an unprecedented study may force certain countries to do some soul searching. Contrary to what a few policy makers advocate, the study reveals that high levels of atmospheric carbon dioxide (co₂) can retard plant growth. The three-year study, conducted at the Stanford University, California, usa, is raising questions about a long-held assumption: by emitting more co₂, our cars and factories create new sources of plant nutrition.

The study is part of the Jasper Ridge Global Change Project - an experiment designed to demonstrate how a typical California grassland ecosystem will respond to future global environmental changes. Scientists assume that in 100 years from now, atmospheric co₂ levels would double up, temperature would rise by 1.1