"A growing number of African countries are depleting their natural resources -- or will shortly be doing so -- faster than they can be replaced," said WWF President, Chief Emeka Anyaoku, in presenting the findings to a Johannesburg conference.

The report put Egypt, Libya and Algeria at the head of a list of nations of the continent already living well beyond their ecological means.

But nine others were also using up their bio-capacity -- Morocco, Tunisia, Ethiopia, Kenya, Uganda, Senegal, Nigeria, South Africa and Zimbabwe.

The Swiss-based WWF, previously known as the World Wide Fund for Nature but now identified only by the initials and its panda logo, issued the report, "Africa-Ecological Footprint and Human Well-being" together with a US-based research body, the Global Footprint Network.

It said that despite over-consumption of resources in some countries, Africa's overall ecological footprint at 1.1 hectares of land and sea -- still behind the continent's total biocapacity of 1.3 hectares per head of population.

And the African figures are still well below the global average footprint of 2.2 hectares per person which, with 1.8 hectares available, is running at a rate suggesting humanity will need two planets by 2050.

But the big danger for the continent is that its current population of some 680 million is growing rapidly and is predicted to double, meaning Africa will account for nearly a quarter of the world's people by 2050.

Although development is vital for Africans, at the lower end of the United Nations' human welfare index, they have to "work with, rather than against, ecological budget constraints," said Global Footprint Network director Mathis Wackernagel.

"Development that ignores the limits of our natural resources ultimately ends up imposing disproportionate costs on the most vulnerable and the most dependent on the health of natural systems, such as the rural poor," he added. (Reporting by Robert Evans; Editing by Jon Boyle)