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The Global Islands Invasive Vertebrate Eradication Database: A tool to improve and facilitate restoration of island ecosystems

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Islands are important for the conservation of biodiversity because they house 20% of terrestrial plant and vertebrate species, have suffered 64% of IUCN-listed extinctions and have 45% of IUCN-listed critically endangered species. Yet islands make up only about five percent of the earth’s surface. The main cause of extinction and endangerment to biodiversity on islands is the presence of invasive vertebrates. Fortunately, many future extinctions can be prevented by eradicating invasive vertebrates from islands. To assess the current state of this conservation tool, we are compiling a global database of terrestrial vertebrate eradications from islands, including successes and failures. To date, in the Global Islands Invasives Vertebrate Eradication Database we have documented approximately 950 island eradication attempts involving 28 species of invasive vertebrates in 12 families. These are preliminary data and will be updated and checked for accuracy as part of the Island Invasives: Eradication and Management conference, Auckland 2010. Most eradication attempts have been of rodents (textgreater350) and bovid ungulates (textgreater160). Moderate numbers of eradication attempts have been of cats (textgreater90), suid ungulates (textgreater55), and rabbits (textgreater45). Most projects have been on islands smaller than 500 ha (68%) and in temperate climates (72%). Targeting eradications on larger and more tropical islands would lead to the protection of more biodiversity. To this end, our vision is to maintain an accurate, web-accessible, regularly updated database that can be used to promote and improve the protection of island ecosystems by eradicating invasive vertebrates.
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Island invasives: eradication and management
74
INTRODUCTION
Islands are the epicentre of the extinction crisis. While
islands make up only ve percent of the earth’s surface
area, they support 20% of all biodiversity, including a
disproportionately high level of endemic species (Kier
et al. 2009). This biodiversity is particularly fragile and
the vast majority of extinctions have been island species.
For example, about 95% of bird, 90% of reptile and
70% of mammal extinctions have been on islands. These
extinctions are primarily the result of the introduction of
invasive vertebrates to islands. Fortunately, techniques
to remove invasive vertebrates from islands are available
and the practice is becoming an accepted conservation
management tool. To better understand how this tool has
been used, and to improve its future use, we developed,
and are populating, a database of all vertebrate eradication
efforts on islands (www.islandconservation.org/db).
The eradication of invasive vertebrates from islands is
among the most challenging and benecial actions land
managers can take to restore islands and protect threatened
species. Collating and understanding the lessons learned in
previous efforts to eradicate invasive vertebrates are critical
to improving and promoting this valuable conservation
tool. Published global reviews of eradication efforts
include regional approaches for all taxa (Clout and Russell
2006; Genovesi and Carnevali 2011; Lorvelec and Pascal
2005) and global approaches for individual taxa such as
goats (Capra hircus; Campbell and Donlan 2005), cats
(Felis catus; Nogales et al. 2004; Campbell et al. 2011),
rodents (Howald et al. 2007), and mongoose (Herpestes
spp.; Barun et al. 2011). These provide valuable reviews
of the eradication efforts for these species and regions.
Most importantly, these reviews provide land managers
The Global Islands Invasive Vertebrate Eradication Database: A tool to
improve and facilitate restoration of island ecosystems
B. Keitt1, K. Campbell1, A. Saunders2, M. Clout3, Y. Wang1, R. Heinz4, K. Newton4, and B. Tershy4
1Island Conservation, Center for Ocean Health, University of California, Santa Cruz, 100 Shaffer Road, Santa Cruz,
C. 95060 USA. <brad.keitt@islandconservation.org>. 2Landcare Research, Private Bag 3127, Waikato Mail Centre,
Hamilton 3240, New Zealand. 3Invasive Species Specialist Group, University of Auckland, Tamaki Campus, Private Bag
92019, Auckland, New Zealand. 4Ecology and Evolutionary Biology Department, Center for Ocean Health, University
of California, Santa Cruz, C. 95060 USA.
