Assessing biological and environmental effects of a total solar eclipse with passive multimodal technologies

On 21 August 2017, a total solar eclipse crossed the continental United States, providing a unique natural experiment to observe how wildlife and plants respond to rapid and drastic changes in photic conditions using a multi-modal suite of tools. We installed passive time-lapse and infrared cameras, sound recorders, and data loggers in the Central Platte River Valley of Nebraska to study this phenomenon. The eclipse lasted about three hours, and complete obscuration of the sun (totality) lasted for about 2 min and 30 sec. Light values, measured with time-lapse camera systems, decreased 67% on average during totality relative to the daily mean light value. Ambient temperatures decreased by 6.7 degrees C on average (12% of the daily mean) approximately 11-16 min after totality; concurrently, humidity increased by an average of 12% of the daily mean. We found evidence for altered acoustic activity in response to the eclipse, including site and species-specific changes in the call activities of late season breeding birds and insects in the orders orthoptera and hemiptera. In addition, acoustic indices were differentially correlated with changes in photic and thermal conditions. However, we did not observe changes in flowering plants nor detect bat activity at known night roost and foraging areas. Historically, observations during rare occurrences, such as a total solar eclipse, were anecdotal or limited in scope, and thus, how they changed the light, sound, and meteorological conditions on the landscape were difficult to validate and measure. In comparison, anthropogenic disturbances, including impacts from light pollution and climate change, often take place slowly over long periods, and therefore, can be complex and challenging to assess. Documentation of this stochastic occurrence, with an immediate change in environmental conditions, highlights the utility of passive multimedia technologies to increase our capacity to monitor ecosystem dynamics and chronicle the variations of abiotic properties of a landscape and concomitant responses of organisms with varying sensory abilities.