An average of 7.3 million hectares of forest, an area about the size of Sierra Leone or Panama, was destroyed annually in the last five years, the Food and Agriculture Organisation(FAO) said on Monday.
The loss between 1990 and 2000 was 8.9 million hectares a year.
Deforestation was most extensive in South America, where an average of 4.3 million hectares was lost annually over the last five years, followed by Africa with 4 million hectares, the Rome-based agency said while presenting The Global Forest Resources Assessment 2005 (FRA 2005).
North America and Oceania saw smaller forest losses over the same period, while forest areas in Asia and Europe grew, the FAO said.
"While good progress is being made in many places, unfortunately forest resources are still being lost or degraded at an alarmingly high rate," said Hosny El-Lakany, the agency's assistant director-general for forestry.
Forests now cover nearly four billion hectares or 30% of the world's land area. However 10 countries account for two-thirds of all forest area: Australia, Brazil, Canada, China, the Democratic Republic of the Congo, India, Indonesia, Peru, the Russian Federation and the US.
Oceania lost 356,000 hectares a year between 2000-2005, while North and Central America together lost 333,000 hectares a year during the period.
Forests help offset increasing
industrial carbon emissions
Asia moved from a net loss of around 800,000 hectares a year in the 1990s to a net gain of one million hectares per year between 2000 and 2005, primarily as a result of large-scale afforestation reported by China.
Forest areas in Europe continued to expand, although at a slower rate than in the 1990s.
Primary forests with no visible signs of past or present human activities account for 36% of total forest area, but are being lost or modified at a rate of six million hectares a year through deforestation or selective logging.
FRA 2005 also found that new forests and trees are being planted at increasing rates, but plantations still account for less than 5% of forest area, it notes.
However, the UK-based Rainforest Foundation said the FRA 2005 figures are misleading, inaccurate and understate the real extent of deforestation and damage to forests globally.
Major methodological flaws in the UN's report according to the Rainforest Foundation:
- the UN figure for 'net' deforestation is grossly misleading, as it conceals the fact that most deforestation is taking place in the world's tropical rainforests, whereas most of the reforestation and natural re-growth of forests is taking place in the northern hemisphere, and much of this consists of plantations rather than forests;
- the UN figure is based on a definition of forest as being an area with as little as 10% actual tree cover, which would therefore include areas that are actually savannah-like ecosystems and badly damaged forests;
- areas of land that presently have no trees on them at all, but that are 'expected' to regenerate, are also counted as forests;
- the UN includes in its data for existing areas of forest those that are covered by industrial tree plantations, which are actually lacking some of the key functions of true forests.
"It is a global disgrace that, after decades of concern about the world's declining forests, the United Nations still can't even produce an accurate assessment of how much forest is actually left," Simon Counsell of the foundation said.
He said the new Forest Resources Assessment repeats the bad science of previous assessments, which have been widely criticised, and obscures the real extent of deforestation.
Forests have multiple functions, including conservation of biological diversity, soil and water, supplying wood and non-wood products, providing recreation opportunities and serving as carbon sinks.
While most forests are managed for multiple uses, FRA 2005 found that 11% are designated principally for the conservation of biological diversity - and such areas have increased by an estimated 96 million hectares since 1990.
Around 348 million hectares of forests are used to conserve soil and water, control avalanches and desertification, stabilise sand dunes and protect coastal areas.
One-third of the world's forests are mainly used for production of wood, fibre and non-wood products, and more than half have production of these products as one of their management objectives.
Forests are particularly important as carbon sinks: the amount of carbon stored in forest biomass alone is about 283 gigatonnes (Gt) of carbon, though it decreased globally by 1.1 Gt annually between 1990 and 2005.
Carbon stored in forest biomass, deadwood, litter and soil together is roughly 50% more than the amount of carbon in the atmosphere.