Food and fuel are the two main sectors which affect the environment, according to a report released on the eve of World Environment Day. How the world is fed and fuelled will in a large part define development in the 21st century as sustainable or as moving towards dead end, it says.

According to the report, sustainability goals can begin through dramatic improvements in household patterns of food and energy use -including heating and cooling systems, gadgets and appliances and the way people travel.

A shift in diet away from animal-based proteins to more vegetable-based foods is required to dramatically reduce pressures on the environment, it added.

The report, Environmental Impacts of Consumption and Production: Priority Products and Materials , has been prepared by the International Panel for Sustainable Resource Management.

The report estimated that a 50 per cent growth in population by 2050 will offset whatever efficiency gains are possible in terms of reducing the impacts on agriculture. "A substantial reduction of impacts would only be possible with a substantial worldwide diet change, away from animal products," it said.

The report challenged some widely held views such as rising affluence is directly proportional to improvement in environment.

"In the case of carbon dioxide, a doubling of wealth leads typically to an increase of environmental pressure by 60 to 80 per cent. In emerging economies, this is even higher," panel co-chair Ernst von Weizsaecker said.

"In the case of food, rising affluence is triggering a shift in diets towards meat and diary products. Livestock now consumes much of the world's crops and, by inference, a great deal of freshwater, fertilizers and pesticides linked with that crop production in the first place," Weizsaecker added.

The report also questioned the current ways of combating climate change. For example, for many of the developed economies, 20-30 per cent of a country's pollution is happening abroad via imports. "Given this fact, perhaps the current way of structuring agreements on emission reduction targets is becoming obsolete," panel co-chair and World Conservation Union president Ashok Khosla said.