Biosphere 2

Could humans maintain an ecosystem on the Moon or Mars?

In 1991, 8 researchers locked themselves inside this 3.14-acre sealed structure in the Arizona desert for 2 years to test just that. It remains the largest and longest experiment of its kind, ever.
Biosphere 2 was built to be an isolated, self-sufficient ecosystem, modelled after the Earth itself (“Biosphere 1”), to inspire a next generation of explorers. Considered a success by many, it did NOT go according to plan. Let’s look at the design, the mission and the science.


Construction began in 1987, cost $150million and took 4 years. The iconic ‘space frame’ structure, inspired by geodesic domes, achieved an almost perfectly airtight seal so that the levels of oxygen and carbon dioxide could be monitored throughout the experiment.

Inside are 7 distinct biomes: a rainforest (1900 m2), ocean with coral reef (850 m2), mangrove wetlands (450 m2), savannah (1300 m2), desert (1400 m2), intensive agricultural (2500 m2) and a human living space, with scientific labs, workshops and a library.

Each biome included an array of endemic plants, insects and small animals. These were built up gradually in the years and months leading up to enclosure and designed to maintain equilibrium and recycle the carbon dioxide of the crew.

The agricultural biome was designed to produce 100% of the inhabitants’ food needs. They grew staple crops like sweet potatoes and rice, bananas and papaya, coffee and herbs, raised chickens, goats and pigs, and had an aquaponics system recycling nutrients and growing tilapia.
The mangrove wetlands biome transplanted from Southwest Florida, together with anaerobic holding tanks and the aquaculture system, were designed to recycle all human and domestic animal waste.

Though the largest energy demand (light to grow plants) was supplied by the sun, the site included three electric generators to power cooling in the summer, heating in the winter, and dehumidification of the air – in addition to lights, radios, lab equipment & etc.
Despite this, the daily temperature swings caused significant expansion and contraction of the internal atmosphere; to maintain relatively even pressure, two enormous diaphragms, or “lungs” were designed, which would raise and lower while maintaining the air-tight seal.


Biosphere 2 was a media sensation. Coming at the height of the early environmental sustainability movement, the engineering, crew selection process and sealing event were carefully scripted, and were covered extensively by national and international news.

On September 26, 1991, the eight Biospherians passed through the airlock and closed it behind them. They quickly settled into daily routines of farm work, food preparation, ecosystem upkeep, conducting experiments, and maintaining their own physical and psychological health.

Doctor Roy Walford, one of the crew, had prescribed a low-calorie, nutrient-dense diet to the crew. They lost an average of 16% of their body weight in the first year. Before long, the combination of hard labor and calorie-restriction began to drain on morale.

While many of the plants thrived, most small animals and virtually all pollinating insects died, while pests like cockroaches flourished. The lack of wind caused a shortage of woody biomass, while crop diseases spread rapidly on contaminated hand tools.

The mission took a psychological toll on the crew. “Before the first closure mission was half over, the group had split into two factions and, according to [Jane] Poynter, people who had been intimate friends had become implacable enemies, barely on speaking terms.” – Wiki

In November 1992, the crew began eating seed stocks that had not been grown in B2. In January 1993, oxygen levels had fallen to 14.5% (from starting 20.9%), and a decision was made to pump supplemental oxygen into the facility – without informing the media.

In order to deal with the shortage of calories and high CO2, the crew shifted agricultural production toward fast-growing, heavy-sequestering crops. By the last quarter of the mission, 65% of the planted area was only three crops: beets, sweet potatoes, and lab-lab beans.

At the close of Mission 1, the project faced heavy criticism for lack of scientific reproducibility and lack of transparency about interventions. After a brief Mission 2, the holding company lost financial control and B2 passed through several owners the ensuing years.


The headline story of Mission 1 was the drop in oxygen, precipitating the pumping-in of extra oxygen around month 15. This drop in O2 was not as surprising as the LACK of corresponding rise in CO2. Plants, soil and animals always deal proportionally in both.
The answer was two-fold:

  1. The rich, organic soil transplanted into the biomes was respirating much more than expected.
  2. The concrete was absorbing the excess CO2 produced by the soil through carbonation, which was turbocharged by the elevated CO2 levels.

On Mission 2, productivity of the agricultural biome was much higher thanks to improved crop management practices, like hand-pollenating crops, decontaminating hand tools often, introducing predator species for specific pests, and washing off fungus by hand.

Several large-scale experiments have been conducted since Mission 2. In one, ecosystem productivity of the desert and rainforest biomes were monitored closely and compared to generate baseline estimates of ecosystem-level daily O2 and CO2 consumption and production.
In another, scientists studied the effect of severe drought on the rainforest over 4 months. They found that carbon storage decreased ~70%, and the plants released several airborne chemicals – called terpenes – which may be used to track ecological stress.

The ocean biome has been used to study the effects of acidification (increased CO2 in water). Researchers found larger than expected damage to coral reefs, reduction in phytoplankton populations, changes to fish growth and development, and cascading effects on food webs.
In addition, Biosphere 2 has become a hub for scientific research and innovation. For example, there’s a landmark study taking place now on agrivoltaics, or solar panels over gardens. The shade increases plant growth, and the plants cool the solar panels. Huge win!

The study of enclosed ecosystems and off-world habitats continues as well. Just last week, a new closed-environment research facility, SAM, built from the Biosphere 2 test module, completed its first week-long mission at B2, and will complete their second mission this week.

The Biosphere 2 facility itself still exists, and you can go there and walk through the biomes today! There’s also an amazing documentary about it called ‘Spaceship Earth’, and an online simulation tool/game of the ecosystems at