Part of the Biosphere 2 complex in the Santa Catalina foothills on June 20, 2025,in Oracle, Ariz., U.S.

Part of the Biosphere 2 complex in the Santa Catalina foothills on June 20, 2025,in Oracle, Ariz., U.S.

Inside Biosphere 2's giant glass pyramid, tropical trees stretch 80 feet above the forest floor. Crazy ants, so named because of their erratic movements, scurry below.

Part of the Biosphere 2 complex in the Santa Catalina foothills on June 20, 2025,in Oracle, Ariz., U.S. Image: Caitlin O'Hara/for NPR ...

And the closed system and technology allows scientists to gather scads of data. "It's really one of the most heavily instrumented rainforests in the world," said de Leeuw. Scientists can even measure ...

It was then leased to Columbia University, which used Biosphere 2 to understand the impacts of carbon dioxide on plants. It is now owned and run by the University of Arizona.