Till date, human intervention and pest attacks were blamed for the forest degradation of Orissa, but Cuttack-based Wildlife Society of Orissa has come out with a new logic. "Orissa's forests have been hit by an ecological disaster. Eupatorium weed, a fast growing pernicious and exotic plant with that flowers which took root in open forest areas a couple of decades ago, is affecting the forests growth of the state," said Mr Biswajit Mohanty, WSO secretary.