / Accepted: 18 September 2013
ÓSpringer Science+Business Media Dordrecht 2013
Abstract Biological invasions are among the
greatest threats to global biodiversity, but in contrast
to most other global threats, they suffer from specific
communication issues. Our paper presents the first
new addition to the widely cited IUCN list of ‘‘100 of
the world’s worst invasive species’’, a list created a
decade ago in response to these communication issues.
We briefly present this list, the recent removal of one
species from that list, and the rationale to include a
novel, 100th species to replace it. The new species of
this list, giant salvinia (Salvinia molesta), was chosen
by the community of invasion biologists (over 650
experts from over 60 countries). This new addition to
the list will draw public attention to the damage caused
by invasive alien species and it will help stimulate the
necessary discussion of this critical issue in science
and policy circles.
Keywords Salvinia molesta Biological
invasions ISSG
Introduction
Although invasive alien species (IAS) are regarded as
the second largest threat to biodiversity worldwide
(after habitat loss; Clavero and Garcia-Berthou 2005;
Simberloff et al. 2013), and their economic cost
probably exceeds US$300 billion per year worldwide
(Pimentel et al. 2000; Genovesi 2011), the increased
adoption of specific legislation by many nations has
had limited effect on the rate of new introductions
(McGeoch et al. 2010). In Europe for example, over
twelve thousand alien species have been documented
(Hulme et al. 2009), with an increase of over 76 % in
alien species over the last 40 years (Butchart et al.
2010). Despite the progress of a large, dedicated
community of researchers and managers worldwide,
management successes against invasive alien species
are still outnumbered by new introductions. Obvi-
ously, our improved knowledge about the harm they
can cause, better management procedures to prevent
new introductions, and more efficient eradication
protocols remain insufficient (Genovesi 2011). New
introductions in fact parallel the increase in intercon-
tinental transportation of goods and people, which
allows species to overcome long distances and geo-
graphical barriers. In addition, owing to the frequent
time lags between introduction and observed impact,
G. M. Luque (&)C. Bellard C. Bertelsmeier
E. Bonnaud F. Courchamp
Ecologie, Syste
´matique et Evolution, UMR CNRS 8079,
Univ Paris-Sud, Orsay, France
e-mail: gloria.luque@u-psud.fr
P. Genovesi
Chair IUCN SSC Invasive Species Specialist Group,
Institute for Environmental Protection and Research,
Rome, Italy
D. Simberloff
Department of Ecology and Evolutionary Biology,
University of Tennessee, Knoxville, TN, USA
123
Biol Invasions
DOI 10.1007/s10530-013-0561-5
the full extent of current invasions will not be
recognized for several decades (Essl et al. 2011).
Biological invasions might also increase further in the
future because of global environmental changes, in
particular climate and land use changes (Walther et al.
2009; Bellard et al. 2013).
Need to communicate about IAS
Although the current biodiversity crisis has generated
concern both among the general public and with
decision makers, IAS have proven difficult to deal
with. In particular, awareness of the threat represented
by biological invasions is impeded by the lack of a
clear, identifiable target, owing to the tremendously
high number of IAS and the even higher number of
species that have the potential to become invasive.
Consequently, not only are the programs aiming to
limit the impacts of IAS still insufficient, but also the
very awareness of the threats caused by IAS remains
diffuse. Given these difficulties, invasion biologists
have recognized that the need to communicate more
efficiently and authoritatively is a key to success. Yet,
among so many species of microorganisms, plants,
invertebrates, and vertebrates, marine, freshwater, and
terrestrial alike, communication efforts are often
diluted, whereas specific targets are better at eliciting
attention from the public and decision makers. In
1999, the International Union for the Conservation of
Nature (IUCN), through its Invasive Species Special-
ist Group (ISSG) of the Species Survival Commission,
set up a remarkable communication tool to address this
issue: a list of 100 high-profile invasive species, all
known to be tremendously harmful and prompting a
dire need for conservation action. Subsequently, the
list of ‘‘100 of the world’s worst invasive alien
species’’ has boosted global awareness.
