JOHANNESBURG—South Africa must manage its transition away from coal-fired power generation systematically and not rush a switch to renewable energy sources, Mining and Energy Minister Gwede Mantashe said on Thursday. “I am not saying coal for ever, … I am saying let’s manage our transition step by step rather than being emotional,” Mantashe told a mining conference, when asked how China’s pledge to not build new coal power stations abroad would affect South Africa. “We are not a developed economy, we don’t have all alternative sources,” he added. South Africa aims to cut coal’s share of the energy mix to less than 60 percent by 2030 from around 75 percent now while increasing the share of wind and solar power to around 25 percent. The minister pointed to China’s own energy needs as an example of what could go wrong if a transition is attempted too quickly. “Xi Jinping is …