Question #90127
1 Answer
All of the above.
Explanation:
The most common cause of the boundary changing is habitat loss due to overgrazing. The overgrazing of North Africa changed North Africa from a productive agricultural region to desert. In Northern Nigeria the overgrazing is causing a habitat loss that keeps pushing the boundary of the Sahara desert ever more south.
The next most effective change agent is precipitation. An increase in average rainfall will cause the desert to recede. A decrease in precipitation will cause the desert to grow and encroach on the grasslands.
A change in temperature will have no effect by itself. However an increase in temperature coupled with a decrease in rainfall will have a major effect on the boundary. The grasses will die from lack of water and evaporation. If there is an increase in rainfall coupled with an increase in temperature the desert will recede and potentially turn into a tropical rainforest. A decrease in temperature will help the grassland to increase regardless of the changes in precipitation.
Invasive trees will shade and protect the grasses. The growth of trees will push the desert back. In places trees are artificially planted to protect the grasslands.
