| A | B |
|---|
| desalination | limited freshwater resources |
| petrochemicals | oil and gas products |
| Saudi Arabia dependent for | agricultural products |
| oil-rich countries | lack water resouces |
| Rift Valley | crack in Earth surface |
| savanna | grasslands with scattered trees |
| escarpments | edge of plateaus of Africa coast |
| Lake Chad | threatened with extinction |
| south of Sahara | lies in Tropics |
| Sahel's enviromental challenge | desertfication |
| discourage European explorers | cataracts and steep escarpments |
| to domesticate | use of wild thing for human purposes |
| urbanization | people move from countryside to city |
| South Africa | apartheid |
| Subsistance farming | provides for family |
