Final answer:
Desertification is frequently caused by slash-and-burn agriculture, which depletes soil nutrients and leads to land degradation and the conversion of fertile land into desert.
Step-by-step explanation:
Desertification is often the result of slash-and-burn agriculture, an agricultural technique where forests are cleared by cutting down the trees and then burning the remaining plant material. This practice, often used in tropical forests, leads to nutrient loss in the soil, which in turn causes desertification. When the nutrient-rich topsoil is lost, the land becomes unsuitable for plant growth, further exacerbating the trend towards desertification. This leads to what was once forested land turning into desert, highlighting the serious impact on Earth's ecosystems, with estimates suggesting that all tropical forests could disappear by 2090 if current rates of deforestation continue.