By Rebecca Harrison

JOHANNESBURG, July 6 (Reuters) - For the millions of Africans who live in makeshift shacks and struggle to feed their families, global warming may not seem like a top priority.

But pop stars performing at the Johannesburg leg of the Live Earth concerts said on Friday Africa could end up suffering most from climate change and pleaded with the world to help protect the poorest continent by doing their bit for the environment. Singer and songwriter Angelique Kidjo of Benin said the impact of climate change in Africa first hit home when she visited drought-ravaged northern Kenya and saw dead cattle, shrivelled crops and hungry children.

"That for me is a wake-up call, because if we can't eat then we can't sustain ourselves," she told a news conference ahead of the concert on Saturday. "We don't eat cameras, we don't eat cars, we eat food."

Global warming has already begun to bite in Africa as the effects of extreme weather such as cyclones and droughts prompt poor, rural Africans to move to cities in an often chaotic wave of urbanisation, officials say.

The line-up for the Johannesburg show -- which along with eight other concerts around the world aims to raise awareness about climate change -- includes Kidjo, British soul singer Joss Stone, perennial reggae-pop bank UB40 and a host of local acts.

The concerts are modelled on the Live Aid famine relief gigs of 1985 and Live 8 anti-poverty concerts in 2005, which catapulted Africa and its woes into the global spotlight. The stars insisted global warming was just as relevant for the continent.

"This global problem will compound the already dire conditions on our continent -- the last thing Africa needs is a lack of fresh water when people are already in short supply," said South African pop singer Danny K said.

"From Africa we say to the world - please assist us in turning back the clock and addressing this problem."

News reports said Live Earth was forced to switch venues for the Johannesburg concert due to lack of interest in a country where millions live below the poverty line, living hand to mouth in tin shacks.

But organiser Joanna Little said Live Earth ditched an out-of-town venue in favour of a stadium in the suburbs to limit the environmental impact of thousands of people driving there. She insisted ticket sales were going well.

One of the environmental groups working with Live Earth said Africans were less guilty of wrecking the planet than people in rich countries, but were more vulnerable to the impact of climate change given their direct reliance on trees for basic fire wood and rain water to drink.

"This is a poverty issue," said Amy Spriggs from South Africa's Conservation Alliance Team, which is working with Live Earth. "Climate change will affect the poor the most and they emit the least."

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