Biosphere 2, Arizona – Climate change and space research

North of Tucson, Arizona and the Santa Catalina mountains about an hour from Saguaro National Park sits an interesting looking complex. If you didn’t know it was there, it is easy to overlook because it sits far back into the foothills. It looks like a giant greenhouse and moon base. But what is it? That is Biosphere 2.

The Santa Catalina mountains with some of the support buildings in the middle ground (mission control, greenhouses for isolating plants and animals before they entered the biosphere, etc).


The concept

Biosphere 2 was built at the end of the 1980s. It is a completely self-contained environment (air-tight, water-tight, etc); theoretically, humans could live in self-sufficiently. It was meant to show that we could build a building like it for colonising the moon and other planets. The idea was that a group of people would live in the biosphere and take care of all of their own needs.

The rainforest biome greenhouse

Biosphere 2 was and still is an engineering marvel. In addition to creating an environment where colonists could live and work, they also had to be able to grow all of their own food. They also needed to be able to have all of the facilities that would keep them alive: water filtration/restoration, power generation, etc. There were also some physics problems. How would they deal with pressure changes when the air temperature in the complex changes?

Another view of the crew’s living quarters, including the library in the tower

You can see the result of taking all of this into account in the image below. The human residence section of the biosphere was small. It included the tower marked as the human habitat, which housed the library and study area, and the living quarters and kitchen below there. To deal with the pressure, two “lungs” became part of the design. These were circular buildings connected to the biosphere that could expand or contract as needed. As a result, the biosphere wasn’t going to have its glass windows blown out by rising air pressure.

Image from:

One thing not pictured here (it would be slightly to the left if the image were larger) was the power generation facility. Natural gas generators supplied all the power needed.

One of the biosphere’s “lungs”


During its time as a biosphere for interplanetary research, it hosted 2 missions. The first was 24 months (September 1991 to September 1993) and the second was 6 months (March to September 1994). During their time, they set new records in agricultural production and closed ecological systems, some of which still stand today.

Part of the desert biome

Mission 1

The Occupants

The first mission had 8 members, known as “biospherians”. They lived in Biosphere 2 for exactly 2 years but they were not the only ones. There were also animals, such as chickens, pigs, goats and fish (tilapia) included for food production. A biosphere also isn’t a biosphere without plants, thousands of them.

Part of the desert biome

The biosphere included biomes for the desert, mangrove, coral reef, savannah and rainforest. A technique known as “species-packing” was used. The idea was to include as many species as possible because a lot of them were going to die as the system before the system became stable. The biomes suffered somewhat because they did not have to put up with natural challenges (e.g. the rainforest and mangrove biomes’ trees were not as strong because they did not have to withstand the wind). However they were viable, could help sustain the biosphere and were analogous to their Earth counterparts.

Desert biome

In addition to some species dying, the biospherians also faced some challenges. Eight people entered the structure for 2 years without much contact with friends, family and the outside world. As a result, they suffered the same psychological effects as other enclosed systems (e.g. scientists in the Antarctic) – bickering, splitting into factions, avoiding contact, etc. However, they did not sabotage each other’s work as other studies have found.

Part of the mangrove biome
Food, Oxygen and carbon dioxide

The biosphere’s agricultural section grew about 85% of their total food. Their diet was very rich in nutrients but it was low in calories, which led to them losing an average of 16% of their body weight as they ate mostly fruits, vegetables and grains. However their health was excellent.

As a result of their diet and nutrient-rich food, fertiliser (from their waste) had to be filtered before it went to crops. Even after filtering, there were problems with bacterial explosions in the soil. There were so many bacteria, all of which used oxygen for their processes and produced carbon dioxide. The result was competition with the biospherians for oxygen and an increase in the amount of carbon dioxide.

Overlooking the ocean/coral reef biome

There was also an additional problem: concrete. The biosphere used concrete foundations and support structures. This type of concrete also trapped oxygen over time. At the worst point, the biospherians felt like they were living at 14,000 feet (approx. 4,260 metres). It was causing problems for them, such as fatigue and sleep apnea.

Part of the savannah biome

In the end, this eventually lead to the most controversial aspect of the project: oxygen was added to the system. Critics cite this as a failure of the project; others say it was due to unknown factors and needed to protect the health of the biospherians.

Another view of the ocean/coral reef biome
The biomes
The rainforest with waterfall

There were also some challenges to the biomes. While the rainforest biome is in its own, separate section, the other biomes are adjoining. As a result, the desert had too much condensation. There was also less light entering the biome than expected and there was also some jumping of plant species between biomes (e.g. morning glories overran the rainforest biome).

There were also some species that took over or died. Most insects and all vertebrates died. However, coackroach and greenhouse ant populations exploded to the point where the biospherians had to become their predators (just killing, not eating).

The canopy and lowest layer are all well-developed but the middle layers are still growing in after being thinned previously

Mission 2

Determined to overcome the challenges that plagued the first mission, mission 2 was much shorter due to other reasons: politics, disputes, mismanagement, dissolution of the founding company and banks taking over the project. Nothing new came of the second mission, although they were able to produce 100% of their food.


Since 1994, Biosphere 2 has changed hands a couple of times. Columbia University acquired it in 1995 and changed it into an environmental research station and ran experiments until 2003. In 2005 the University of Arizona took over research management and then in 2011 they bought the entire complex, which they still own today.

A lot of the research done currently is related to water and nutrient movement within the soil. The agricultural section, which has a built-in slope, usually has experiments where researchers add water at the top and take measurements at the bottom. This includes water loss, nutrient loss, and other measurements.

My visit

I think a visit to Biosphere 2 is worth it. I went on a Sunday and there was barely anyone there. Before you go, you should download the tour app. Guided tours are no longer available due to the pandemic. Instead, this app guides you. There is also a podcast on Spotify you can listen to in order to learn more about Biosphere before arriving. It is about 1 hour long and can be found in the app.

Wisteria on the way out

You start from the visitors centre, where you show your tickets before entering. You then walk towards the biosphere and see it from the outside, following the guide telling you about the aim of the original projects. Then you enter and hear about the experiences of the biospherians, what each part housed, how they lived, and the outcome of their research. The tour also gives you information about the current research in the biosphere (mostly climate change research).

I found the facility absolutely amazing and I recommend that anyone who is nearby should visit. The biomes especially were an amazing experience. I wish I had been able to go closer to the ocean biome and see the fish and other inhabitants better.

For the late 1980s, the crew habitation section (rooms, kitchen, library, etc) was state-of-the-art and it is still in good condition. However, by today’s standards and comfort, they are lacking. Communication technology at that time was very limited and very little was installed in Biosphere 2.

I wish they had gone into more depth during the tour. There were 16 stops in total but a lot of the information given was superficial and was repeated on information plaques at various points. I think it would have been more interesting to get different information.

Getting there and planning your visit

Biosphere 2 is located on route 77. You have to have a car to get there as no public transport reaches the complex.

You can reserve tickets online. The current prices are as follows:

UA stands for University of Arizona

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