'Make Poverty History': the slogan has caught the imagination of the world - and particularly of our generation. Young people all over the globe are seized with the belief that the obscenity of dire poverty - which, for example, causes the needless death of an African child every three minutes - could be ended within our lifetimes. The rock star Bono spoke for us at the Live 8 conference this summer: 'This is our moment. This is our time. This is our chance to stand up for what is right.'

But making poverty history - while absolutely essential - is only half of the task that faces our generation. For though poverty is, indeed, the worst form of pollution, the world faces many other threats to its future - such as the rapid loss of species and ecosystems, the frighteningly widespread erosion of precious topsoil and, above all, the increasing threat of global warming.

Unless the world develops in harmony with the environment, poverty can never be ended. Poor people, even more than the rest of us, depend for their survival on the essential services - like freshwater, fertile soil and clean air - that nature provides. Climate change, though threatening us all, will hit the poorest hardest as droughts and famines increase and sea levels rise. Development has to be sustainable if it is to last.

'Make Sustainable Development the Future' does not have the same ring to it as a slogan as 'Make Poverty History'. Somebody - maybe a TUNZA reader - needs to come up with a snappy way of making it catch the public imagination. But the two goals are inseparable, and both must be reached within our lifetimes if the world is to have a worthwhile future. We pledge ourselves to do all we can to achieve both of them - and look to our leaders to do the same.