President Thabo Mbeki has signed into law South Africa's new Biodiversity Act, which is hailed by some as the most significant environmental legislation adopted in 10 years of democratic government.

Because of its incredibly rich biological diversity - the sum of all species of indigenous animals and plants - South Africa is ranked the third most biologically important nation in the world, after Brazil and Indonesia.

The new act now gives the highest possible political protection to this biodiversity.

Among other things, it requires full environmental impact assessments before the introduction of any genetically modified organisms (GMOs).

The act also makes provision for communities to share the profits of any exploitation of natural materials involving their indigenous knowledge.

An example is the case of the San/Bushmen communities who will benefit from a commercial slimming product derived from the Hoodia cactus plant, which they have known for centuries, chewing its leaves as an appetite suppressant.

"The act regulates for the first time what we call 'bio-prospecting'," explained Environmental Affairs and Tourism director-general Chippy Olver.

"For companies to be able to bio-prospect, they will now have to go through a regulatory system which gives protection to indigenous communities."

Also for the first time, the act gives a legal framework for agreements such as the contract between the National Botanical Institute (NBI) and United States horticultural company Ball to develop commercially valuable hybrids from some indigenous South African plant species.

And it will make it significantly more difficult for developers to damage or destroy any biologically sensitive natural areas.

"Up to now, we've had no specific legislation dealing with biodiversity," said Olver.

"You've got some general principles floated in the National Environmental Management Act and in the provincial ordinances.

"But this existing legislation has been very fragmented, and for the first time we have a law specifically focused on the conservation of biodiversity."

The act creates a basic legal framework in terms of which the environment minister can promulgate a national biodiversity strategy and action plan.

It also provides for the identification of biodiversity "hotspots" and "bio-regions", which will then be given legal recognition.

Different government agencies and stakeholders will be obliged to mesh their plans - provincial plans or integrated development plans at local government level - with these national biodiversity plans, resulting in a co-ordinated approach, Olver explained.

The act would not require developers to get additional permits, he suggested. "But it will add a very important dimension, because over the next few years all these bio-regions will be given legal recognition, and then any environmental impact assessment will have as its point of departure the bio-regional plan."

The act also covers alien invasive species, which are a major threat to biodiversity, and puts obligations on private landowners and the government to clear alien invasive vegetation from their properties.

It also establishes the South Africa National Biodiversity Institute (Sanbi), which is the legal successor of the current NBI.

"This is probably the most exciting biodiversity move we've made in years," Olver said.