(BS2) Ecological test project, a “planet in a bottle”, in Arizona, US. Under a sealed glass dome, several different habitats are recreated, with representatives of nearly 4,000 species, including man, to see how well air, water, and waste can be recycled in an enclosed environment and whether a stable ecosystem can be created.
Experiments with biospheres that contain relatively simple life forms have been carried out for decades, and a 21-day trial period 1989 that included humans preceded the construction of BS2. However, BS2 is not in fact the second in a series: the Earth is considered to be BioSphere 1.
The sealed area covers a total of 3.5 acres and contains tropical rainforest, salt marsh, desert, coral reef, and savanna habitats, as well as a section for intensive agriculture. The major problem has been in maintaining satisfactory oxygen levels, which in late 1993 became so erratic that additional oxygen had to be pumped in. The rainforest was thriving 1994 but the plankton levels in the ocean were too low to sustain the corals; the climate was too moist for the desert plants and the desert was being overrun by grasses and shrubs.
The people within are entirely self-sufficient, except for electricity, which is supplied by a 3.7 megawatt power station on the outside (solar panels were considered too expensive). A new team of six people entered BS2 in March 1994, to stay for 10 months. They replaced the original team of eight in residence 1991–1993.
The cost of setting up and maintaining the project has been estimated at $100 million, some of which will be covered by paying visitors, who can view the inhabitants through the geodesic glass dome.