How the Biosphere 2 experiment changed our understanding of the Earth

BBC News

6 hours ago

In the early 1990s, a small team tried to survive in a hermetically sealed space containing replicas of Earth's ecosystems. Their trials and discoveries still have repercussions today.
Glittering in the vast expanses of the Arizona desert lies a structure that seems torn straight out of the pages of science fiction.
Inside a massive complex of glass pyramids, domes and towers, spread across three acres (1.2 hectares), stands a tropical rainforest topped by a 25ft (7.6m) waterfall, a savannah and a fog desert. They sit alongside a mangrove-studded wetland and an ocean larger than an Olympic swimming pool which includes its own living coral reef.
It's seemingly a little capsule of Earth, which is why the structure is called Biosphere 2 – named after our own planet, Biosphere 1.
The desolate landscape forms the perfect backdrop for the futuristic experiment that once took place here. In the early 1990s, eight people locked themselves inside, sealed off from the outside world for two years, to explore the challenges of living in a self-contained system – a prerequisite for building colonies in outer space. They fed themselves from the crops they grew, they recycled their own wastewater and they tended to the plants that produced their oxygen.
In terms of sustaining human life, the experiment did not go well. As one commentator put it in the 2020 documentary Spaceship Earth, "everything that could go wrong went wrong". Oxygen levels plummeted, making the inhabitants sick, while carbon dioxide (CO2) levels increased. Countless animals died, including the pollinators the plants needed to reproduce. And although the "biospherians" did survive on their homegrown food, they lost weight to the point where they became a case study for calorie restriction. When supplementary oxygen needed to be brought in, commentators decried the project as a failure, calling it a "flop" and "new-age drivel masquerading as science".
In recent years, however, many experts have come to see the Biosphere 2 experiment in a new light, with valuable lessons about ecology, atmospheric science and importantly, the irreplaceability of our own planet.
Lisa Rand, a historian of science at the California Institute of Technology, argues that these lessons are especially worth revisiting today as billionaires advance private space programmes and float the idea of space colonies while our own planet is increasingly suffering from climate change and other man-made problems. And to environmental scientists, the Biosphere 2 experiment also demonstrates the value of bold experiments to better understand how the natural world works.
In fact, today, the facility is bustling with scientists testing the effects of climate change on its living ecosystems. Far from helping humans escape Earth, Biosphere 2 seems to have become one of our best tools to understand Biosphere 1.
"It wasn't a failure," Rand says. "I think it was actually ahead of its time."
Though the Biosphere 2 experiment is often described as a test run of a future space colony on the Moon or Mars, the project in fact had deep environmental roots, says Mark Nelson, one of the eight biospherians and a founding director of the non-profit Institute of Ecotechnics.
The idea for Biosphere 2 came from a group of people – including Nelson – living in an ecovillage on a New Mexico ranch who spent their time organic farming and doing performance art and carpentry. The group's founder, John Allen, dreamed of building a self-contained system to better understand Earth's complexities and find ways of using technology to more peacefully exist with the natural world, Nelson says.
The project was bankrolled by billionaire Ed Bass, who put about $150m towards Biosphere 2 (equivalent to $440m today, or £330m). Under Allen's leadership, building began in 1984. It was – and remains – the largest building of its kind to be nearly fully sealed off from the atmosphere, Nelson says.
Though none of its ecosystems was a perfect model of its real-world counterpart, each one was designed with similar kinds of vegetation, along with a selection of insects, fish, and birds, says John Adams, the current deputy director of Biosphere 2. A patch of farmland was included to grow crops. An underground system of piping and pumps controlled everything from temperature to humidity. Other systems recycled wastewater for crop irrigation and harvested drinking water from condensation in the air conditioning units. Biosphere 2 was intended to operate for a century, but when the biospherians entered the facility in September of 1991, "it was such a vast experiment that none of the eight of us had any certainty we could last one way or another for two years in there," Nelson recalls.
Nelson and Adams see the events that unfolded inside not as failures, but as the outcomes of an experiment, as would occur in any other scientific study. "In science, there's no such thing as a failed experiment," Adams says.
The most pressing issue for the biospherians was the decline in oxygen levels, which dropped from normal levels – roughly 21% of the atmosphere – to about 14% after 16 months. That's equivalent to oxygen levels at about 3,350m (11,000ft) above sea level. Until supplementary oxygen was brought in, the biospherians grew tired and weak from altitude sickness, making farming and other work arduous, Nelson recalls. These and other problems took scientists a while to figure out, says David Tilman of the University of Minnesota Twin Cities, who was part of a committee of ecologists that reviewed the experiment after it concluded. "It was very clear to us that the problem was much more complex than you might imagine at first," he says.
Experts worked out that the cause was the extremely rich, young soils that had been introduced to fuel rapid growth of crops and other vegetation. This created a lot of food for bacteria and fungi, which, like us, consume oxygen and emit CO2. The trees and shrubs in the new ecosystems – which take up CO2 and release oxygen – were too young and too outnumbered by microbes to counterbalance this effect. "I think that was a really important lesson to learn: that that [soil] microbiome, even though we can't see it, is extremely influential," Adams says.
Fortunately, the rise in CO2 – a greenhouse gas that heats up the atmosphere – was buffered by the fact that much of it got soaked up by the facility's concrete surfaces. The biospherians also did their best to stem the rise as well as boost oxygen levels. They cut dead grasses in the savannah and trimmed fast-growing rainforest species to stimulate new growth – storing the cut vegetation in dry conditions to slow down its decomposition, a process that releases CO2, Nelson says. They also planted fast-growing plants like sugarcane and created a bed of algae in the basement – but oxygen levels still waned.
