The last Biosphere 2 project ended 18 years ago. Correction: The failed Biosphere 2 project ended 18 years ago. That's right, our only real attempt to create an artificial, materially closed ecological system ended in complete failure.
For all our accomplishments as a species, we have yet to develop a closed ecosystem that can support human life for the long term. The task of building a functioning biosphere has proven to be exceptionally difficult and it's obvious that there are some major gaps in our understanding of how ecosystems work — gaps that are holding us back.
Biosphere 2 was an important and eye-opening project because it revealed to us not only the difficulty of managing a closed ecosystem and the fragility of human psychology, it also showed us how challenging it will be for us to manage Biosphere 1 — the Earth's biosphere — should things really start to get out of whack.
Consequently, Biosphere 2 should not be considered a failure, but rather a wake-up call to scientists, environmentalists, politicians and the general public. Cynicism should be replaced with the understanding that it was an idea ahead of its time — but an important idea nonetheless.