Invasive species eradication |03 September 2020

Aldabra Atoll, one of the world’s largest atolls and Seychelles’ crown jewel, is, like many World Heritage Sites, at risk from invasive alien species, photo: © Adam Plezer, courtesy of the Seychelles Islands Foundation.

Aldabra’s success story shared amongst the giants of Unesco World Heritage Sites

A team of international scientists have devised a new monitoring and reporting framework to help protect World Heritage Sites from almost 300 different invasive alien species (IAS) globally including, rats, cats and invasive ants.

Lead author Dr Ross Shackleton joined invasive species experts from around the globe – including Seychelles Islands’ Foundation’s Dr Nancy Bunbury – who propose the new ‘tool’ to help protect World Heritage Sites like the Aldabra Atoll, the Galápagos, and the Serengeti from future threats.

Unesco World Heritage Sites are areas of outstanding universal value and conservation importance to humanity. However, they are threatened by a variety of global change drivers, including biological invasions from a range of terrestrial, freshwater and marine species.

The team of researchers and practitioners, who assessed the status and management of biological invasions in 241 natural and mixed World Heritage Sites from documents collated by Unesco and the International Union for Conservation of Nature (IUCN), found that reports on IAS were inconsistent. While some reports were ‘very informative’, they were hard to compare because no systematic method of reporting IAS distribution and impacts was followed.

Dr Shackleton added, “Detailed information on IAS management undertaken in World Heritage Sites was available for fewer than half of the sites that listed IAS as a threat. There is clearly a need for an improved monitoring and reporting system for biological invasions in World Heritage Sites and likely the same for other protected areas globally.”

The new framework devised by the scientists, which has been applied to seven World Heritage Sites, covers data collection and reporting on; IAS pathways, presence, impacts, management, predicting future threats and management needs, the status of knowledge, identifying gaps, and, assigning an overall ‘threat score’ to the protected area.

One of the co-authors, Dr Arne Witt, said, “We need urgent action right now to reduce the severity of these threats that include a range of invasive alien plant species – such as Mimosa pigra and Prosopis juliflora – and we believe that the development of this monitoring and reporting framework is a step in the right direction to protecting areas moving forward.”

Based upon a previous review of invasive plants in the Serengeti-Mara ecosystem, Dr Witt added, “Failure to act could, for instance, see the devastation of the Serengeti-Mara ecosystem as we know it and that would have a major impact upon the annual wildebeest migration.”

Dr Heinke Jäger concurs, “Invasive mammals and pathogens in the Galápagos threaten some of the animals made famous by Darwin, such as the giant tortoise and Darwin’s finches.”

In testing the devised framework, which categorises the level of threat posed by IAS as ‘very high’, ‘high’, ‘moderate’ and ‘low’, the researchers have already yielded more information than from past monitoring initiatives. For example, the IAS threat level indicated in the 2017 IUCN World Heritage Outlook for the Serengeti, Keoladeo, Doñana and the Vredefort Dome sites was ‘data deficient’ or ‘low threat’ or ‘not listed’, whereas all of these World Heritage Sites are now categorised as facing ‘moderate’ to ‘high’ threats from biological invasions.

Co-author Prof. David Richardson said, “World Heritage Sites face growing threats from a range of biological invasions which impact upon native biodiversity and the delivery of ecosystem services. Not only that but invasive alien species are a financial burden as costs for management can be extremely high.”

“One key element of the new framework is listing all invasive alien species present where we can track the changes in threat or implementation of effective management over time.”

This is exemplified by work done on Aldabra where, according to SIF co-author Dr Bunbury, “There has been a decrease in the number of IAS listed due to effective eradications, highlighting management success at the site over the last few years.”

Dr Bunbury adds that “World Heritage sites were ideal test sites for the reporting framework but it is applicable to all protected areas and we hope will become a standardised tool for assessing IAS impacts and management globally”.

SIF’s chief executive, Dr Frauke Fleischer-Dogley, adds, “We are delighted that Aldabra was included as a key case study in this research that allowed us to share our lessons learnt and best practices within a network of sites of outstanding universal value (OUV). Generally resources to manage protected areas are scare and therefore to be able to maintain the OUV of World Heritage Sites requires effective management and cost efficient IAS eradication and control. Humanity accepted these sites as gifts and by doing so accepted universal responsibility to look after them, this also means making the necessary resources available.  Our contribution is to share how eradications can be highly effective if the right decisions are made.”

The researchers’ recommendations also include making funding available to conduct surveys at all under-resourced World Heritage Sites, to inform the reactive ‘state of conservation’ assessments undertaken by Unesco and IUCN, and that monitoring could be enhanced by members of the public via ‘citizen science’ projects.

Full paper reference

Shackleton, R.T., Bertzky, B., Wood, L.E., Bunbury, N., Jäger, H., van Merm, R., Sevilla, C., Smith, K., Wilson, J.R.U., Witt, A.B.R. and Richardson, D.M., ‘Biological invasions in World Heritage Sites: current status and a proposed monitoring and reporting framework,’ (In press), Biodiversity and Conservation, DOI: 10.1007/s10531-020-02026-1

The paper is available at the following link: https://link.springer.com/article/10.1007/s10531-020-02026-1

Contributed by SIF