Madden, H.

Mate choice and nest cavity selection are directly linked to reproductive performance in seabirds, and disruption of these can result in breeding failure. The Redbilled Tropicbird Phaethon aethereus mesonauta breeds on inaccessible and remote islands, nesting primarily in natural rock cavities. I examined the relationship between reproductive performance and mate and nest cavity fidelity on St. Eustatius from 2012 to 2016, corresponding to four successive breeding seasons. The majority of nest failures occurred during the incubation stage. Pairs that failed in their first breeding attempt and laid a replacement clutch were more likely to be faithful to their mate and nest cavity within and between seasons than pairs that bred successfully. Only two replacement clutches (3.8%) were laid after the loss of a chick in the first breeding attempt, whereas the remaining 50 replacement clutches (96.2%) were laid after the loss of an egg. The stage at which pairs split had no influence on mate or nest cavity retention the following season. There were no significant differences in the weight or morphological measurements of chicks from pairs that retained their nest mate and/or cavity and those that switched. The results of this study suggest that switching nest mate or nest cavity does not necessarily improve subsequent breeding success among Red-billed Tropicbirds on St. Eustatius.

Key words: mate fidelity, nest cavity fidelity, Phaethon aethereus mesonauta, reproductive performance

Contact: Hannah Madden (Hannah.Madden@cnsi.nl)

Black rats (Rattus rattus) probably arrived on St. Eustatius along with the first Europeans. While a nuisance for the human population, their negative impacts are felt far more by the island’s fragile ecosystems, and are a significant threat to its biodiversity. In response, a rodent control project, funded by the Ministry of Economic Affairs, was launched in 2017. This project was implemented by the Caribbean Netherlands Science Institute (CNSI) and was previously presented in this magazine in 2017 (BioNews 6). This follow-up article will discuss the results of the ecological part of the project which focused on the red-billed tropicbird (Phaethon aethereus) nesting site on Pilot Hill, on the north-western coast of the island. Here, the decision was made to implement a rodent control project based on previous tropicbird monitoring programs that have been conducted since 2012.

Red-Billed Tropicbird

As the only species of seabird nesting on St Eustatius, the red-billed tropicbird is an iconic species for the island. A pelagic seabird, it spends most of its life out on the open sea and as a result, little is known of their behaviour when they are away from land. Their breeding biology and behaviour is more easily - and thus more extensively - studied as they return to shore to nest within the steep, rocky cliffs and slopes of Pilot Hill. 

Tropicbirds do not spend their time building nests. Instead, a pair will find a suitable cavity in which to lay their egg on the bare ground and shelter their offspring once it hatches. On average, the parents will spend six weeks protecting the egg, as they take turns incubating and hunting for flying fish and squid in the open sea. One parent usually remains in the nest constantly during incubation and during the first couple  weeks of chick rearing. It takes roughly twelve weeks for a newly hatched chick to grow into a well-fed fledgling, although shortly before gaining their independence, fledging chicks lose some of their weight as the parents stop feeding them. 

Population Concerns

Like many other seabird species, the global red-billed tropicbird population is in decline. According to the latest IUCN assessment in 2018, there are between 3,300 and 13,000 mature individuals globally, with an estimated total population not exceeding 20,000 birds. Invasive rodents such as rats and mice are cited as one of the biggest threats to seabird populations on oceanic islands. Tropicbirds are especially vulnerable as their nest sites are easily accessible by rodents, they have a long incubation period, and chicks inside the nest are unable to escape from predators. On St. Eustatius, camera traps have documented egg predation by rats inside nesting cavities. Over half of the nesting attempts fail each season, which is significant considering tropicbird females lay a single egg per clutch. The cause of most of these nest failures could not be determined, but rats are thought to be a factor.

Local Monitoring Programs

Monitoring of red-billed tropicbirds was started by Hannah Madden (STENAPA, CNSI) in 2012, and assisted by Kevin Verdel (Utrecht University), Max Oosterbroek (Van Hall Larenstein), and Eline Eggermont (Utrecht University) during the course of the rodent control project (2017-2019). Tropicbirds nest at several locations around the island, but the site on Pilot Hill is monitored because it is relatively accessible and thought to be the largest nesting area on St. Eustatius.

