Natural resources and biological diversity are a priceless heritage the world can ill afford to lose, President Thabo Mbeki said yesterday.

Speaking at the opening of the fifth World Parks Congress in Durban, he said these held the key to many of the challenges facing humanity, including pharmaceutical properties and the genetic base to strengthen essential foodstuffs.

"We cannot afford to lose these resources; that is why this congress is crucial to people's well-being," he told 2 500 delegates, among them some of the world's leading environmentalists, attending the premier conservation event at the port city's International Convention Centre.

However, conservation efforts faced enormous constraints, Mbeki said.

"These include threats to biological diversity from land degradation, climate change, human settlement and alien invasive (plant) species.

"They include lack of funds, high levels of poverty in and around protected areas, poaching and plant theft, and threats from extractive industries".

The president also warned on globalisation.

Quoting the United Nations Millennium Declaration, he said: "We believe that the central challenge we face today is to ensure that globalisation becomes a positive force for all the world's people".

"At present, its benefits are very unevenly distributed".

According to congress organisers, Mbeki made a lightning change to his schedule on Monday to get to Durban and deliver the opening address, but his thunder was stolen on the podium by Nelson Mandela and the former president's IUCN co-patron, Queen Noor of Jordan.

The pair, who entered to a standing ovation minutes before the president, proved a hard act to follow.

Mandela, wearing one of his trademark shirts and clutching a stick, received another standing ovation when he stood to speak, and yet another when he left.

He captured his audience's attention immediately, saying: "You may be curious to hear what an old man without a job, power or office, and with roots far in the past, is going to say about future challenges".

The future, the 85-year-old Mandela told them, was in the hands of today's youth.

"Without the youth, the future is not secure," he warned, saying young people were under-represented in many areas of protected areas management.

One of the greatest challenges for the future of protected areas was to correct this situation.

Another was combining environmental protection with economic relief for the poor. In this regard, Mandela praised the efforts of the Working for Water Programme, which has employed thousands of poor South Africans in recent years in its efforts to eradicate invasive alien plants.

Queen Noor, who spoke before Mandela, said the setting aside by governments of over ten per cent of the world's land for protected areas over the past decade represented "the most significant collective land-use decisions in history".

The WPC's theme, "Benefits Beyond Boundaries", was particularly relevant, "reflecting the way a shift is necessary if these areas are to survive", said the beautiful blonde queen, who dazzled her audience in a fairytale pink dress stitched with sequins.

Mbeki said another "central issue" on the common global agenda was that of poverty and underdevelopment.

"The mere search for food among poor people, who have limited access to the various means to sustain life available to people in the developed world, has put pressure, and will continue to put pressure, on the national parks in poor countries," he warned.

"Mere exhortations to poor people to value and respect the ecosystems contained within national parks will not succeed. It is critically important that alternative means of livelihood be found for the poor of the world, so that they are not forced to act in a manner that undermines the global effort to protect these ecosystems," he said.

The WPC ends on September 17. – Sapa.