100 of the world’s worst invasive species
This list of 100 species was derived according to two
criteria: their serious impact on biodiversity and/or on
human activities, and their potential to illustrate
important issues surrounding biological invasions
(Lowe et al. 2004). To ensure the inclusion of a wide
variety of examples, only one species from each genus
was selected. As a result, the 100 species belong to
many taxonomic groups, from microorganisms to
plants and vertebrates (Fig. 1). They come from all
continents and have impacts on local biodiversity and
ecosystem functioning, and on agriculture, forestry, or
aquaculture; they affect landscape or real estate values
and constitute health hazards, as allergens or as
disease vectors. Two points were relentlessly empha-
sized as this list was promoted. First, absence from the
list does not imply that a species poses a lesser threat.
Second, these are not the 100 worst invaders, but 100
among the worst. Evidently, it would be very hard to
rank diverse species with such varied impacts. The
aim of this list was to highlight the importance of
invasive alien species, by emphasizing those that
belong to the list, but avoiding at all cost downplaying
the importance of the thousands of species not on this
list.
This list has been a tremendous success in terms of
communication, with over 1,000 citations in the
scientific literature and a number of similar lists
promulgated for different regions or environments
(e.g., Streftaris and Zenetos 2006; Vila
`et al. 2009).
Among the achievements is the successful global
eradication of the rinderpest virus, a mere decade after
the list was constructed, which reduced it to 99 species
(World Organisation for Animal Health 2011). Sub-
sequently, it was decided to replace the eliminated
species, to keep the list at 100, rather than working to
reduce it progressively. This course of action has the
double advantage of highlighting yet another major
invader and insisting on the fact that species that are
not on the IUCN 100 list can nonetheless be among the
worst invaders worldwide. On the contrary, constantly
reducing the list would have given the misleading
impression that IAS were getting gradually fewer.
The selection of the 100th species
To this effect, it was decided to enlist the community
of invasion biologists in selecting the new, 100th IAS
for the list. As it would be difficult to get a meaningful
consensus from a pool of tens of thousands of IAS
species, we first selected a reasonable number of
candidates among which the community was invited
to choose. Following the same thinking behind the
development of the original list, this approach was not
meant to be an accurate and objective selection of the
worst invaders, but rather a rational selection of some
G. M. Luque et al.
123
of the worst, as it is difficult to classify objectively and
quantitatively one species as worse than another. We
thus amassed invasive alien species inventories/
checklists from 16 global and national databases,
including the ISSG Global Invasive Species Database
(GISD), CABI Invasive Species Compendium (ISC)
and DAISIE (Delivering Alien Invasive Species
Inventories for Europe), and selected over 10,000
IAS that we ranked based on the number of times they
were listed. We then accounted for emerging threats,
i.e., species that are not yet widespread but that are
known to have major impacts and/or a high spread
rate, so that they would rise in the ranking. We
selected the first 50 species and assigned to each of
them a score of (1) spread: the number of continents
already invaded and (2) impact: ecological, economic
and/or health. We finally eliminated the species in
genera that were already represented in the 100-list, as
well as those that had a strong positive value (cultural
or economic). We then selected the 10 species with the
highest sum of scores. These 10 species were six
aquatic and four terrestrial organisms, five plants and
five animals. They came from South and North
America, Asia, Europe and Oceania and had strong
ecological, economic and/or health impacts. They
included organisms that are invasive throughout the
world, such as the American waterweed Elodea
canadensis, but also still localized but very fast
spreading organisms, such as the lionfish Pterois
volitans, or species with very high local impact, such
as the Burmese python Python molurus bivittatus. The
address of a dedicated web site (Courchamp 2013) was
distributed via various networks to the invasion
biology community throughout a period of 3 months.
The site included a description of the selection
protocol, a short presentation of the 10 candidates
and an explanation on how to vote online for the latest
and 100th representative of the IUCN ‘‘100 of the
worst’’ list. We used the Condorcet Vote, a procedure
that selects the candidate (here a species) that would
win by majority rule in all pairings against the other
candidates (Courchamp 2013). It requires only one
round of voting.
A total of 652 experts from 63 countries voted, and
they selected giant salvinia, Salvinia molesta, as the
100th species to join the IUCN list of ‘‘100 of the
world’s worst invasive alien species’’. It is a free-
floating aquatic fern (Fig. 2) native to southeastern
Brazil, first observed outside its native range in 1939.
