Biosphere 2: the once infamous live-in terrarium promising for climate research

Opening the door to a glass pyramid, a visitor steps from the arid heat of Arizona into a coastal fog desert that stretches toward a savanna. A Lilliputian ocean laps against a rocky shore. A passageway leads to a steamy rain forest where vine-necklaced trees tower 90 feet high. Here in Biosphere 2, the world’s largest controlled environment dedicated to climate research, scientists can tinker with scaled-down ecosystems by switching off sprinklers and cranking up the thermostat to learn about the effects of global warming out in the real world.

The facility has long been shadowed by its ill-fated 1991 maiden mission to establish an analog of a self-sustaining colony on another planet. But after some retooling and successful, high-profile studies —including one that revealed warming oceans are killing corals — the giant terrarium (led by the University of Arizona since 2011) is finally living up to its potential as a site for novel research.

In its half-acre rain forest, scientists are probing how tropical ecosystems might weather late-21st-century heat and drought. Researchers hope to experiment with radical coral reef restoration methods in the enclosure’s million-gallon ocean soon, and in March 2022 the operation will unveil a Mars analog that reprises the original founders’ dream of mimicking a plant-filled habitat on a lifeless alien world. Biosphere 2 is effectively like a time machine that can preview a climate-altered Earth “by changing the concentrations of gases in the atmosphere to those that we think are going to exist in the future to see how the planet could fare,” says the facility’s current director Joaquin Ruiz.

Outer space on Earth
Biosphere 2 launched 30 years ago, on September 26, 1991, when a crew of eight—including a physician, botanist, and marine biologist—began a two-year residency inside this 3.14-acre terrarium. The structure, a prototype for an extraterrestrial habitat, was conceived by a counterculture theater troupe that partnered with businesspeople to form a company called Space Biosphere Ventures. It was intended to be a hermetically sealed ecosystem where several biomes, 3,000 species of plants and animals, and a farm would provide the “biospherians” with all the air, water, and food they needed. “At the time, a lot of scientists said it literally could not be done, that the whole thing was going to turn into green slime,” says Jane Poynter, one of the original biospherians and founder of spaceflight company Space Perspective.

Light bulb moment
Scientists did, in fact, learn something important from what went wrong: the soil was too rich in organic matter, and its thriving bacteria gobbled up too much oxygen. At first, the researchers could not track down the excess carbon dioxide those microbes should have released as a byproduct of that oxygen consumption. Eventually, they found it had chemically bonded with concrete in the building. “It was a light bulb moment,” says John Adams, Biosphere 2’s current deputy director. “They could trace, molecule by molecule, where [carbon] was going and where it was being stored in ways that they couldn’t outside” in the real world.

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