Natural resources (economically referred to as land or raw materials) occur naturally within environments that exist relatively undisturbed by mankind, in anatural form. A natural resource is often characterized by amounts of biodiversity existent in various ecosystems. Natural resources are derived from the environment. This is currently restricted to the environment of Earth yet the theoretical possibility remains of extracting them from outside the planet, such as the asteroid belt. Many of them are essential for our survival while others are used for satisfying our wants. Natural resources may be further classified in different ways.