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Global biodiversity is declining at an increasingly fast clip, taking down with it natural services such as freshwater provided by rivers and streams and storm protection from barrier islands and marshes, all of which are critical to human societies.

An upcoming meeting in Nagoya, Japan, aims to set conservation targets that will halt this downward trajectory by 2020.

But some conservation experts think that the 20 new goals being considered by the 10th conference of the parties at the Convention on Biological Diversity fall short of what's really needed, especially after an earlier goal set for 2010 have not been met. Experts hope to see the new goals strengthened before negotiations end later this month.

Causes of biodiversity loss

Biodiversity loss can be caused by many different human actions, such as overhunting, pollution and land clearing for farming. For example, companies and individuals clear out parts of the Amazon rainforest to plant crops or to log.

"There are very strong private incentives for people to convert habitat and undertake actions that cause the loss of biodiversity," said Charles Perrings of Arizona State University and lead researcher on a policy paper published this week in the journal Science that makes new recommendations for the convention's goals. "For them, they are usually good reasons, like producing food for their family or protecting themselves against pathogens, but nevertheless it has consequences for the rest of us."

Such human needs likely explain why few nations have documented a reduction in the rate of biodiversity loss, the convention's sole target for 2010 set eight years ago, he added.

"The target itself didn't address the driving forces behind biodiversity loss, "Perrings said. "The 2020 targets do better."

The new targets—labeled "SMART"for "specific, measurable, ambitious, realistic and time-bound" —include an array of strategies that attempt to both directly and indirectly safeguard biodiversity. These include identifying and eradicating invasive alien species, eliminating overfishing and harmful incentives such as agricultural subsidies, and educating the public about the values of biodiversity.

Not enough

But it is not enough for the targets to be SMART, Perrings said. He and his international team argue in their paper that more emphasis needs to be placed on the real interests that people have in biodiversity, from its use for food and fuel, to its benefits for aesthetics and health.

"A lot of people have this impression that it's just about species,"said Frank Larsen, a conservation scientist with Conservation International, a nonprofit environmental group based in Washington, D.C. "We are losing species—and that's a big concern that we need to deal with—but we should not forget that nature supports human societies."

In fact, a 2002 study published in Science found that protected areas conserve benefits worth more than 100 times theircost, added Larsen, who was not involved in either paper.

Still, there are trade-offs to be made. It will not be in everyone's best interest to conserve species everywhere, and species that are needed for one set of services may differ from another set, Perrings said. Protecting a watershed requires a range of species with a variety of root systems, for example, while planting a monoculture of the greatest carbon-absorbing trees is best for sequestrating carbon dioxide emitted into the atmosphere.

There are many other complex interdependencies between the targets, such as the dual targets of phasing out harmful subsidies and conserving 15 to 20 percent of terrestrial areas, note the researchers. Some targets will need to be implemented in sequence, conditional on the  goal being achieved.

Other oversights highlighted by the team include the strict 10-year timeframe, which may not work across all 20 targets.

"Some things are just more urgent than others," Perrings said. "The problem of invasive species, including emergent zoonotic diseases, is probably not something we can wait 10 years to solve, while it will frankly take forever to make all people aware of the values of biodiversity."

Further, a changing climate and growing global population could alter conservation priorities over the next 10 years.

Below each of the new 2020 targets, delegates at the conference will create a set of indicators for use in measuring progress toward the goals. Perrings and his colleagues suggest that most of their recommended changes could simply be addressed here.

However, Larsen worries that the points laid out by the team may be too detailed and therefore distracting from the meeting's primary goals. "It's very important that we set these ambitious political targets and make world leaders agree upon them,"he said. "And then we can work out the specifics. Sometimes you can get lost in the details."

"We are losing nature fast and we are adding more and more people,"Larsen added. "The window of opportunity is now, so we need to act. This meeting is a very good time."

This article was provided by OurAmazingPlanet, a sister site of LiveScience.