Global Ecology and Conservation

Since the introduction of non-native rodents to the Caribbean region, these invaders have successfully occupied many, if not most, islands where they pose tremendous threats to native biodiversity and ecosystems. The objective of our study was to conduct a preliminary assessment of the relative abundance of invasive alien rodents in different vegetation types on the small Caribbean island of St. Eustatius, which has no native rodent species. We used tracking tunnels (baited ink cards placed in tunnels to identify the prints of animals lured to the card) to determine the presence of rodent species. We collected data in 25 25 m (n ¼ 13) and 5 5m (n ¼ 130) plots to determine whether elevation, number of tree species, canopy cover or other microhabitat components were correlated with rodent relative abundance. Invasive rodents are present in varying relative abundances in rural areas on St. Eustatius. House mice (Mus musculus) were not recorded inside the terrestrial protected areas, whereas black rats (Rattus rattus) were detected in all elevations and all but one vegetation type sampled. We determined significant correlations between some of the habitat characteristics, especially elevation, canopy height, leaf litter cover and number of tree species, which showed significant collinearity with 27 of 45 pairwise comparisons. There was a significant correlation between rodent relative abundance and the number of tree species, but not between elevation, number of living trees, number of shrubs, rainfall, canopy cover, canopy height, leaf litter cover, leaf litter depth, or slope. There was a significant difference within vegetation types for the frequency of traps containing rat versus mouse tracks. Our study was impacted by two major hurricanes in September 2017.

Elkhorn coral (Acropora palmata) populations provide important ecological functions on shallow Caribbean reefs, many of which were lost when a disease reduced their abundance by more than 95% beginning in the mid-1970s. Since then, a lack of significant recovery has prompted rehabilitation initiatives throughout the Caribbean. Here, we report the first successful outplanting and long-term survival of A. palmatasettlers reared from gametes collected in the field. A. palmata larvae were settled on clay substrates (substrate units) and either outplanted on the reef two weeks after settlement or kept in a land-based nursery. After 2.5 years, the survival rate of A. palmata settlers outplanted two weeks after settlement was 6.8 times higher (3.4%) than that of settlers kept in a land-based nursery (0.5%). Furthermore, 32% of the substrate units on the reef still harbored one or more well-developed recruit compared to 3% for substrate units kept in the nursery. In addition to increasing survival, outplanting A. palmata settlers shortly after settlement reduced the costs to produce at least one 2.5-year-old A. palmataindividual from $325 to $13 USD. Thus, this study not only highlights the first successful long-term rearing of this critically endangered coral species, but also shows that early outplanting of sexually reared coral settlers can be more cost-effective than the traditional approach of nursery rearing for restoration efforts aimed at rehabilitating coral populations.

Caribbean dry forests are among the most endangered tropical ecosystems on earth. Several studies exist on their floristic composition and their recovery after natural or man-made disturbances, but little is known on the small Dutch Caribbean islands. In this study, we present quantitative data on plant species richness and abundance on St. Eustatius, one of the smallest islands of the Lesser Antilles. We collected and identified trees, shrubs, lianas and herbs in 11 plots of 25 x 25 m in different vegetation types. We compared their floristic composition and structure to vegetation surveys from roughly the same locations in the 1990s and 1950s. We found substantial differences among our 11 plots: vegetation types varied from evergreen forests to deciduous shrubland and open woodland. The number of tree species ≥10≥10 cm DBH ranged between one and 17, and their density between three and 82 per plot. In spite that all plots were subject to grazing by free roaming cattle, canopy height and floristic diversity have increased in the last decades. Invasive species are present in the open vegetation types, but not under (partly) closed canopy. Comparison with the earlier surveys showed that the decline of agriculture and conservation efforts resulted in the regeneration of dry forests between the 1950s and 2015. This process has also been reported from nearby islands and offers good opportunities for the future conservation of Caribbean dry forests.

Fishers and divers are the major resource users of Caribbean coral reefs. On Curaçao and Bonaire, reef condition is good relative to the Caribbean average, but fishes and corals have greatly declined over the last few decades. We interviewed 177 fishers and 211 professional SCUBA divers to assess their views on the extent and causes of degradation. Fishers know fish stocks are severely depleted and declining, whereas divers were aware of declines but had “shifted baselines” and consider the reefs healthy. Fishers and divers differ in perceptions of the causes and appropriate remedies for decline. Fishers generally blame external factors such as changes in climate, currents, or industrial fishing offshore, whereas divers primarily blame overfishing and coastal development. Nevertheless, the great majority of both fishers and divers support more management of both fishing and diving. Thus the social climate is ripe for balanced and strong restrictions on both groups for reef recovery and sustainable use. Exclusion of both fishers and divers from protected areas of significant size around the islands would be a major step forward towards the long-term conservation of reef resources.