It has since spread widely throughout the tropics and
subtropics across the world and is currently found in
31 countries on 4 continents (Fig. 2). This plant is
moved in part by the trade in ornamental plants for fish
tanks and ponds. The presence of giant salvinia is
prominent in slow-moving, quiet freshwater systems.
Its fast growth rate, under optimal conditions, enables
this plant to double its abundance in only a few days. It
forms 10–20 cm thick floating mats (Fig. 2) that
prevent light penetration of the water column, reduc-
ing oxygen content and degrading water quality for
Fig. 1 Taxonomic representation of 100 of the world’s worst alien invasive species
The 100th of the world’s worst invasive alien species
123
aquatic organisms, drastically damaging these eco-
systems over large areas (Fig. 2). In addition, dense
mats of salvinia can impede water-based transport,
reduce water quality, impair aesthetic values, clog
irrigation and power generation intakes, and harm
local fisheries (Julien et al. 2002). Maintaining giant
salvinia at low levels is generally attempted by the use
of herbicides, which are notoriously costly. Biological
control programs can achieve local successes but have
not controlled salvinia in other areas, nor prevented its
spread (Room et al. 1984; Julien et al. 2002).
Although salvinia definitely deserves its place in
the list, other species among the 10 candidates, and
beyond, could have been selected instead. The new
status of salvinia does not make it suddenly more
invasive, more damaging or more rapidly spreading.
Nor has the need to remove it from invaded areas, or to
prevent new introductions, suddenly become more
critical. However, a listing in this very special
catalogue will surely grant this species some extra
attention, which will help impede its establishment
and spread from now on. Invasion biologists also
expect and hope that this new addition to the list will
draw public attention to the damage caused by IAS in
general. The IUCN list of ‘‘100 of the world’s worst
invasive alien species’’ is a potent communication
tool. One of the expectations of the invasion biology
community when building this list was, oddly, that it
would help them to remove species from it, as often as
possible. Control of alien invasive species, even
eradication when possible, is crucial to preserve
biodiversity and lower costs for human societies.
However, although reactive programs are required,
they remain far more expensive than proactive
programs (Kaiser and Burnett 2010). Prevention, early
detection, and rapid response are the three pillars of
success, and this rest on effective communication.
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The 100th of the world’s worst invasive alien species
123
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All continents, excluding Antarctica and the Artic, have been affected by incursion from alien freshwater fish species. Australia has not been spared. Four hundred and fifty species have now been declared on the ornamental importation list, making management a real challenge. With approximately 25 non-native species documented, Papua New Guinea (PNG) has likely some problems with invasive freshwater fish. Many of these species have been intentionally introduced to increase access to food as a protein source for remote communities or have spread naturally from western parts of Java and Indonesia, and now constitute a large biomass on some floodplain areas in PNG. The Torres Strait is located between PNG and northern Queensland and was previously a land bridge, though now under higher sea levels the region exists as a series of approximately 300 islands. The threat of further range extension of freshwater fish from PNG into northern Queensland via the Torres Strait Islands is significant, with two invasive fish species already recorded on northern islands of the Torres Strait (climbing perch, Anabas testudineus which has been continually recorded for the past decade; and recently the GIFT tilapia, Oreochromis niloticus). Here we present a case to control further spread of invasive freshwater fish species towards Australia, using a Land and Sea Ranger program, where Rangers are trained to be confident in the identification of pest fish species and to implement strategies to protect their borders from potential future incursions. The success of this program relies on Rangers to continue partaking in surveillance monitoring of coastal waters, checking and controlling for any new invasive species moving from PNG into Australian waters. We outline the biosecurity obligation under Article 14 of the Treaty between the two nations, which identifies the importance of conservation and protection of coastal floodplains from invasive species, and the spread between both nations.
