As written by Fred Pearce on Tuesday” December 6″ 2011

Halting tropical deforestation gained a new level of urgency at the Durban climate change summit on Sunday: the practice contributes roughly twice as much to global warming as recent estimates suggest.

The news comes as Brazil announced that deforestation in the Amazon has reached its lowest level since monitoring began in 1988. But talks at Durban to reduce tropical deforestation even further using carbon offset money from industrialised nations have failed to progress.

The new figures suggest stopping deforestation could cut global carbon emissions by as much as three billion tonnes a year – the equivalent of more than one-third of fossil fuel emissions. They come from the first global assessment of carbon flows between ecosystems and the atmosphere” using millions of ground measurements as well as remote sensing” since 1994.

The statistics were buried in data published earlier this year in Science (DOI: 10.1126/science.1201609) by the Global Carbon Project” a network of experts on the carbon cycle. They were highlighted here in Durban by ecologist Bob Scholes of South Africa's Council for Scientific and Industrial Research.

One reason for the changed estimate is that researchers have finally disentangled emissions from deforestation – at 2.9 billion tonnes a year – from the amount soaked up by regrowth of natural forests on logged and abandoned land” which is put at 1.6 billion tonnes.

In the past” the two have often been lumped together” giving a lower net loss of carbon from tropical forests. But the logged and degraded forests where this regrowth happens are increasingly being targeted by governments and agribusiness to grow oil palm and other cash crops – so natural regrowth will decline.

Another reason for the change comes from factoring the effect of deforestation beyond the tropical rainforests.  “The next major wave of deforestation is happening in Africa. Not in the moist forests but in the adjacent dry forests”” said Scholes. “They have half as much carbon per hectare” but they have twice the area.”

They are also much easier to transform into farmland than are the rainforests” making them a tempting target” he added.

Despite deforestation” however” the world's forests still manage to absorb 2.4 billion tonnes of carbon from the atmosphere each year. But as science here has raised the stakes for protection of the world's forests” UN negotiations aimed at finding money to do that are in crisis.

Talks to create a UN programme known as Reducing Emissions from Deforestation and Forest Degradation (REDD) went backwards. Western nations pulled back on promised funding to protect forest carbon” and Brazil led developing countries in a retaliatory vetoing of rules for the detailed carbon reporting needed to underpin the scheme” said Louis Verchot of the Centre for International Forestry Research.

The rules as presently drafted mean that “countries can now claim that REDD will reduce emissions” which may never happen”” said Roman Czebiniak of Greenpeace. Negotiations continue next year in Qatar. But whatever the rule book eventually adopted by REDD negotiators” large-scale funding for protecting carbon in forests will probably happen only if there is a global deal on carbon emissions. And the talk in the corridors here at the weekend was that 2015 was now the earliest date for such a deal.