Natural resources occur naturally and include materials like rocks, minerals, soil, rivers, and plants and animals. They satisfy human needs and can be used to create value. Humans are also a resource because through developing skills, they can develop other resources by adding value to physical materials. Any material from the earth that is used by living things and satisfies human needs is considered a natural resource. Resources can be biotic, like forests and animals, or abiotic, like air and water. Some resources are renewable, like sunlight, while others are non-renewable.