Invasive species

The remote Caribbean island of Redonda, part of Antigua and Barbuda, is home to numerous species of plants and animals found nowhere else on earth. It is also home to invasive black rats and non-native goats that are wiping out the island’s native, rare wildlife, conservationists say.

To help the island’s flora and fauna, the Government of Antigua and Barbuda is now initiating a plan to remove all goats and rats from the island. The Redonda Restoration Program program has been formed by the Antigua & Barbuda Government and the Environmental Awareness Group (EAG) in collaboration with organizations like Fauna & Flora International, British Mountaineering Council, Island Conservation and Wildlife Management International Ltd.

Following climate change, IAS are recognised as the second-most serious long-term threat to island ecology, worldwide. Of all IAS issues, by far the most serious is the problem of roaming livestock. On most islands this concerns the eubiquitous domestic goat. 

In addition to major inventories of invasive species (see the first 4 reports below) and the development of a joint strategy, as part of the Wageningen BO research program, IMARES has also led the way to several pilot-scale interventions, in close cooperation with island partners. Current studies include work to document the positive effect of feral cat control on survival of endangered ground-nesting seabirds in Saba, control and eradication of the Giant African Landsnail on Statia and control of goat grazing inside the Washington Slagbaai park in Bonaire. Within the European Netherlands, IAS are also recognized as a key scourge to both nature and economy and in 2015 stringent new legislation was implemented not only in the Netherlands, but throughout the EU. See below, for a full listing of IMARES recent work in this area of concern.

The problem of roaming livestock is particularly acute in the Caribbean Netherlands. It is a major impediment to agricultural development and nature conservation on St. Eustatius, as it also typically is on other islands in the region. In support of a government-led culling program, we here conducted a baseline study of livestock abundance and distribution on the island in the final quarter of 2013. In doing so we provide the first quantitative assessment of livestock densities ever in the Dutch Caribbean.

Abstract: 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 hunting 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.

Since the first sightings of the lionfish in the Caribbean, the local marine ecosystems have experienced severe problems due to predation and competition by this invasive species. Since 2008, the lionfish problem is also present in the coastal ecosystems of the Cayman Islands. In order to manage this ecological threat, The Department of Environment (DOE) of the Cayman Islands requires both comprehensive ecological and economic information. Although ecological research on the lionfish invasion in the Caribbean region is increasing rapidly, socio-economic studies investigating the societal impact of this ecological threat are still rather lacking. This pilot study aims at providing an insight into the potential impacts of lionfish proliferation in the Cayman Islands on the tourism industry by revealing the perception of the lionfish problem by visitors to the Cayman Islands and measure the willingness to pay (WTP) of these tourists for managing this invasive species. These findings provide important information for the final calculation of the overall economic impact of lionfish on the Cayman Islands as well as providing a basis for possible funding schemes for the management of the lionfish problem.

An extensive visitor survey among 326 visitors shows that on average 60% of the respondents are in principle willing to pay (WTP) an environmental fee, managed by a nature organization, which would contribute to management of the lionfish problem. Depending on the valuation method chosen and taking into account the distinct characteristics of stay-over and cruise tourists, the total potential annual contribution of visitors for lionfish management in the Cayman Islands is determined at a minimum of USD8 million and a maximum of USD 26.3 million. From these findings we conclude that the support among visitors to manage the lionfish problem is already substantial but could be further increased by improving communication to visitors about lionfish related issues. 

eDNA as a tool to monitor invasive species, Priliminary results presented at Association of Marine Laboratories Scientific Meeting,

Merida, Mexico, May 2017. 

The purpose of this Position Statement is to highlight the pest status that non-native iguanas can attain when introduced to tropical and sub-tropical regions outside their native range, and to emphasize the devastating environmental and economic impacts they can cause.

Common Green Iguanas (Iguana iguana) and, more recently, Spiny-tailed Iguanas (Ctenosaura similis and C. pectinata) (Fig. 1) have been moved around the world, primarily for the pet trade. The intentional and unintentional release of iguanas has led to the establishment of uncontrolled invasive populations in more than 19 countries, with subtropical and tropical islands being most vulnerable (Table 1). To date, no country has been able to eradicate these species once a breeding population has become established.

Invasive iguanas can exhibit explosive population growth and reach staggering densities. On the small island of Grand Cayman, Green Iguanas have increased from a few individuals to hundreds- of-thousands within a decade. Invasive iguanas are causing multimillion-dollar impacts on infrastructure, agriculture, tourism, long-term food security, and biodiversity. For example, invasive Green Iguanas are a known airport safety hazard in Florida, Puerto Rico, and The Bahamas. They are also known to short-circuit power lines in cities, and their burrows have caused road collapses and coastal erosion (Fig. 2). Invasive iguanas can cause severe agricultural damage and defoliate native and ornamental plants (Fig. 3). Spiny-tailed Iguanas are a proven nuisance in Gasparilla Island, Florida, defoliating native plants and causing thousands of dollars in damages to homes and landscaping. In places where native and non-native iguanas co-occur, the survival of the natives is threatened through competition for food and space. In addition, hybridization with Green Iguanas is now the main threat to the survival of Lesser Antillean Iguanas (Iguana delicatissima) (Fig. 4).

