Multi-Dimensional Remote Sensing Analysis Documents Beaver-Induced Permafrost Degradation, Seward Peninsula, Alaska

Benjamin M Jones,Chandi Witharana,Melissa K Ward Jones,Allen C Bondurant,Clayton D Elder,Ken D Tape,Benjamin V Gaglioti,Charles E Miller,Jason A Clark

doi:10.3390/rs13234863

Benjamin M Jones, Chandi Witharana + Show 7 more

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https://doi.org/10.3390/rs13234863

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Abstract

Beavers have established themselves as a key component of low arctic ecosystems over the past several decades. Beavers are widely recognized as ecosystem engineers, but their effects on permafrost-dominated landscapes in the Arctic remain unclear. In this study, we document the occurrence, reconstruct the timing, and highlight the effects of beaver activity on a small creek valley confined by ice-rich permafrost on the Seward Peninsula, Alaska using multi-dimensional remote sensing analysis of satellite (Landsat-8, Sentinel-2, Planet CubeSat, and DigitalGlobe Inc./MAXAR) and unmanned aircraft systems (UAS) imagery. Beaver activity along the study reach of Swan Lake Creek appeared between 2006 and 2011 with the construction of three dams. Between 2011 and 2017, beaver dam numbers increased, with the peak occurring in 2017 (n = 9). Between 2017 and 2019, the number of dams decreased (n = 6), while the average length of the dams increased from 20 to 33 m. Between 4 and 20 August 2019, following a nine-day period of record rainfall (>125 mm), the well-established dam system failed, triggering the formation of a beaver-induced permafrost degradation feature. During the decade of beaver occupation between 2011 and 2021, the creek valley widened from 33 to 180 m (~450% increase) and the length of the stream channel network increased from ~0.6 km to more than 1.9 km (220% increase) as a result of beaver engineering and beaver-induced permafrost degradation. Comparing vegetation (NDVI) and snow (NDSI) derived indices from Sentinel-2 time-series data acquired between 2017 and 2021 for the beaver-induced permafrost degradation feature and a nearby unaffected control site, showed that peak growing season NDVI was lowered by 23% and that it extended the length of the snow-cover period by 19 days following the permafrost disturbance. Our analysis of multi-dimensional remote sensing data highlights several unique aspects of beaver engineering impacts on ice-rich permafrost landscapes. Our detailed reconstruction of the beaver-induced permafrost degradation event may also prove useful for identifying degradation of ice-rich permafrost in optical time-series datasets across regional scales. Future field- and remote sensing-based observations of this site, and others like it, will provide valuable information for the NSF-funded Arctic Beaver Observation Network (A-BON) and the third phase of the NASA Arctic-Boreal Vulnerability Experiment (ABoVE) Field Campaign.

Highlights

During pre-fieldwork planning in the summer of 2021, we discovered what we interpreted as a beaver-induced permafrost degradation feature in very high resolution satellite (VHRS) imagery
The observations made in this study using time series remote sensing imagery that document the coupled response of ing data and the combination of manual and automated image analysis techniques allowed us to reconstruct (1) the timing of beaver engineering on permafrost degradation, (2) widening of the creek valley, (3) an increase in the stream channel network, (4) lowering of peak growing season NDVI, and (5) a prolonging of the spring snowmelt period associated with the beaver-induced permafrost degradation feature
We used multi-dimensional remote sensing observations to document the occurrence, reconstruct the timing, and highlight the effects of beaver activity on a small creek valley confined by ice-rich permafrost on the Seward Peninsula, Alaska

Summary

Introduction

Recent and widespread environmental change in the Arctic is affecting ecosystems [13,20,21,22], the carbon cycle [23,24,25], infrastructure [26,27,28], socioecological systems that subsist on the numerous resources provided by Arctic lands and waters [29,30,31,32], and leading to a host of permafrost-region hazards [33]. Feedbacks associated with the cumulative effects of changes occurring in physical, ecological, and social systems are difficult to quantify and remain an active field of study [34,35,36]. The increase of beaver populations following a cessation in over trapping is well documented, as they reoccupy their native lands and waters with both positive and negative effects [40,41,42]

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