For the 2017-2018 season, a grid of bait stations was established across the entire study area. For the 2018-2019 nesting season, half of the study area was treated with brodifacoum rodenticide, whereas the other was left untreated. Brodifacoum is a second-generation anti-coagulant that kills rats and other rodents within 5 days of ingestion. Bell Laboratories, Inc., which has supported a number of invasive species management projects on other islands, generously donated FINAL™blox and AMBUSH bait stations for the project. 

Preliminary Results 

The relative abundance of rodents at the nest site was assessed via tracking pads, which were set out at 25m intervals every month in a predetermined grid. Tracking pads (pictured below) are rectangular pieces of cardboard with an ink section, baited with peanut butter to attract rodents and capture their prints. Using these methods, the relative abundance of rodents was found to have decreased significantly from 86.7% before treatment, to <2.0% post-treatment. Apart from rat and mouse prints, we also tracked small lizards, crabs, and insects.

Using the nest survival model in the program MARK, the survival rates of nests from the best-fitting model was 33.6% in the 2017-2018 season and 35.7% in 2018-2019. Nest age was the most important explanatory variable for survival in the incubation and chick rearing stage, and overall, suggested that nests and chicks were more likely to survive as nest age increased.For every one day increase in nest age, the odds of an egg surviving increased by 5.9%. For every one day increase in nest age, the odds of a chick and nest surviving increased by 4.6% and 4.3% respectively. The figure below represents the increase in daily survival rate percentage as nest age increases.  Our results are consistent with various studies that have demonstrated an increase in nest survival rates as nest age increases.

Rodent Control Alone is Not Enough to Save Tropicbirds

Much has been written about the detrimental impacts of rodents on seabird populations. Contrary to expectations, however, rodenticide treatment over the study period did not result in an increase in nest survival rate compared with previous years. This could be because  adult tropicbirds may be large and aggressive enough to fend off invasive rodents. Furthermore, a number of factors may have limited the success of the project. These include the limited number of accessible nests, the absence of a ‘control’ nest site for comparison, and crab interference with bait stations. Thus, despite successful rodent control, nesting success still declined compared with previous years. Although this might seem alarming, natural fluctuations in nest survival rates are common among seabirds. 

Tropicbird survival is likely affected by other,  undetermined factors. Possible external factors include pollution, foraging areas, prey availability, oceanographic conditions, and/or extreme weather. It should be noted that our study commenced following two category five hurricanes, which impacted the island in September 2017. Nevertheless, this is the first study of its kind focusing on rodent control and red-billed tropicbird survival, and we hope that our results will be useful for conservation efforts on other islands. 

This February, one tropicbird chick regurgitated ±10 cm of plastic tape, after it was fed by its parents. Plastic ingestion is a growing problem among many oceanic bird species and requires further research as little is known about the exact scale of this problem and its long-term health effects. Finally, we suggest that red-billed tropicbird monitoring continue, as more information will aid in the conservation and  survival of the species. All the information collected between 2012 and now will form an essential tool to help us determine the most effective conservation strategies to safeguard this majestic seabird on St. Eustatius.

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.

Raw observation data of the Red bellied racer on St.Eustatius from 2017-2018, including: location, length, elevation and weather conditions.

Please contact Hannah Madden for more information.

In the December 2017 edition of BioNews, we provided an overview of the results of two population assessments of the Bridled Quail-dove (Geotrygon mystacea) that had been conducted that year. This article provides the results of a third assessment that was conducted eight months after two major hurricanes impacted St. Eustatius.

The Bridled Quail-dove is a regionally endemic species in the family Columbidae that, on Statia, is only found in upper elevations of the Quill (above ~150m) and inside the crater. It is easily distinguished from other dove species by the torquoise patch on its neck and white stripe (bridle) under the eye. With its habit of wandering the forest floor during daylight hours in search of food (seeds, fruits and the occasional gecko or snail), observant hikers are likely to spot this bird. Activity and breeding are very much dependent on rainfall, and the dove is sensitive to hurricanes and extended periods of drought. Similar to other Columbids, the Bridled Quail-dove lays clutches of two eggs in a flimsy nest made of twigs up to six meters above the forest floor. Bridled Quail-doves do not fare well in areas of human activity and numbers have declined across the species’ range, presumably due to habitat loss, but also due to hunting and predation by invasive mammals such as the Black Rat (Rattus rattus). 

