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

Mapping the economic loss of ecosystem services caused by the invasive plant species Antigonon leptopus on the Dutch Caribbean Island of St. Eustatius

Invasive species are a worldwide threat to biodiversity, especially on Caribbean islands. Through their impact on the structure and functioning of ecosystems, they also affect ecosystem services. Therefore, invasive species can have profound socio-economic effects. On the Dutch Caribbean Island of St. Eustatius, the invasive perennial vine Coralita is present on roughly 33% of the Island. While ecological damage is evident, effective management strategies are still lacking. This study links the ecological, cultural and societal effects of the invasion to the economy of the Island by estimating the ecosystem service losses due to Coralita in monetary value. We have spatially assessed the economic value of five main ecosystem services (tourism, non-use value, carbon sequestration, archaeology and local cultural and recreational value) to the different habitats on the Island and estimated the loss of these values under three scenarios of Coralita cover: 0%, 3% and 36% dominant cover. The baseline scenario of 0% demonstrated a total ecosystem service value of $2.7 million per year, concentrated on the Quill volcano. The 3% and 36% scenario showed a yearly loss of $39,804 and $576,704, respectively, with the largest losses located on the northern and eastern slopes of the Quill. These areas should be prioritised for management and the known potential gain per area enables choice of strategy, based on cost-benefit considerations. To reduce further economic loss by Coralita, we urgently advise an immediate management strategy and ongoing research into eradication and restoration methods.

Antigonon leptopus invasion is associated with plant community disassembly in a Caribbean island ecosystem

Invasions by non-native plant species are widely recognized as a major driver of biodiversity loss. Globally, (sub-)tropical islands form important components of biodiversity hotspots, while being particularly susceptible to invasions by plants in general and vines in particular. We studied the impact of the invasive vine A. leptopus on the diversity and structure of recipient plant communities on the northern Caribbean island St. Eustatius. We used a paired-plot design to study differences in species richness, evenness and community structure under A. leptopus-invaded and uninvaded conditions. Community structure was studied through species co-occurrence patterns. We found that in plots invaded by A. leptopus, species richness was 40–50% lower, and these plots also exhibited lower evenness. The magnitude of these negative impacts increased with increasing cover of A. leptopus. Invaded plots also showed higher degrees of homogeneity in species composition. Species co-occurrence patterns indicated that plant communities in uninvaded plots were characterized by segregation, whereas recipient plant communities in invaded plots exhibited random co-occurrence patterns. These observations suggest that invasion of A. leptopus is not only associated with reduced species richness and evenness of recipient communities in invaded sites, but also with a community disassembly process that may reduce diversity between sites. Given that A. leptopus is a successful invader of (sub-)tropical islands around the globe, these impacts on plant community structure highlight that this invasive species could be a particular conservation concern for these systems.

A weed risk analytical screen to assist in the prioritisation of an invasive flora for containment

Prioritising weeds for control and deciding upon the type of control and its associated investment are fundamental to weed management planning. Risk analysis is central to this process, combining the activities of risk assessment, risk management and risk communication. Risk assessment methodology has a rich history, but management feasibility has typically been a secondary matter, dealt with separately or not at all. Determinants of management feasibility for weeds include the stage of invasion, weed biology, means of control and cost of weed control. Here, we describe a simple weed risk analytical screen that combines risk assessment with species traits that influence management feasibility. We consider stage of invasion, species biological/dispersal characteristics and plant community invasibility in a preliminary analysis of the risk posed by the non-native plant species on Christmas Island in the Indian Ocean. For each of 31 high-risk species considered to be ineradicable under existing funding constraints, we analyse the risk posed to two major plant communities: evergreen closed-canopy rainforest and semi-deciduous scrub forest. Weed risk ratings are combined with ratings for species-intrinsic feasibility of containment (based on a measure that combines time to reproduction with potential for long distance dispersal) to create preliminary rankings for containment specific to each community. These rankings will provide a key input for a more thorough analysis of containment feasibility – one that considers spatial distributions/landscape features, management aspects and the social environment. We propose a general non-symmetric relationship between weed risk and management feasibility, considering risk to be the dominant component of risk analysis. Therefore, in this analysis species are ranked according to their intrinsic containment feasibility within similar levels of risk to produce an initial prioritisation list for containment. Shade-tolerant weeds are of particular concern for the closed-canopy evergreen rainforest on Christmas Island, but a greater diversity of weeds is likely to invade the semi-deciduous scrub forest because of higher light availability. Nevertheless, future invasion of both communities will likely be conditioned by disturbance, both natural and anthropogenic. The plant communities of Christmas Island have undergone significant fragmentation because of clearing for phosphate mining and other purposes. With a substantial number of invasive plant species firmly established and having the potential to spread further, minimising future anthropogenic disturbance is paramount to reducing community invasibility and therefore conserving the island’s unique biodiversity.

