Effect of human beings on Nature 104 Ecology 19 Human ecology 15 Environmental aspects 12 Congresses 9 Human beings 9 Pollution 9 Environmental policy 8 Conservation of natural resources 7 Economic development 5 Effect of environment on 5 History 5 Climatic changes 4 Human geography 4 Natural resources 4 Population 4 Nature conservation 3 Periodicals 3 Philosophy 3 Social conditions 3 Study and teaching 3 Agriculture 2 Christianity 2 Deforestation 2 Economic conditions 2 Environmental protection 2 Food supply 2 Forests and forestry 2 Housing 2