OmnivoreOrganisms that feed both on autotrophs and other heterotrophs.
Open access resourceA resource to which no control on access is applied; therefore, the resource can be accessed by any individual at any time.
Opportunity costs When economists refer to the “opportunity cost” of a resource, they mean the value of the next-highest-valued alternative use of that resource.
Option valueThe expected value of future information from or about natural resources. Conserving resources today maintains the option of resource value in the future.
OrbitThe path of a body or particle under the influence of a gravitational or other force. For instance, to go around the Earth or other body in an orbit.
Organic1. Relating to an organism. 2. Derived from an organism.
OrganismAny form of life.
Orographic rainfallOccurs when warm, moist air is forced to rise over elevated land. The air is cooled as it rises, leading to condensation, cloud formation, and rainfall.
Over-exploitationExploitation to the point of diminishing returns. Overexploitation of natural resources — through unsustainable hunting, fishing, or extracting raw material — has serious implications for biodiversity. The social costs of overexploitation are high, leaving communities with little alternatives for employment and possibly even food.
OvergrazingOccurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods.
Ownership (as defined in the Paris Declaration)The Paris Declaration of March 2005 on the effectiveness of development cooperation establishes ownership as one of the fundamental principles of cooperation. Ownership as a core principle means that the countries receiving development aid are primarily responsible for the initiatives implemented in the context of development cooperation.