Irma and Maria were the first recorded category five hurricanes to hit the Windward Islands, and while Statia was spared extensive infrastructural damage in urban areas, its forest ecosystems did not fare so well. According to a recent publication by Eppinga and Pucko (2018), an average of 93% of tree stems on Statia and Saba were defoliated; 83% lost primary/secondary branches, 36% suffered substantial structural stem damage, and average tree mortality was 18% (with mortality being almost twice as high on Statia than Saba). 

Our pre-hurricane assessment in May 2017 was initially encouraging, with an estimated 1,030 (standard error [SE] = 275, 95% confidence interval [CI] = 561-1,621) quail-doves across its local habitat of 440 hectares, possibly the highest known density in the region. Post-hurricanes, in November, we repeated the surveys and recorded decrease of around 22% in the population to 803 (SE = 208, 95% CI = 451-1,229). Nevertheless, we feared that the population would continue to decline as a result of hurricane-induced habitat degradation and the negative impacts of severe vegetation damage, loss of vegetation cover, food limitation, and increased predation.

We repeated surveys in May 2018, hoping to coincide with the quail-dove’s peak breeding season. However instead of the usual ~70 transects, we had to walk a total of 255 transects in order to detect sufficient doves for analysis. No doves were heard calling, most likely as a result of delayed breeding, and only 32 were detected during 2018 surveys compared with ~92 in previous years. As expected, the quail-dove population continued declining in May 2018 (-76% compared with May 2017) and is currently very small at around 253 individuals (SE = 105, 95% CI = 83-486). 

Reduced survival and reproduction, and thus abundance fluctuations at low numbers, could lead to local extirpation. Because of the life-history characteristics shared by members of the family Columbidae (e.g., early maturity and short lifespan), conservation efforts are now urgently required. Although survival and reproduction rates of the Bridled Quail-dove on Statia are poorly understood, Black Rats are present in all vegetation types within the terrestrial protected areas. Management of these invasive mammalian predators within the dove’s range is needed as a first step towards increasing reproduction and survival, and therefore population recovery to pre-hurricane levels, of this highly vulnerable species.

The authors are grateful to St. Eustatius National Parks Foundation for granting permission to conduct surveys in the Quill National Park. Thanks to funding by the Dutch Ministry of Economic Affairs (now Ministry of Agriculture, Nature and Food Quality (LNV)) under their Nature Fund initiative, a rodent control project, facilitated through the Caribbean Netherlands Science Institute (CNSI), is running on St. Eustatius. The end date of this project was recently extended to October 2019. 

The Lesser Antillean Iguana, Iguana delicatissima (Laurenti 1768) is a Lesser Antillean endemic (Anguilla to Martinique, with the exception of Saba and Montserrat). The IUCN Red List status of this species was recently elevated from Endangered (Breuil et al. 2010) to Critically Endangered (van den Burg et al. 2018a). Population declines are driven by habitat loss, anthropogenic mortality, and invasive predators, but on many islands the declines are the result of hybridization with and displacement by the non-native invasive Iguana iguana (Linnaeus 1758) (Knapp et al. 2014; Vuillaume et al. 2015; Breuil et al. 2010; van den Burg et al. 2018a). In fact, genetically pure populations currently inhabit only 22% of the species’ historic distribution, and populations have been extirpated on Antigua, Barbuda, St. Kitts, Nevis, St. Martin/Maarten, Grand-Terre, Marie Galante, and Les Îles des Saintes. Recent discoveries of non-native iguanas on La Désirade and Dominica are extremely worrisome (e.g., Association Ti-Té 2017) and highlight the need for region-wide biosecurity improvements. Remnant populations on islands invaded by Iguana iguana (Anguilla, St. Barthelémy, St. Eustatius, Basse-Terre, and Martinique) also are likely to become extirpated unless on-going hybridization is prevented and remaining non-native iguanas removed. With few remaining populations and continuing anthropogenic pressure, information about these last populations’ health and threats are crucial to the species’ survival.

The Dutch Caribbean island of Sint Eustatius (21 km2) supports a small remnant I. delicatissima population (Debrot et al. 2013; van den Burg et al. 2018b; Fig. 1). Although this population almost certainly experienced declines since European settlement as a result of extensive island-wide agricultural practices (e.g., Chambers and Chambers 1842), numbers declined even further due to intensified hunting practices at the end of the 20th Century. The recently discovered threat of hybridization plus low recruitment, low availability of nesting sites, and anthropogenic mortality pose an ongoing severe threat (Debrot et al. 2013; van den Burg et al. 2018b). We hereby expand on a public survey undertaken in 2012 (Debrot and Boman 2014) to assess current threats and causes of mortality within the I. delicatissima population on St. Eustatius and make recommendations for the recovery of this remnant population.

