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action agricultural air pollution Background Paper biodiversity biodiversity conservation biological diversity biological resources carbon dioxide causes CFCs chemicals chlorine concentrations Chlorofluorocarbons consumption contribute cropland crops damage decade decline deforestation degradation desertification developing countries earth's atmosphere ecological ecosystems efforts emissions energy environmental estimated extinction fish fossil fuel fuelwood future genetic diversity global climate change Global Environment global warming greenhouse effect greenhouse gas concentrations greenhouse gases growing habitat halons human activities human population impacts important increase industrialized countries Interparliamentary Conference land levels loss marine methane metric tons million hectares Montreal Protocol natural resource needs nitrous oxide occur oceans organisms ozone depletion ozone layer percent phase-out plants and animals policies population growth potential problems production programs protected areas reduce regional response result scientists species stratospheric ozone sustainable development threats tropical forests unsustainable urban waste wetlands world population