Extensive land cover change across Arctic–Boreal Northwestern North America from disturbance and climate forcing. (17th September 2019)

• Record Type: Journal Article
• Authors: Wang, Jonathan A.; Sulla‐Menashe, Damien; Woodcock, Curtis E.; Sonnentag, Oliver; Keeling, Ralph F.; Friedl, Mark A.
• Is Part Of: Global change biology. Volume 26:Number 2(2020)
• Page Start: 807
• Page End: 822
• Publication Date: 2019-09-17
• Subjects: Arctic -- Boreal forest -- deciduous forest -- evergreen -- forest disturbance -- land cover change -- plant functional type -- remote sensing -- shrub encroachment -- wildfire; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.14804
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: A multitude of disturbance agents, such as wildfires, land use, and climate‐driven expansion of woody shrubs, is transforming the distribution of plant functional types across Arctic–Boreal ecosystems, which has significant implications for interactions and feedbacks between terrestrial ecosystems and climate in the northern high‐latitude. However, because the spatial resolution of existing land cover datasets is too coarse, large‐scale land cover changes in the Arctic–Boreal region (ABR) have been poorly characterized. Here, we use 31 years (1984–2014) of moderate spatial resolution (30 m) satellite imagery over a region spanning 4.7 × 10 6 km 2 in Alaska and northwestern Canada to characterize regional‐scale ABR land cover changes. We find that 13.6 ± 1.3% of the domain has changed, primarily via two major modes of transformation: (a) simultaneous disturbance‐driven decreases in Evergreen Forest area (−14.7 ± 3.0% relative to 1984) and increases in Deciduous Forest area (+14.8 ± 5.2%) in the Boreal biome; and (b) climate‐driven expansion of Herbaceous and Shrub vegetation (+7.4 ± 2.0%) in the Arctic biome. By using time series of 30 m imagery, we characterize dynamics in forest and shrub cover occurring at relatively short spatial scales (hundreds of meters) due to fires, harvest, and climate‐induced growth that are not observable in coarse spatial resolution (e.g., 500 m or greater pixel size) imagery. Wildfires caused most of Evergreen Forest Loss and Evergreen Forest Gain and substantial areas of Deciduous Forest Gain. Extensive shifts in the distribution of plant functional types at multiple spatial scales are consistent with observations of increased atmospheric CO2 seasonality and ecosystem productivity at northern high‐latitudes and signal continental‐scale shifts in the structure and function of northern high‐latitude ecosystems in response to climate change. Abstract : Climate change and disturbances are rapidly altering Arctic–Boreal land cover, but such changes are poorly quantified, confounding studies of northern high‐latitude change. We used multidecadal time series of 30 m satellite remote sensing to map and quantify areas of vegetation change across NASA's Arctic–Boreal Vulnerability Experiment (ABoVE), spanning much of western Canada and Alaska, and found that 13% of the domain experienced land cover change. Fire and logging drove net declines of Evergreen Forest area by 15%, while post‐disturbance recovery expanded Deciduous Forest area by 15% and climate warming expanded Shrub and Herb area by 7%.