the preservation and careful management of the environment and of natural resources

conservancy - the official conservation of trees and soil and rivers etc.
soil conservation - protection of soil against erosion or deterioration
oil conservation - the conservation of petroleum resources
water conservation - the conservation of water resources

    preservation     saving

(physics) the maintenance of a certain quantities unchanged during chemical reactions or physical transformations

conservation of charge / conservation of electricity - the principle that the total electric charge of a system remains constant despite changes inside the system
conservation of energy / law of conservation of energy / first law of thermodynamics - the fundamental principle of physics that the total energy of an isolated system is constant despite internal changes
conservation of mass / conservation of matter / law of conservation of mass / law of conservation of matter - a fundamental principle of classical physics that matter cannot be created or destroyed in an isolated system
conservation of momentum - the principle that the total linear momentum in a closed system is constant and is not affected by processes occurring inside the system
parity / conservation of parity / space-reflection symmetry / mirror symmetry - (physics) parity is conserved in a universe in which the laws of physics are the same in a right-handed system of coordinates as in a left-handed system

    principle

an occurrence of improvement by virtue of preventing loss or injury or other change

    improvement     betterment     advance