Nearly every person in South California, which is an incredibly high density of population? The entire bottom half of California is practically a desert, literally home to one of the hottest deserts in the entire planet the Mojave which contains the appropriately named Death Valley.
How about the people that live in parts of Arizona, Nevada, Utah, much of southern Texas, and New Mexico? And thats just in the United States. What about people in other continents like Africa and Asia? Large areas of those continents contain entire countries whose borders never leave desert or hills and mountains. Nearly the entire Middle East and top half of Africa is desert. A large part of Australia is desert, its like more than 50% of the continent. 1/5 of the entire land area of Earth is a desert.