Public Release: 

Want to save 41 percent of the planet's highly threatened vertebrates? Work on islands

Mapping our world's most vulnerable island species, and a key threat to their survival

Island Conservation

New research discovers that nearly half the Earth's highly threatened vertebrates occur on islands. However, effective management of invasive species, a primary driver of extinctions on islands, could benefit 95 percent of the 1,189 threatened island species identified.

The paper, published in the journal Science Advances, describes the analysis of a database that maps the global distribution of highly threatened vertebrates and invasive species on islands. It lays the fundamental groundwork for planning conservation actions to prevent extinctions.

To guide conservation planning to prevent island extinctions, conservation biologists from the Coastal and Conservation Action Laboratory at the University of California at Santa Cruz (UCSC), Island Conservation, BirdLife International, and the International Union for the Conservation of Nature (IUCN) Species Survival Commission (SSC) Invasive Species Specialist Group created the Threatened Island Biodiversity Database.

The Threatened Island Biodiversity Database is the first of its kind. The database is a culmination of an intensive systematic review of over 1,000 available datasets, publications and reports, as well as consultation with more than 500 experts worldwide with specialized knowledge about native and invasive species on islands.

From this investigation, researchers identified and mapped all 1,189 land-based amphibians, reptiles, birds, and mammals, listed as Critically Endangered or Endangered on The IUCN Red List of Threatened SpeciesTM breeding on 1,288 islands. They then documented whether introduced, damaging (invasive) vertebrates, such as rats and cats, occurred on the same islands. The dataset also contains important social, political, and ecological information about each island, critical for informing conservation decision-making.

"The opportunities to prevent extinctions are now laid out right in front of us. This knowledge base of threatened island biodiversity can really empower more efficient and better-informed conservation planning efforts, which is exactly what our planet needs right now," commented Dr Dena Spatz, Conservation Biologist at Island Conservation and lead author on the paper who began this work at the UCSC Lab.

Why Islands?

Islands are isolated landmasses surrounded by ocean that hold many of the most threatened species in the world. For example, the Floreana Mockingbird in the Galápagos Islands, Ecuador disappeared from its island-namesake Floreana in the 19th century, mere decades after human colonization. The mockingbird was primarily driven extinct from the island (extirpated) by invasive species, including invasive rodents and feral cats which remain on Floreana and prevent its safe return. The few hundred individuals left of this Critically Endangered bird are now confined to tiny predator-free islets adjacent to Floreana.

Unfortunately, this is a common story for island wildlife, which suffer disproportionately from endangerment and extinction as compared with plants and animals on continental land-masses. Islands represent merely 5.3 percent of the world's land area, yet have hosted 61 percent of all recorded extinctions since 1500 . The majority of these extinctions were driven by invasive species, particularly rodents and cats, responsible at least in part for 44 percent of bird, mammal, and reptile extinctions in recent centuries.

There is hope on islands.

For some islands it is possible to implement biosecurity--preventing invasive species from arriving and becoming a threat. And for many islands with invasive species, it is possible to completely remove the interlopers, which has led to remarkable native species recovery stories around the world . On Anacapa Island in the Channel Islands, California, the successful removal of invasive rats led to positive outcomes for the Vulnerable Scripps's Murrelet, and the recent discovery of the Endangered Ashy Storm-petrel.

To prevent extinctions, Dr. Spatz and colleagues realized the need to take this effective conservation strategy to scale and created The Threatened Island Biodiversity Database, a foundational tool to pinpoint which species to protect, and where.

Dr Stuart Butchart, Chief Scientist at Birdlife International and co-author on the paper commented, "The datasets assembled for this paper support the most comprehensive assessment yet of the distribution of threatened species on islands, and where they occur with invasive alien vertebrates. The analysis underpins ongoing efforts to determine on which islands preventing invasions and controlling or eradicating invasive species would provide the greatest contribution to global biodiversity conservation."

While the species threatened by invasive vertebrates make up almost half of all highly threatened land vertebrates world-wide, they occur on a fraction of the Earth's landmass and on <1 percent of the world's islands. Many of these islands were found to be relatively small and with minimal human habitation, especially those with threatened reptiles and birds. These islands represent a significant opportunity to address the biodiversity crisis.

Dr Piero Genovesi, co-author and Head of Wildlife Service - ISPRA Institute for Environmental Protection and Research and Chair of the IUCN SCC Invasive Species Specialist Group, commented, "The database validates the importance of islands globally for biodiversity conservation and lays the groundwork for pinpointing efficient and effective conservation action at global and regional scales."

