"We should be just as worried about biodiversity loss," said Diane Srivastava, a University of British Columbia zoologist who helped write the paper, which appeared this week in the prestigious journal Nature.
"One of the intents of this paper is to really demonstrate ... what the consequences will be of biodiversity loss and to point out that these are the same magnitude as climate change."
The paper was commissioned as part of a special issue of the journal published in advance of a United Nations conference on sustainable development, to be held later this month in Rio de Janeiro, Brazil.
Srivastava, along with 16 other scientists from five countries, poured over the results of more than 600 experiments done over two decades assessing how the loss of biodiversity will impact human societies.
"If we can get consensus among this group, this really is the ecological consensus — not just what 17 friends happened to dream up," she said.
As human populations grow in both size and expectation, Srivastava said plants and animals are becoming extinct at a rate not seen in eons.
Studies suggest about one-quarter of the earth's mammal species will be gone in 20 years. Others say the oceans have lost about 90 per cent of their large fish. There are now about 17,000 endangered species in the world.
"We know that's a massive underestimate because we don't even know how many species there are in the world," Srivastava said.
The authors found the studies had several conclusions in common.
Complex, diverse ecosystems do a more complete and efficient job of using resources. They're more productive, more stable and better resist disease, pests and shocks such as extreme weather events.
The rate of environmental degradation accelerates as species disappear. Losing species at the top of a food web, such as large predators, reduces productivity all the way down.
They also found much evidence to suggest that the positive effects of biodiversity become more apparent when considered over longer time scales and larger areas. And, they concluded, time is running short.
"The need to explore more realistic scenarios of diversity change that reflect how human activities are altering biodiversity is now urgent," the report says.
"The gains from simplifying ecosystems are often local and short term, whereas the costs are transmitted to people in other locations, or to future generations."
Srivastava said biodiversity losses usually occur through small-scale, local projects — an industrial project here, a drained wetland there. The solutions can be similar.
But she said Canada is headed in the wrong direction. Legislative changes planned by the Conservative government would shift legislative protections from ecosystems and habitats to specific species.
"Something like 80 per cent of our endangered freshwater species will not be covered any more," she said.
Srivastava said estimates have put an annual value of $33 trillion on the ecological services provided through diverse, healthy ecosystems. Those benefits are not being accounted for in current policy debates, she said.
"We're suggesting a different cost-benefit analysis."