You might have heard snippets of conversations about food and water shortages, changing climates, and other worrisome topics. If you've brushed them off as unimportant or unrealistic, you might want to reconsider that. If you think that humans are too small to impact their environment or cause disasters, consider this — it's already happened.
During the 1930s, when the Great Depression was already wreaking havoc on the lives of millions, a series of droughts hit the American prairies. The droughts were simply natural events, but the damage done to the land — and subsequently to the residents' lives — could have been easily prevented.
During this period, dust clouds reaching about 200 miles in width would blanket entire towns. The clouds blocked out the sun and covered everything in dust.