1. 2. a large amount of water covering an area that is usually dry
  2. 5. a situation in which there is not enough food for a great number of people
  3. 8. wild animals collectively
  4. 11. the action or process of converting waste into reusable material
  5. 13. the natural home or environment of an animal, plant, or other organism
  6. 15. If you reduce something, you make it smaller in size or amount, or less in degree
  7. 17. the process by which land changes into desert
  8. 18. is all the animals, plants, and other things in the world that are not made by people, and all the events and processes that are not caused by people
  9. 20. a mixture of smoke, gases, and chemicals
  1. 1. this is the study of the relationships between plants, animals, people, and their environment
  2. 3. a long period of time during which no rain falls
  3. 4. (of a species) seriously at risk of extinction.
  4. 6. to become liquefied by warmth or heat
  5. 7. the introduction of harmful materials into the environment
  6. 9. the clearing or thinning of forests by humans
  7. 10. is a process that occurs when gases in Earth's atmosphere trap the Sun's heat
  8. 12. the composite or generally prevailing weather conditions of a region
  9. 14. material or things that are no longer wanted or needed
  10. 16. keep safe or rescue (someone or something) from harm or danger
  11. 19. all the living things in an area and the way they affect each other and the environment