Commercial production of GM trees is likely in the near future in Latin America and Asia, the charity says, despite what it alleges is inadequate research into their environmental impacts. It is calling for a global moratorium on commercial releases until more is known about their possible effects, and a public debate on the use of GM tree technology.
Possible risks include the escape of insect-resistant genes into natural forest, which could have a "devastating" effect on the insect populations vital to support forest life, and the creation of "superweed" trees that would deprive all others in the search for water and nutrients. "This is a global accident waiting to happen," said Francis Sullivan, director of programmes at WWF-UK.
Already GM versions of at least 24 trees, including silver birch, Scots pine, Norway spruce, teak, apple and cherry have been released into the environment, according to WWF's research. Unconfirmed reports suggest at least another six species, almond, pear, cocoa, coffee, elm and larch, are undergoing transgenic trials.
While public and media attention has been focused on GM crops and foodstuffs, biotechnology companies "have been sowing the seeds of a quiet GM revolution in the world's forests", the charity says. Leading firms such as Monsanto are setting up joint ventures with forestry companies to produce millions of GM tree seedlings.
The new trees are being designed to grow more quickly, be more tolerant of weedkillers and resistant to pests, and have different reproductive cycles and wood structures to assist industries such as paper-making. But the new genes they bring may have unforeseen effects in the forest that would destabilise the ecosystem and harm wildlife, WWF claims. Tree pollen can travel up to 400 miles, raising a serious threat of genetic pollution, which would be long-lasting as trees live for many years, it says.
In Britain, the charityis calling on the Government to take all necessary action to reduce the genetic pollution risk, including the use of only female trees in trials. It is also calling for environmental impact assessments before any GM trees are released commercially.
Since 1988, WWF says, there have been at least 116 GM tree trials in 17 countries, involving 24 species. In the past three years, the number has doubled, with 44 new trials in 1998 alone.
"Once the GM genie is out of the bottle there is no going back," said Mr Sullivan. "This technology must only be used if we are confident that it will not have a negative impact on the forest, and on the wildlife and people they support."
Jean-Paul Jeanrenaud, director of the forests programme at WWF-International, said: "It is far too early to judge whether biotechnology can make a safe and effective contribution to the forest sector. Governments must declare a moratorium on the commercial release of GM trees until enough research has been conducted and proper safeguards put in place."
There have been five field trials of GM trees in Britain, all of which are now discontinued. Three were completed normally: two trials of eucalyptus conducted by Shell in Kent, one in 1993 and one in 1995, and a trial of paradise apple carried out by the University of Derby in 1995. But two trials of poplars by the biotechnology company Astra Zeneca, at Jealott's Hill, Bracknell, Berkshire, one due to be completed by 2002 and the other by 2004, were destroyed by eco-activists in July this year.