Landscape Change Detected over a Half Century in the Arctic National Wildlife Refuge Using High-Resolution Aerial Imagery

Abstract

Rapid warming has occurred over the past 50 years in Arctic Alaska, where temperature strongly affects ecological patterns and processes. To document landscape change over a half century in the Arctic National Wildlife Refuge, Alaska, we visually interpreted geomorphic and vegetation changes on time series of coregistered high-resolution imagery. We used aerial photographs for two time periods, 1947-1955 and 1978-1988, and Quick Bird and IKONOS satellite images for a third period, [2000][2001][2002][2003][2004][2005][2006][2007]. The stratified random sample had five sites in each of seven ecoregions, with a systematic grid of 100 points per site. At each point in each time period, we recorded vegetation type, microtopography, and surface water. Change types were then assigned based on differences detected between the images. Overall, 23% of the points underwent some type of change over thẽ 50-year study period. Weighted by area of each ecoregion, we estimated that 18% of the Refuge had changed. The most common changes were wildfire and postfire succession, shrub and tree increase in the absence of fire, river erosion and deposition, and ice-wedge degradation. Ice-wedge degradation occurred mainly in the Tundra Biome, shrub increase and river changes in the Mountain Biome, and fire and postfire succession in the Boreal Biome. Changes in the Tundra Biome tended to be related to landscape wetting, mainly from increased wet troughs caused by ice-wedge degradation. The Boreal Biome tended to have changes associated with landscape drying, including recent wildfire, lake area decrease, and land surface drying. The second time interval, after~1982, coincided with accelerated climate warming and had slightly greater rates of change.

Landscape impacts of 3D‐seismic surveys in the Arctic National Wildlife Refuge, Alaska

“…The numerous small thermokarst ponds (up to ~5 m diameter) are caused by thawing of the upper surface of ice wedges that separate the ice‐wedge polygons. Thermokarst such as this has recently become widespread across large areas of undisturbed tundra in northern Alaska, and is now common on upland surfaces of the 1002 Area (Jorgenson et al 2018) (photo: M. Nolan).…”

“…Thermokarst occurred due to trails on ice‐rich permafrost in the 1002 Area, which thawed and caused ground subsidence and formation of thermokarst depressions (most commonly, pits and troughs above degrading ice wedges) after medium‐ or high‐level initial disturbance (Appendix : Fig. S15, Jorgenson et al 2018). This process was not evident in the first few years (Fig.…”

“…9), presumably due to the warming climate and positive feedbacks from impounded surface water. A recent remote‐sensing interpretation of landscape change (1949–2007) estimated that ice‐wedge degradation had changed 12% of the Arctic tundra within the northern foothills and coastal plain of the Arctic NWR (Jorgenson et al 2018).…”

Tracking the Land Use/Land Cover Change in an Area with Underground Mining and Reforestation via Continuous Landsat Classification

“…The former usually causes loss of vegetation, destruction of buildings, and soil degradation, while the latter results in reconstruction of the modified LULC through activities such as reforestation [9][10][11][12][13][14][15][16]. Monitoring LULC changes can provide critical information related to eliminating disturbances and developing new land management plans, which will benefit both the environment and the management of a mining area [17][18][19]. Because LULC changes occur at large spatial and temporal scales, traditional field surveys, such as geodetic surveys and cadastral surveys, have proven to be inadequate for documenting dynamic and long-term changes to LULC due to the high costs of fieldwork.…”

Changes in vegetation cover and snowmelt timing in the Noatak National Preserve of Northwestern Alaska estimated from MODIS and Landsat satellite image analysis

“…Recent changes in arctic tundra ecosystems may be related to and landscape wetting or drying and snow cover dynamics. For instance, in a study of land cover change using high-resolution aerial imagery for the Arctic National Wildlife Refuge (ANWR) in northeastern Alaska, Jorgenson, Jorgenson, Boldenow, and Orndah (2018) estimated that 18% of the area had been notably altered over the past 50 years, mainly by wildfire and post-fire succession, shrub and tree increase in the absence of fire, river erosion and deposition, and ice-wedge degradation. Boreal forest cover further south showed changes associated with landscape drying and decreases in lake area.…”