Abstract Islands are important for the conservation of biodiversity because they house 20% of terrestrial plant and
vertebrate species, have suffered 64% of IUCN-listed extinctions and have 45% of IUCN-listed critically endangered
species. Yet islands make up only about ve percent of the earth’s surface. The main cause of extinction and endangerment
to biodiversity on islands is the presence of invasive vertebrates. Fortunately, many future extinctions can be prevented
by eradicating invasive vertebrates from islands. To assess the current state of this conservation tool, we are compiling a
global database of terrestrial vertebrate eradications from islands, including successes and failures. To date, in the Global
Islands Invasives Vertebrate Eradication Database we have documented approximately 950 island eradication attempts
involving 28 species of invasive vertebrates in 12 families. These are preliminary data and will be updated and checked
for accuracy as part of the Island Invasives: Eradication and Management conference, Auckland 2010. Most eradication
attempts have been of rodents (>350) and bovid ungulates (>160). Moderate numbers of eradication attempts have been
of cats (>90), suid ungulates (>55), and rabbits (>45). Most projects have been on islands smaller than 500 ha (68%) and
in temperate climates (72%). Targeting eradications on larger and more tropical islands would lead to the protection of
more biodiversity. To this end, our vision is to maintain an accurate, web-accessible, regularly updated database that can
be used to promote and improve the protection of island ecosystems by eradicating invasive vertebrates.
Keywords: Endangered species, threatened species, endemic species, biodiversity, alien species, extinction
Fig. 1 Locations of all of the recorded eradications of invasive vertebrates from islands for which location data are
available (n=664).
Pages 74-77 In: Veitch, C. R.; Clout, M. N. and Towns, D. R. (eds.). 2011. Island invasives: eradication and management.
IUCN, Gland, Switzerland.
Keitt, B.; K. Campbell, A. Saunders, M. Clout, Y. Wang, R. Heinz, K. Newton, and B. Tershy. The Global Islands Invasive Vertebrate Eradication
Database: A tool to improve and facilitate restoration of island ecosystems
75
with information on which combinations of island size,
technique, invasive species, and non-target species are
feasible, and which combinations may have a high risk of
failure. However, to date, there has been no global review
of all vertebrate eradications on islands.
Here we present our vision for a web accessible
database, including an initial analysis that provides
details on eradication attempts including data on island
characteristics, methods used, and contacts. Our goal is
to highlight the most successful techniques, assess trends
in eradication methods, and facilitate communication
between practitioners to improve success. The database
allows analysis of eradication effort for individual target
species, and facilitates analysis of trends across different
target invasive vertebrates.
It is important to note that this is an unnished product,
and we report here on preliminary data as of 15 December
2009. The Island Invasives: Eradication and Management
Conference of February 2010 was used as a forum to
validate and improve the database followed by a more
thorough analysis and presentation at a later date.
METHODS
Data were mined from the published, grey, and
unpublished literature. The bulk of the database came
from the published summary articles for rodents (Howald
et al. 2007), goats (Campbell and Donlan 2005), and cats
(Nogales et al. 2004; Campbell et al. 2011). Additional data
were collected through web searches, telephone interviews,
emails, and specic requests directed at practitioners.
The database provides details of every documented
eradication attempt, which is dened to include failures,
successes, and follow up attempts on the same islands either
after a failure or a reinvasion. Data categories were selected
to provide information about each action, including specic
details on methods, using drop down menus to facilitate
analysis, and text elds to allow detail to be captured.
For some analyses, all target invasive vertebrates were
assigned a category of herbivore, carnivore, or omnivore
(Table 1). Contact information and citations were provided
where possible.
The methods used to populate the database have likely
led to an underestimate of historical eradications, as those
are less likely to be included in published papers or reports,
and the people familiar with those projects are no longer
involved in the eld. The data also likely underestimate
the failure rate for eradications, as failures are less likely to
be reported. For these reasons, we tried to reach as many
individual people as possible to encourage them to report
older eradication efforts and failed eradications in the
database.
Data on location (latitude and longitude), island size,
country, and oceanographic region were extracted from
the Global Islands Database (GID) (Depraetere 2007). For
islands that were not in the GID we used the Meridian Data
Global Island Database. Locations were veried using
Google Earth and corrected if necessary.
RESULTS
As of 15 December 2009, we documented 949 vertebrate
eradication attempts on islands globally (Fig. 1), involving
27 species of mammal and one species of bird. The three
earliest documented eradication attempts were in 1673,
1686, and 1709. All three were of large ungulates and all
three failed. The rst documented successful eradication
was of goats in 1857 on Norfolk Island, Australia.
