The authors argue that a sustainable future depends fundamentally on our ability to manage these trade-offs. They advocate an ecological approach to land/water/environmental problems and argue for viewing precipitation as the gross water resource.
Distinguishing between terrestrial aquatic ecosystems, they show how an ecological approach can be expressed in water-related trade-offs, incorporating criteria for long-term resilience.
Based on per capita needs for an acceptable nutritional diet, the authors analyse the amounts of water needed for global food production by 2050 and identify potential sources. Drawing on small-scale experiences in Africa and Asia, they also cover the vulnerability of the semi-arid tropics, disentangling it into green and blue water scarcity components.