Earth Day

5. trash, such as paper, cans, and bottles, that is left lying in a public place
6. protect something, especially an environmentally or culturally important place or thing from harm or destruction
8. decayed organic material used as a plant fertilizer
10. the layer of gases that surround the planet
12. the production and discharge of something, especially gas or radiation
13. a species, family, or other, group of animals or plants having no living members, no longer in existence
16. a contract, agreement capable of being renewed
18. use again
19. relating to or determined by the sun

1. the natural home or environment of an animal, plant, or other organisms
2. the surroundings or conditions in which a person, animal, or plant lives or operates
3. contaminate (water, air, or a place) with harmful or poisonous substances sustainable able to be maintained at a certain rate or level
4. maintain something in its original or existing state
7. a biological community of interacting organisms and their physical environment
9. reuse discarded objects in such way as to create a product of a higher quality or values than the original
11. a place to dispose of refuse and other waste material by burying it and covering it over with soil, especially as a method of filling in or extending usable land
14. a colorless unstable toxic gas
15. relating to or derived from living matter
17. the branch of biology that deals with the relations of organisms to one another and to their physical surroundings