(BBC News) -- The Prince of Wales has warned of the "catastrophic" consequences of inaction on issues such as climate change, at a UN sustainability conference in Brazil. Prince Charles said he had "watched in despair" at the slow pace of progress on the "critical issues of the day," in a pre-recorded video address in Rio. He urged world leaders to adopt a more integrated approach to issues such as climate change and food security. Waiting for the worst to happen would be "too late to act at all", he said.