Biological bonanza in Kenya's threatened forest

The Matthews Range of mountains rises from the arid brown plains of northern Kenya like a green tropical island; its peaks looming above the dusty haze blanketing the otherwise featureless landscape.

The flat lands that surround it stretch for almost 100km in any direction, leaving the Matthews blissfully isolated.

The isolated mountain range is described as a "sky island"

It has been this way for at least 10 millennia, the dry sea lapping against its shores - sometimes rising, sometimes falling in a tide driven by periods of global warming and cooling that has always kept it cut off from the rest of East Africa's forests.

But that isolation has also helped protect the Matthews from any serious human encroachment.

The Samburu tribes who graze their cattle in the surrounding grasslands have for most of their history left it largely untouched, retreating there only when drought forces them to search for grazing or when the elders harvest plants used for traditional medicines.

The Samburu tribe use the Matthews Range to find plants for medicines

It is what the scientists have dubbed a "sky island": a remarkably untouched patch of tropical highland forest that has been allowed to evolve in its own direction, free of influence from the rest of the region by that dry gulf too vast for most plants and insects to cross.

"It's impressive to see how intact this forest really is," says Quentin Luke, panting and sweating on the flanks of one of the higher peaks.

Over his shoulder, he slings a bag filled with plants he's collected on the trek that have never been seen here before. By the end of two weeks, he would find more than 150.

Indicator species

Mr Luke is one of Kenya's most respected botanists and he's been contracted by the Nature Conservancy, a US-based conservation organisation that arranged the first comprehensive scientific survey of the ecology of the Matthews Range.

In all, there are about a dozen international and Kenyan scientists taking part in the study, and according to the expedition organiser Matt Brown, Mr Luke's findings go a long way towards meeting at least two of their five objectives.

The expedition team has found many new species while trawling through the Matthews

"We want to document a biological inventory of these hills. We also want to work out the current condition of the habitat and assess the level of threat to the ecosystem," he said.

The team also aims to identify some key "indicator species" that the local Namanyak community can use to monitor the health of the forest; they plan to transfer some of their skills to the Namanyak game scouts who police the hills; and finally record what the local elders know of the forest.

Their ultimate aim is to preserve the Matthews, not just for what the scientists expect will be a biological bonanza, but for the "ecological services" the forest provides to the surrounding communities such as clean water and dry-season grazing.

But those communities are growing fast, and the pressure on the Matthews is growing with it. Here and there along the flanks of the hills, dark green scars run vertically up the slopes - clear evidence, says Mr Luke, of fires caused by honey hunters who use smoke to drive bees out of their hives.

The group is taking a pragmatic approach.

Matt Brown says: "It obviously doesn't work just to fence off the area and keep people out and claim that you're helping them by protecting the forest for future generations.

"It's really about focusing on that balance between people and wildlife and finding ways that they can continue to sustainably use the forest."

The Northern Rangelands Trust (NRT) is central to the project. A Kenyan organisation that creates community-based conservancies, the NRT convinced the Samburu tribes surrounding the Matthews to join their scheme.

But there is not much point in forming a conservancy without a scientific understanding of what is going on in forest. Which is why the NRT invited the Nature Conservancy in for its study.

For entomologist Dino Martins, there is plenty to look at.

With a butterfly net tucked under his arm and a back-pack full of specimen jars, Mr Martins has been scouring the valleys and creeks for butterflies and dragonflies.

"They're really good indicators of the health of an ecosystem," said Mr Martins. "They can't survive without good, clean water and lots of food-sources."

And by that measure, the ecosystem appears to be healthy indeed. In the space of two weeks, Mr Martins managed to record 125 butterfly species - roughly 15% of all Kenya's butterflies, and more than twice that of all the UK.

"Those insects also tell us the ecosystem has been very stable, and the high diversity especially of butterflies suggests that the forest has been here not just for a 1,000 or 10,000 years but actually for several million years."

It's a conclusion that Quentin Luke agrees with. Among the plants he's most interested in is the Matthews Cycad - a huge palm-like tree with bottle-green fronds that dot the forest.

The cycad's origins stretch back 280 million years when they dominated the landscape. They are a true living fossil and a hint that perhaps the Matthews Range can trace its origins back that far as well.

"They are a weird species that has male and female plants and an unusual system of pollination," Mr Luke said.

"And apart from one or two other forests in East Africa, we don't find this particular species anywhere else in the world."

And anywhere else, that fact alone might justify saving the Matthews. But here, with growing numbers of cattle looking for grass to graze and humans looking for timber to burn, there need to be other reasons to protect it.

The Nature Conservancy and the Northern Rangelands Trust are convinced they can find it.