JOHANNESBURG — In South Africa ’s oldest township, volunteers in wetsuits jump into the thigh-deep water of the polluted Jukskei River to untangle a net that's designed to trap garbage but damaged by heavy rains. Without the nets, the shacks of low-lying Alexandra on the outskirts of Johannesburg could face disastrous flooding.

What You Need To Know

World leaders with the Group of 20 rich and developing nations will meet this weekend in Johannesburg for the bloc’s first summit in Africa

Host South Africa wants to prioritize issues affecting poor countries, including responses to disasters made worse by climate change

South Africa will urge rich countries and international financial institutions to help more, and it's a plea also being made at global climate talks in Brazil

But cli

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