The orange bellied racer, Alsophis rufiventris (Duméril, Bibron & Duméril, 1854), is one of four Alsophis species endemic to the Caribbean Lesser Antilles. Historically, it was found on St. Eustatius, Saba, and St. Kitts and Nevis but was extirpated from St. Kitts and Nevis during the 1900s, so that it is now confined to the Dutch Caribbean (Sajdak & Henderson, 1991; Savit et al., 2005). Thus, only two populations exist with a combined range of just 34 km2, which is 10.9% of the known historical range (Sajdak & Henderson, 1991; Savit et al., 2005; Daltry & Powell, 2016). Despite being the most geographically widespread colubrid genus in the West Indies, little is known about the ecology of most Alsophis species (Savis et al., 2005; Daltry & Powell, 2016). Here, we provide new dietary and natural history information that was collected during a field study of A. rufiventris on St. Eustatius from September 2016 to February 2017, as well as other ad hoc observations.

Twenty-five participants attended an informative workshop on invasive species on November 28th and 29th 2017. The Caribbean Netherlands Science Institute (CNSI) hosted the workshop on St. Eustatius under the Nature Awareness project, which is funded by the Ministry of Agriculture, Nature and Food Quality (LNV) (formerly Ministry of Economic Affairs). The workshop was facilitated by three marine and terrestrial biologists from Naturalis Biodiversity Center in the Netherlands (Dr. Bert Hoeksema, Dr. André van Proosdij, and MSc. Niels Schrieken). Participants included staff and students from STENAPA and CNSI as well as relevant government sectors such as Public Health, Agriculture & Fisheries, and Harbor.

Beginning with an overview of terminology on Day 1, the differences between indigenous, cryptogenic, exotic, introduced, and invasive species were explained, with examples of vectors for introduction such as boats, planes, and the pet & ornamental plant trade. Islands are particularly vulnerable to invasive species because many islands are relatively small and isolated. Yet, islands represent the greatest concentration of biodiversity and species extinctions (40% of fauna at risk of extinction; 80% known extinctions since 1500).

Once an invasive species arrives on an island, early detection is crucial to avoid excessive eradication costs and negative side-effects once it becomes established. Actions that can be implemented include species alert lists, action plans, effective border controls, public awareness, invasive species management teams, government policy (and enforcement), and quarantine import documents.

Botanist Dr. André van Proosdij led an afternoon field excursion on land species (plants) during which the group visited areas affected by non-native/invasive flora and compared differences between the sites. Participants used skills developed in the workshop to determine to what extent an area is impacted by invasive flora at present and to predict how it could look in the future if no effort is made to control these. Mexican Creeper, also known as Corallita (Antigonon leptopus), is one of the most pervasive invasive terrestrial plant species on St. Eustatius, covering around one-third of the island and smothering native vegetation in its path. There is no known effective control of this plant, and even free-roaming goats and sheep do not find it palatable. In the sea, the invasive seagrass species Halophila stipulacea has become notorious for aggressively replacing local seagrass species. Because this happens out of sight, most people are not aware of it.

Dr. Bert Hoeksema kicked off Day 2 with an overview of St. Eustatius’s non-indigenous terrestrial animals and potential new arrivals. He highlighted the dangers of existing invasive species such as the giant African land snail (Achatina fulica), which led to an interactive discussion by the stakeholders who are already working to combat this species. Also discussed were the threats of potential invasive species – which may exist on other islands but have not yet reached St. Eustatius – and how to prevent these crossing borders. These include species such as the vervet monkey (Chlorocebus pygerythrus), Cuban tree frog (Osteopilus septentrionalis), red palm mite (Raoiella indica), green mussel (Perna viridis), and much more.

 Dr. Bert Hoeksema also gave a similar presentation on marine animals recorded from St. Eustatius and other areas in the Caribbean and the West Atlantic. The lionfish (Pterois volitans and P. miles) is well known but not many workshop participants were aware of the orange cup coral (Tubastraea coccinea) that entered the Caribbean in the 1930s by vessels and appears to thrive well on artificial substrates.

