Economic, technological, and demographic changes after World War II created new pressures on species, habitats, and human environments. Concerns about human impacts on the environment mounted. Rachel Carson, Charles Elton, Barry Commoner, and others articulated concerns about pesticides and other harmful substances in air and water, introduced species, escalating extinction rates, and the modification and fragmentation of habitats. Ecologists, economists, and philosophers like Paul Ehrlich, Garrett Hardin, John Kenneth Galbraith, Lynne White, Norman Myers, and Arne Naess attributed these problems to varied causes, including population growth, tragedies of the commons, excessive resource consumption and disparities in consumption, militarism, the misuse of science and technology, externalities, and anthropocentrism. In response to these developments and to increasing awareness of the limitations of utilitarian conservation, a preservationist approach to conservation that seeks to protect species and regardless of their economic value became prominent.