The avian community is an effective barometer of how climate change is impacting our environment. The Institute for Biodiversity and the Environment (IBE) at William Jessup University has as one of its core research projects the Pacific Crest Trail (PCT) Biodiversity Megatransect, which is an ongoing survey of the montane avian diversity and phenology along the PCT. Central to the research is the novel, noninvasive (not requiring the capture or handling of animals) use of automated recording devices to continuously inventory and monitor biological diversity across the wilderness regions of the entire length of the PCT (from Mexico to Canada, 2,650 miles). While interpreting these recordings can be costly, requiring hundreds of interpreter hours, this approach provides the needed level of replication in the dataset for the use of hierarchical statistical models, such as multi-species occupancy models (MSOMs), to estimate species richness, distributions, population status of individual species (i.e., occupancy), and breeding phenology in response to underlying climatic variables. Alternatively, the PI, Dr. McGrann and his National Park Service and Ca. Dept. of Fish and Wildlife collaborators, recognize tremendous potential value in using bioacoustic indices, calculated from the recordings themselves using a computeralgorithm, as a metric of species richness. Although bioacoustic indices have been shown to positively correlate with species richness, it remains unclear how well acoustic indices perform at large spatiotemporal scales and across heterogeneous landscapes. This study is working to address questions of how well the acoustic complexity index (ACI) correlates with estimated species richness under varying survey conditions. Results have the potential to inform the budding discipline of soundscape ecology and the application of bioacoustic indices in large-scale biodiversity monitoring programs worldwide that employ passive acoustic monitoring devices.
Over the past two decades, ecologists have increasingly recognized the value of passive acoustic recording technologies as a non-invasive approach for acquiring data on large assemblages of vocalizing species, including birds, amphibians, and bats. Due to the promise of this approach in addressing theoretical questions on how biodiversity is responding to global environmental change, vast amounts of acoustic data are being accumulated by researchers world-wide. As a consequence, a new scientific discipline has emerged – soundscape ecology. However, interpreting all this acoustic data by human experts to identify vocalizing species presents logistical challenges and is often cost prohibitive. The purpose of this research is to fill a significant knowledge gap in the field of soundscape ecology.
One of our goals in our research is to describe the relationship at large spatial scales between the widely used bioacoustic index, the acoustic complexity index (ACI), and that of estimated avian richness based on the interpretation of recordings of the singing bird community. Since 2010, IBE’s Pacific Crest Trail Biodiversity Megatransect (PCTBM) – a large-scale and long-term study of passerine climate-diversity relationships along the Pacific Crest National Scenic Trail (PCT) – has employed lightweight, automated bird recorder units (ARUs) that can be packed in on foot and deployed at remote survey sites along the trail. The PCTBM has generated over 4,000 5- and 7-min. recordings of the singing bird community across surveys sites along 1,700 miles of the PCT in California, from Mexico to Oregon. To date, only about 2,000 of these recordings have been interpreted by expert observers who identified all the species vocalizing on each of the recordings. The PCTBM has so far produced 4 peer-reviewed articles on the climatic and environmental drivers of montane avian diversity and breeding phenology.
Although interpreting the recordings in this manner can be labor-intensive, requiring hundreds of interpreter hours, this approach provides the needed level of replication in the dataset to provide detection histories for species and to estimate detection probability for use in multispecies occupancy models (MSOMs). MSOMs can be employed to provide estimates of species richness, population status and distributions of individual species (i.e., the occupancy state), and breeding phenology (i.e., the date of highest singing activity). Furthermore, this approach allows us to track the response of these parameters to climate change and other sources of environmental change over time.
The labor-intensive interpretation of the PCTBM’s recordings highlights the tremendous potential value in using bioacoustic indices as an alternative metric for species richness in large-scale studies. A bioacoustic index employs a computer algorithm that summarizes the acoustic energy produced and estimates the diversity of sounds in the soundscape, including sounds produced by the singing bird community. Although bioacoustic indices have been shown to positively correlate with species richness, it remains unclear how well bioacoustic indices perform at large spatiotemporal scales and across heterogeneous landscapes. In this study, we propose to address questions of how well the ACI correlates with estimated species richness under varying survey conditions (e.g., wind/stream noise, anthropogenic noise) and habitat types. Results from this study have the potential to revolutionize the application of bioacoustic indices in large-scale monitoring programs worldwide that employ passive acoustic monitoring devices.
In addition to the above climate-diversity and soundscape ecology research questions. The PCTBM has also piloted the use of environmental DNA (eDNA) techniques to survey aquatic vertebrates. Where the PCT intersects waterbodies, including streams and lakes, water is run through a portable filtering apparatus to collect samples of organic matter. The eDNA, collected onthese filters, is then analyzed in lab polymerase chain reaction to determine rare/secretive aquatic vertebrates presence in aquatic systems simply based on the DNA (from sloughed-off cells) leftbehind in the water. Although eDNA, over the past 10 years, are increasingly applied in wildlife studies, they have never before been applied at such a large geographic scales and in remote settings. This work promises to provide an important baseline on the distributions of rare species in these remote montane ecosystems.
In previous years, on seven separate field seasons, we have implemented surveys along the PCT across 3,578 survey sites, including the entire length of California (1,700 mi) in 2006 and several sections (hundreds of miles long) in California in subsequent years (2010, 2015, 2016, 2017, and 2019 as of the date of this writing).
With the scientific theory supporting the research fully-matured, the methodology peer-reviewed, and the logistics well thought-out and previously executed, the PCTBM is primed to be implement at a larger spatial-temporal scales across the entire length of the PCT from Mexico to Canada (2,650 mi). The overarching goal of the PCTBM is to become established as a regular monitoring program that informs the decision-making response of government agencies addressing climate change and other sources of global environmental change. Further, the PCTBM spans multiple administrative units (Federal, State, and Private lands) and promises help inform decision-makers across these boundaries on their climate change response.
We are currently seeking funding to support the future implementation of the program across the entire length of the PCT. Further, this program allows undergraduates at WJU’s Science Honors Program, as well as other collaborating universities, to come alongside research faculty and other collaborating scientists.