The Zone is the scene of an ambush on a patrol of Troopers by the Freedom Fighters, there to rescue a batch of prisoners. It actually turns out that it was all a plan of Doctor Robotnik to introduce Tonic, supposedly Sonic the Hedgehog's brother, but actually Metamorphia. After a fight, Metamorphia escapes down one of the Zone's waterfalls.
Outside of Sonic the Comic
"Jungle" is also the name of the third Zone from the Sonic the Hedgehog Master System game, but bears little resemblance, other than the fact they are both set in a jungle.