The paper highlights a handful of these islands where conservation efforts would be important. For example, Gough Island, a UK Overseas Territory of the St. Helena and Tristan da Cunha island group in the Atlantic Ocean, is home to six species that are highly threatened, such as the Tristan Albatross. Invasive mice co-occur on the island as well, threatening the survival of the Albatross, and other threatened species.

"The global nature of the paper offers a comparative look at threats to biodiversity and conservation opportunities. Furthermore, it provides national and regional governments and NGOs with critical biodiversity information assembled on a global platform, which can inform and stimulate promotion, fundraising, and action to protect species from extinction," concluded Dr Spatz.

Next steps are to apply the information gathered from this dataset to key conservation planning efforts at global and regional scales, combining other factors affecting the feasibility of implementing island conservation interventions to identify the most important islands where we should focus global efforts to prevent extinctions.


Paper link (when published):

Threatened Island Biodiversity Database:

Title and authors:

Globally threatened vertebrates on islands with invasive species by Dena R. Spatz, Kelly M. Zilliacus, Nick D. Holmes, Stuart H. M. Butchart, Piero Genovesi, Gerardo Ceballos, Bernie R. Tershy, Donald A. Croll. Published in Science Advances, Oct. 2017.

About the partners

Island Conservation (IC) is our world's only global, not-for-profit conservation organization whose mission is to prevent extinctions by removing invasive species from islands. We work where the concentration of both biodiversity and species extinction is greatest - islands. Removing a primary threat - introduced invasive vertebrates - is one of the most critical interventions for saving threatened plants and animals and restoring island ecosystems. Once invasive species are removed, native island species and ecosystems recover with little additional intervention. Since 1994, Island Conservation and partners have deployed teams to protect 994 populations of 389 species on 66 islands. IC is headquartered in Santa Cruz, CA with field offices in Australia, the Bahamas, British Columbia, Chile, Ecuador, Hawaii, New Zealand, Palau, and Puerto Rico.

Coastal Conservation Action Lab at UCSC: Our lab brings science and action together to solve conservation problems. We use science to identify and prioritize conservation problems. We then work with agencies and NGOs to develop and test cost effective solutions that can be taken to scale. Much of our work has focused on seabirds and island ecosystems, but we will apply our approach to any ecosystem where it can make a profound difference.

BirdLife International is the world's largest nature conservation Partnership. Together we are 120 BirdLife Partners worldwide - one per country - and growing with 13 million members and supporters, over 7,000 local conservation groups and 7,400 staff.

BirdLife's vision is a world rich in biodiversity, where people and nature live in harmony. We are driven by our belief that local people, working for nature in their own places but connected nationally and internationally through our global Partnership, are the key to sustaining all life on this planet. This unique local-to-global approach delivers high impact and long-term conservation for the benefit of nature and people.

BirdLife is widely recognised as the world leader in bird conservation. Rigorous science informed by practical feedback from projects on the ground in important sites and habitats enables us to implement successful conservation programmes for birds and all nature.

IUCN is a membership Union uniquely composed of both government and civil society organisations. It provides public, private and non-governmental organisations with the knowledge and tools that enable human progress, economic development and nature conservation to take place together. Created in 1948, IUCN is now the world's largest and most diverse environmental network, harnessing the knowledge, resources and reach of more than 1,300 Member organisations and some 10,000 experts. It is a leading provider of conservation data, assessments and analysis. Its broad membership enables IUCN to fill the role of incubator and trusted repository of best practices, tools and international standards.

IUCN provides a neutral space in which diverse stakeholders including governments, NGOs, scientists, businesses, local communities, indigenous peoples' organisations and others can work together to forge and implement solutions to environmental challenges and achieve sustainable development. Working with many partners and supporters, IUCN implements a large and diverse portfolio of conservation projects worldwide. Combining the latest science with the traditional knowledge of local communities, these projects work to reverse habitat loss, restore ecosystems and improve people's well-being.

The Invasive Species Specialist Group (ISSG) is a global network of scientific and policy experts on invasive species, organized under the auspices of the Species Survival Commission (SSC) of the International Union for Conservation of Nature (IUCN). ISSG aims to reduce threats to natural ecosystems and the native species they contain by increasing awareness of invasive alien species, and of ways to prevent, control or eradicate them.

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