well...

if humans left for one thing the domestic pig population would revert back to wild boars in 5-6 weeks, scary if you've been on the other end of a charging boar.also dogs that get out of their cages, kennels,homes,and other containment to probably form packs and hunt or just die waiting for dog chow.now some animals like birds with clipped wings will just die.nuclear reactors would meltdown quickly leaving large gaps in the world void of life for a good wile. (chernoble,russia i know i didn't spell that right.)the nuclear reactor melteddown and the people that lived there for 1-2 days are now suffering from cancer.now far as the ecosystem you probably mean the endangered species,global warming,etc now endangered species are not just those due to over hunting and poaching some of them on the list were just dieing off, or having trouble competeing aginst human introduced plants that don't belong in that ecosystem kudzu in southern america, rabbits in austraila and oscars in a lake nearby my house. (the're killing off all the blue gills.)and the problem with global warming there is a small probably totaly untrue piece of information that i have obtained about methane (a green house gas for those who don't know)being trapped in side ice at the poles so if we all of a sudden immediately THIS EXACT SECOND stop produceing green house gases totaly absoutely not a single car the methane levels will skyrocket and what ever is going to hapen that can't be very good happens BUT,this is probably just bogus