Biosecurity of invasive species in isolated ecosystems

MAMMAL ERADICATION PROGRAMS to prevent extinction of threatened native vertebrate species:

Islands present a great opportunity and need for biodiversity conservation as they host 75% of known extinction species since 1500 as well as 36% of species classified as Critically Endangered on the IUCN Red List.

Given the relevance of these territories and also the increasing pace of biodiversity loss of the last decades, it is important to develop a framework which would allow us to prioritize projects for conservation in isolated ecosystems.

Such frameworks must include considerations on financial resources, political will as well as stakeholders involvement. Moreover, it is important to mention that a big obstacle arises from the availability of reliable data on species distributions which would consequently influence the assessment of eradication options. Finally, political feasibility must be carefully considered and incorporated through an objective methodology as it would eventually impact the outcome for invasive mammal management.

The methodology for assessment of mammal eradication programs potential is as follows:

Ecological Conservation Feasibility:

1. What is the extent of potential conservation gains from eradication on native vertebrates (Current Conservation Risk)
2. Include only in the list of islands those where eradication is technically feasible (Potential Conservation Risk)
• The delta between CCR and PCR would show remaining only those where the eradication was not feasible (threat level remained the same)
• Operational cost can also be computed to enhance the utility assessment and prioritize those islands projects are more financially feasible

Socio-Political Feasibility:

       3. Socio-political feasibility is assessed through the use of expert-elicitation method

In conclusion, with the adoption of such framework, it has been possible to identify a selected number of islands which could be prioritized in the strategy towards alien mammal species eradication to achieve the highest yield of benefits for local vertebrates.

Important as well to consider re-invasion (or new invasion) risk and post-project biosecurity, however data for this assessment is limited it is therefore advised to carry out an estimation case by case.

Eradication of invasive mammals is a key first step in the conservation of island regions. After such mission is accomplished, the restoration of habitats and ecosystems as well as assisted colonization or conservation translocations for those species where eradication does not exist can occur.  

PREVENTATIVE APPROACH to managing invasive alien species:

Prevention against the invasion of alien species on island is a cost-effective approach to biosecurity.

In order to optimize resources and effective actions, it is important that islands globally collaborate via set up routines to continuously exchange resources and information on best practices which will eventually improve outcomes through preventive conservation.

"The introduction of IAS can result in direct and indirect impacts to island biodiversity through predation, introgression, competition for limited resources, habitat alteration, and ecosystem degradation." 

The priority on IAS is shared globally through the adoption of Aichi Biodiversity Target #9 which states that "by 2020, invasive alien species and pathways are identified and prioritized, priority species are controlled or eradicated, and measures are in place to manage pathways to prevent their introduction and establishment” (CBD 2017).

Prevention:

Prevention is the most cost efficient mechanism in island biosecurity programs. It includes quarantine, biosecurity inspection and education. Preventions methodology vary depending on the vulnerability as well as the uses of the island which might impact the vectors of IAS introductions (for example, in New Zealand: thorough inspections of cargos with trained dogs, issue warrants to companies with comply with random inspections, and boost commerce on strategic locations; in Mexico: more bottom up conservation where workshops are held for sensibilization with local communities, educational events for local communities and individuals; in the US: if the land is only of military use then it's restricted and control is centralized).

Early Detection:

These represent the second line of defence in situ so that the IAS can be targeted proactively. Programs for early detection must have adequate resources to tackle the invasive introduction of any kind of alien species (also those less detectable). These methods include remotely triggered camera traps, rodent chew cards or blocks, tracking cards, trained detection dogs, and routine surveys via foot, airplane, or helicopter. Moreover, the conduction of risk analysis on specific species or imports would allow a more accurate prioritization customized to island specific requirements.

Response:

Correct assessment and risk analysis of the IAS is important in order to outline the appropriate strategy in response to the invasive species. Moreover, it is valuable to draft action and communication charts in alignment and collaboration with all stakeholders in order to achieve the most inclusive resolution. Finally, it is very important to assess the potential ecological impact of the response plan also on non IAS.

References

Holmes N.D., D.R. Spatz, S. Oppel, B. Tershy, D.A. Croll, B. Keitt, P. Genovesi, I.J. Burfield, D.J. Will, A.L. Bond and A. Wegmann, (2019), Globally important islands where eradicating invasive mammals will benefit highly threatened vertebrates, PLoS One 14(3)

Matos J., A. Little, K. Broome, E. Kennedy, F.A. Sánchez, M. Latofski-Robles, R. Irvine, C. Gill, A. Espinoza, G. Howald and K. Olthof, (2018), Connecting island communities on a global scale: case studies in island biosecurity, Western North American Naturalist 78(4)