Galápagos goat eradication: how thinking archipelago-wide changed island restoration

What this paper is about

Islands are home to a disproportionate share of the world's most unique and endangered species. But introduced mammals, including goats, rats, and cats, have devastated island ecosystems worldwide. Over the past three decades, eradicating these invasive animals has become one of the most effective tools in conservation.

This paper documents one of the most ambitious island restoration efforts ever undertaken: the removal of feral goats from the Galápagos Islands. Known as Project Isabela, the effort removed more than 140,000 goats from over 500,000 hectares, an area larger than Rhode Island, at a cost of $10.5 million.

The reinvasion problem

The researchers identified a serious obstacle: even after successful eradication, goats kept coming back. Fishermen and others were deliberately reintroducing goats to cleared islands as a political bargaining tool against conservation authorities. At least twelve intentional introductions or reintroductions were documented across the archipelago since 1990, roughly one every 20 months.

Each reintroduction was expensive to fix. Six goats reintroduced to Santiago Island in 2009 cost $32,393 to detect and remove, three years after the island had been declared goat-free.

The archipelago-wide solution

Rather than clearing one island at a time, the team implemented a strategy to eradicate goats from the entire Galápagos archipelago simultaneously. Remove every source population and there is nothing left to reintroduce from.

The paper argues that the main obstacles to island restoration are no longer technical. It is now possible to clear even very large islands of invasive mammals. The real challenges are political will and processes, funding, and community support.

The approach also became more cost-effective over time. The ground-based eradication on Santiago Island cost $110 per hectare. Subsequent aerial-based campaigns on Isabela Island cost $9 per hectare, a tenfold reduction, as teams developed expertise, infrastructure, and efficient techniques including helicopter hunting and "Judas goats" fitted with radio collars to lead hunters to remaining animals.

Key findings

• Island size is no longer the main obstacle to invasive mammal eradication. The real barriers are now political will, funding, and community support.
• An archipelago-wide approach significantly reduces the risk of reinvasion by removing all readily available source populations.
• Costs fall substantially across successive campaigns as knowledge, equipment, and institutional capacity are built and reused.
• Aerial hunting combined with Judas goat technology can clear very large islands cost-effectively.
• Deliberate reintroduction by local actors is a real and underappreciated threat to restoration investments.

Ecological recovery

The biodiversity results are already emerging. The endangered Galápagos rail had not been recorded on Floreana Island since the late 1980s. It has now reappeared following vegetation recovery after goat removal. Eight endemic plant species listed by the IUCN have increased in both number of populations and total individuals, including the endangered Scalesia atractyloides, which had been feared extinct. Its recovery after goat eradication on Santiago Island was so rapid that its endangered status is now being reconsidered.

The authors also note an unintended consequence: blackberry, an invasive plant, has spread more aggressively in some highland areas following goat removal, as the herbivore pressure that had been suppressing it was lifted. This is a useful reminder that eradication of one invasive can create space for others, and that restoration requires ongoing monitoring.

Limitations and caveats

• The Galápagos context is unusual: goats cannot easily arrive from the mainland (1,000 km away) and are not farmed commercially on the islands, which makes an archipelago-wide strategy more achievable than in most settings.
• Full ecological recovery data are not presented in this paper. The authors note that biodiversity benefits are "in the process of revealing themselves" at the time of publication.
• The social and political dimensions of restoration, including the deliberate reintroductions used as leverage by fishermen, are acknowledged but not fully analysed.