Seven hundred and eighty six successful eradications
were reported and 41 of those were later reinvaded. Fifty
two eradications are listed as unknown, i.e. there was
information indicating an eradication event took place but
no data were available on the outcome, and eight were listed
as incomplete. Ninety eradications were listed as failed
Table 1 Invasive vertebrates in the database assigned to
omnivore, carnivore and herbivore categories.
Omnivore Carnivore Herbivore
Gallirallus australis Alopex lagopus Bos taurus
Macaca mulatta Canis familiaris Capra hircus
Mus musculus Felis catus Castor canadensis
Rattus rattus Herpestes javanicusEquus caballus
Rattus exulans Mustela vison Lepus nigricollis
Rattus norvegicus Mustela erminea Myocastor coypus
Sus scrofa Mustela furo Oryctolagus cuniculus
Trichosurus vulpecula Mustela nivalis Ovis aries
Procyon lotor Petrogale penicillata
Suncus murinus
Vulpes vulpes
Table 2 Number of eradication attempts and success rate
globally for select invasive vertebrates. An eradication event
is defined as a successful or failed eradication attempt plus
any follow up efforts on the same island.
Invasive vertebrate Number of events Failure rate %
Rattus 348 12.1
Goat 165 4.8
Cat 90 12.5
Pig 56 3.9
Rabbit 48 4.6
Fox 42 2.5
Mus 48 26.8
Mustelid 29 13.0*
Other 113
Total 949 9.1
*50% of the eradication events in the database for mustelids list
unknown for the eradication status so the reported failure rate is
likely inaccurate for this group.
Fig. 2 Cumulative number of successful invasive vertebrate
eradications on islands over time.
Keitt et al.: Islands Vertebrate Eradication Database
Island invasives: eradication and management
76
eradication attempts. The success rate for all eradications
with a known outcome was 91% (n=835, Table 2). Location
data were available for 664 islands and the subsequent
analyses that involve location data are restricted to these
islands.
Since that rst successful eradication over 150
years ago, rats (Rattus spp.) have become the invasive
vertebrates most frequently eradicated from islands, with
348 reported eradication attempts, followed by goats with
165 eradication attempts (Table 2). The pace and scale of
eradications have increased dramatically during this time
(Fig. 2). After the rst successful eradication in 1857 there
were only 27 eradication attempts during the next 80 years
(through 1940). From 1940-1980 there were 118 vertebrate
eradication attempts, or about three per year. Since 1980,
the rate of vertebrate eradications on islands has increased,
with about 600 eradications between 1980 and 2009, or
about 20 eradications per year (Fig. 2).
Along with increased frequency of eradications also
came an increase in the size of islands from which invasive
vertebrates were eradicated. The invasive vertebrate species
that have been eradicated from the largest islands are goats,
pigs and Arctic foxes (Alopex lagopus) (Fig. 3). Most of
the largest islands had eradications implemented in the last
20 years (Fig. 4). Some of the attempts on large islands
are near completion (e.g., removal of goats from Isabela,
412,000 ha). Other more ambitious island projects are
being planned such as the eradication of rodents, cats and
brushtail possums (Trichosurus vulpecula) from Stewart
(170,000 ha) (Beaven 2008).
Eradications have been attempted in 33 different
countries, with New Zealand having 313 eradication events,
followed by Australia with 154, and the United States with
139. France and Mexico have had 67 and 38 eradication
events, respectively. The distribution of eradications is
primarily in temperate regions. Of the 664 eradication
events reported with latitudes for the islands, 436 have been
attempted in temperate regions (23.5 to 60 degrees North
and South latitudes) and only 180 in the tropics (between
23.5 and -23.5 degrees latitude). No eradications above 60
degrees latitude North or South were reported. Failure rate
in the temperate regions was 7.6% (31 of 405) and 13.2%
(21 of 159) in the tropics.
DISCUSSION
The rst documented attempts to eradicate invasive
vertebrates from islands were over 250 years ago, with the
rst successful attempt over 150 years ago in Australia.
These early attempts to eradicate invasive vertebrate
species began what is now a leading component of the
conservation of island ecosystems and the protection of
threatened species. Collecting details about current and
historical vertebrate eradication attempts, including success
rates, methods, costs, and island characteristics is required
if this management tool is to be promoted and improved.
