Scientists now realise that life can exist considerable distances below the ground. Microbes known as "extremophiles" seem to thrive in the high temperatures and pressures that exist several hundred feet below the earth's surface. The hot geysers of Yellowstone Park and Iceland have already yielded some unusual lifeforms that are widely used in industry. More examples are still being discovered from some of the deepest boreholes drilled into the earth's crust.
BIG WOODS OF ARKANSAS
Last year ornithologists published details of one of the rarest birds on earth, the ivory-billed woodpecker, which was thought to have been extinct for 60 years. It came back from the dead when scientists recorded sightings in the dank swamps of the Big Woods of Arkansas - a huge wilderness area that had been systematically logged. The woodpecker is sometimes described as the Lord God bird, because when naturalists first set eyes on it they were often heard proclaiming "Lord God!"
TEPUIS MOUNTAINS OF VENEZUELA
This impressive range of table-top sandstone mountains in southern Venezuela is still relatively unexplored thanks to their sheer rock walls that rise 1,000m from the forest floor. One of the tallest, Roraima, is said to have been the inspiration for Arthur Conan Doyle's Lost World. "The flora of these mountains is diverse, partly due to the range of environmental conditions and habitats they support, and partly due to their biogeographical isolation," says William Milliken, a botanist at Kew Gardens. "About a third of all the plant species so far discovered in these mountains occur nowhere else on earth."
There are about 70 "uncontacted" groups of indigenous people in the world and the majority of these live in the Amazon region of Brazil, according to Survival International. Some are entire tribes, such as the Tsohom Djapa of the Javari valley, while others belong to an uncontacted part of a contacted tribe, like the Totobiegosode, a sub-group of the Ayoreo tribe. Many are threatened by the encroachment of incomers looking for timber, minerals or farmland. "Governments must act now to protect uncontacted peoples, otherwise they will be consigned to history," Survival's director Stephen Corry said.
MOVILE CAVE OF ROMANIA
This cave near the Black Sea in south-eastern Romania was discovered by accident in 1986. When cavers began to examine it in detail, they were astounded by its unusual flora and fauna. To date more than 30 species have been described and all are endemic to the cave. Life in the cave relies on chemosynthetic microbes that live off the hydrogen sulphur that wells up from underground sources.
BLACK SMOKERS OF THE ATLANTIC RIDGE
More is known about the surface of Mars than the floor of our deepest oceans. In some regions, living organisms thrive around the sulphur-rich plumes that emanate from "black smokers" - chimney-like structures of mineralised rock that form when superheated water from deep volcanic rocks spews into the cold depths of the ocean. They support extraordinary lifeforms, including giant tubeworms.
Like many large islands, Madagascar is rich in endemic species. Zoologists are still discovering new species of frogs and mammals, such as the golden bamboo lemur, and botanists believe Madagascar to be among the top three global hotspots for endemic plants. Kay Vollesen and John Dransfield of Kew Gardens have recently discovered 80 new species of palm plants, varying from 80ft-tall giants to the 8in-high pencil-thin Dypsis tenuissima, which can be found in a single mountain range in the south of the island. There are some 12,000 plant species on Madagascar, more than 90 per cent of which occur nowhere else.
KUPE-BAKOSSI OF CAMEROON
Kupe-Bakossi is the most botanically diverse region in tropical Africa and contains a total of 2,440 species of plant. Until recently much of the area was unexplored, until a scientific expedition led by a team from Kew Gardens. Botanist Martin Cheek said: "One in every 10 plants that we encountered in Kupe-Bakossi at the beginning of the survey was new to science." Among the new species found by the Kew team included an orchid, Ossiculum aurantiacum, and a new shrimp plant, Justicia leucoxiphus.
The Sentinelese, who live on North Sentinel Island in the Andamans, agressively avoid contact with other tribes, including their neighbours, firing arrows at helicopters and killing anyone who strays into their territory. Other isolated tribes of the Andamans such as the Jarawa and the Shompen have had only limited contact with outsiders in the past decade.
THE ULUGURU MOUNTAINS OF TANZANIA
The Ulugurus in eastern Tanzania support three endemic bird species and are home to many plants and animals that are either wholly endemic to the mountains or shared with other East African mountain forests. There are believed to be 15 species of vertebrates and more than 150 species of invertebrates only found in the Ulugurus, together with up to 100 endemic plant species. Dr Richard Thomas of Bird Life International says that the range is an example of a largely unexplored biodiversity hotspot for birds. "Around 2 per cent of the world's land area is home to 20 per cent of its bird species," he says.
THE ANNAMITES OF VIETNAM AND LAOS
This mountain range has produced some spectacular discoveries over the past 15 years. The first and most dramatic was the vu quang ox which was found in 1992. Since then zoologists have found a new species of striped rabbit, a deer called the giant muntjac and an entire family of squirrel-like rodents. The Annamites are remote, which has helped preserve their biodiversity.
BLUE MOUNTAINS OF AUSTRALIA
The wollemi pine was thought to have died out millions of years ago, until one was found in 1994 living in the remote canyons of the Blue Mountains, 200km west of Sydney. Botanists likened it to finding a dinosaur alive today. Fewer than 100 trees have so far been catalogued and their exact location is a secret. Tony Kirkham, the head of Kew Garden's arboretum, says: "When habitat remains undisturbed, the fragile ecology of an area and the interaction between plants and animals can continue. By preserving habitats you are preserving individual species, many of which may yet be undiscovered."
LAKE VOSTOK IN ANTARCTICA
Below 4,000m of solid ice lies the huge body of liquid water known as Lake Vostok. The largest "underground" lake in Antarctica is 250km long, 40km wide and 400m deep. Nobody knows whether anything lives there but the US space agency Nasa and the Russian academy of sciences are planning to break through the ice to sample Vostok's water for life. If it does, it will have been isolated from the rest of the biosphere for thousands of years.Reuse content