Description:
Arctic vegetation has undergone enormous change in the past, most notably in response to the glacial and interglacial periods of the Quaternary. Data from many sources and at several scales suggest that recent climate change is already affecting terrestrial Arctic ecosystems. Comparisons of historical and contemporary aerial photographs provide evidence that Arctic vegetation has already undergone significant shifts in recent decades, foreshadowing changes that are likely to come. Satellite monitoring provides a broad-scale, repeatable measure of these changes. The Normalized Difference Vegetation Index (NDVI) is a remotely sensed index of productivity, allowing spatial and temporal trends to be examined and related to changes observed on the ground. NDVI has been changing steadily since the 1980s over much of the Arctic reflecting an increase in productivity related to the increases in shrub cover. This map presents trends in productivity derived from a 1982–2005 time series of GIMMS-G AVHRR vegetation indices (NDVI). Significant positive trends, showing as green, indicate an increase in both peak productivity and growing season. Negative trends, showing as red, represent forested areas not recently disturbed by fire that declined in productivity.