The Galapagos islands could be about to witness the first disappearance of a species in the 170 years since Charles Darwin's historic visit, after scientists warned that the mangrove finch has been driven to the brink of extinction.
There are fewer than 50 pairs of the birds, the rarest of all of Darwin's finches, left on the group of islands. Despite occupying just one square kilometre of mangrove forest, their habitat is under threat from the arrival of humans.
Darwin's finches are the primary example of evolution through natural selection and a living link to the scientific breakthrough that enabled us to understand our own ancestry.
The Galapagos islands, a volcanic archipelago 150 kilometres off the east coast of Ecuador, are a treasure trove of rare species, whose isolation from the outside world has made them a vital area of study for scientists.
Dr Glyn Young, from the Durrell Wildlife Foundation, said: "To lose one of the species of Darwin's finches would be to lose a vital chapter of scientific history."
The finch is an elusive bird and Darwin himself never saw it during his survey. Today it survives in just two patches of mangrove forest on the north-east coast of the largest island in the chain, Isobela.
While no exact figures exist, Dr Young, who is now leading a project to save the species, said its population was previously more widespread on Isobela.
The arrival of ever greater numbers of people has had the unwanted side effect of introducing species to their unique eco-systems. On Isobela this has meant the invasion of rats, cats and a voracious species of parasitic flies that attack the nests of the mangrove finch.
To these threats has been added the expansion of the illegal fishing sector, and fishermen have begun harvesting sea cucumbers and cutting down mangrove forests for firewood.
According to Dr Young, the mangrove finch has the smallest range of any bird in the world and is now dangerously isolated.
Darwin's finches are composed of 13 closely related species, collected during his stay on the islands in 1835. Although of a broadly similar size, the differences in the size and shape of their beaks demonstrated a high level of adaptation. Darwin did not immediately realise what he had discovered and it was only through the review of his research by the ornithologist John Gould, three years later, that the breakthrough in our understanding of evolution was made.
"The Galapagos is the workshop of evolution," said Dr Young. "We have one last chance to keep an oceanic archipelago ecosystem intact. Hawaii, the Pacific Islands, Madagascar have become an absolute mess."
Today, as many as 27,000 people live in Galapagos and more than 100,000 tourists visit every year. This influx has been compounded by a voluble and politically organised fishing lobby that has sought, often by illegal means, to expand fishing. The harvesting of the islands' marine riches has seen the introduction of long lining - an indiscriminate form of fishing that has devastated stocks in other areas of the world. Demand for sea cucumbers has led to fishermen illegally cutting down large areas of the mangrove forest vital to the ecology of the islands.
In a last-ditch effort to rescue the mangrove finch, an alliance of conservation groups, including the Charles Darwin foundation, the Durrell Wildlife foundation and the Galapagos Conservation Trust, has launched a programme to control invasive species and breed the birds in captivity.
"At this point, intervention by conservationists is their only hope of survival," said the Galapagos Conservancy, as it launched an appeal to save the bird.
Relatively little is known about the breeding patterns of the finches, which are thought to hatch eggs on a two or three-year cycle.
"At this stage in human development, with the damage we are doing to the planet, we can't afford to lose another species," said Leonor Sztjepic, from the Galapagos Conservation Trust. "And this is an iconic species. One that has impacted on our understanding of history. We have a duty to protect it."
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