To ellaborate, the series ended like this:
It was a glorious day, the long celebrated Bunch Beetles returning to eat the creeper weeds that grow out of control. However, the last bunch beetle (and the Sinclair family) find out that the breeding grounds (the swamp) has been decimated, replaced with a factory that manufactures Wax fruit! So, Wesayso, being one step ahead, sends out deadly poison to kill the creeper weeds. This kills all the plants. So then, there is no food (Fran says, "We can't live on Ding dongs and Ho Hos!"), Wesayso does it again, rigging volcanoes to go off, in a poor attempt to make it rain, blocking out the sun, causing the ice age. Huddled together, the Sinclair family ends with Earl saying (naiively) that Dinosaurs have been around for hundred's of years, and they won't just disappear.
Very very very somber way to end a show, and teach us to be careful of our planet, but it did effectively end the series.