1. Pollution (air, water and soil)
2. Global Warming
3. Overpopulation
4. Natural Resource Depletion
5. Waste Disposal
6. Climate Change
7. Loss of Biodiversity
8. Deforestation
9. Ocean Acidification
10. Ozone Layer Depletion
11. Acid Rain
12. Water Pollution
13. Urban Sprawl
14. Public Health Issues
15. Genetic Engineering