By Richard Black
Environment Correspondent, BBC News website
A ten-year survey in Cameroon by scientists from the UK's Royal Botanic Gardens at Kew has turned up more than 200 previously unknown plants.
Macropodiella pellucida clings to life in waterfalls and rapids; it is listed as 'endangered'
The researchers have found a higher diversity of plants in the Kupe-Bakossi region than any other site in tropical Africa.
Highlights include new species of coffee, spectacular orchids and new relatives of the fig.
The researchers say their work has led to local conservation initiatives.
Kupe-Bakossi lies around 100 kilometres north of Douala, Cameroon's second city - a two-hour journey by bumpy road.
At the end of it is a treasure-trove of specimens for the hungry botanist; which is why organisations including the Cameroon National Herbarium, Conservation and Research for Endangered Species (CRES), the British government's Darwin Initiative and Kew have spent a decade exploring it.
"Of any area that's been surveyed in Africa, this contains the highest number of species," Kew's Conservation Project Co-ordinator Ben Pollard told the BBC News website.
Since surveying began in 1995, the Kew team and their seasonal armies of volunteers from the conservation charity Earthwatch have found 2,440 different kinds of plant living in the region - around one in ten of them new to science.
"They range from a tiny plant called Macropodiella pellucida, which is smaller than a fingernail, to giant canopy trees more than 45 metres high," recalled Ben Pollard, "and included 187 species of orchid."
Rocks and falls
Kupe-Bakossi is a highly diverse region, with two extinct volcanoes - Mwanenguba and Edib - river valleys, grassland and some of the wettest forest in Africa.
This diversity is one of the reasons why so many plant species can find a niche here.
Nodonema lineatum lives only on inselbergs; it is listed as 'vulnerable'
Distinctive features include 'inselbergs' - uplifted areas of rock rising above the ground like islands in the forest.
Sir Arthur Conan Doyle used the concept in his book 'The Lost World'; high on their South American inselberg, isolated from the surrounding region and so immune from the prevailing local thrusts of evolution, dinosaurs found a way to persist into the modern era.
The Kew team found no dinosaurs on their inselbergs, but did turn up plant species which live only on these secluded heights, such as the delicate Nodonema lineatum.
More than 200 of Kupe-Bakossi's plants are at risk of extinction, according to the Red List of threatened species maintained by IUCN, the World Conservation Union; and human activities on the regions' fringes could constrain its future.
"There is urbanisation to the east and south of the area," said Ben Pollard, "and there are huge banana and rubber plantations, which lead to erosion problems and possibly pollution, with substances like fertilisers being picked up by the wind and rained out over the forest.
"There are also reports of illegal logging, which is very worrying.
"However, our colleagues from CRES are working with local communities, and several areas are now going to be protected."
After a decade of research, vast tracts of Kupe-Bakossi remain unexplored.
The Kew team intends to probe these areas as fully as possible over the coming years, and perhaps discover more new and spectacular species.