The negative impact of salvage logging on birds

Charred forest following a fire in the North Cascades, Washington. Ground vegetation is just beginning to return.A new study  finds that the practice of salvage logging after forest fires has severe negative impacts on bird diversity and abundance.

Salvage logging has become a political hot-button issue of late. The practice involves removing burned tree trunks and other woody debris such as branches and snags after a forest fire. Proponents believe that salvage logging, in addition to salvaging economically valuable wood, can reduce the risk of future wildfires and the spread of pests although these claims are disputed.

Jorge Castro and fellow researchers conducted an experiment in the Sierra Nevada National Park of Southern Spain where the Lajuron fire burned 1300 hectares of pine forest. They set up plots where they implemented one of three treatments:

1) Non-intervention in which all burned trees were left standing

2) Partial cut in which 90% of burned trees were felled and the main branches of felled trees
were lopped off, but all the cut biomass was left on the ground; and

3) Experimental salvage logging in which all trees were removed (minus the stumps) and were mechanically chopped.

They found that salvage logging decreased bird abundance by about 50% and bird diversity by about 40% at the community level. The researchers offer likely explanations:

"First, decaying wood provides a large increase in food supply thanks to the larvae of insects that develop inside the burned trunks, which favors coexistence of a higher number of bird species and individuals. Second, the more complex habitat structure provided by snags may provide safe sites for foraging, perching, or nesting, which favors selection of these treatments."

In addition, the study found that salvage logging transformed the existing bird communities. In the plots subject to no intervention, researchers encountered mostly the same mid to late-successional bird species that would be found in the unburned forest. In the plots subject to salvage logging, they found mostly early successional bird species common to open fields and cultivated land.

This is  particularly problematic from a conservation perspective because in the Mediterranean region pine forests and associated bird species are relatively uncommon compared to open fields agricultural areas. Also seed dispersing birds were less common in the salvaged plots indicating the practice may set-back the natural process of succession that occurs after wildfires.

One alternative proposed by the researchers is to do limited salvage logging within a landscape mosaic that also includes leaving some burned trees standing.

Overall, this study adds to the growing body work of showing the ecological problems associated with salvage logging. Hopefully, this study and others like it will make their way to policy makers deciding the future management of our forests.

Follow up question: Does anyone know what is the current status of salvage logging policies in North America and Europe?

--Reviewed by Rob Goldstein

CASTRO, J., MORENO-RUEDA, G., & HÓDAR, J. (2009). Experimental Test of Postfire Management in Pine Forests: Impact of Salvage Logging versus Partial Cutting and Nonintervention on Bird–Species Assemblages Conservation Biology DOI: 10.1111/j.1523-1739.2009.01382.x