In 1951, the Advisory Committee on Arid Zone Research was established within UNESCO to organize the first systematic investigations into problems affecting and lands. As time passed, some 200 desert research institutes located in 40 countries collaborated in the production of the 30 large volumes of the UNESCO Arid Zone Research series. The agronomists and soils scientists at work on this project soon began pointing out that large amounts of productive land were being lost to agricultural use through a process they came to call "desertification". Their warnings, however, received comparatively little notice until world attention was caught by a severe drought in the West African Sahel that in the five years from 1968 to 1972 destroyed most of the livestock on the Sahelian pastures and threatened the lives of their human inhabitants.