All noisy on the Western front
First, a bit of shameless self promotion: High Country News recently launched two brand new monthly podcasts! Rants from the Hill, the audio version of Michael Branch's essays on life in Nevada's high desert, which have appeared on our Range blog for the past year or so, will be available at the beginning of each month. West of 100, which will bring you compelling stories and ideas with West-wide significance, just as the magazine does, will come out around mid-month. Follow the links in the titles to subscribe.
The first episode of West of 100, "The sound of silence," looked at an increasingly threatened and underappreciated natural resource: sound. In recent years, scientists have started paying more attention to how the mix of sounds made by critters, people and the earth itself in a given area -- the "soundscape" -- changes over time and space. And they've taken a deeper look at how all those sounds interact -- how, for instance, the introduction of manmade noise to an ecosystem impacts how birds communicate, or species' ability to detect predators.
Just as our podcast went live, an ongoing study in New Mexico on how noise from oil and gas development impacts the environment made public intriguing new findings -- that, as Katrina Marland, blogging for American Forests put it, "industrial noise can literally transform a landscape," influencing which plants grow and which birds thrive.
Before we get into the details, here's some background on the groundbreaking study, which is unique because researchers were able to control for noise from oil and gas activity, allowing them to study its direct impact on birdlife. They looked at sites with nearly identical plants, weather, topography, and predator-prey relationships. One set of sites was infiltrated by noise from compressors, while the other wasn't. From Mary Woodsen's 2010 HCN story:
(T)he number of nests was virtually the same across both types of sites. "And some species seemed to prefer noise," Francis says. Finding 94 percent of house finches nesting near compressors was a bit of a shock... And talk about surprises in small packages -- 92 percent of black-chinned hummingbirds set up shop amid the noise.
The biggest surprise: Contrary to expectations, the birds that reared the most young nested closest to compressors, even though they most likely could not hear predators coming.
Two years into the project, Francis set up artificial nests baited with quail eggs to find out why. Motion-triggered cameras near the fake nests identified the principal predator -- the western scrub jay. But the jays couldn't hack the noise. Nearly twice as many foraged in quiet sites as noisy ones... And no other predator took their place.
How did the finches and hummers cope with the noise? "House finches are known for being able to adjust the pitch of their songs up or down, depending on what kind of background noise they're competing with," Francis says. "And hummingbirds naturally use high frequencies that carry above compressor noise."
Now, Francis and his team have documented the cascading impacts of the noise-driven change in avian occupation. The scrub jays, which avoided noisy areas, feed on the seeds of pinon pine trees. They extract them from cones, then bury them in the ground for safekeeping, going back for some but overlooking others. Those forgotten stashes can eventually sprout new trees.
In the noisy study sites jays stayed away from, Francis found four times fewer pinon seedlings, but more flowers, which hummingbirds pollinate. Mice munched on pinon seeds in the noisy areas, but they don't squirrel them away like jays do, and therefore, don't help the trees reproduce.
The takeaway? Marland puts it well: "(T)here will always be a ripple effect for forests that border industrial sites or other noisy places. How different will these forests look 10 years from now? 50? The treeline could be pushed back little by little with each decade, just by simple noise."
It's a good reminder that our thumbprint on nature is often far more complex than we imagine.
Cally Carswell is the assistant editor at High Country News.
Photo: A black-chinned hummingbird. These hummers thrived in the noisy sites in the New Mexico study. Licensed under Creative Commons, courtesy flickr user mnchilemom.