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Limnological Response of Las Curias Reservoir, San Juan, Puerto Rico: Successful Management of the Invasive Aquatic Fern, Salvinia molesta
Article
Full-text available
  • Nov 2023
The anthropogenic deterioration of aquatic ecosystems affects water resources due to agricultural malpractices, pollution from domestic septic tanks, recreational activities, and poor watershed management, among other factors. This study examines the management of Las Curias Reservoir, San Juan, Puerto Rico, after the 2016 arrival of the invasive aquatic fern Salvinia molesta. In September 2019, a community-led initiative introduced the Cyrtobagous salviniae weevil, an effective biological control agent for S. molesta, and commenced a mechanical removal campaign using an aquatic harvester. Limnological sampling (September 2019 to September 2022) and drone flights were employed to measure physicochemical and floating plant cover changes, respectively, in the reservoir. Monitoring of weevils in the reservoir demonstrated rapid establishment and dispersal, which resulted in visible damage including browning of plants and eventually sinking of entire mats. From 23 July 2019, the reservoir surface was predominantly covered by salvinia, occupying an area of 17.7 ha (100% coverage). This coverage decreased to 12.6 ha (71%) by 29 January 2021. By 12 August 2022, the coverage had been substantially reduced to just 1.1 ha, representing only 6% of the reservoir surface. In 2022, the reservoir recorded an average dissolved oxygen concentration of 2.4 mg L−1 (±0.0, n = 144), the highest in the study period and indicative of ecosystem recovery. After three years of control efforts, dissolved oxygen, pH, and specific conductance returned to levels recorded prior to Salvinia molesta introduction. This ecosystem recovery, a first in Puerto Rico, could be attributed to early use of mechanical control and the long-term impact of biological control.
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‘Trojan fish’: Exploring haplotypic and genotypic diversity of introduced Gambusia holbrooki in India
Article
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Assessing haplotypic and genotypic diversity is crucial for comprehending biological invasion dynamics and devising effective management strategies. In India, Gambusia spp. were introduced in the early twentieth century for mosquito biocontrol, but recent studies have demonstrated their detrimental impact on native biota. The present research employs molecular tools to investigate the haplotypic and genotypic diversity of Gambusia species in India. The findings reveal a greater distribution of Gambusia holbrooki and a lesser occurrence of Gambusia affinis in India. The study underscores that G. holbrooki was initially brought into India from Europe and later multiple times from other regions across the globe. Our global haplotypic network shows the presence of a single G. affinis haplotype, which is narrowly distributed in the northeastern part of India. Additionally, our population genetic analyses exhibit a low genetic variability and significant population genetic structuring among G. holbrooki populations. This study emphasizes the significance of evaluating haplotypic and genotypic diversity to develop a comprehensive understanding of the invasion history and dynamics of introduced species, thereby aiding in the development of effective management strategies that mitigate their negative impact on native biota.
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Population increase and range expansion of White-winged Parakeets (Brotogeris versicolurus) in Puerto Rico
Article
Full-text available
  • Oct 2023
Puerto Rico has experienced multiple introductions of Psittaciformes that have established self-sustaining populations, and the White-winged Parakeet (Brotogeris versicolurus) has been considered the most successful introduced psittacine species on the island. In this study, we evaluated their population size, calculated growth rates, and estimated the breeding proportion in two populations by performing roost counts for four consecutive years in addition to evaluating their range expansion. We also assessed their diet and breeding ecology. Population estimates of the parakeets during the study period showed a steady increase, with a maximum of ca. 3,010 individuals (± 673 SD) in the San Germán population, and ca. 3,128 individuals (± 762 SD) in the San Patricio population. Both populations exhibited a geometric mean population growth rate of 1.25 per year. As expected, the data indicates that the populations experienced a lag-phase prior to exponential growth. This is supported by the island-wide sighting trends and range expansion. Moreover, we detected range expansion during our study through the colonization of new areas. The population estimates and population growth rates, along with the sighting trends and their wide distribution, makes the White-winged Parakeet the most successful psittacine species in Puerto Rico. The factors leading to their invasion success are likely to include propagule pressure, their diet breadth, and their capability as primary nesters in the abundant termite mounds on the