Environmental Affairs Minister Marthinus van Schalkwyk has warned that in less than 50 years time, the northern regions of South Africa could once again be malaria-danger zones as a result of climate change.

He also told a media briefing at Kirstenbosch Botanical Gardens in Cape Town that as early as 2020 the number of South Africans 'at high risk' of contracting the killer disease could quadruple.

Mr Van Schalkwyk and Professor Brian Huntley of the SA National Biodiversity Institute detailed a number of worrying findings in recent research about the expected impacts of climate change in South Africa.

The minister warned that over the next 50 years, climate change "may well define the worst social, economic and environmental challenges ever faced" by South Africa and the world as a whole.

"Climate change could lead to provinces like Mpumalanga, Limpopo, the North West, KwaZulu-Natal and even Gauteng becoming malaria zones by 2050, with the number of South Africans 'at high risk' quadrupling by 2020 - at an added cost to the country of between 0.1% and 0.2% of GDP," Mr Van Schalkwyk said.

But he also announced several initiatives being taken by cabinet in its Climate Change Response Strategy.