Scientists argue river restoration projects must change focus

Monday, November 26 2012

More than $1 billion a year has been spent since 1990 on river restoration in the United States, yet fish stocks in many areas are not recovering to the anticipated extent.  One reason may be the lack of attention being paid to who is feeding on whom in river ecosystems.

This is the conclusion of a team of scientists, including U-Idaho Department of Fish and Wildlife Professor Dennis Scarnecchia and retired U-Idaho Fisheries Resources Professor James Congleton, who have been examining restoration efforts in the Columbia River Basin. Their conclusions will be published in the Proceedings of the National Academy of Sciences (PNAS) this week.

Until recently, most river restoration efforts have focused on repairing the physical damage to a river’s habitat structure and quality caused by dams and channelization. The assumption has been that fish populations will bounce back once the habitat is restored.

The authors argue that it is time to acknowledge that these approaches may not be working well enough, and suggest that restoration efforts could be more effective if greater importance were placed on understanding the complex food webs that support biotic communities.

They identify three priority food web-related issues that may have a negative impact on successful river restoration: uncertainty about habitat carrying capacity, the proliferation of chemicals and contaminants in rivers and the emergence of hybrid food webs that consist of both native and non-native species, including troublesome invasive species.

“Food web studies can be challenging to design and implement, but without them we will lack adequate understanding of how aquatic systems have functioned in the past, how food webs affect restoration efforts today, and how novel systems with more non-native species will function in the future,” said Scarnecchia.

They call for a new management framework which would incorporate food-web considerations into watershed management efforts. Such a framework, they say, could help test current assumptions about restoration as well as lead to discoveries of species interactions that could have an impact on the outcome of restoration efforts.

Such discussions have begun among the state, federal and tribal agencies concerned with restoring the Columbia River. The authors say that these discussions have raised awareness of the key role food webs play in restoration efforts and will influence discussions about how to prioritize future restoration activities.

Ultimately, the authors argue, implementing a food web perspective will lead to improved approaches to river management and improve the ability of river restoration experts and watershed managers to meet their legal obligations under the US Endangered Species Act.