The Global Islands Invasive Vertebrate Eradication
Database project was designed to summarise information
on all invasive vertebrate eradications and enable analyses
that can: 1) help land managers and funders understand
the applicability and limitations of eradication as a tool; 2)
enable eradication practitioners to share information that
facilitates iterative improvement, and 3) identify regions
and target species for which eradication is under-utilised.
Preliminary analysis of the Global Islands Invasive
Vertebrate Eradication Database indicates that the frequency
of vertebrate eradications on islands is increasing. This
demonstrates that conservationists, land managers, and
funders have recognised and embraced the technique (Figs
2 and 4). Furthermore, the size of islands that have been
attempted has increased. While not a perfect measure of
cost, size of the island is positively linked to the cost of
an eradication, thus the increase in size of islands with
eradication is an indicator of the increased nancial support
for invasive vertebrate eradications from governments and
funders.
New Zealand leads to protect island ecosystems, with
313 invasive vertebrate eradications attempted, which is
more than the next three countries combined. This in part
explains why a disproportionate number of eradications
have been reported from temperate regions (Fig. 1).
However, this concentration of eradications in temperate
areas is unlikely to be the most efcient distribution of
eradication effort to protect global biodiversity since most
biodiversity is located in the tropics (Dirzo and Raven
2003).
Greater efcacy is also desirable in tropical latitudes.
The rate of failed eradication efforts in the tropics is almost
twice the rate in temperate areas. The reasons for this
disparity are not known. However, the lack of seasonality
in tropical environments may be a key factor. Many
eradication campaigns take advantage of seasonal periods
of reproduction and/or food stress for the target animal.
For example, the over 40 Arctic fox eradications in the
Fig. 3 Scatterplot showing area of islands where
eradications have occurred for select species of invasive
vertebrates.
Fig. 4 Cumulative area in hectares of invasive vertebrate
eradications over time for carnivore, herbivore and
omnivore vertebrate eradications on islands.
77
Aleutian Islands, United States were undertaken during the
winter when the target animal was primarily restricted to
the coastlines (Ebbert 2000) The recommended strategy for
rodent eradications is to apply bait when the target population
is experiencing a food related, seasonal population decline
(Howald et al 2007) and when reproduction is at its lowest.
In tropical systems, these seasonal advantages are often
more nuanced or completely absent.
It is not surprising that some invasive vertebrate species
are harder to eradicate than others, based on success rates
of eradication attempts (Table 2). Rodent eradications as
a group experienced the highest failure rates, with 12.8%.
This is likely due to the complexity of rodent eradications
and the difculty associated with putting every individual
animal at risk during an eradication campaign. Surprisingly,
at 12.5%, cat eradications had a similar failure rate to
rodents. This is likely due to both the difculty of detecting
small numbers of cats on an island and the ability of cats
to learn avoidance of available eradication techniques.
The high failure rate for cats suggests a tendency among
practitioners to underestimate the effort necessary to
complete an eradication.
Invasive vertebrate eradication is becoming an
increasingly accepted pathway to restoring native species
and ecosystems, and is increasing in frequency, geographic
distribution, size, and complexity. The Global Islands
Invasive Vertebrate Eradications Database is designed to
provide context for what types of eradications are simple
or challenging and also to encourage communication
between experienced practitioners and land managers that
are protecting biodiversity on islands. It should not only
be used by eradication practitioners, but also by island
land managers, government agencies and foundations.
However, its ongoing utility depends on everyone who
conducts an eradication taking the time to input their own
work and review other relevant entries.
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Keitt et al.: Islands Vertebrate Eradication Database
... systematically track eradication events over time. The development of a global database in 2010 provided a necessary standardized framework to systematically document the methods and outcomes of eradications implemented worldwide 20,21 . The database has since undergone a decade of systematic data reviews with rigorous data quality controls 22 , resulting in a unique compendium of global invasive vertebrate eradications that can be analyzed to provide an understanding of the global contribution of invasive vertebrate eradications as a key island restoration tool. ...
