ACROSS
2. a substance that is released into the environment by human activities and interferes with the function of organisms that evolved in the absence of the substance or with lower levels.
3. species that remains restricted to the area where it evolved.
6. conversion of dry grassland to desert.
10. actively altering an area in an effort to restore an ecosystem that has been damaged or destroyed.
11. of a region, the genetic variation within species, variety of species, and variety of ecosystems.

DOWN
1. species that faces extinction in all or a part of its range.
4. field of applied biology that surveys biodiversity and seeks ways to maintain and use it nondestructively.
5. low pH rain that forms when sulfur dioxide and nitrogen oxides mix with water vapor in the atmosphere.
7. threatened region that is habitat for species not found elsewhere and is considered a high priority for conservation efforts.
8. high atmospheric layer with a high concentration of ozone (O3) that prevents much ultraviolet radiation from reaching Earth’s surface.
9. species likely to become endangered in the near future.