We can attain sustainability when we meet our own present needs without compromising the ability of our future generations to meet their needs. To survive, we need natural resources but also social and economic resources. The concept of sustainability assumes that these resources are finite, and so should be used conservatively and carefully.
Though it is most difficult to replace the natural resources (like oxygen, water, food, oil), sustainability is not just about environmentalism. Instead, it is the balance between the environment, equity, and economy. A sustainable society is one that is socially responsible, and focuses on environmental protection and dynamic equilibrium in both human and natural systems.