Answer : 3. "forest improving to deserts"
Explanation :

Answer: C) forest improving to deserts Explanation: Desertification is a type of land degradation in which a relatively dry area of land becomes increasingly arid, typically losing its bodies of water as well as vegetation and wildlife.   Conversion of a grassland or an already arid land into a desert through indiscriminate human actions magnified by droughts.   Hence, forest improving to deserts is refers to desertification.