How bringing back the wild yam is feeding the hungry in drought-hit Madagascar

This year's Guardian and Observer campaign supports four charities fighting global climate injustice. Here, we look at the work of East African farmers and Kew scientists

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Every December, the arrival of rain signals the beginning of the hungry season" in Madagascar. It will be months before the next rice harvest on the island, which is experiencing the worst drought in 40 years in the south of the country. One million people are struggling to find food in the region due to what the World Food Programme described as the first climate-induced famine".

Global heating was not the main cause yet, scientists concluded in a recent study, blaming poverty and a heavy reliance on annual rains instead. But in the face of increasingly unstable rice production - the main staple - as Madagascar becomes hotter and drier, the yam, an unloved tuber, has become a source of hope in the one of the poorest countries in the world that is not in conflict.