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Habitat degradation, invasive species and overexploitation are currently the three main threats to biodiversity. Here we present a study on the population status of two sympatric flying fox species, Pteropus ornatus (endemic) and P. tonganus (native), and the impact of hunting and predation by the feral cat Felis catus in New Caledonia. The study of flying fox roost occupancy in the North Province shows a 33% disapearance in 40 years. The flying fox population on Grande Terre is estimated at about 735,000 individuals (of both species) and the annual hunting rate at 7%. Integrated stochastic modelling of this population suggests that current harvesting levels could lead to a decline of up to 80% in the next 30 years. Temporary hunting ban and/or protected areas appear, in addition to being combinable, to be the most acceptable and effective management options for hunters. An analysis of the data available worldwide shows that all forms of cats prey on bats in all habitats and that this threat is probably largely underestimated. Finally, initial results suggest that flying fox predation by feral cats in New Caledonia is of the same order of magnitude as hunting. This study proposes a framework for assessing the sustainability of hunting game species in an integrated adaptive management approach, taking into account other threat factors such as invasive species.
... When the ecological consequences of doing nothing are very large and the problem is urgent, the risks of action are clearly justified and forecasting would only delay a response. For example, removing rodents from small oceanic islands has immediate, large, and proven benefits for biodiversity (Howald et al., 2007;Keitt et al., 2011). The value of information provided by forecasting would, in this case, be small relative to the cost of delaying action. ...
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Restoration and conservation innovations face numerous challenges that often limit widespread adoption, including uncertainty of outcomes, risk averse or status quo biased management, and unknown trade‐offs. These barriers often result in cautious conservation that does not consider the true cost of impeding innovation, and overemphasizes the risks of unintended consequences versus the opportunities presented by proactive and innovative conservation, the intended consequences. Simulation models are powerful tools for forecasting and evaluating the potential outcomes of restoration or conservation innovations prior to on‐the‐ground deployment. These forecasts provide information about the potential trade‐offs among the risks and benefits of candidate management actions, elucidating the likelihood that an innovation will achieve its intended consequences and at what cost. They can also highlight when and where business‐as‐usual management may incur larger costs than alternative management approaches over the long‐term. Forecasts inform the decision‐making process prior to the implementation of emergent, proactive practices at broad scales, lending support for management decisions and reducing the barriers to innovation. Here we review the science, motivations, and challenges of forecasting for restoration and conservation innovations.
Chapter
Invasive species pose the highest overall threat to seabirds, affecting the most species and the greatest impact based on the timing, scope, and severity. Invasive mammals have been proven the most harmful on seabird breeding islands, and important advances have been made towards solutions to prevent, control, or eradicate these impacts to seabirds. Biosecurity aims to prevent new invasive species from arriving, and as the most cost-effective strategy considered is a cornerstone for island restoration. Great strides have been made in eradicating invasive mammals from islands, with more than 1500 efforts on nearly 1000 islands worldwide and clearly documented benefits for seabirds. Considerable synergy exists for implementing seabird solutions on islands to achieve conservation goals for other biotas and benefits for human communities. For many seabird species, implementing tractable invasive species solutions will be a critical component of boosting resilience to projected climate change impacts.
Thesis
Islands support the greatest numbers of endemic species but are highly vulnerable to human activities. In particular, the introduction of invasive, predatory mammals (e.g., rodents) has resulted in sharp declines of island fauna due to a lack of evolved behavioral capacities to avoid depredation. Because of this, invasive species are considered to be one of the most detrimental impacts to biodiversity. To combat this biodiversity loss, the eradication of invasive mammals is now a primary conservation tool, with > 700 attempts globally. However, mammal eradications are predicated on the assumption that islands will naturally return to their pre-invaded condition. Yet many restored islands differ from their uninvaded counterparts, partly due to innate behaviors (e.g., philopatry) of highly mobile, keystone species which can limit dispersal to restored islands in the first place. Even when dispersal to restored islands is successful, the process of community reassembly may lead to an entirely different community due to variability in colonization rates and interactions between species, such as competition. The partitioning of limited resources based on behavioral adaptations or phenotype can lead to niche specialization, enabling the coexistence of closely related species. Despite the key potential for competition to shape community assemblages, there have been few opportunities to observe how these processes unfold as colonizing species reassemble into communities, especially so for vertebrates. One way to measure niche specialization is through examining species’ performances as they relate to differing resources across varying ecological conditions. Traditionally, this is done by quantifying a species’ niche breadth, or the extent of resources used by the species, and comparing the overlap of resources used between species; those species with limited niche breadth are considered to be specialized, and little niche overlap can be indicative of competitive exclusion. More recent perspectives of resource use have found differences in niche specialization between populations and even individuals. Seabirds are essential to functional island ecosystems. By connecting intertidal, marine, and terrestrial communities, they are integral components of food webs and act as island ecosystem engineers through the provisioning of nutrient subsidies, which promotes biodiversity. Aotearoa New Zealand supports the greatest number of endemic bird species; but through both European and Polynesian expansion, multiple mammalian species have been introduced to a majority of Aotearoa’s islands. Mammal eradication, initiated in the early 1900s, has led to > 100 islands that are in some form of recovery, providing a series of islands in different stages of recolonization by the world’s largest share of endemic seabird species. This is a unique opportunity to examine factors driving ecological recovery that will improve management strategies globally. The objectives of my doctoral research are to: (1) quantify changes to seabird communities due to invasive species introductions and assess whether eradication and active restoration are sufficient to promote recovery; (2) identify if and to what extent seabirds may compete for nesting space at post-eradication islands; and (3) assess model transferability to understand changes during passive island recovery.
