ITC Journal 1997-3/4302

tion requires temporal data collection to monitor whether the environment is degrading or otherwise changing. The third question is: How can remote sensing and GIS contribute to the policy tools of generating policy, pro-viding information and ensuring participation by all stakeholders? SUSTAINABLE DEVELOPMENT Sustainable development has been defined in many That changes continually occur at many spatial (eg, global, regional, local) and temporal (eg, ice ages, defor-estation, fire) scales is obvious to any observer. For example, change may occur in the species occupying a site, amount of nitrate in ground water or crop yield from a field. Change may also occur in human welfare indices such as health or education. To assess whether such changes are sustainable is a non-trivial problem. Possibly the greatest advantage of the debate about sus-tainable development is that the long-term capacity of the Earth to sustain human life through a healthy and properly functioning global ecosystem is becoming a normal political goal