Species extinction and loss of biodiversity could be as devastating for the earth as climate change and air pollution. That's the finding of a new study by a group of scientists from nine countries. The research aims for the first time to comprehensively compare the consequences of biodiversity loss with other possible environmental issues caused by humans.

Ecologist and University of Michigan assistant professor, Bradley Cardinale, who helped write the study, says, "Loss of biological diversity due to species extinctions is going to have major impacts on our planet, and we better prepare ourselves to deal with them. These extinctions may well rank as one of the top five drivers of global change."

The study, which suggests that more moves must be made to strengthen biodiversity at all levels, has just been published online in the Nature journal.

Research conducted over the last 20 years has showed that production increases in ecosystems with the widest biodiversity. This raised worries that today's high extinction rates from harvesting increases, habitat reduction and other environmental issues, could affect vital issues such as food production, pure water and a stable climate.

But until this study, it had been difficult to separate the effects due to the loss of biodiversity against problems caused by human activity.

Lead author of the research, David Hooper, a Western Washington University biologist, says it had been believed that the effects of biodiversity were minor, but the findings of the new study suggests that future species loss has as big an effect on reducing plant production as global warming and pollution.

The international team took data from 192 published studies and experimental to compare how different worldwide environmental factors affected the growth of plants and how fungi and bacteria attacked dead plants.

They found that in places were species loss was low, affecting up to 20% of local plant species, there was a negligible impact on plant growth in the ecosystem and in species diversity.

In areas with 21-40% extinction, plant growth was expected to fall by between 5-10%, which is equivalent to the likely impact of global warming and rising ultraviolet radiation caused by major ozone reduction.

In the highest levels of species loss, from 41-60%, the impact would be similar to major factors of environmental change, including pollution of the ozone, acid decay of forests and pollution of nutrients.

The seriousness of the findings has surprised some of the team and indicates that environmental policymakers should take into account the potential effects of biodiversity loss, says David Hooper.

The biggest challenge still remains - how the loss of biodiversity and other major environmental changes will combine to change the ecosystem, says fellow author, Emmett Duffy, from the Virginia Institute of Marine Science.

As well as Bradley Cardinale, assistant professor at the University of Michigan School of Natural Resources and Environment and in the Department of Ecology and Evolutionary Biology, David Hooper and Emmett Duffy, several other researchers worked on the study.

They were E. Carol Adair from the University of Vermont and the National Center for Ecological Analysis and Synthesis, Santa Barbara; Kristen Matulich, from the University of California Irvine; Bruce Hungate, from Northern Arizona University; Jarrett E.K. Byrnes, from the National Center for Ecological Analysis and Synthesis; Andrew Gonzalez, from McGill University, Montreal, Canada; Lars Gamfeldt, from the University of Gothenburg, Sweden; and Mary O'Connor, from the University of British Columbia, Canada, and the National Center for Ecological Analysis and Synthesis.

The research was financed from grants from the National Center for Ecological Analysis and Synthesis and the National Science Foundation.