Worldwide Fund for Nature: see World Wildlife Fund.

Nature Conservancy, nonprofit organization established in 1951 to preserve or aid in the preservation of natural environments. It protects wilderness areas in the United States and Canada and is affiliated with similar groups in Latin America and the Caribbean. It maintains the world's largest private system of nature sanctuaries.

International Union for the Conservation of Nature and Natural Resources (IUCN) or World Conservation Union, international organization founded in 1948 to encourage the preservation of wildlife, natural environments, and living resources. Its members include private individuals, nongovernmental organizations and governments. The IUCN promotes research in the preservation of threatened species, ecology, sustainable development, and environmental law, education, and training.

Principle of physics according to which the energy of interacting bodies or particles in a closed system remains constant, though it may take different forms (e.g., kinetic energy, potential energy, thermal energy, energy in an electric current, or energy stored in an electric field, in a magnetic field, or in chemical bonds [see bonding]). With the advent of relativity physics in 1905, mass was recognized as equivalent to energy. When accounting for a system of high-speed particles whose mass increases as a consequence of their speed, the laws of conservation of energy and conservation of mass become one conservation law. Seealso Hermann von Helmholtz.

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or law of conservation

In physics, the principle that certain quantities within an isolated system do not change over time. When a substance in an isolated system changes phase, the total amount of mass does not change. When energy is changed from one form to another in an isolated system, there is no change in the total amount of energy. When a transfer of momentum occurs in an isolated system, the total amount of momentum is conserved. The same is true for electric charge in a system: charge lost by one particle is gained by another. Conservation laws make it possible to predict the macroscopic behaviour of a system without having to consider the microscopic details of a physical process or chemical reaction.

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Planned management of a natural resource or of a particular ecosystem to prevent exploitation, pollution, destruction, or neglect and to ensure the future usability of the resource. Living resources are renewable, minerals and fossil fuels are nonrenewable. In the West, conservation efforts date to 17th-century efforts to protect European forests in the face of increasing demands for fuel and building materials. National parks, first established in the 19th century, were dedicated to the preservation of uncultivated land not only to provide a safe haven to wildlife but to protect watershed areas and help ensure a clean water supply. National legislation and international treaties and regulations aim to strike a balance between the need for development and the need to conserve the environment for the future.

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Maintenance and preservation of works of art, their protection from future damage, deterioration, or neglect, and the repair or renovation of works that have deteriorated or been damaged. Research in art history has relied heavily on 20th- and 21st-century technical and scientific advances in art restoration. Modern conservation practice adheres to the principle of reversibility, which dictates that treatments should not cause permanent alteration to the object.

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(1933–42) U.S. unemployment program. One of the earliest New Deal programs, it was established to relieve unemployment during the Great Depression by providing national conservation work primarily for young unmarried men. Recruits lived in semimilitary work camps and received $30 a month as well as food and medical care. Projects included planting trees, building flood barriers, fighting forest fires, and maintaining forest roads and trails. It employed a total of 3 million men during its existence.

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