The United Nations says in a new report that we must take unprecedented efforts to reverse the trend by 2010, if we expect such habitats as coral reefs and tropical rainforests to survive.

The report, Global Biodiversity Outlook 2, from the secretariat of the UN Convention on Biological Diversity, says: "The direct causes of biodiversity loss show no sign of abating."

Before the extinction of the dinosaurs, scientists say there were five other mass extinctions caused by natural catastrophes between 205 and 500 million years ago. The extinctions of our era, the result of gradual destruction, are on par with those likely caused by asteroids, volcanoes, and other serious natural disasters.

The causes cited by the UN won't surprise anyone. The world's population has swelled beyond 6.5 billion and it is infringing on animal and plant habitats, creating dangerously high levels of greenhouse gases, and introducing "alien species" into ecosystems.

The report includes a "red list" of 844 animals and plant species that are known to have gone extinct in the last 500 years. Experts consider this a conservative number.

The report was presented to mark the start of a UN environment program meeting in Curitiba, Brazil.