The results of the farm-scale evaluation of GM crops, announced yesterday by Defra, showed that some varieties could have a serious impact on our already beleaguered butterfly populations.

The trials have confirmed Butterfly Conservation's worst fears about the possible introduction of this new technology, which could greatly exacerbate the problems facing butterflies and other wildlife. Particularly worrying is the major reduction in numbers of much-loved species such as Small Tortoiseshell and Peacock, which were reduced by up to 50% in GM crops compared to conventional ones.

Our surveys have demonstrated that many common butterflies have already declined substantially due to agricultural intensification. The results would be a further nail in the coffin of these beautiful species as well as many other insects, which are an important part of the food chain and together comprise two-thirds of our biodiversity.

Numbers of Peacock butterflies were reduced by up to 50% in GM crops. (Jim Asher / Butterfly Conservation)

Butterfly Conservation is also concerned that the trials only reveal the tip of the ice-berg of potential problems with GM crops, as they only looked at herbicide resistant varieties. A far bigger threat for butterflies, moths and other insects, is posed by GM crops containing insecticidal genes. These could have a direct impact on butterflies and other species breeding in and around crops and would have serious consequences if the genes were passed to wild plants through interbreeding.

The introduction of GM crops could undermine recent government initiatives to encourage more wildlife friendly farming. Our research into agri-environment schemes such as Countryside Stewardship shows that they are beginning to reverse the downward trend of some butterflies. The new Entry Level scheme (currently being piloted) also looks promising in helping conserve widespread butterflies and farm biodiversity.

Dr Martin Warren, Chief Executive of Butterfly Conservation said: "Butterflies have already been devastated by intensive agriculture and the trials of GM crops show that they could be given another major blow. The government has recently made great advances in encouraging wildlife friendly farming, it would be disastrous if this was undermined by introducing a potentially damaging new technology. On the basis of these trials we urge government not to permit the commercial growing of GM crops because of the likely adverse impact on biodiversity."

To learn more about the important work of Butterfly Conservation, why not visit their web site at: http://www.butterfly-conservation.org/

If you would like to be able to identify the butterflies around local farmland and in your back garden, why not purchase a copy of Britain's Butterflies by David Tomlinson and Rob Still. Buying the book supports the work of Butterfly Conservation. Click on the book cover to find out more.