Nature Effect of human beings on 104 Ecology 19 Human ecology 19 Environmental aspects 12 Congresses 10 Human beings 9 Pollution 9 Environmental policy 8 Conservation of natural resources 7 Philosophy 6 Religious aspects 6 Christianity 5 Economic development 5 Effect of environment on 5 History 5 Climatic changes 4 Human geography 4 Natural resources 4 Population 4 Science 4 Study and teaching 4 Agriculture 3 Influence on nature 3 Nature conservation 3 Periodicals 3 Social conditions 3 Deforestation 2 Doctrines 2 Economic conditions 2