Nature Naturaleza 17 Conservación y protección del medio ambiente 8 General 8 Environmental conservation and protection 7 Social Science 6 Conservation 5 Ecology 5 Environmental protection 5 Effect of human beings on 4 Environnement 4 Pollution 4 Protection 4 Ciencias sociales 3 Conservation of natural resources 3 E ́cologie 3 Ecologie 3 Environmental Pollution 3 Human ecology 3 Natural resources 3 Nature conservation 3 Recursos naturales 3 Religious aspects 3 Aspect religieux 2 Ciencias Sociales 2 Ciencias políticas 2 Derecho 2 E ́cologie humaine 2 Education 2 Environmental Monitoring 2