From wildfires to invasive species, today’s environmental changes are affecting entire landscapes. Protecting endangered species and necessities like clean drinking water requires us to work at the same broad scale, which is exactly why my research focuses on monitoring animals across the landscape. My work began with one of North America’s most famous endangered species, the spotted owl.
Spotted owls live only in the forests of western North America, and one of the most urgent threats to this endangered species is the closely related barred owl. Human changes to the habitat of the Great Plains have allowed barred owls to expand across the entire continent, and now this aggressive bird is in direct competition with the smaller and more docile spotted owl. California’s Sierra Nevada is the forefront of this invasion, and conservationists need to understand the barred owls’ progress in order to protect spotted owls from extinction.
To meet this need, my team and I deployed recording units across 2,300 square miles of mountains in northern California – making our study three times the size of a conventional owl monitoring project, and one of the largest acoustic monitoring efforts in the western hemisphere. In just two summers, we collected over 500,000 hours of audio data, which I processed with custom owl hoot identification tools. Once I had settings that correctly identified owls and ignored everything else (well, mostly…we still had to validate the results!), I could efficiently determine which sites were occupied by owls. I then used the resulting data to estimate the rate of barred owl population growth.
The results were startling. In just one year, the barred owl population had grown by a factor of 2.6 – in the first year they were recorded at just 8% of our sites but in the next they were recorded at 21% of our sites. Based on the rate of barred owl population growth, protecting the future of the spotted owl in the Sierra Nevada required swift action. And it wasn’t just a question of saving the spotted owl: barred owls feed on a much wider range of prey than spotted owls, meaning that barred owls could destabilize the entire ecosystem.
As a result, a team composed of state and federal agencies, academic groups, and private industry biologists was formed, and they conducted experimental barred owl removals across the Sierra Nevada. The acoustic monitoring program was the backbone of this effort because it allowed the team to locate barred owls and to measure their progress. The effort was successful: the audio data indicated that the barred owl population has been reduced to below the levels we documented in the first year of monitoring and that spotted owls are recovering.
But that isn’t all we can do with the audio data: I am using a novel machine learning algorithm to identify several hundred species of birds. We have also identified coyotes, frogs, and insects, as well as the sounds of machines and the eerie silence they leave in their wake. Just as we’re expanding the species we can study, we’re also expanding survey coverage to include over 7,000 square miles – nearly the entire Sierra Nevada. This means that when managers are making decisions like how to prevent catastrophic wildfires, they’ll have information about entire biological communities, not just a few species. This is important because holistic management leads to better outcomes.
The more we can unlock the latent potential of the sounds of the Sierra Nevada, the better we can conserve its unique biological and cultural history – and plan for its future. If we succeed, it can continue to do things like provide a home to thousands of species and drinking water for most of California. So, if you’ve ever used a computer or watched a movie, you’ve benefited from the Sierra Nevada ecosystem.
This work is possible in part because of the spotted owl’s popularity and legal protections, which ensure continued support to develop novel approaches to ecological monitoring. Already, our work on this project has been cited by researchers in China, India, England, Spain, Panama, and the U.S., which means that spotted owl conservation is helping not just the spotted owl and not just the Sierra Nevada ecosystem, but species around the world. Environmental change is rapid and vast, but thanks in part to the spotted owl, we’re developing the tools we’ll need to understand that change – and adapt to it.