Aided by satellites and supercomputers, and mobilized by the evident environmental damage of the last century, humans have a real chance to begin balancing economic development with sustaining earth’s ecological webs, said Dr. William C. Clark, a biologist at Harvard who heads an international effort to build a scientific foundation for such a shift.

The prospect of managing the planet is attracting more than 100 world leaders and thousands of other participants to the United Nations’ World Summit on Sustainable Development, which starts on Monday in Johannesburg.