Environmental policy Sustainable development 54 Environmental protection 49 Environmental economics 33 Human ecology 29 Economic development 25 Natural resources 24 Environmentalism 23 Environmental law 22 Climatic changes 21 India 20 Environmental management 17 Pollution 15 Environmental aspects 14 Green movement 13 Economic aspects 12 Global environmental change 11 Political aspects 11 Economics 10 Environmental degradation 9 Environmental ethics 9 Environmental sciences 9 International relations 9 Ecology 8 Greenhouse gas mitigation 8 Global warming 7 Natural Resource Economics, (New March 2000) 7 Nature 7 International cooperation 6 Policy and Planning 6