Since raising livestock has been profitable for the people of Botswana, they continue to exploit the land with dramatically increasing numbers of animals. From 1966 to 1991, the livestock population grew from 1.7 million to 5.5 million. Similarly, the human population has increased from 574,000 in 1971 to 1.5 million in 1995, a 161% increase in 24 years. "Over 50% of all households in Botswana own cattle, which is currently the largest single source of rural income." "Rangeland degradation or desertification is regarded as the reduction in land productivity as a result of overstocking and overgrazing, or as a result of veld product gathering for commercial use. Degradation is exacerbated by the effects of drought and climate change."