Biosphere 2, privately funded ecological research project in which eight people lived sealed in a 3.15-acre (1.28-hectare) structure for two years (Sept. 26, 1991–Sept. 26, 1993). Located in Oracle, Ariz., about 35 mi (56 km) north of Tucson, and designed to depend on the outside only for electricity and sunlight, Biosphere 2 was intended to test the feasibility of a self-sustaining space colony. It contained over 3,500 plant and animal species and attempted to reproduce five ecosystems (see ecology)—desert, grassland, marsh, ocean, and rain forest. The human inhabitants (four men and four women) were to grow all their food and recycle their wastes, but used some seed stocks as food. The project's validity was questioned by scientists who criticized the plan to use outside electricity, the presence of stores of food and animal feed, and other aspects. A decline in the oxygen level led to the pumping of oxygen into the complex in 1993. A second crew entered Biosphere in Mar., 1994, but various disagreements and allegations of mismanagement made by the chief financial backer, Edward Bass, finally led to the abandonment of attempts at self-sufficient living. From 1995 to 2003 the management of the project was taken over by Columbia Univ., which used the facility for education and scientific research on environmental issues.