In the final analysis, when viewed in the national perspective, the effects on agriculture are the most troublesome aspect of desertification in US. For it comes at a time when we are losing over a million acres of rain-watered crop and grass land per year to higher uses--- shopping centers, industrial parks, housing development, and water dump--- regardless of the economic need of the US to export agricultural products or of the world’s need for US food and fiber. The higher uses of rain-watered crop and grass land are criticized by the author because _____