Earth's Resources and Environmental Protection

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Across
  1. 5. National forests provide 150 million visitor days of these.
  2. 6. The amount of Nitrogen average air contains.
  3. 9. The type of forestry where the number of trees harvested does not exceed the number replaced by new growth.
  4. 12. The amount of timber harvesting worldwide used for fuel.
  5. 13. Anything created through natural processes that people use and value.
  6. 14. The ability for one substance to be used for another.
  7. 15. Generated by fission or fusion.
Down
  1. 1. Elevated levels of impurities in the environment caused by human activity.
  2. 2. Energy of moving water being used to generate electricity.
  3. 3. A layer of Earth is bulldozed over garbage each day.
  4. 4. Form so slowly that they cannot be replaced when used.
  5. 7. Oil, natural gas, and coal are known as these.
  6. 8. The amount of dollars spent on the construction of new sewage-treatment plants since mid 1960's.
  7. 10. Chemicals that are harmful even in very low concentrations.
  8. 11. The amount of HECTACRES of Earth's land surface that is covered with forest and woodland.