A few hotspots around the world hold the key to the survival of a large proportion of the world's endangered species. Tim Hirsch visits one of them as part of Planet Under Pressure, BBC News Online's series on some of the world's biggest environmental problems.
An island of nature rising above a vast green ocean of sugar cane and cattle pasture, the Murici forest in north-east Brazil could lay claim to be the most important patch of forest in the world.
It is barely the size of Manhattan in New York, and despite being protected in Brazilian law, continues to face severe threats which could wipe out the unique species it harbours.
Packed with a much greater concentration of threatened species than any similar-sized section of Amazon rainforest, it is something of a "Noah's Ark".
Climbing into the forest with its exotic chorus of birdsong, liana vines hanging from the majestic trees and vast spider webs spanning the trail, I got a taste of the vanished wilderness which greeted the Portuguese explorers when they arrived in Brazil 500 years ago.
MURICI FOREST FRAGMENT
Size of Manhattan (60 sq km)
289 bird species recorded
15 threatened with extinction, 5 "critically"
Unique snakes, frogs, butterflies and plants
2% of ecosystem remaining
Clinging on to survival are birds such as the Alagoas antwren, discovered here just 20 years ago, and found nowhere else in the world apart from one other even smaller fragment of forest nearby.
Murici is the largest remaining remnant of an ecosystem which once stretched for hundreds of kilometres along the coast of North-Eastern Brazil, and has very nearly been destroyed through five centuries of deforestation to make way for sugar planting and cattle production.
Hotspot within a hotspot
It is part of the much larger Atlantic Forest of South America, a mosaic of contrasting ecosystems, each of which has evolved a unique group of species.
The Atlantic Forest as a whole is recognised as one of the world's "biodiversity hotspots", where a large number of endangered species face intense pressure from human activities.
7% of original forest remaining
Stretches from near Equator to edge of tropics
Rises from coast to 2,700m
104 bird species threatened with extinction
With less than 2% remaining, mostly in minute isolated patches on the hilltops, the north-eastern forest - of which Murici is part - is a hotspot within a hotspot.
Yet worldwide conservation efforts have until very recently entirely ignored these forests, concentrating instead on regions such as the Amazon, which in contrast still has some 85% of its area intact.
Under intense pressure from Birdlife International and Brazil's North-East Ecological Society (SNE), the government finally recognised Murici as an "ecological station" in 2001.
In theory, this affords the forest the highest level of protection, but in practice few concrete steps have been taken to reduce the threats which continue to assault the embattled wildlife.
The Alagoas antwren is clinging onto survival
Ironically, it was the quest for "green" alternatives to fossil fuels following the 1970s oil crisis which reduced Murici to half its former size.
Government incentives to run vehicles on alcohol produced from sugar led to a new wave of deforestation to expand the cane plantations.
In recent years as a health-conscious world started to lose its sweet tooth, lower sugar prices reduced that pressure, but gave rise to a new one as many former cane fields were converted to cattle pasture.
Livestock grazing further and further up the slopes has literally eaten still more into the forest.
Fight over land
Murici is also caught up in the chronic social conflict which plagues much of rural Brazil, with the landless poor becoming increasingly militant in their attempts to settle on the large estates which occupy the majority of the countryside.
This has led to a big increase in the population living on the margins of the forest, with many settlers venturing into the reserve to collect firewood and hunt wildlife - many birds are captured either for the pet trade or as ornaments.
Farmer Antonio Nestor says new ways of making a profit are needed
The government's land reform agency, Incra, is much criticised in the area for the way in which it allocates plots of land to poor settlers in such environmentally sensitive areas.
"Incra settles people with no regard for the environment. They forget about legal reserves, about the forest, and expect someone else to sort it out. It makes Ibama's role very difficult in these areas," said Jailton Fernandes, the local representative of the Brazilian environment agency, Ibama.
Ibama itself is criticised both by local landowners and by poor settlers for expecting others to enforce its own rules by informing on anyone they see abusing the forest - which could cause friction and even violence within the community.
The owner of the Boa Sorte (Good Luck) fazenda, Antonio Nestor, is helping with a project run by environmental groups to plant new trees in deforested areas in a modest attempt to link up some of the isolated forest fragments.
"A big problem here is to find an economic alternative to sustain our business. Once you start to re-forest, you have to find another way of making a profit if you stop planting and raising animals," said Mr Nestor.
Potential income sources under consideration as part of the project are ecotourism, and the use of "carbon credits" under the Kyoto climate change agreement, where, for example, energy companies fund reforestation to offset greenhouse gas emissions.
But here is another irony - the very industry which caused much of the original deforestation is now recognising that it has a strong self-interest in preserving what is left.
Not far from Murici, the vast Serra Grande sugar factory has a similar-sized patch of forest within its own estate, and is now putting significant efforts into conserving wildlife - even re-introducing large mammals such as tapir and capybara, the world's largest rodent.
Much of the forest was cut down for sugar cane plantations
The company's property manager, Jose Bakker, explains:
"Sugar production is very demanding on water. If we don't have a good forest to preserve the water source, we are gone."
But Mr Bakker says that without a major government effort to link up the "green islands" of Alagoas, the species they still support will inevitably disappear.
"There's no political will, and we don't have time. We have to work as fast as we can because if not, it's like making gardens instead of preserving nature," he said.