SEE ALSO Overview The overcrowded ark TALKING POINT Sustainable development - are we doing enough?  WEBLINKS Ernst Weizsaecker website The BBC is not responsible for the content of external internet sites

Biggest environmental "vice":
International conferences.

Most recent major consumer purchase:
Household starters for my eldest son’s wedding.

What is most important about sustainable development?
Sustainable development means more wealth, particularly for the poorest, and less consumption of nature’s treasures - it is completely unsustainable to go on as we are now. You could say it means doubling wealth and halving resource use - improving the efficiency of our use of natural resources by a factor of four.

Amory Lovins at the Rocky Mountain Institute has shown that cars can be built which do 150 miles a gallon. I have seen buildings which use one tenth of the energy that similar ones currently use.

A “factor four” world may take 30 to 40 years. It is simply an analogy to the twentyfold increase in labour productivity which has taken place over the last 200 years.

AUDIO "8000km are driven to put a strawberry yoghurt on the table"

Is there a conflict between reducing poverty and protecting the planet?
Yes, in a business as usual world, no in a "factor four" world. A business as usual world means growth, which usually means extracting more resources. At the Wuppertal Institute we have never been anti-growth or anti-wealth - we simply think it is possible to overcome the inherent conflict between poverty eradication and nature protection by technological means.

Consumption: how much is too much?
Arrogance and wasteful consumption by the affluent are destructive. We can live as conveniently as we do, but we have to do it in a much more elegant way. In the winter we import kiwi fruit from New Zealand – which uses five litres of kerosene for every kilo of fruit flown here. This is neither necessary nor rational.

Technology: threat or saviour?
Technology can be extremely helpful, but has also been part of the problem. It has essentially been expansion technology, but in the limited world we live in, expansion cannot go on infinitely.

Biotech and nuclear are typical “technological fix” ideas. We are now discovering that nuclear power is not itself sustainable and the long-term effects of bio-technology are anything but clear. I’m not in an ideological sense against these, but if we can solve the respective problems simply by becoming more efficient, instead of by additional hi-tech methods, I think we go the more elegant way.

What should be done?