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Feral cats are directly responsible for a large percentage of global extinctions, particularly on islands. We reviewed feral cat eradication programs with the intent of providing information for future island conservation actions. Most insular cat introductions date from the nineteenth and twentieth centuries, whereas successful eradication programs have been carried out in the last 30 years, most in the last decade. Globally, feral cats have been removed from at least 48 islands: 16 in Baja California (Mexico), 10 in New Zealand, 5 in Australia, 4 in the Pacific Ocean, 4 in Seychelles, 3 in the sub-Antarctic, 3 in Macaronesia (Atlantic Ocean), 2 in Mauritius, and 1 in the Caribbean. The majority of these islands (75%; n= 36) are small (≤5 km²). The largest successful eradication campaign took place on Marion Island (290 km²), but cats have been successfully removed from only 10 islands (21%) of ≥10 km². On Cousine Island (Seychelles) cat density reached 243 cats/km², but on most islands densities did not exceed 79.2 cats/km² (n= 22; 81%). The most common methods in successful eradication programs were trapping and hunting (often with dogs; 91% from a total of 43 islands). Frequently, these methods were used together. Other methods included poisoning (1080; monofluoracetate in fish baits; n= 13; 31%), secondary poisoning from poisoned rats (n= 4; 10%), and introduction of viral disease (feline panleucopaenia; n= 2; 5%). Impacts from cat predation and, more recently, the benefits of cat eradications have been increasingly documented. These impacts and benefits, combined with the continued success of eradication campaigns on larger islands, show the value and role of feral cat eradications in biodiversity conservation. However, new and more efficient techniques used in combination with current techniques will likely be needed for success on larger islands.
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Data on eradication operations against alien mammals on New Zealand islands show that there was a substantial increase in the number of successful eradications in the 1980s and 1990s. The most significant change has been in the ability to eradicate rodents from increasingly large islands (to over 11,000ha), using aerial poisoning techniques. Based on the New Zealand experience, there are good prospects for further eradications of alien mammals from islands around the world, facilitating ecological restoration and the recovery of threatened species. However, instances of reinvasion of rats (Rattus spp.) and stoats (Mustela erminea) onto previously cleared islands illustrate the importance of prevention, effective monitoring and a fuller understanding of invasion risks.
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Introduced mammals are major drivers of extinction. Feral goats (Capra hircus) are particularly devastating to island ecosystems, causing direct and indirect impacts through overgrazing, which often results in ecosystem degradation and biodiversity loss. Removing goat populations from islands is a powerful conservation tool to prevent extinctions and restore ecosystems. Goats have been eradicated successfully from 120 islands worldwide. With newly developed technology and techniques, island size is perhaps no longer a limiting factor in the successful removal of introduced goat populations. Furthermore,. the use of global positioning systems, geographic information systems, aerial hunting by helicopter specialized bunting dogs, and Judas goats has dramatically increased efficiency and significantly reduced the duration of eradication campaigns. Intensive monitoring programs are also critical for successful eradications. Because of the presence of humans with domestic goat populations on large islands, future island conservation actions will require eradication programs that involve local island inhabitants in a collaborative approach with biologists, sociologists, and educators. Given the clear biodiversity benefits, introduced goat populations should be routinely removed from islands.