island. Currently, the growth rate of the invasive White-winged Parakeet population does not appear to be limited by predators, resources, or nest availability, and we expect them to continue increasing and expanding their range. Keywords biological invasions, Brotogeris versicolurus, islands, population growth, Psittacidae, Puerto Rico Resumen Incremento poblacional y expansión de la distribución del perico aliblanco (Brotogeris versicolurus) en Puerto Rico • Puerto Rico ha experimentado múltiples introducciones de Psittaciformes, los cuales han establecido poblaciones autosostenibles, y Brotogeris versicolurus ha sido considerada la especie de psitácida introducido más exitosa en la isla. En este estudio, evaluamos sus tamaños poblacionales, calculamos sus tasas de crecimiento y estimamos la proporción de individuos reproductores mediante la realización de conteos de dormideros por cuatro años consecutivos en dos poblaciones. Además, evaluamos la expansión de su área de distribución y su dieta y ecología reproductiva. Las estimaciones de la población de pericos durante el periodo de estudio mostraron un aumento constante, con un máximo de unos 3.010 individuos (± 673 DE) en la población de San Germán, y de unos 3.128 individuos (± 762 DE) en la población de San Patricio. Ambas poblaciones mostraron una tasa media geométrica de crecimiento poblacional de 1.25 individuos por año. Como era de esperar, los datos indican que las poblaciones experimentaron una fase de latencia (“lag-phase”) antes del crecimiento exponencial. Las tendencias de avistamiento en toda la isla y la expansión del área de distribución respaldan esta afirmación. Además, durante nuestro estudio detectamos una expansión del área de distribución mediante la colonización de nuevas zonas. Las estimaciones poblacionales y las tasas de crecimiento de la población, junto con las tendencias de avistamiento y su amplia distribución, convierten a Brotogeris versicolurus en la especie de psitácida de mayor éxito en Puerto Rico. Los factores que han contribuido a la invasión de Pericos aliblancos posiblemente incluyen la presión de propágulo, su amplitud de dieta, y su capacidad como anidadores primarios en montículos arbóreos de termitas, los cuales son abundantes en la isla. Actualmente, la tasa de crecimiento de la población invasora de esta especie no parece estar limitada por depredadores, recursos o disponibilidad de nidos, y esperamos que siga expandiendo su área de distribución. Palabras clave Brotogeris versicolurus, crecimiento poblacional, invasiones biológicas, islas, Psittacidae, Puerto Rico Résumé Augmentation de la population et expansion de l’aire de répartition du Toui à ailes variées (Brotogeris versicolurus) à Porto Rico • Porto Rico a connu de nombreuses introductions d’espèces de Psittaciformes, qui ont établi des populations autonomes, et le Toui à ailes variées (Brotogeris versicolurus) est considéré comme le psittacidé introduite le plus prospère sur l’île. Dans la présente étude, nous avons estimé la taille des populations de Toui à ailes variées, calculé les taux de croissance et évalué la proportion de la population qui se reproduise dans deux populations, en effectuant des comptages au dortoir pendant quatre années consécutives, ainsi qu’une évaluation de l’expansion de leur aire de répartition. Nous avons également évalué le régime alimentaire et l’écologie de reproduction de l’espèce. Les estimations des populations au cours de la période d’étude ont mis en évidence une augmentation constante, avec un maximum d’environ 3 010 individus (écart-type ± 673) dans la population de San Germán, et d’environ 3 128 individus (écart-type ± 762) dans la population de San Patricio. Les deux populations ont connu une croissance moyenne géométrique de 1,25 par an. Comme prévu, les données indiquent que les populations ont traversé une phase de latence avant de croître de manière exponentielle. Cela est confirmé par les tendances des observations sur l’ensemble de l’île et par l’expansion de l’aire de répartition. Au cours de notre étude, nous avons détecté une expansion de l’aire de répartition en observant la colonisation de nouvelles regions. Les estimations et les taux de croissance des populations, ainsi que les tendances des observations et la large répartition de l’espèce, font du Toui à ailes variées le psittacidé le plus prospère à Porto Rico. Les facteurs qui ont contribué à cette invasion sont probablement la pression exercée par les individus colonisateurs, la diversité de leur régime alimentaire et leur capacité à nicher dans les nids de termites arboricoles qui sont nombreux sur l’île. Actuellement, le taux de croissance des populations envahissantes de Toui à ailes variées ne semble pas être limité par les prédateurs, les ressources alimentaires ou la disponibilité des nids, et nous prévoyons que cette espèce continue d’augmenter et d’étendre son aire de répartition. Mots clés Brotogeris versicolurus, croissance de la population, îles, invasions biologiques, Porto Rico, Psittacidae
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Alien Marine Species in the Mediterranean - the 100 'Worst Invasives' and their Impact
Article
Full-text available
  • Dec 2006