We thus make the following tiered recommendations, which apply to all countries with tropical or sub-tropical regions, and especially islands:

For countries where non-native iguanas are not present: Develop and enforce country-specific regulations to ban importation and prevent the accidental introduction of non-native iguanas.

For countries where non-native iguanas are present in captivity, but have not been detected in the wild: Implement education programs focused on responsible pet ownership, encourage pet sterilization, ban the release of iguanas into the wild, and provide a sanctioned repository for unwanted captive iguanas.

For countries where non-native iguanas have been recently detected in the wild, but have yet to establish breeding populations: Immediately implement well-coordinated and resourced action plans to humanely remove all non-native iguanas before eradication becomes unfeasible (see AVMA guidelines: https://www.avma.org/KB/Policies/Pages/Euthanasia-Guidelines.aspx)

For countries with established breeding populations of non-native invasive iguanas in the wild:

Humanely eradicate existing populations where possible; if eradication is unsuccessful, implement continual management actions to control population growth and prevent further expansion. 

Managing the pathways by which non-native species are introduced and spread is consid- ered the most effective way of preventing species invasions. Tourism and outdoor recrea- tion involve the frequent congregation of people, vehicles and vessels from geographically diverse areas. They are therefore perceived to be major pathways for the movement of non- native species, and ones that will become increasingly important with the continued growth of these sectors. However, a global assessment of the relationship between tourism activi- ties and the introduction of non-native species–particularly in freshwater and marine envi- ronments–is lacking. We conducted a systematic review and meta-analysis to determine the impact of tourism and outdoor recreation on non-native species in terrestrial, marine and freshwater environments. Our results provide quantitative evidence that the abundance and richness of non-native species are significantly higher in sites where tourist activities take place than in control sites. The pattern was consistent across terrestrial, freshwater and marine environments; across a variety of vectors (e.g. horses, hikers, yachts); and across a range of taxonomic groups. These results highlight the need for widespread biose- curity interventions to prevent the inadvertent introduction of invasive non-native species (INNS) as the tourism and outdoor recreation sectors grow. 

We studied the bird communities of five contrasting semi-natural habitats of Lac Bay, Bonaire, South- eastern Caribbean, during the fall of 2011. A total of 420 point counts were conducted in five different habitats and 63 species were detected. Of these, 31 (49%) were migrants, 24 (38%) were residents, 6 (10%) occurred both as residents and migrants and 2 (3%) were migrants that possibly or irregularly breed. Most migratory species were shorebirds and waders (76%). The bird communities of the ve habitats studied showed signi cant differences in species composition and associated community parameters. Mangrove thicket and salt at habitats had roughly a two-fold higher total species richness and a four-fold higher migratory species richness compared to woodland habitats. In woodland habitats, breeding residents dominated, whereas migratory shore and waterbirds dominated in salt at habitat. The Northern Waterthrush, Parkesia noveboracensis, and Barn Swallow, Hirundo rustica, were the numerically most important migratory passerines. The Reddish Egret, Egretta rufescens, a globally Near-Threatened species, ranked among the top 10 most abundant species of the Lac Bay salt at habitat. Our results suggest that the relatively expansive hypersaline wetlands of Bonaire (of which Lac is only a small part) may be of special signi cance to migratory shore and waterbirds. In contrast to other areas of the Caribbean, invasive exotic birds so far play a minor role in the communities studied. 

Curaçao and Bonaire form part of the Netherlands Antilles, while Aruba has a “status aparte” within the Kingdom of the Netherlands. All three islands are relatively arid compared to a typical Caribbean island, with mean annual rainfall of 409-553 mm, and experience several periods of drought lasting two or more years each century. A short history of the islands is given, and protected areas are described. The laws and regulations protecting amphibians and reptiles are complex, with general laws originating from the Kingdom of the Netherlands participation in international conventions (such as CITES) together with supplemental laws of the Netherlands Antilles and individual islands. Sea turtles are generally well protected, although their nesting beaches would be vulnerable to a rise in sea level. Among the terrestrial herpetofauna, only the Aruba Island rattlesnake (Crotalus unicolor) is on the IUCN Red List, being Critically Endangered. The status of this species and others of particular interest is described. The Curaçao Island snake (Liophis triscalis) should probably be included as Vulnerable or even Endangered, though there is insufficient information at present. Iguana iguana populations on the different islands, and the Curaçao whiptail (Cnemidophorus murinus murinus) on Klein Curaçao, are distinctive and significant for conservation. An overview is given of introduced amphibians and reptiles and their possible effects on the native fauna. The arid climate of the islands may hinder the establishment of invasive species, which are often not able to survive in the bush and thus reduces their impact on native species.

Raw data of lion fish observations counts on St.Eustatius.

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