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Endemism and species richness are highly relevant to the global prioritization of conservation efforts in which oceanic islands have remained relatively neglected. When compared to mainland areas, oceanic islands in general are known for their high percentage of endemic species but only moderate levels of species richness, prompting the question of their relative conservation value. Here we quantify geographic patterns of endemism-scaled richness ("endemism richness") of vascular plants across 90 terrestrial biogeographic regions, including islands, worldwide and evaluate their congruence with terrestrial vertebrates. Endemism richness of plants and vertebrates is strongly related, and values on islands exceed those of mainland regions by a factor of 9.5 and 8.1 for plants and vertebrates, respectively. Comparisons of different measures of past and future human impact and land cover change further reveal marked differences between mainland and island regions. While island and mainland regions suffered equally from past habitat loss, we find the human impact index, a measure of current threat, to be significantly higher on islands. Projected land-cover changes for the year 2100 indicate that land-use-driven changes on islands might strongly increase in the future. Given their conservation risks, smaller land areas, and high levels of endemism richness, islands may offer particularly high returns for species conservation efforts and therefore warrant a high priority in global biodiversity conservation in this century.
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Invasive mammals are the greatest threat to island biodiversity and invasive rodents are likely responsible for the greatest number of extinctions and ecosystem changes. Techniques for eradicating rodents from islands were developed over 2 decades ago. Since that time there has been a significant development and application of this conservation tool. We reviewed the literature on invasive rodent eradications to assess its current state and identify actions to make it more effective. Worldwide, 332 successful rodent eradications have been undertaken; we identified 35 failed eradications and 20 campaigns of unknown result. Invasive rodents have been eradicated from 284 islands (47,628 ha). With the exception of two small islands, rodenticides were used in all eradication campaigns. Brodifacoum was used in 71% of campaigns and 91% of the total area treated. The most frequent rodenticide distribution methods (from most to least) are bait stations, hand broadcasting, and aerial broadcasting. Nevertheless, campaigns using aerial broadcast made up 76% of the total area treated. Mortality of native vertebrates due to nontarget poisoning has been documented, but affected species quickly recover to pre-eradication population levels or higher. A variety of methods have been developed to mitigate nontarget impacts, and applied research can further aid in minimizing impacts. Land managers should routinely remove invasive rodents from islands <100 ha that lack vertebrates susceptible to nontarget poisoning. For larger islands and those that require nontarget mitigation, expert consultation and greater planning effort are needed. With the exception of house mice (Mus musculus), island size may no longer be the limiting factor for rodent eradications; rather, social acceptance and funding may be the main challenges. To be successful, large-scale rodent campaigns should be integrated with programs to improve the livelihoods of residents, island biosecurity, and reinvasion response programs. Resumen: Los mamíferos invasores son la mayor amenaza a la biodiversidad insular, y los roedores invasores son probables responsables de la mayoría de las extinciones y cambios en los ecosistemas. Las técnicas para la erradicación de roedores de las islas fueron desarrolladas hace 2 décadas. Desde entonces ha habido un desarrollo y aplicación significativa de esta herramienta de conservación. Revisamos la literatura sobre erradicaciones de roedores invasores para evaluar su estado actual e identificar acciones para hacerlo más efectivo. Mundialmente, se han efectuado 332 erradicaciones de roedores exitosas, identificamos 35 erradicaciones fracasadas y 20 campañas con resultados desconocidos. Los roedores Invasivos ha sido erradicados de 284 islas (47,628 ha). Con la excepción de dos islas pequeñas, se utilizaron rodenticidas en todas las erradicaciones. Se utilizó Brodifacoum en 71% de las campañas y en 91% de la superficie tratada. Los métodos más frecuentes de distribución de rodenticida (de más a menos) son estaciones de cebo, aplicación manual y aplicación aérea. Sin embargo, las campañas de aplicación aérea abarcaron 76% de la superficie tratada. Se ha documentado la mortalidad de vertebrados nativos debido a envenenamiento accidental, pero las especies afectadas recuperan, o superan, rápidamente los niveles poblacionales previos a la erradicación. Se ha desarrollado una variedad de métodos para mitigar los impactos no deseados, y la investigación aplicada puede ayudar a minimizar los impactos aun más. Los gestores de recursos deben remover rutinariamente a roedores invasores de islas <100 ha que carezcan de vertebrados susceptibles de envenenamiento no deseado. Para islas más extensas y para las que requieren de mitigación de envenenamientos no deseados, se requiere de la consulta de expertos y de mayores esfuerzos de planificación. Con la excepción de Mus musculus, es posible que el tamaño de la isla ya no sea el factor limitante para la erradicación de roedores, más bien, la aceptación social y el financiamiento pueden ser los retos principales. Para ser exitosas, las campañas a gran escala deben estar integradas por programas para mejorar las condiciones de vida de los residentes, de bioseguridad insular y de respuesta a reinvasiones.
