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Subject
- Conservation of natural resources139
- Ecology27
- Renewable energy sources26
- Wildlife conservation26
- Climatic changes18
- Recycling (Waste, etc.)16
- Endangered species14
- Biodiesel fuels9
- Environmental protection9
- Citizen participation5
- Biodiversity conservation4
- Nature conservation4
- Solar energy4
- Environmental aspects3
- Forest management3
- History3
- Natural resources3
- Pollution3
- Sustainable architecture3
- Building materials2