Human activities even before capitalism have created and spread desserts. Basically, humans have been clearing out forests to make crop lands since the dawn of agriculture. But crop lands are susceptible to desertification because tree trucks/canopies block wind, and their roots hold soil preventing erosion from wind/landslides/floods.

Capitalism and the industrial revolution speed up trends that previously took centuries and millenia into ones that occur over years and decades. There will likely come a time, if we don't reverse course, where the amazon will be deforested and become a dessert.