How can people develop the economy under a semi-arid or arid climate?

well there are many ways people can develop their economy under a semi arid or arid climate. for eg. if you think about the middle east, most of the climate in that region is semi arid but the economy is still developing. The other way people can develop their economy is to grow plants which require less water and plants which can only grow in arid areas. They can trade things aswell, so yea basically there are many things. Unless you bring up some specifics in your question there are a lot of possibilities.