One in five of the world's 3.8 lakh plant species is threatened with extinction and human activity is doing most of the damage. Scientists from Britain's Botanic Gardens at Kew, London's Natural History Museum and the International Union for the Conservation of Nature found that more than 22 per cent of species were endangered, critically endangered or vulnerable. The findings were released ahead of a United Nations Summit scheduled for mid-October in Nagoya, Japan where governments are due to set new targets for trying to conserve more of the world's plants and animals. As this was the first time a global analysis of the threat to the world's plants had been undertaken, the scientists said it would serve as a baseline to measure conservation efforts.