A Seasonal Trend Analysis (STA) of monthly normalized difference vegetation index (NDVI) imagery for Europe from 1982 to 2007. An area of interest in Germany has been circled. The seasonal response graph shows that vegetation productivity has increased throughout the winter and spring, and to a lesser extent in the autumn between the start of the series in 1982 (the green line) versus 2007 (the red line). The graph also shows that spring has advanced by about a month over this period of time. However, the late summer shows a slight decline in productivity.