Human and livestock densities are generally high with the fertile plains heavily cultivated with
cotton, wheat, and mango orchards (Roberts 1991). The Thal Desert, bounded by the Indus,
Chenab and Jhelum Rivers, is more sparsely populated and is dominated by tropical thorn forest
and sand dunes (Roberts 1991). Mean winter temperatures can fall as low as 5.6uC in January
and rise to 42.3uC in June (Pakistan Meteorological Department, Lahore, unpubl.). Annual
rainfall is mainly concentrated during the monsoon months (July–September).