Cresswell, W.

Island ecosystems are recognised as high priority for biodiversity conservation, with invasive species a significant threat. To investigate prioritisation invasive species control, we conducted cost-effectiveness analysis of donkey control on Bonaire, Caribbean Netherlands. Successful prioritisation must take account of ecological, economic and social aspects of conservation. Further improvements are possible where impacts are measured across ecosystem boundaries, and management is tied to funding. We modelled the expected ecological impacts of control options, estimated costs, and connected this to the willingness of beneficiaries to fund such projects. Finally we surveyed experts to understand the social acceptability of donkey control. Of the control options, eradication is predicted to have the highest ecological impacts across two ecosystems, and to be cost-effective over the long term. Costs of all control options were within user willingness to pay. Social acceptability was highest for fencing, and lowest for lethal control. Though eradication offers the highest ecological benefits, we suggest that lower initial costs and higher social acceptability make fencing the better choice for Bonaire in the immediate future. In this way we illustrate the importance of considering economic and social impacts alongside the ecological in environmental conservation, and present an integrated application for prioritising conservation choices.

Coral reefs are in decline worldwide. While coral reef managers are limited in their ability to tackle global challenges, such as ocean warming, managing local threats can increase the resilience of coral reefs to these global threats. One such local threat is high sediment inputs to coastal waters due to terrestrial over-grazing. Increases in terrestrial sediment input into coral reefs are associated with increased coral mortality, reduced growth rates, and changes in species composition, as well as alterations to fish communities. We used general linear models to investigate the link between vegetation ground cover and tree biomass index, within a dry-forest ecosystem, to coral cover, fish communities and visibility in the case study site of Bonaire, Caribbean Netherlands. We found a positive relationship between ground cover and coral cover below 10 m depth, and a negative relationship between tree biomass index and coral cover below 10 m. Greater ground cover is associated to sediment anchored through root systems, and higher surface complexity, slowing water flow, which would otherwise transport sediment. The negative relationship between tree biomass index and coral cover is unexpected, and may be a result of the deep roots associated with dry-forest trees, due to limited availability of water, which therefore do not anchor surface sediment, or contribute to surface complexity. Our analysis provides evidence that coral reef managers could improve reef health through engaging in terrestrial ecosystem protection, for example by taking steps to reduce grazing pressures, or in restoring degraded forest ecosystems.

Highlights​

• Ecosystems are intrinsically linked, but conservation across boundaries is limited.
• User fees applied across ecosystem boundaries may improve conservation funding.
• Divers will fund terrestrial conservation, if coral improvements are expected.
• On Bonaire these funds would be large enough to cover terrestrial grazer control.

While ecological links between ecosystems have been long recognised, management rarely crosses ecosystem boundaries. Coral reefs are susceptible to damage through terrestrial run-off, and failing to account for this within management threatens reef protection. In order to quantify the extent to that coral reef users are willing to support management actions to improve ecosystem quality, we conducted a choice experiment with SCUBA divers on the island of Bonaire, Caribbean Netherlands. Specifically, we estimated their willingness to pay to reduce terrestrial overgrazing as a means to improve reef health. Willingness to pay was estimated using the multinomial, random parameter and latent class logit models. Willingness to pay for improvements to reef quality was positive for the majority of respondents. Estimates from the latent class model determined willingness to pay for reef improvements of between $31.17 - $413.18/year, dependent on class membership. This represents a significant source of funding for terrestrial conservation, and illustrates the potential for user fees to be applied across ecosystem boundaries. We argue that such across-ecosystem-boundary funding mechanisms are an important avenue for future investigation in many connected systems.