Inside Earth’s miniature twin: How Biosphere 2 redefined view of the blue orb

In the middle of the Arizona desert stands a surreal, glass-enclosed world. A sealed replica of Earth's ecosystems that was once dismissed as an eccentric dream. Today, it is one of the most ambitious and influential ecological laboratories on the planet.

Known as Biosphere 2, this 1.2-hectare "mini Earth" houses a rainforest, ocean, desert, savannah, mangrove, and agricultural land — all under glass, reports BBC.

Originally launched in 1991 as an experiment to test human survival in a self-contained environment, Biosphere 2 has since evolved into a vital scientific platform for understanding Earth's climate and ecosystems.

Though the first experiment involving eight people living inside for two years was marred by technical problems and public criticism, experts now say the lessons drawn from the project are more relevant than ever.

What began as a bold and at times chaotic effort to simulate life beyond Earth has turned into a critical tool for understanding how to preserve life on this one, the report says.

"It [Biosphere 2] wasn't a failure. I think it was actually ahead of its time," says historian of science Lisa Rand of Caltech to BBC.

The early experiment faced severe oxygen depletion, rolling carbon dioxide levels, and ecological imbalances, including the disappearance of pollinators. But these issues, rather than rendering the project a failure, revealed just how finely balanced and fragile the Earth's systems are.

A model Earth under glass

Constructed with funding from billionaire Ed Bass, Biosphere 2 was designed as a closed-loop ecological system — an artificial Earth, or "biospheric package."

It was sealed off from the outside world and built to explore how humans could live in similar environments on the Moon or Mars.

But it soon became clear that replicating Earth was far harder than imagined.

Oxygen dropped to levels equivalent to being at 11,000 feet altitude. Carbon dioxide soared. Crops grew, but the eight "biospherians" grew weak, surviving only on calorie-restricted diets.

Insects meant to pollinate plants died and the microbes in the fertile soil consumed oxygen faster than the young plants could produce it.

As the crisis unfolded inside, critics outside dismissed the experiment as pseudoscience. But scientists today argue that these failures were themselves critical discoveries.

Most controlled natural lab

Now operated by the University of Arizona, Biosphere 2 has become a cornerstone of ecological research.

It allows scientists to simulate the future — studying how coral reefs respond to rising acidity, how forests survive drought, and how ecosystems change under extreme conditions.

"If we warm the ocean," asks marine geoscientist Diane Thompson, "will these solutions work not just now, but decades into the future?"

Its rainforest chamber, for instance, has helped ecologists learn how trees adapt to heat and water stress.

Recent studies showed that some trees survive drought by tapping deep soil moisture, while others release compounds that may help seed rainclouds.

In its artificial ocean, researchers are testing whether exposing coral to stress can make them more resilient to climate change.

Despite its experimental nature, Biosphere 2 has offered one enduring truth: there is no substitute for Earth.

Recreating even basic life support systems under glass required staggering resources, and still fell short, states the BBC report.

"It was very clear to us that the problem was much more complex than you might imagine at first," ecologist David Tilman, who reviewed the project's outcomes, told BBC.

The estimated cost to replicate the Earth's systems, if done at scale, could reach tens of thousands of dollars per person, per month. And that would still not guarantee life.

With billionaires proposing Martian settlements, scientists involved in Biosphere 2 urge caution. "We're all biospherians," Nelson says. "And we only have one biosphere [Biosphere 1/ Earth] that actually works."