Which is not a result of population growth in sub-saharan africa?

Since there are no options, let's think about possible options: 

A population growth means that there are more people, and it's mostly caused by more births. 

It does not result in longer life spans - although the other way it's true, longer life spans do contribute to population growth (since there are more people)

A population growth will not likely contribute to a surplus of food- instead, food will likely be scarce (since there are more people to feed)

Answer barren with few trees, in the northern hemisphere;