Which of the following questions can be answered scientifically? 1) should we just let the river flow where it wants? 2) what can be done to stop erosion? 3) is erosion control worth the financial costs? 4) can planting cover crops reduce erosion?

1. in what ways have non-native species been beneficial? 2. what are some of the hypotheses for the collapse of honeybee colonies? 3. distinguish between regional and functional extinction. 4. why is it difficult to measure background extinction rates? 5. what three factors are most important in causing extinction rates to climb?