Drylands exist as shifting patchworks of productive areas and deserts, and the balance between the two is highly vulnerable to human impact. Desertification is a broadly defined term that encompasses any sort of land degradation in drylands that converts productive areas to deserts (Safriel 2009). Rather than a drought, which is a short-term period of extreme dryness, desertification is a gradual process with nearly irreversible changes on the affected ecosystems. While human-induced causes of desertification are difficult to distinguish from natural causes, both types contribute to some degree (Maiguet and da Silva 1998).
A USGS report (1997) summarizes the process of desertification. Human communities often employ poor irrigation practices that withdraw water faster than it can be replaced. They also introduce herds of livestock, which compact the soil with their hooves, decreasing the capacity to store water. Furthermore, overgrazing can get rid of plant material important for holding together soil. A study by Danfeng et al. (2005) found that the average amount of sheep per family indicated the risk of desertification in a particular region of China. In any arid environment, the harvesting of fuelwood and other plants by humans also contributes to desertification. Without a root system to keep things together, erosion will wear away important soil layers, leaving the land permanently less productive. Natural events such as short-term drought and long-term climate change decrease soil moisture and further aggravate the reduction in productivity (Darkoh 1998).
Although attempts at development drive desertification, the process of desertification hampers economic growth, creating a downward spiral that exacerbates poverty (Cornet 2002). Drylands tend to have high rates of population growth despite low GDP and high infant mortality, and it is impossible to tell whether these factors are the cause or result of desertification (Safriel 2009). Most likely, they are part of a positive feedback loop that continually reinforces desertification in many areas.
Solutions to desertification focus on changes in local management strategies supplemented with action at a global scale. To learn more about sustainable use of drylands see Sustainable Management: Desertification.