Invasive fauna species can impact human health, native wildlife and ecosystems, and the local economy. The green iguana (Iguana iguana) is a perfect example of an invasive species that has spiraled out of control on many Caribbean islands. On Grand Cayman in the Cayman Islands, for example, green iguanas make their homes in trees and buildings located close to water. Roadkill, damage to crops, flowers and plants, and lizards taking a dip in pools are taking their toll on residents. In 2015, scientists estimated the population to be around 152,000; when farmers killed up to 20,000 green iguanas, the population rebounded within about one week. Without adequate control, numbers could soon exceed 1 million.

STENAPA gave an insight into the efforts being made locally to combat the invasive green iguana and lionfish on St. Eustatius. The arrival of the green iguana is terrible news for islands that house the regionally endemic lesser Antillean iguana (Iguana delicatissima), and unfortunately, St. Eustatius has recently fallen victim to this. Following the discovery of an adult female green iguana in 2016, six hybrids were captured during intensive search efforts. This is an ongoing cause for concern on the island. In 2000, the first lionfish were spotted in Bermuda and have since spread across the Caribbean Region. With their voracious appetites and rapid reproductive rates, lionfish pose a severe threat to native fish species. On St. Eustatius they are harpooned and brought back to shore where their stomach contents are analyzed, and the flesh can safely be eaten once the poisonous spines are cut off.

Biologist MSc. Niels Schrieken led the afternoon field session on marine species with a focus on the settlement plate (SETL) project, whereby PVC plates are hung at a depth of one meter below the surface and checked quarterly to inspect the marine species that attach to them. Introduced marine species can easily be detected thanks to this globally applied method, especially in the proximity of harbors. Three SETL plates were installed along Oranje Bay, and the data collected will be submitted to a global database.

SETL project

The SETL-project is a community study which monitors the diversity of species living on a hard surface. This project was launched in 2006 in the Netherlands by GiMaRIS, in close collaboration with the Smithsonian Marine Invasions Laboratory, and is still run by them. The SETL-project is also run locally in the USA by the Salem Sound Coastwatch and is project-based in other European countries and throughout the Ponto-Caspian region (see figure). The plate design has been deployed along both coastlines of northern America and in Hawaii to facilitate comprehensive comparisons. Within the Caribbean Basin, there are sites in Central America but none on the Atlantic side. St. Eustatius could become the first SETL-location for the Caribbean Basin on the Atlantic side.

SETL Methodology

Around 150 SETL plates are deployed each year in The Netherlands at about 12-15 sites, mostly in pleasure craft harbors and ports. A SETL-plate consists of a 14x14x0.5 cm grey PVC plate attached to a brick to keep it horizontal, hanging from a plastic line with a metal core in the water column. It is deployed at a depth of 1 meter under the water line if attached to a floating object, and 1 meter under the low water line in tidal areas if fastened to non-floating structures. Monitoring the plates is best done repetitively. Collected plates can be taken back to the lab for further analyses. When photographed in the field they can be redeployed after photographing. Pictures taken of the plates are divided on an overview photo into 25 grids, and the presence of species is scored for each grid. 

Using SETL data

In the Netherlands, 133 species have been documented on SETL plates over the years. A new species was recorded in the Wadden Sea immediately after the SETL-project started in 2006, which illustrates the project’s potential as an early detection method for species. The SETL-plate is easy to retrieve, making it user-friendly and a great way to make life underwater more visible for the local population and in student projects.

Workshop follow-up

The workshop encompassed interactive sessions and discussions that led to extensive knowledge sharing and development at all levels. A recommendation/discussion document has been created based on particular issues flagged for importance, including inspections/border control, customs, and capacity-building.

CNSI will organize a follow-up session to promote further discussion and to formalize specific action points between key island stakeholders. It will encourage those who could not attend the workshop to become involved and will focus on the creation of a task force and/or training if necessary. The responsibility of various stakeholders for e.g. detection of invasive species will also be discussed.

This news-tem was published by DCNA in BioNews12-2018.

The Caribbean Netherlands Science Institute (CNSI) hosted two “Economic Value of Nature” workshops on St. Eustatius from 3-6 April 2017. These workshops are part of the “Nature Awareness Project” which is funded by the Ministry of Agriculture, Nature and Food Quality (LNV) (formerly Ministry of Economic Affairs) through the Nature Funds (natuurgelden) and facilitated by CNSI. The workshops were led by experts from Wolfs Company and Wageningen University who have visited the island numerous times to conduct research projects, such as The Economics of Ecosystems and Biodiversity (TEEB) study.

