Biosphere 2. External view of Biosphere 2, a greenhouse-like building which investigates the interactions of species within ecosystems. The building can be completely sealed off from the outside world but can be entered through airlocks. The building covers over 76,000 square metres and contains over 3000 species (mostly insects and plants) in rainforest, desert, savannah, marsh and ocean habitats. The project, near Tucson in Arizona, USA, was given the designation 2" because Earth itself is "Biosphere 1". In 1997 Biosphere 2 scientists are examining the effect of raised carbon dioxide levels on plant growth."