m78.    How do droughts and floods impact populations?

At least 80 arid and semi-arid countries with 40% of the world's population experience years-long droughts. Reduced precipitation and higher than normal temperatures cause the droughts; population growth and poor land make it worse. Deforestation, overgrazing, plowing prairies, and irrigating fields intensify the effects of the droughts. However, during the 1970s floods killed more than 4,700 people per year. Cultivation of land, deforestation, overgrazing urbanization, and mining make the effects worse. Thailand loggers were banned from forests after the 1988 floods buried entire villages in mud and logs from clear-cut hillsides.

Contaminated drinking water comes from sediments from erosion; excess nutrients from soil erosion causing algae blooms; from pathogens from sewage and livestock wastes; and from hazardous wastes from industry.

e01.    What is biodiversity?

e02.   Where is life found in the water?

e09.    What is succession?

e15.    What was early life like?

e18.    Does water recover from pollution?

e22.    What do we eat?

e23.    How is soil important to plants?  

g04.    What causes climates to change?

g07.    How did plate tectonics affect the diversity of ecosystems?

g10.   What are earthquakes?

g11.    What is volcanism?

g12.    How are mountains built?

g13.    What makes up earth's climate?

g20.    What is the theory of plate tectonics?

g24.    How does soil move? 

g25.    What are the properties of water? 

g26.    Where is drinkable water found?