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Many European politicians, managers, and scientists believe that non-indigenous species cannot be eradicated and that attempts to do so are hazardous because of frequent undesirable results. This notion seems to be based on the view that successful eradications undertaken in many other parts of the world cannot be generalised. To allow reasoned consideration of this argument, the eradication of non-indigenous vertebrate species performed in the French territories (European and overseas) and their recorded consequences on native fauna and flora are synthesised. Nineteen vertebrate eradication attempts were recorded, with seven mammal species as the targets. Of these attempts four failed for technical reasons and one for reasons undetermined as yet. These operations took place on islands of four biogeographical areas (West-European, Mediterranean, West Indies and Indian Ocean subantarctic) except a continental one (West-European continent). Among these 19 attempts, 13 were conducted according to a global strategy that provided data on the impact of the disappearance of the non-indigenous species on several native species. This impact, never detrimental, was determined for 14 species (one mammal, nine birds, one marine turtle, one crab, one beetle, one plant). Unexpected consequences of the disappearance of the invader were recorded for four native species (29%). This result highlights the poverty of natural historical information for several taxa and the flimsiness of the empty niche concept that is often used to argue for the delay of or to prevent any action again a non-indigenous species. If French territories can be taken as an example, eradications of non-indigenous species are not impossible; a good risk assessment prevents undesirable long-term consequences for native species and several native species benefited from the disappearance of the invader. Furthermore, eradication constitutes a powerful experimental tool for ecology and natural history studies if conceived as both a management and research operation.
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Biodiversity, a central component of Earth's life support systems, is directly relevant to human societies. We examine the dimensions and nature of the Earth's terrestrial biodiversity and review the scientific facts concerning the rate of loss of biodiversity and the drivers of this loss. The estimate for the total number of species of eukaryotic organisms possible lies in the 5–15 million range, with a best guess of ∼7 million. Species diversity is unevenly distributed; the highest concentrations are in tropical ecosystems. Endemisms are concentrated in a few hotspots, which are in turn seriously threatened by habitat destruction—the most prominent driver of biodiversity loss. For the past 300 years, recorded extinctions for a few groups of organisms reveal rates of extinction at least several hundred times the rate expected on the basis of the geological record. The loss of biodiversity is the only truly irreversible global environmental change the Earth faces today.
Chapter
Many European politicians, managers, and scientists believe that non-indigenous species cannot be eradicated and that attempts to do so are hazardous because of frequent undesirable results. This notion seems to be based on the view that successful eradications undertaken in many other parts of the world cannot be generalised. To allow reasoned consideration of this argument, the eradication of non-indigenous vertebrate species performed in the French territories (European and overseas) and their recorded consequences on native fauna and flora are synthesised. Nineteen vertebrate eradication attempts were recorded, with seven mammal species as the targets. Of these attempts four failed for technical reasons and one for reasons undetermined as yet. These operations took place on islands of four biogeographical areas (West-European, Mediterranean, West Indies and Indian Ocean subantarctic) except a continental one (West-European continent). Among these 19 attempts, 13 were conducted according to a global strategy that provided data on the impact of the disappearance of the non-indigenous species on several native species. This impact, never detrimental, was determined for 14 species (one mammal, nine birds, one marine turtle, one crab, one beetle, one plant). Unexpected consequences of the disappearance of the invader were recorded for four native species (29%). This result highlights the poverty of natural historical information for several taxa and the flimsiness of the empty niche concept that is often used to argue for the delay of or to prevent any action again a non-indigenous species. If French territories can be taken as an example, eradications of non-indigenous species are not impossible; a good risk assessment prevents undesirable long-term consequences for native species and several native species benefited from the disappearance of the invader. Furthermore, eradication constitutes a powerful experimental tool for ecology and natural history studies if conceived as both a management and research operation.