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.

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.