The one-day private sector workshop was attended by representatives from NuStar Terminals, St. Eustatius National Parks Foundation (STENAPA), St. Eustatius Tourism Development Foundation, Scubaqua, and the Chamber of Commerce. The goal of the workshop was to improve the participants’ understanding of how the private sector depends on ecosystem services and how they impact these services. During the workshop, participants used the Ecology Scan tool developed by Wolfs Company to identify these impacts and dependencies. Subsequently, company strategies were discussed to maximize opportunities and minimize threats related to the natural environment.  

The three-day public sector workshop was attended by civil servants from various departments such as the Department of Agriculture and Fisheries, public works, public health, infrastructure and economy, and the licensing unit. The goal of this workshop was for nature managers and civil servants to develop an understanding of why valuing ecosystem services is useful for St. Eustatius, and how to use the valuation results in day-to-day operations. Special emphasis was placed on how this information can be used to develop financial and regulatory policy measures that will improve nature management, support the development of a sustainable island economy and maximize the future well-being of Statia’s citizens.

Both workshops consisted of theoretical sessions combined with interactive discussions and exercises. Working groups were asked to develop cases based on identified policy questions or business operations. The results of the assignments give an insight into how the results of the TEEB St. Eustatius study can be used and lead to recommendations for further research.

The objective of both workshops was to raise awareness of the interdependency of nature and socioeconomic prosperity, as well as to build capacity to incorporate this knowledge into policy and business operations on St. Eustatius. In the public sector workshop, this mainly related to the economy of St. Eustatius as a whole, while the private sector workshop focused on the operations of specific companies. 

Participants learned to identify different ecosystems on St. Eustatius and were trained in ecosystem valuation methods and techniques, using specific Statian cases. They also learned about the valuation of ecosystem goods and services studies that have taken place in the Caribbean, as well as their influence on nature conservation, management, investments and policies in the region. The workshop also saw the discussion of factors  that increase the effectiveness of a valuation study, as well as the presentation of socio-economic benefits resulting from influencing nature conservation, management investments, and policies. Additionally, the effects of natural resource conflicts and their relation to ecosystem services were demonstrated.

Background: the value of natural capital on St. Eustatius

Healthy ecosystems such as the island’s coral reef patches and the forests on the hillsides of Boven and the Quill are essential to human well-being on St. Eustatius. The St. Eustatius Strategic Development Plan also acknowledges the importance of the island’s natural attractions to the growth of the tourism sector. Local and global developments have led to an increase in serious threats to these fragile ecosystems, jeopardizing the foundations of the island’s economy. To make well-founded decisions that affect the natural environment on the island, it is key that nature’s contribution to St. Eustatius’ economy and well-being is well understood and highlighted.

Economic valuation of Statia’s main ecosystem services has drawn attention to the economic benefits of biodiversity and has highlighted the growing costs of biodiversity loss and ecosystem degradation. The results of the TEEB St. Eustatius study are presented in four reports on the value of Statia’s nature by Wolfs Company and the VU University in Amsterdam. As a part of this study, a survey, which involved over 1,000 respondents including tourists, residents, and citizens of the European Netherlands, demonstrated that natural capital strongly contributes to the island’s economy and the well-being of its residents.

Estimates put the total economic value (TEV) of the ecosystem services provided by the marine and terrestrial ecosystems of St. Eustatius in 2014 at $25.2 million per year. This TEV and its underlying components can be used to evaluate strategies for effective conservation measures and sustainable development on St. Eustatius. After analyzing the impact of different development scenarios on the value of future ecosystem services, it becomes apparent that there are indeed opportunities to develop the tourism industry. However, expanding the tourism sector beyond levels of sustainable use will cause pressures that the local ecosystems cannot endure. Consequently, degradation of the natural environment will result in fewer tourists coming to St. Eustatius. The current demand on the ecosystems of St Eustatius and unsustainable development practices is projected to decrease the TEV of the island’s natural environment from $25.2 million today to around $18.5 million in 30 years.

Public sector workshop (3 days)

The set-up of the public sector workshop was based on the structure presented in Figure 1. The framework reflects the research steps of a natural capital assessment. By combining theoretical presentations, examples from natural capital assessments elsewhere and practical sessions to apply the theory to the context of St. Eustatius, participants were guided through the research process. 