Spatial-temporal shifts of ecological vulnerability of Karst Mountain ecosystem-impacts of global change and anthropogenic interference

Under the background of global climate change, the natural environment of the southwest karst mountain region is undergoing profound changes. Considering the differences in the relative importance of each index in the vulnerability evaluation system in different periods, this study presents the dynamic weight determination method and then establishes the dynamic weight table of the ecological vulnerability evaluation index in the southwest karst mountain region. At the same time, net primary productivity (NPP) is introduced to help determine the ecological vulnerability classification threshold in different periods, and then the spatial-temporal change pattern and driving mechanism of ecological vulnerability in the past 15 years are analyzed. Results show the following: (1) Dynamic weight determination method has good application in the study of ecological vulnerability in long-term series, and the threshold of vulnerability classification based on NPP can ensure the comparability of ecological vulnerability evaluation results in different periods; (2) From 2000 to 2015, the southwest karst mountain region generally belonged to the moderate vulnerability category, and a decreasing trend is observed from the Sichuan-Yunnan-Guizhou border area to its surrounding region in a spatial distribution pattern; (3) In the past 15 years, the ecological vulnerability of the southwest karst mountain region increased first and then decreased; (4) The spatial-temporal change pattern of ecological vulnerability in the southwest karst mountain region is significantly affected by GDP of different industries, precipitation, soil erosion, rocky desertification. These results would be in particular useful for planning the conservation strategies or assessments of the conservation priorities. In addition, the method employed could provide a technical support and references for the ecological assessment and restoration of other similar karst mountain ecosystem zones in China or worldwide.

Disentangling the effects of plant species invasion and urban development on arthropod community composition

Urban development and species invasion are two major global threats to biodiversity. These threats often co-occur, as developed areas are more prone to species invasion. However, few empirical studies have tested if both factors affect biodiversity in similar ways. Here we study the individual and combined effects of urban development and plant invasion on the composition of arthropod communities. We assessed 36 paired invaded and non-invaded sample plots, invaded by the plant Antigonon leptopus, with half of these pairs located in natural and the other half in developed land-use types on the Caribbean island of St. Eustatius. We used several taxonomic and functional variables to describe community composition and diversity. Our results show that both urban development and A. leptopus invasion affected community composition, albeit in different ways. Development significantly increased species richness and exponential Shannon diversity, while invasion had no effect on these variables. However, invasion significantly increased arthropod abundance and caused biotic homogenization. Specifically, uninvaded arthropod communities were distinctly different in species composition between developed and natural sites, while they became undistinguishable after A. leptopus invasion. Moreover, functional variables were significantly affected by species invasion, but not by urban development. Invaded communities had higher community-weighted mean body size and the feeding guild composition of invaded arthropod communities was characterized by the exceptional numbers of nectarivores, herbivores, and detritivores. With the exception of species richness and exponential Shannon diversity, invasion influenced four out of six response variables to a greater degree than urban development did. Hence, we can conclude that species invasion is not just a passenger of urban development but also a driver of change.