Abstract
Contemporary climate change in Alaska has resulted in amplified rates of press and pulse disturbances that drive ecosystem change with significant consequences for socio-environmental systems. Despite the vulnerability of Arctic and boreal landscapes to change, little has been done to characterize landscape change and associated drivers across northern high-latitude ecosystems. Here we characterize the historical sensitivity of Alaska's ecosystems to environmental change and anthropogenic disturbances using expert knowledge, remote sensing data, and spatiotemporal analyses and modeling. Time-series analysis of moderate—and high-resolution imagery was used to characterize land- and water-surface dynamics across Alaska. Some 430,000 interpretations of ecological and geomorphological change were made using historical air photos and satellite imagery, and corroborate land-surface greening, browning, and wetness/moisture trend parameters derived from peak-growing season Landsat imagery acquired from 1984 to 2015. The time series of change metrics, together with climatic data and maps of landscape characteristics, were incorporated into a modeling framework for mapping and understanding of drivers of change throughout Alaska. According to our analysis, approximately 13% (~174,000 ± 8700 km 2 ) of Alaska has experienced directional change in the last 32 years (±95% confidence intervals). At the ecoregions level, substantial increases in remotely sensed vegetation productivity were most pronounced in western and northern foothills of Alaska, which is explained by vegetation growth associated with increasing air temperatures. Significant browning trends were largely the result of recent wildfires in interior Alaska, but browning trends are also driven by increases in evaporative demand and surface-water gains that have predominately occurred over warming permafrost landscapes. Increased rates of photosynthetic activity are associated with stabilization and recovery processes following wildfire, timber harvesting, insect damage, thermokarst, glacial retreat, and lake infilling and drainage events. Our results fill a critical gap in the understanding of historical and potential future trajectories of change in northern high-latitude regions.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1171-1189 |
| Number of pages | 19 |
| Journal | Global change biology |
| Volume | 25 |
| Issue number | 3 |
| DOIs | |
| State | Published - Mar 2019 |
Bibliographical note
Funding Information:This research was primarily supported by the United States Geological Survey (USGS) Biologic Carbon Sequestration Assessment Program (LandCarbon) and the National Aeronautics and Space Administration (NASA) Arctic-Boreal Vulnerability Experiment (ABoVE). A portion of the work was performed under USGS contract G08PC91508. N.J.P. acknowledges additional funding support from the University of Minnesota's (UMN) Doctoral Dissertation Fellowship and the Marvin E. Bauer Remote Sensing of Natural Resources Fellowship, and thanks Vipin Kumar (UMN) and Thomas Burk (UMN) for stimulating discussions related to spatial and temporal data mining. We also thank A. David McGuire (University of Alaska Fairbanks) and two anonymous reviewers for constructive comments that helped to improve this manuscript. S.J.G. acknowledges support from NASA ABoVE grant NNX17AE44G. We extend our sincere appreciation to everyone involved in the design, implementation, and maintenance of Google's Earth Engine API. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government. N.J.P. conceived and designed the study, wrote the initial manuscript, and executed the analyses. All authors contributed to scientific writing and interpretations. A web interface generated in Google Earth Engine allows the spectral metrics to be generated from the Landsat Archive. Access can be provided on request.
Funding Information:
This research was primarily supported by the United States Geological Survey (USGS) Biologic Carbon Sequestration Assessment Program (LandCarbon) and the National Aeronautics and Space Administration (NASA) Arctic-Boreal Vulnerability Experiment (ABoVE). A portion of the work was performed under USGS contract G08PC91508. N.J.P. acknowledges additional funding support from the University of Minnesota’s (UMN) Doctoral Dissertation Fellowship and the Marvin E. Bauer Remote Sensing of Natural Resources Fellowship, and thanks Vipin Kumar (UMN) and Thomas Burk (UMN) for stimulating discussions related to spatial and temporal data mining. We also thank A. David McGuire (University of Alaska Fairbanks) and two anonymous reviewers for constructive comments that helped to improve this manuscript. S.J.G. acknowledges support from NASA ABoVE grant NNX17AE44G. We extend our sincere appreciation to everyone involved in the design, implementation, and maintenance of Google’s Earth Engine API. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government. N.J.P. conceived and designed the study, wrote the initial manuscript, and executed the analyses. All authors contributed to scientific writing and interpretations. A web interface generated in Google Earth Engine allows the spectral metrics to be generated from the Landsat Archive. Access can be provided on request.
Publisher Copyright:
© 2018 John Wiley & Sons Ltd
Keywords
- Arctic
- boreal forest
- coastal processes
- glaciers
- insect damage
- shrub expansion
- surface water
- thermokarst
- time-series analysis
- wildfire
