Gasbo SciFi Australia

Stargate franchise executive producer and showrunner Joe Mallozzi has given some reasons in his blog why the Stargate Atlantis series was cancelled, "By now, I assume you’ve all heard the news. This will be Stargate Atlantis’s fifth and final season. I’m disappointed but not surprised. We came into this year knowing that renewal would be a longshot. With 100 episodes under our belts, rising production costs, and the US dollar’s steep decline, the odds were stacked against us. Still, we’d heard no definite word either way and if SG-1’s surprising 10-year run taught us one thing, it’s that anything is possible. The circumstances that contributed to SG-1’s longevity were very different but, back then, we hadn’t expected it to get a sixth season pick-up either. The rest can be read at Joe's blog