A number of marine alien species have been described as invasive or locally invasive in the Medi-terranean because of their proliferation, and/or their geographical spread and/or impact on native populations. Based on that information and on the documented impact they have on the biodiversity and socioeconomics of the basin, a preliminary list of the 100 'worst' Invasive Alien Species (IAS) in the Mediterranean has been produced and presented in this work along with details on their impact. Emphasis is given to their impact on socioeconomics (fi sheries/aquaculture, health & sanitation, in-frastructure & building), documented for 43 species. Such selection of the 'worst' IAS was diffi cult and controversial and is expected to attract much attention and scientifi c criticism since not only can the documentation of the impact of IAS be controversial, but also their inventory can be biased towards the effort and resources devoted to the study of the impact of certain species/taxonomic groups. Thus, while marine plants (phytobenthos and phytoplankton) are fairly well studied, less attention has been paid to the impact of vertebrates and even less to invertebrates. Nevertheless, the list highlights the need for continued research on the issue (monitoring aliens and their impact for an integrated ecosystem based management approach over the entire area). The preliminary list can provide the basis for selecting indicator species within the Mediterranean and thus be the common ground to build cooperation about IAS within countries in the region.
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Environmental and Economic Costs of Nonindigenous Species in the United States
Article
Full-text available
  • Jan 2000
ABSTRACT Invading non-indigenous species in the United States cause major environmental damages,and losses adding up to more than $138 billion per year. There are approximately 50,000 foreign species and the number is increasing. About 42% of the species on the Threatened or Endangered species lists are at risk primarily because of non-indigenous species. In the history of the United States, approximately 50,000 non-indigenous (non-native)
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Are we turning the tide? Eradications in times of crisis: how the global community is responding to biological invasions
Conference Paper
Full-text available
  • Jan 2011
INTRODUCTION In 2002, the global community committed to achieve, by 2010, a signifi cant reduction in the loss of biodiversity and -in order to verify what has been done to reach this goal -the UN declared 2010 the International Year of Biodiversity. Unfortunately, the indicators that have been collected in recent years show that there is little to celebrate. The global rate of biodiversity loss appears to have increased, and so have most of the pressures affecting the diversity of life on earth. For example, the overall status of birds in different regions of the world from 1988 to 2008 has declined, with the proportion of threatened birds increasing from 11.1% to 12.2% in that 20-year period (Butchart et al. 2004), and other taxa appear to be in a worse conservation shape (Vie et al. 2009). The continuing loss of biodiversity is particularly alarming on island ecosystems, which host a large proportion of the world endemics. Most threatened species are, in fact, found on islands (Vié et al. 2008); about one-fi fth of the world's threatened amphibian fauna, one-quarter of the world's threatened mammals and more than one-third of the world's threatened birds are endemic to island biodiversity hotspots (Fonseca et al. 2006). And it is these hotspots that have had most of the recent extinctions; 88% of known bird extinctions have been on islands (Butchard et al. 2006), mostly because of biological invasions. Invasive species have in fact been identifi ed as a key factor in 54% of all known extinctions, and the only factor in 20% of extinctions (Clavero and Garcia-Berthou 2005). ARE WE TURNING THE TIDE? Instead of recording a mitigation of the drivers of biodiversity loss, all the evidence confi rms that the number of invasive alien species is rapidly growing in all environments and among all taxonomic groups (Genovesi et al. in press), raising extinction risks for birds, mammals and amphibians (Clavero et al. 2009). The most effective way to address this threat is through a combination of prevention measures, early detection at and near borders, prompt eradication of newly-arrived unwanted aliens, and effective management of established invasive species. Eradication is thus a key component of a global response to invasions, and for this reason Dan Simberloff, in his opening speech at the 2001 international conference on island invasive species, stressed the urgent need for a much wider application of this conservation tool. He challenged decision makers and practitioners to be much more ambitious in their efforts to combat invasions, overcoming the prejudices and groundless opposition that have so far limited the potential range of application of removal campaigns. In the present contribution I will thus discuss developments since 2001, and try to assess to what extent we have been able to respond to the call for more action that was launched on that occasion. ERADICATION: AN EFFECTIVE RESPONSE