Rwanda has a erosion problem. A big erosion problem. It is a densely populated country that lives off agriculture. The hills are gradually being washed away by rivers and rain. Terracing (which would reduce erosion) is a little-known concept here. What you see in the first picture, is a river that is full of mud and sediment being washed downstream and eventually into the Nile. The rocks, are all that will be left when the soil has been washed away.
Some years ago, several provinces started planting trees to reduce soil erosion. Many of these trees were Eukalyptus. Eukalyptus grows fast. Great. But it also requires alot of water. And Rwanda has a water shortage problem. In the second picture you can see the Eukalyptus trees easily: they are the ones with very light green leaves. Eukalyptus also competes with slower-growing local tree species.
The last episode in this story is that now, Eukalyptus trees are apparently no longer planted, and there is a general ban on felling trees.
The last 2 pictures actually have nothing to do with this subject. But it is a beautiful view over the (active) volcano landscape in the North-West of Rwanda.