From outside, Cameroon?s Ngambe-Tikar forest looks like a compact, tangled mass of healthy emerald green foliage.

But tracks between the towering tropical hardwood trees open up into car park-sized clearings littered with logs as long as buses.

Forestry officers say the reserve is under attack from unscrupulous commercial loggers who work outside authorised zones and do not respect size limits in their quest for maximum financial returns.

?I lack words to describe what is going on here,? says Richard Greine, head of the local forestry post, 350 km north of Cameroon?s capital Yaounde. ?Both illegal and authorised exploiters have staged a hold-up on the forest.?

From central Africa to the Amazon basin and Indonesia?s islands, the world?s great forests are being lost at an annual rate of at least 13 million hectares (32 million acres) ? an area the size of Greece or Nicaragua.

The timber business is worth billions of dollars annually, and experts say few industries that size are as murky as the black market in wood. Evidence of rampant deforestation around the globe points in one direction: booming demand in China, where economic growth is fuelling a timber feeding frenzy.

In just the past decade, China has grown from importing wood products for domestic use to become the world?s leading exporter of furniture, plywood and flooring. Chinese firms might not be chopping down the trees themselves, but their insatiable appetite is driving up prices, spurring loggers to open more tracks like those torn through Ngambe-Tikar and drawing huge global investment to the companies.

In Mande village on the fringe of the Cameroon jungle, Pierre, a hunter dressed in tattered shorts and T-shirt, does not know that more than half his country?s original forest cover has been cut down in his lifetime. But he knows the local eco-system has been ravaged.

Once upon a time, wild animals would sometimes stroll right into his compound. ?These days you don?t see any. They don?t fall into our traps anymore. You need to go very far, deep in the forest to see or catch one,? he tells Reuters. As usual, it is the poorest who pay.

The lure of timber

In nearby Democratic Republic of Congo, the lure of timber wealth has seen loggers accused of cheating villagers with deals activists say are a ?shameful relic of colonial times?. A two-year investigation by Greenpeace accused companies, mostly from Germany, Portugal, Belgium, Singapore and the United States, of illegally acquiring titles to about 15 million hectares (37 million acres) of Congolese rainforest after a 2002 moratorium.

In return for small gifts such as farm tools, bags of salt and cases of beer, the firms won logging rights worth hundreds of thousands of dollars, the probe found. The biggest target of the loggers is Afromosia, or African teak, which can sell for hundreds of dollars a cubic metre.

Depressingly similar accusations mar the logging industry in Brazil, home to most of the Amazon basin ? the planet?s largest remaining tropical rainforest.

About a fifth of Brazil?s Amazon has already been destroyed, and Chinese demand for commodities such as iron ore, bauxite and especially soy, has been a big factor in pushing the country?s agricultural frontier further north.

Most illegal logging is done by Brazilians, either poor migrants from the dry northeast or cattle ranchers and soy farmers coming in from the south.

The government has long been criticised for deforestation and has a very public policy of stopping illegal clearing and slowing clearing rates overall. But the frontier area is very remote, and police are underfunded, disorganised and often corrupt.

Spinning the globe further west, the problem is perhaps even more acute in Indonesia. Without drastic action, the United Nations says, 98 percent of its remaining forests will be gone by 2022, with dire consequences for local people and wildlife, including endangered rhinos, tigers and orangutans.

In parts of Borneo and Sumatra, for instance, scientists are still finding new species of animals and plants but fear these could be lost to science before being studied fully. Jakarta says illegal tree felling is ravaging 37 of its 41 national parks, and now accounts for about three-quarters of all logging in Indonesia.

Like the United Nations, it blames a well-organised, shadowy network of multinational firms it says are increasingly targeting its parks as one of the few remaining sources of commercial timber supplies.

The government has deployed soldiers at least three times in recent years to confiscate wood and chase out loggers, and is training quick response ranger teams to police protected areas.

But experts say the new units are crippled by lack of funds, vehicles, weapons and equipment, and face a huge threat from loggers who are often guarded by heavily armed militia led by foreign mercenaries.

?At this rate, by 2012 the forests in Sumatra, Borneo and Sulawesi will be gone, only the forests in Papua will be left,? local environmental campaigner Rully Sumada tells Reuters. ?And if cutting of trees continues, no forest will be left by 2022.?

The plight of forests is a focus of a June 3-15 United Nations meeting in The Hague that gathers signatories of a global pact to save threatened species.

Many poor nations want the rich world to extend the Kyoto Protocol, the main UN plan for fighting global warming, to give farmers credits for letting forests stand rather than sell trees to loggers or clear land for crops.

Trees soak up carbon dioxide as they grow and release it when they rot or are burnt.