coralita

Using Satellite Imagery to Map St. Eustatius Coralita Invasion

Coralita is an invasive plant species, rapidly spreading across St. Eustatius.  A recently published report highlighted the ability to use satellite imagery to systematically map Coralita’s distribution over the island.  The approach could provide key insights into how habitat and vegetation are changing over time to aid in conservationists’ efforts to minimize the negative effects of Coralita and similar invasive species.

Coralita overgrowth (Source: Achsah Mitchell)

Coralita is a fast-growing, climbing vine with beautiful pink or white flowers. Originally from Mexico, Antigonon leptopus started out as a popular garden plant, but has expanded its territory and is now aggressively invading natural areas. Its fast-growing nature means it can outcompete most native species for terrain, quickly making it the dominant species, and reducing overall diversity. This is especially the case on St. Eustatius, where ground surveys indicate the plant already appears on 15-33% of the island.

Mapping Techniques

One of the biggest issues in controlling invasive species is accurately accounting for its presence, particularly if data needs to be collected over a wide area. This is where satellite imagery can help by providing an affordable, high spatial resolution option. A new collaborative study from the Utrecht University, University of Zurich, Wageningen University, and the Technical University of Braunschweig provided key insight by using such satellite imagery to identify Coralita. The method is successful, as areas dominated by Coralita emit a relatively distinct electromagnetic signal that can be detected by satellites. Once the distribution of Coralita has been mapped using this technique, it is possible to identify the environmental conditions associated with Coralita’s presence. This approach provides a relatively low-cost solution that is powerful, accurate and repeatable; key in identifying and monitoring its spread in the future.

“In creating this map,” said Elizabeth Haber, first author of this study, “it was my hope to produce something that could be useful for those who are caring for and protecting the incredibly special nature on Statia.”

Results

Using this method, researchers sampled 162 locations across St. Eustatius and estimated that Coralita was the dominant canopy cover (>50%) on over 3% of the island (64 ha). Perhaps more importantly, this map also showed that Coralita was not randomly distributed but generally found, for example, in areas of water accumulation, near roads or near drainage channels. Furthermore, Coralita was often found in grasslands and areas of development and is relatively rare in natural forests, highlighting how human disturbances can promote the spread of Coralita. It is important to note that data filtering and physical limitations of using satellite imagery means that Coralita growing under trees or shrubs or in smaller patches is likely underrepresented in this study.

Map of the distribution of Coralita on St. Eustatius (Haber et al., 2021)

 

Conservation Implications

Even with the physical limitations, the fact that this study is cost effective and repeatable means that consistent comparisons of Coralita’s distribution can be made over time. These comparisons are vital in understanding how populations and habitats are shifting, granting conservationists a fantastic tool in forecasting the spread of invasive species. Arguably the greatest asset of the Caribbean is its vast biodiversity. Already threats of climate change, habitat loss, invasive species and urban development are upsetting this fragile balance. St. Eustatius, although small, is home to several endemic plant species, two of which are the Statia morning glory and Statia milkweed, along with the critically endangered Lesser Antillean Iguana which could all be threatened by the habitat alterations of Coralita growth.

To read more, please find the full report on the Dutch Caribbean Biodiversity Database using the link below.

https://www.dcbd.nl/document/high-spatial-resolution-mapping-identifies-...

 

Article published in BioNews 48

 

Date
2021
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
St. Eustatius
Author

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

Abstract
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.

Keywords
BES Islands, Coralita, economic value, invasive species, spatial assessment, scenario
mapping

Date
2021
Data type
Scientific article
Theme
Education and outreach
Research and monitoring
Journal
Geographic location
St. Eustatius

Final report: Corallita Pilot Project, Study on the ecology and possible control methods of the invasive plant species Antigonon leptopus (Corallita or Mexican Creeper)

This one-year pilot project aims to provide an insight in the ecology of Antigonon leptopus (Corallita) an invasive vine, which is overgrowing the native vegetation (Photo 1). This pilot project is just a first step in controlling the Antigonon leptopus. This research was done on a small scale and under controlled circumstances. Our ideas are just for small scale use in town but also to eradicate ‘hotspots’ to prevent further spreading especially near the National Parks. The government with STENAPA as a consultant should take further actions to continue this project and put it as a high priority. The first step was made and we hope this will contribute in containing the species and monitoring the species closely. More research on the life circle and possible natural enemies and its sensitivity for herbicides should be done in order to start a larger scale eradication campaign. The project does not stand on its own, the vine contributes in the prevention of soil erosion on the island. A full size project including replanting/reforestation with native species and renewed agricultural activities should be set up for the long term.

Objectives

  • The primary research aim is to reduce and control the growth of Corallita on St. Eustatius and to prevent the species from invading the national parks. In order to achieve this, it is necessary.
  • To gather information about the ecology of the species, such as its life cycle, dispersal, germination capacity, use of the species by animals etc. • To gather information about how the species will react on different potential control methods.
  • Inform the local community about control methods if usable results are obtained.

Discussion and conclusion

Three weeks after the first treatment at Gallow Bay no regrowth was observed, this means the herbicide does work with smaller concentration (12.5% and 25%) on short term. After six weeks the first regrowth was observed. The tubers are still intact after the first treatment. It is not known how many times the treatment with these concentrations is needed.

In both plots of Sandy Road the plants have regrowth after 7½ weeks. Our observation on 13th January 2007 showed that a lot of Corallita was growing from the border into the plots covering the soil. The treatment did work but probably needed a second treatment if there is regrowth of 30-40cm. Further monitoring of large plots (during one year) is needed to make sure smaller concentrations will kill the plants. Tubers should de dug up and checked on viability. New plots should be selected.

 

 

Date
2007
Data type
Research report
Theme
Research and monitoring
Geographic location
St. Eustatius
Image