extinction megafauna possible events must occurred provide ecosystem plant species thus triggering lasting ecological state shift ref name academic journals ''boreas international journal quaternary research'' ''geografiska annaler'' title swedish ''journal quaternary science'' ''quaternary geochronology'' ''quaternary international'' ''quaternary research'' ''quaternary science reviews'' ''the quaternary times'' see also international union quaternary research palynology year problem geochronology references external links http qraorguk uk quaternary research association https webarchiveorg web http wwwtcdie geography iqua indexhtm irish quaternary association http wwwquaternarygroupcamacuk cambridge quaternary formally godwin institute quaternary
Social science Geography Physical geography Quaternary science