A project to map every place in the world's second-largest tropical forest where trees have been cut down will be announced today.

A purpose-built camera will be sent into space to record every clearing and logger's track in the Congo Basin in Africa to determine how much of the forest is left.

The camera will be fixed to a satellite and should be operational by the end of 2010 as part of an initiative to save the Central African tropical forest from being chopped down.

At twice the size of France, the Congo Basin forest is exceeded in extent only by the Amazon but it is estimated that loggers, many of them illegal, destroy an area the size of 25,000 football pitches every week.

Forests absorb huge quantities of carbon but it is released when they are cut down and their preservation is regarded as one of the biggest challenges by those trying to slow the greenhouse gas emissions that drive climate change.

Douglas Alexander, the International Development Secretary, will announce extra funding to save the forest today when he explains the camera project. It will record the forest in more detail than before.

Ministers agreed to push for the camera, which will be built by the Rutherford Appleton Laboratory in Oxfordshire, because of the need to get more than the current limited information about the state of the forest, which is in one of the most inaccessible and volatile regions of the world. To decide where efforts should be concentrated, politicians and scientists need to know where the impact of logging is worst.

Mr Alexander is expected to say in his speech: “Avoiding deforestation is crucial in the fight against climate change. As the world's second-largest rainforest, the Congo Basin must be at the heart of our response.

“The basin houses a quarter of the world's rainforest, but already an area the size of 25,000 football pitches is cleared of trees every week.

“Protecting the rainforest will help us all in the fight against climate change and also the 50 million people who rely on the Congo forests for their livelihoods.”

Last year, shortly before his elevation from Chancellor to Prime Minister, Gordon Brown announced a £50million fund to be used to protect the Congo Basin. It is expected that it will be reported that the fund has been increased by millions of pounds, perhaps doubling in size, after contributions from other bodies.

Ministers believe that by protecting the forest from destruction they will be acting in the interests of the indigenous peoples, many of whom rely on it for their livelihoods.

Once the detailed satellite pictures have been taken, they will be beamed to a new receiving station that is expected to be built in Central Africa, the first in the region.

Printouts of the pictures can then be taken to villagers to show them what is happening to their environment. With computers virtually non-existent in many of the jungle communities, the extent of deforestation revealed is expected to be a surprise to many inhabitants.

At 770,000 square miles (two million sq km), the Congo Basin contains an estimated 26 per cent of the world's remaining rainforest and has been described as the world's “second lung”. A study by the United Nations revealed that more than two thirds of the forest could be lost by 2040 unless the rate of tree removal is greatly reduced.

The forest featured this week in an atlas of Africa published by the United Nations Environmental Programme to show, using satellite images, how the continent has changed in the past 36 years.

The “before and after” satellite images of the Congo Basin revealed that huge chunks of the virgin forest had been lost.

The United Nations estimates that 3,600 square miles are still being lost annually. Logging, the spread of agriculture and human population rises are the biggest threats.

It is estimated that the forest is home to 50 million people, 10,000 species of plants, 1,000 species of birds and 400 species of mammals.

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