TO INVASIONS There is increasing evidence that successful invasive species removal campaigns have played a crucial role in improving the conservation status of several taxonomic groups. Many endemic and rare species have recovered following the eradication of invasives threatening their persistence. An assessment of red list data has shown that 11 bird, fi ve mammal and one amphibian species have improved their conservation status as a result of eradications of invasive species (McGeoch et al. 2010). These positive outcomes are also the result of the signifi cant improvements in the science of eradication over recent decades. As discussed by Alan Saunders in this volume (Saunders et al. 2011), the number of multi-species eradications is constantly increasing, and the experience gathered in the last 20 years now minimises the risk of undesired effects of eradications, ensuring selectivity of the removal methods and minimised impacts on the environment. Furthermore, we are increasing our ability to predict potential ecosystem changes caused by the removal of invasive species, and adaptive implementation of eradications has prevented or rapidly mitigated potential unexpected chain reactions (see Courchamp et al. 2011; Morrison 2011). We can now target much more challenging taxonomic groups, such as plants and terrestrial invertebrates. Regarding the latter, up to a few years ago invertebrates were generally considered as not eradicable, with few exceptions. In his paper of 2002, Simberloff stressed the need to test whether eradication of insects on continents was really out of the question. The Abstract Biological invasions are a major driver of the ongoing loss of biodiversity, and if the global community wants to reverse this trend it is crucial that formal commitments be transformed into action. On the basis of the more than 1000 eradications attempted worldwide, we can now say that eradication projects are a powerful conservation tool that has contributed to improving the conservation status of several threatened species. The growing sophistication of the scientifi c and technical basis of eradications now allows us to target much larger areas than in the past, and the eradication of species in much more challenging taxonomic groups. Also, it is now possible to minimise the risk of undesired effects of eradications, ensuring selectivity of the removal methods and minimised impacts on the environment. Despite these advances, the implementation of removal campaigns is still limited, partly by prejudices and ignorance, but also by serious concerns from a part of society, which we need to take seriously into account. It is important to ensure a correct and transparent fl ow of information. If the global community wants to fulfi l the commitment to reverse the present rate of biodiversity loss, it is crucial to increase the application of invasive species removal campaigns and to support large scale fl agship projects, as well as by developing frameworks that permit the rapid detection and removal of newly established invasive species.
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Impacts of Biological Invasions: What's What and the Way Forward
Article
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Study of the impacts of biological invasions, a pervasive component of global change, has generated remarkable understanding of the mechanisms and consequences of the spread of introduced populations. The growing field of invasion science, poised at a crossroads where ecology, social sciences, resource management, and public perception meet, is increasingly exposed to critical scrutiny from several perspectives. Although the rate of biological invasions, elucidation of their consequences, and knowledge about mitigation are growing rapidly, the very need for invasion science is disputed. Here, we highlight recent progress in understanding invasion impacts and management, and discuss the challenges that the discipline faces in its science and interactions with society.
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Will Climate change promote future invasions?
Article
  • Jul 2013
Biological invasion is increasingly recognized as one of the greatest threats to biodiversity. Using ensemble forecasts from species distribution models to project future suitable areas of the "100 of the world's worst invasive species" defined by the IUCN, we show that both climate and land use changes will likely cause drastic species range shifts. Looking at potential spatial aggregation of invasive species, we identify three future hotspots of invasion in Europe, northeastern North America, and Oceania. We also emphasize that some regions could lose a significant number of invasive alien species, creating opportunities for ecosystem restoration. From the list of 100, scenarios of potential range distributions show a consistent shrinking for invasive amphibians and birds, while for aquatic and terrestrial invertebrates distributions are projected to substantially increase in most cases. Given the harmful impacts these invasive species currently have on ecosystems, these species will likely dramatically influence the future of biodiversity. This article is protected by copyright. All rights reserved.
