FORESTS are increasing in countries across the world after centuries of being destroyed for their wood and to make way for people, according to research.

By measuring the density of trees rather than simply the area on which they grow, scientists have calculated that forests are increasing in almost half of the world’s 50 most wooded nations.

Forests are still diminishing in some countries, such as Brazil and Indonesia. In others, such as China, they are now expanding, although world stocks are still about 2.5 per cent lower now than in 1990.

Stocks of trees increased most rapidly in Spain and Ukraine, and were lost most quickly in Indonesia, Nigeria and the Philippines between 1990 and last year. The area covered by trees increased most quickly in Vietnam, Spain and China, and reduced most quickly in Nigeria and the Philippines, according to the study.

The greatest total gain of the number of trees and the area of forest was made in China and the US. Indonesia and Brazil lost the most, while in India forest coverage is now stable.

The researchers, whose study is published in the journal Proceedings of the National Academy of Sciences, said the findings offered hope that forestry loss worldwide would be reversed within a few years.

“An increasing number of countries and regions are from deforestation, raising hopes for a turning point for the world as a whole,” they said.

“Amid widespread concerns about deforestation, growing stock has in fact expanded over the past 15 years in 22 of the world’s 50 countries with the most forest. An increasing number of countries show gains.”

The study was carried out by six academics and non-governmental forestry experts, including Alexander Mather, of the University of Aberdeen.

The improvements in tree density are thought by the team to be the result of better forest management and advances in agriculture, which have enabled farmers to produce more food per acre, thereby reducing their need to encroach on wooded areas. “This great reversal in land use could stop the styling of a ‘Skinhead Earth’ and begin a great restoration of the landscape by 2050, expanding the global forest by 10 per cent — about 300 million hectares, the area of India,” said Jesse Ausubel, the director of the programme for the human environment at Rockefeller University in New York.

Pekka Kauppi, of the University of Helsinki, said: “Without depopulation or impoverishment, increasing numbers of countries are experiencing transitions in forest area and density. While complacency would be misplaced, our insights provide grounds for optimism about the prospects for returning forests.”

Data from before the middle of the last century are at best sketchy, but where available they appear to support Dr Kauppi’s hypothesis.

French forestry records dating back to the Middle Ages show an arboreal renaissance, apparently unaffected by population increases. By 1800 forest cover in France had fallen to less than one third of the level three centuries before. After industrialisation, however, the trend suddenly reversed. Forest cover has risen steadily since. Dr Kauppi explained: “The main obstacles to forest transition are fast-growing, poor populations who burn wood to cook, sell it for quick cash, and clear forest for crops.

“Harvesting biomass for fuel also forestalls the restoration of land to nature. Through paper recycling and a growing reliance on electronic communication, people help the transition by lessening demand for wood products.”

Wealth is one of the clearest indicators of a country’s success in reversing deforestation. Of the countries surveyed, all of those with a GDP per capita greater than $4,600 (£2,400) — roughly equivalent to that of Chile — had increased their forest cover since 1990.

However, the opposite was not always true. Many less developed countries also experienced increases in forest cover: widespread replanting in China over the last five years even offset Brazil’s annual loss of 3.1 million hectares.

Industrialised nations have shown that reforestation need not come at the expense of the timber industry. In the past 15 years Indonesia has felled a vast area of forest but harvested less timber than the US, which actually gained growing stock.

The findings offer some hope for endangered species, for which forest habitat loss is often the biggest threat, and for the campaign to reduce carbon dioxide emissions, which are believed to be causing global warming.

Because trees and other plants absorb CO2 they are regarded as a valuable tool in removing it from the atmosphere.

Conversely, if they are cut down, enormous quantities of CO2 are released into the atmosphere.

Paul Waggoner, of the Department of Forestry and Horticulture in Connecticut, said: “A rapid forest transition at a global scale would mean that atmospheric CO2 might not rise as fast as many fear.”

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