A disastrous and often sudden event. How sudden? Many disaster researchers argue that ecological catastrophe is significantly different from natural disaster, because human-caused environmental degradation slowly lays the groundwork for collapse. See Whyte's Climate Change: An Unprecedentedly Old Catastrophe and the LEAP Manifesto, or consider the invasion of the Emerald Ash Borer (McCallum), and the 2013 Mississauga ice storm (Climate Change Project).