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Establishment in Australia of two insects for biological control of the floating weed Salvinia molesta Mitchell
Article
In attempts at the biological control of Salvinia molesta in Australia, the curculionid Cyrtobagous sp. was released at eight sites and became established at seven of them. At these seven sites, air temperatures ranged from less than 0°C to more than 45°C and the mean concentration of nitrogen in S. molesta ranged from 1·18 to 1·82% of dry weight. Establishment was effected by releasing 200 adults, and the shortest time for extensive damage to be caused to the weed was four months. Cyrtobagous sp. dispersed in undamaged S. molesta at rates of a few metres per month. The pyralid Samea multiplicalis Gn. was released, and became established, at three sites and spread at least 170 km north and south in 20 months. At the sites colonised, air temperatures ranged from less than 0°C to more than 45°C and the mean nitrogen concentration in Salvinia molesta ranged from 1·34 to 3·30% of dry weight. Establishment was effected by releasing 800 larvae, and the shortest time for extensive damage to be caused to S. molesta was three months. Contrasts in the biology and ecology of the two species of insects are discussed briefly as is competition between them for food. In late 1983, Cyrtobagous sp. had achieved control of S. molesta at five sites, while Samea multiplicalis had achieved control at none. It is suggested that S. multiplicalis might perform better in locations which experience maximum temperatures lower than those in the present distribution.
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Global indicators of biological invasion: Species numbers, biodiversity impact and policy responses
Article
Aim Invasive alien species (IAS) pose a significant threat to biodiversity. The Convention on Biological Diversity’s 2010 Biodiversity Target, and the associated indicator for IAS, has stimulated globally coordinated efforts to quantify patterns in the extent of biological invasion, its impact on biodiversity and policy responses. Here, we report on the outcome of indicators of alien invasion at a global scale. Location Global. Methods We developed four indicators in a pressure‐state‐response framework, i.e. number of documented IAS (pressure), trends in the impact of IAS on biodiversity (state) and trends in international agreements and national policy adoption relevant to reducing IAS threats to biodiversity (response). These measures were considered best suited to providing globally representative, standardized and sustainable indicators by 2010. Results We show that the number of documented IAS is a significant underestimate, because its value is negatively affected by country development status and positively by research effort and information availability. The Red List Index demonstrates that IAS pressure is driving declines in species diversity, with the overall impact apparently increasing. The policy response trend has nonetheless been positive for the last several decades, although only half of countries that are signatory to the Convention on Biological Diversity (CBD) have IAS‐relevant national legislation. Although IAS pressure has apparently driven the policy response, this has clearly not been sufficient and/or adequately implemented to reduce biodiversity impact. Main conclusions For this indicator of threat to biodiversity, the 2010 Biodiversity Target has thus not been achieved. The results nonetheless provide clear direction for bridging the current divide between information available on IAS and that needed for policy and management for the prevention and control of IAS. It further highlights the need for measures to ensure that policy is effectively implemented, such that it translates into reduced IAS pressure and impact on biodiversity beyond 2010.
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Spatial Economic Analysis of Early Detection and Rapid Response Strategies for an Invasive Species
Article
Economic impacts from invasive species, conveyed as expected damages to assets from invasion and expected costs of successful prevention and/or removal, may vary significantly across spatially differentiated landscapes. We develop a spatial-dynamic model for optimal early detection and rapid response (EDRR) policies, commonly exploited in the management of potential invaders around the world, and apply it to the case of the Brown treesnake (Boiga irregularis) in Oahu, Hawaii. EDRR consists of search activities beyond the ports of entry, where search (and potentially removal) efforts are targeted toward areas where credible evidence suggests the presence of an invader. EDRR costs are a spatially dependent variable related to the ease or difficulty of searching an area, while damages are assumed to be a population-dependent variable. A myopic strategy in which search only occurs when and where current expected net returns are positive is attractive to managers, and, we find, significantly lowers present value losses (by $270 m over 30 years). We find further that in the tradeoff between search costs and damages avoided, early and aggressive measures that search some high priority areas beyond points of entry even when current costs of search exceed current damages can save the island more ($295 m over 30 years). Extensive or non-targeted search is not advised however.
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