... & Fishwick, 198 4; Repetto, 198 8; Whitehead et al. , 198 8; Food and Agriculture Organization of the United Nations, 198 9; Weber, 198 9; El-Baz, 199 1; Mouat & Hutchinson, 199 5; Hoekstra & ... exploited commercially in Sustainable Natural Resources Management 90 a variety of ways (Pratt & Gwynne, 197 7; Child et al. , 198 7; Hoekstra & Shachak 199 9). It is also true that ... 199 7. Temperate Agroforestry Systems. CAB International, ISBN 0-85 199 -147-5, Wallingford, Oxfordshire, United Kingdom. Hoekstra, T. W. & M. Shachak, technical editors. 199 9. Arid Lands Management: ...