Man depends on plants for his food – directly through crops and indirectly through animals – and all our staple foods are derived from only about 30 species of plants. Yet we continue to fell the forests and clear land, exterminating plants that could possibly avert disasters in the future – just as the apparently useless wild wheat discovered in Turkey in 1948 proved to be resistant to certain diseases, including four races of rust, and is now used to breed rust-resistant hydrids. The author lists some of the disasters now occurring, such as siltation of waterways resulting from erosion due to forest destruction – some bulk cargoes are now diverted round Cape Horn due to silt in the Panama Canal. He asks, how severe must ecological disasters become before we recognise our dependence? Dr Jarvis works for IUCN's Threatened Plants Committee (TPC) at the Royal Botanic Gardens, Kew.