WHEN is logging not logging? When it is ''ecological thinning'' in national parks, according to the governments of New South Wales and Victoria.

The two states are conducting trials in national parks on both sides of the Murray River. Under the project, trees will be cut down at 22 sites over about 400 hectares of the Barmah National Park in Victoria and the Murray Valley National Park in NSW. Most of the timber will be burnt as firewood.

Victoria and NSW are conducting trials in national parks on both sides of the Murray River. Credit:Justin McManus

The study will examine whether felling smaller trees gives more established trees a better chance of surviving in the parched environment.

But environment groups say the practice is an excuse to log in national parks, and will lead to them being opened up to more commercial activity.