Detecting the drivers of forest change in Alaska and the Arctic
Scientists are using satellites to collect detailed data on forest change in remote parts of Alaska and the Arctic.
Rapid warming in the Arctic and boreal regions of Alaska is affecting boreal forests and tundra ecosystems in a number of ways. Higher temperatures and changes in precipitation have led to a higher incidence of wildfire and increased tree mortality from
Satellite data collected over the past thirty years show that far northern North America is getting greener. Vegetation density data (1–8-kilometer resolution) from the Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments show overall growth (greening) trends in tundra vegetation and dieback (browning) trends in boreal forests, with areas with a greening trend dominating (see figure). NASA research has produced new information products at finer spatial scales that, alongside interagency modeling efforts, provide a more detailed understanding of the underlying causes of these trends and their impacts on
Interagency atmospheric modeling studies supported by DOE, USGS, NSF, and NASA have provided further understanding of the drivers and impacts of these trends on the environment. Analyses of surface carbon dioxide measurements from 1986–2006 suggest that in spite of overall browning trends and changes in fire frequency, the boreal forest region stored more carbon than it released to the atmosphere over this time period. Further north, despite an observed greening trend the Arctic region has not contributed to carbon emissions overall, with the increases in carbon uptake from the atmosphere in summer balanced out by increased releases during the fall .
2 Raynolds, M.K. and D.A. Walker. 2016. Increased wetness confounds Landsat-derived NDVI trends in the central Alaska North Slope region, 1985–2011. Environmental Research Letters 11 (8). https://doi.org/10.1088/1748-9326/11/8/085004
3 Carroll, M., M. Wooten, C. DiMiceli, R. Sohlberg, and M. Kelly. 2016. Quantifying Surface Water Dynamics at 30 Meter Spatial Resolution in the North American High Northern Latitudes 1991–2011. Remote Sensing 8. http://dx.doi.org/10.3390/rs8080622
4 Welp, L.R., P.K. Patra, C. Rödenbeck, R. Nemani, J. Bi, S.C. Piper, and R.F. Keeling. 2016. Increasing summer net CO2 uptake in high northern ecosystems inferred from atmospheric inversions and comparisons to remote-sensing NDVI. Atmospheric Chemistry and Physics 16: 9047–9066. https://doi.org/10.5194/acp-16-9047-2016