van Andel, T.

A social-ecological perspective on ecosystem vulnerability for the invasive creeper coralita (Antigonon leptopus) in the Caribbean: A review

Highlights

• Review on coralita invasion (Antigonon leptopus) on islands yielded 46 papers.

• Main influencing factors are overgrazing, human disturbance and climate change.

• Very little empirical evidence on factors influencing invasivity.

• Invasion by coralita is a symptom of land degradation, not the cause.

• Best management options are forest conservation, reforestation and grazer exclusion.

Abstract

The Caribbean islands are a hotspot for biodiversity, harboring 2.3% of the world's endemic plant species on just 0.18% of the earth surface. Due to habitat degradation, invasive species are considered a major environmental problem on these islands. The vine coralita (Antigonon leptopus Hook. & Arn.) is the most abundant invasive species on the Dutch Caribbean island of St. Eustatius. Forming thick, monospecific carpets, it is seen as a threat to biodiversity. Insight is needed as to the ecological and social factors that influence the local ecosystem's vulnerability for invasion by A. leptopus. We used a Social-Ecological Systems framework for a literature review to answer our research questions: 1) What is currently known about the social and ecological factors that make an ecosystem vulnerable for invasions by invasive species and A. leptopus in particular? 2) How much empirical evidence is provided to back up the claims made in the reviewed literature? and 3) Which research and management priorities can be identified for St. Eustatius based on this analysis? Our review yielded 46 relevant documents, of which only 21 were peer-reviewed scientific articles. We assessed the level of empirical support for each of the factors mentioned in the reviewed literature and used these to shape our conceptual Social-Ecological model. Three major factors appeared to be responsible for the vulnerability of ecosystems for A. leptopus invasion: overgrazing by feral animals (16 papers), anthropogenic disturbance (19) and climate change (6). Empirical evidence for the relation between A. leptopus invasion and social and ecological factors is scarce: only anthropogenic disturbance and overgrazing were supported by quantitative data (three papers each). Our literature review also indicates that the invasion of A. leptopus on St. Eustatius is more a symptom than a cause in itself. Efforts to manage coralita by chemical or manual removal are futile if not combined with active vegetation restoration and grazer exclusion. Conservation efforts have led to an increase in forested areas on the island, in which coralita is not present. More experimental research is needed to inform policy and management decisions, preferably on the effects of feral grazer exclusion and shading by native trees on the recovery of natural vegetation in areas now dominated by coralita.

Date
2019
Data type
Scientific article
Theme
Research and monitoring
Geographic location
St. Eustatius

A quantitative assessment of the vegetation types on the island of St. Eustatius, Dutch Caribbean

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.

Date
2016
Data type
Scientific article
Theme
Research and monitoring
Geographic location
St. Eustatius