The workshops began by defining ecosystems and ecosystem services and identifying relevant stakeholders. Participants then helped determine threats to the selected ecosystems, and developed scenarios to assess the changes in ecosystem service benefits over time and their impact on different stakeholders. Different types of values and available valuation techniques were discussed to quantify this socioeconomic impact and data requirements were established based on selected valuation techniques. The workshop ended with a discussion on how the valuation results could support policy-making processes and how these results could be efficiently communicated to relevant stakeholders and decision-makers.  

Private sector workshop (1 day)

The different steps of the Ecology Scan formed the basis of the private sector workshop set-up. Each step comprised a presentation with theory and practical examples as well as an exercise. The first step, “select the scope”, provided participants with an overview of the TEEB St. Eustatius study and described how private companies interact with ecosystem services. In following steps, participating companies determined the most relevant ecosystem services to their business and how these services are developing over time. They then defined the risks and opportunities associated with the identified priority ecosystem services. The assignment in the final step challenged participating companies to come up with innovative strategies to address the risks and opportunities identified in the previous steps.

Post-workshops on natural capital of St. Eustatius

The aim of both the public and private sector workshops was to increase the understanding of natural capital on St. Eustatius. During both workshops, participants extensively discussed how the results of TEEB St. Eustatius study can be used to inform policymakers on the island. The most important issues that were identified are:

• Spatial planning
• Damage assessment
• Managing erosion and roaming cattle
• Biosecurity
• Including ecosystem services in investment decisions

Furthermore, the ecosystem services that were identified as important, but were not covered in TEEB St. Eustatius are:

• Water provisioning
• Agricultural production

To follow up on the workshop and continue to raise awareness about the value of natural capital on St. Eustatius, Wolfs Company developed a toolkit for St. Eustatius that can be used by e.g. CNSI and STENAPA to reach out to stakeholders. The kit includes a tailor-made version of the ecology scan (used in the private sector workshop) to evaluate the interaction of businesses on St. Eustatius with their natural surroundings. The tool is based on locally relevant ecosystem services and can be used to assess risks and opportunities for businesses related to these services. Furthermore, a tool for the public sector was developed to map out the effects of government interventions (e.g. goat management, erosion control) on ecosystem services. This tool is also based on locally relevant ecosystems, services, and stakeholders on St. Eustatius. The set-up of the tool is a multiple criteria analysis which qualitatively assesses ecosystem changes. A repository of relevant reports related to natural capital on St. Eustatius has also been created. CNSI staff are trained to use the toolbox and continue the training on ecosystem services on St. Eustatius.

All participants were enthusiastic about the knowledge they gained, and CNSI looks forward to a continued discussion on the topic of valuation of nature on St. Eustatius. The tools learned in these workshops were especially relevant following Hurricanes Irma and Maria, enabling relevant stakeholders to assess the economic damage caused to natural capital by these natural disasters.

This news-item was published by DCNA in BioNews 11-2018.

The Lesser Antillean Iguana (Iguana delicatissima) is an endangered species threatened by habitat loss and hybridization with non-native Green Iguanas (Iguana iguana). Iguanadelicatissima has been extirpated on several islands, and the Green Iguana has invaded most islands with extant populations. Information is essential to protect this species from extinction. We collected data on 293 iguanas including 17 juveniles from St. Eustasius, one of the few remaining I. delicatissima strongholds. Genetic data was leveraged to test for hybridization presence with the Green Iguana using both mitochondrial and nuclear genes, including 16 microsatellite loci. The microsatellites were also analysed to estimate genetic diversity, population structure and effective population size. Using molecular and morphological data we identified 286 I. delicatissima individuals captured during our first fieldwork effort, and seven non-native iguanas captured during a second effort, showing hybridization occurs within this population. Comparing homologous microsatellites used in studies on Dominica and Chancel, the I. delicatissima population on St. Eustatius has extremely low genetic diversity (HO=0.051; HE=0.057), suggesting this population is genetically depauperate. Furthermore, there is significant evidence for inbreeding (FIS=0.12) and weak spatial genetic structure (FST=0.021, p=0.002) within this population. Besides immediate threats including hybridization, this population's low genetic diversity, presence of physiological abnormalities and low recruitment could indicate presence of inbreeding depression that threatens its long-term survival. We conclude there is a continued region-wide threat to I. delicatissima and highlight the need for immediate conservation action to stop the continuing spread of Green Iguanas and to eliminate hybridization from St. Eustatius.