The World Summit on Sustainable Development opened today in Johannesburg, South Africa, with more than 40,000 delegates gathering to discuss issues such as water, energy, health, agriculture, and biodiversity. South African President Thabo Mbeki opened the 10-day summit by urging attendees to bridge the gap between “islands of wealth” and “a sea of poverty.” That’s a tall order, since the conference is characterized by a dramatic gap between rich nations and poor, with the former hoping to focus during the meeting on environmental concerns and the latter more interested in discussing ways to improve standards of living. The summit has already been marked by clashes between police and protesters, and friction both within and outside of the official conference halls is expected to continue. No formal treaties will be signed at the conference, but delegates do hope to draft a “credible and meaningful” action plan to be presented to heads of state next week. More than 100 world leaders are expected to attend the summit — not including President Bush, leader of the world’s largest economy and biggest polluter.