The need for development is as great as ever, but future development cannot simply follow the model of the past. This is true for the world as a whole, and for every community in this country.

The global picture is striking. A quarter of the world's people have to survive on incomes of less than US$1 a day. A fifth have no access to health care. Huge though the challenge may seem, it is becoming larger: the world's population will increase by half, another three billion people, by 2050.

This country does not have problems on such a scale. But we cannot stand aside from these issues. Global prosperity must increase, and be more widely shared. Meanwhile, in the UK, economic growth remains vital for a better quality of life: for education, healthcare and housing, to tackle poverty and social exclusion, and to improve standards of living through better goods and services.

In the past, economic activity tended to mean more pollution and wasteful use of resources. We have had to spend to clean up the mess. A damaged environment impairs quality of life and, at worst, may threaten long term economic growth - for example, as a result of climate change. And too many people have been left behind, excluded from the benefits of development but often suffering from the side-effects.

We have to find a new way forward. This is the challenge of sustainable development. For the future, we need ways to achieve economic, social and environmental objectives at the same time, and consider the longer term implications of decisions.