While some "extinctions" within the ecosystems were expected as they settled into an equilibrium, the vanishing of pollinating insects was an unexpected problem for plant life. Nelson attributes this to an explosion in the population of longhorn crazy ants that prey on pollinators, while ecologist Brian McGill of the University of Maine suggests they may have died off because the glass enclosing Biosphere 2 blocked ultraviolet light, which the insects needed to find flowers. "Bees in particular see in the UV spectrum," he says.
The issue wasn't urgent as most of the ecosystems' flowering plants were long-lived, but some biospherians pollinated a few species by hand, brushing pollen into flowers so seeds could form, Nelson says. The long-term plan was to control the ant populations and introduce new pollinators from the outside world.
Scientists made other interesting observations. Some trees, they realised, became weak and more prone to breaking, likely because of the lack of wind, which triggers trees to produce "stress wood" that strengthens them, McGill says. Marine biologist and geoscientist Diane Thompson, who now directs marine research at the facility, says that scientists also learned a lot about the kinds of light that corals need to thrive in captivity.
But the most important lesson from the biospherians' experience, experts agree, is the realisation of how difficult it would be to live anywhere else than on Earth. Humans can't exist in isolation; they come in "biospheric packages", as Nelson puts it, and recreating these complex systems is no easy task. While Tilman reckons that some of the problems may have been solvable, it was clear during his visit to the facility that it was a long way away from being able to sustain human life. "It really impacted me when I saw that, because… my initial guess was that you would probably make it work," he says. Now, "I firmly believe that this really is our only planet ever".
By extension, the experiment therefore deeply underscored the need to protect our planet in an intact state. Consider the immense technological costs – not to mention the hard physical work by the biospherians – to keep the atmosphere and life support systems intact. Tilman estimates that, if future space colonies are anything like Biosphere 2, they'd cost $82,500 (£61,000) per person a month to live in, and even that would be no guarantee of sustaining human life. "It's incredibly expensive to try to replace the services that the Earth's ecosystems provide for free to humanity," Tilman says.
To Nelson, realising that his own survival was entirely dependent on the health of the ecosystems around him was transformative, as he wrote in his book Life Under Glass. Being a biospherian meant living as sustainably as possible – using the gentlest of farming practices, avoiding pollution anywhere inside Biosphere 2, and respecting every oxygen-producing plant. "Just being in a small system where you see that reality – that you're part of that system, and that system is your life support – changes the way you think at a very deep level," Nelson says.
When the experiment concluded in 1993, these messages were largely overshadowed by the negative media coverage around the project, Rand says. In her view, this was because of how it appeared to clash with widely-held views at the time.
Many experts had rigid views of how science should be done and didn't consider it a legitimate experiment. It had been funded by a wealthy individual rather than a government and conducted by self-taught science generalists rather than scientists with PhDs from academic institutions. Rand believes this would be far less controversial today.
Meanwhile, because the public saw the project as a "glass ark" or a model of a future space colony, the biospherians were seen to be "cheating" when one of them was taken to hospital due to a finger severed in a rice-hulling machine, or when they installed the oxygen pump, Rand says. "I think it's fair to speculate that the events that were perceived by journalists [and the public] as failures might have been seen as normal, valid experimental results if the project took place now," she says.
The negative media perception – as well as disagreement around how to manage Biosphere 2 after the original experiment ended – created challenges for those overseeing the project, Adams says. In 1996, Ed Bass handed over management of the facility to Columbia University and eventually gifted it to the University of Arizona. Scientists at those institutions saw the unique opportunity that Biosphere 2 provided, says Adams.
Ecologists who study how living systems work usually do so by analysing what happens in the aftermath of vicissitudes like heatwaves or drought, McGill says. But in order to predict how climate change, for instance, will alter Earth's ecosystems in the future, they need to recreate future conditions and see how living beings respond. Like a time machine, Biosphere 2 allows them to do just that. From its very first experiment, "Biosphere 2 was just a really cool and vivid stake in the ground about the need for ecology to be predictive," McGill says.
Today, Biosphere 2's rainforest is the stage for experiments testing how its real-world counterparts might fare under global warming. One study dialled up the temperature and found the forests to be surprisingly resilient to heat; rather, it's the drought associated with warming that hurt them. More recently, the ecologist Christiane Werner from the University of Freiburg, Germany, and her colleagues exposed the forest to a 70-day drought. They learned how some trees survive by tapping into deep, moist soil layers and that drought-stressed trees release more compounds called monoterpenes, which form airborne particles that could potentially serve as seeds for much-needed rain clouds. Thanks to Biosphere 2, "you can send a whole grown forest into a drought and then monitor all these processes along the way", she says.
The coral reef, meanwhile, was the site of one of the first experiments to show that as the oceans become more acidic – which happens when they absorb CO2 – this makes it harder for corals to grow and thrive. Now, scientists are simulating severe heatwaves in Biosphere 2's mini-ocean, and plan to test whether probiotics or exposing corals to heat before transplanting them onto the reef can make them more resilient. "If we warm the ocean," Thompson asks, "will those solutions work – not just now, but decades into the future?"
Adams says he hopes that Biosphere 2 can do for ecologists what the Large Hadron Collider is doing to improve physicists' understanding of particle physics, and what the James Webb Telescope is doing for astronomers striving for deeper glimpses into the universe.
But ecology's mega-experiment doesn't only help us better understand the intricacies of the living world and how it's changing amid planetary upheaval. Its story, Nelson says, should also inspire and help every one of us to take better care of our only life-sustaining planet, Biosphere 1. Ultimately, we are all biospherians.
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