Yes, they do. (Well, of course that something has to happen, but it doesn't have to be human-related interaction.) http://www.viennatimes.at/news/General_News/

Yes, they do. (Well, of course that something has to happen, but it doesn't have to be human-related interaction.) http://www.viennatimes.at/news/General_News/2012-08-26/28744/Underground_explosion_kills_fish_in_the_Danube http://www.viennatimes.at/news/General_News/2012-08-26/28744...