This image of the day from NASA shows how the Normalized Difference Vegetation Index (NDVI), an indicator of photosynthetic activity or the “greenness” of the landscape, has changed over the past three decades (1982-2011) in the far northern latitudes of the Arctic. Rising temperatures in the Arctic are impacting the region's vegetation as described in a March 2013 publication in Nature Climate Change.
Researchers have documented that vegetation seasonality is diminishing, which means that there is an increase in plant growth. While treeless tundra ecosystems of
the circumpolar Arctic were once dominated by grasses, tall shrubs and trees have started to grow in their place. Boreal forests are also responding to a warmer Arctic; these forests showed different responses depending on whether conditions were drier (decreased photosynthesis) or wetter (increased photosynthesis) than usual.
References and related readings are available here.
Information on how scientists use remote sensing to study vegetation from space can be found here.