Effect of human beings on Nature 488 Human ecology 215 History 140 Environmental aspects 84 Climatic changes 80 Environmental conditions 77 Social aspects 74 Environmental degradation 48 Environmental protection 46 Ecology 43 Environmental policy 40 Global environmental change 31 Conservation of natural resources 30 Philosophy 30 Economic aspects 29 Social ecology 28 Natural history 27 Human beings 25 Human geography 24 Social change 24 Urbanization 24 Effect of environment on 23 Environmentalism 23 Nature conservation 23 Pollution 23 Global warming 22 Human-animal relationships 22 Rural-urban migration 21 Population policy 20