Darkness in the Day

August 13, 2018

On August 21, 2017, the moon aligned between the earth and sun, casting a shadow that moved over the United States from Oregon to South Carolina, passing through Nebraska. Dubbed The Great American Eclipse, thousands of people flocked to the state to witness the once in a lifetime event.

A group of people watch the solar eclipse at a prairie in Lincoln, Nebraska. Photo by Michael Forsberg

In addition to the thousands of people wearing cardboard glasses and staring at the sun, we wanted to know if the eclipse would have an influence on the biota within the path of totality, specifically in central Nebraska.

Path of solar eclipse totality on August 21, 2017.

 

Aside from the opportunity to see an astronomic rarity, this phenomenon provided a unique natural experiment to investigate the use of a combination of remote sensors, collectively referred to a multimodal technologies, to measure biological and environmental changes.

Published in the journal Ecological Indicators (check it out here: https://authors.elsevier.com/c/1XU-4,XRNLZ25V), our research was a collaboration among the University of Nebraska at Kearney, Platte Basin Timelapse, Crane Trust, and Center for Global Soundscapes. We incorporated a multimodal suite of tools, including time-lapse cameras, sound recorders, and environmental sensors, to assess how a drastic and rapid reduction in light influenced various wildlife, plants, and atmospheric conditions.

We found that the total solar eclipse altered environmental conditions in several ways that triggered changes in the calling activity of insects and birds.

A group of people watch the solar eclipse at a prairie in Lincoln, Nebraska. Photo by Michael Forsberg

We used timelapse cameras set at 30-second intervals to document changes in sun illumination. The light on the landscape was never completely dark but rather mimicked the illumination of sunrise or sunset. To see how the light changed across Nebraska, check out this video by Mariah Lundgren that highlights a few PBT camera locations, two of which were used in our study.

After analyzing the images and quantifying the proximate change in illumination, we calculated the light declined by 66% of the average daily mean. Temperature decreased an average of 12°F and humidity increased an average of 20%. The following visualization shows how light and temperature changed during the eclipse on wet meadow near the Platte River.

Timelapse images, photo-derived light value (yellow line), and temperature (blue line) were recorded at Mormon Island Wet Meadow Complex, south of Grand Island, NE. The following visualization shows how light and temperature changed during the eclipse on a wet meadow near the Platte River. (Emma Brinley Buckley)

Spectrograms, acoustic indices, and auditory surveys from sound recordings revealed numerous changes in the soundscape. Orthoptera, such as katydids and crickets, changed the amount, timing, and frequency of their calling. We identified changes in the call activity of late-season breeding birds, for example, sedge wrens increased singing during totality. We also observed a phenomenon known as an ‘eclipse wind’, where sounds associated with wind, such as rustling grasses or branches, decreased closer to totality.

A spectrogram, or visual representation of sound, recorded from 10:30 am to 3:30 pm on August 21, 2017. In the spectrogram, note the decline in insect calling frequency near totality and reduced vertical streaking closer to totality from decreased wind. Of interest in the sound recordings, the first clip has higher frequency insect calls, the second clip of totality has increased sedge wren vocalizations, and the third recording shows how the wind increased again. (Emma Brinley Buckley)

We also hypothesized that the eclipse might influence bat behavior, nocturnal/crepuscular wildlife, or flowers that rely on light-cues. We deployed ultrasonic microphones and trailcams at a known night roost and foraging site to detect bat activity, as well as trail cameras on active wildlife corridors and specific plants such as moonflowers (Datura stramonium, which bloom at night), young sunflowers (Helianthus annuus, which orient towards the sun), and morning glories (Ipomoea purpurea, which bloom during the day). Despite our efforts, we did not observe any out of the ordinary changes from bats, plants, or on wildlife trails during the eclipse.

The use of passive multimodal technologies allowed us to collect many different types of information (i.e. visual, auditory, atmospheric) across multiple sites at a high temporal frequency. This meant we could acquire continuous data to help us better understand our fast-changing natural world, without having to be physically at a location and manually measuring change.

Many of the sound recorders were in isolated locations far from populated areas, but when the moon completely eclipsed the sun and totality began, the cheers, howls, and celebratory yells of distant spectators were heard on every sound recording. I took in the event in solitary silence, one eye squinting through my eclipse monocle, the other half of the cardboard glasses duct taped to my camera lens, and my attention focused solely on the sky to witness the celestial spectacle.

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PBT team photo. Summer 2023

About PBT

We are a group of storytellers using timelapse photography and multimedia storytelling to explore watersheds. PBT has been in motion since 2011.

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