Plants, animals and the places where they live are being wiped out at a quickening pace, leading to a loss of biodiversity that could threaten whole ecosystems, say scientists meeting in South Africa this week.

The international group of experts warns that Canada and more than 100 other signatories to a United Nations convention have failed to live up to a pledge to significantly curb biodiversity loss by 2010.

Andrew Hendry, a biologist at McGill University in Montreal, said while there are hopeful signs some countries may be altering the way they manage species and protect habitats, the overall picture remains grim.

"In some places, it's worsening," Hendry said before heading to the four-day conference in Cape Town that starts Tuesday. "We continue to see major problems in a lot of tropical countries, particularly where people are quite poor."

The 600 scientists attending the meeting of the non-governmental organization Diversitas will focus on measures to stem the loss of various species, including everything from trees and sharks to plants and insects in the Amazon rainforest.

Researchers say that greater tracts of land are being swallowed up by commercial interests to feed a growing appetite for natural resources like lumber and water.

But that push by corporate mining, forestry and fishing outfits is reshaping ecosystems by taking away food sources, reducing land masses and polluting natural habitats.

Conservative estimates show an area of tropical rainforest larger than California has been converted for food and fuel, the scientists say.

"Species extinction rates are at least 100 times those in pre-human times and are expected to continue to increase," said Georgina Mace, vice-chairwoman of Diversitas.

'On verge of crisis'

In particular, scientists say freshwater species are at grave risk of extinction as the demand for resources grows steadily and sources diminish.

Klement Tockner of a German institute that specializes in freshwater issues said extinction rates of species in those ecosystems are four to six times higher than other land-based or marine species.

"There is clear and growing scientific evidence that we are on the verge of a major freshwater biodiversity crisis," he said in a statement. "Threats to freshwater biodiversity have now grown to a global scale."

Hendry, a professor of ecology and evolution, said the loss of various freshwater species usually affects the world's poorest by compromising water purification and disease regulation, along with people's ability to access water for farming and fishing.

"If you start pulling things out of the environment, then many of the services that are provided by these ecosystems, such as clean water, can be compromised," he said.

Hendry said 123 countries signed the UN Convention on Biological Diversity in 2003, with many doing little to slow the pace of species erosion. But he said some countries are starting to see the value in maintaining and protecting healthy ecosystems.

Costa Rica and Ecuador have invested heavily in habitat protection, which is paying off in a growing trade in eco-tourism.

Hendry said Canada has made minor gains in safeguarding some species by creating protected areas and investing in the Species at Risk Act, but it hasn't gone far enough.

He said it hasn't adequately responded to environmental concerns over the Alberta tarsands, collapsed fish stocks and the fate of the polar bear due to the loss of Arctic ice.