Background information

In 2002 the European Space Agency launched its Environmental Satellite, ENVISAT, to monitor the Earth using a battery of instruments. One device can detect light reflected back by vegetation. It gauges  plant chlorophyll content, which is one way of measuring how actively plants are growing.

What do the maps show?

The map shows a colour range of cream to green, with shades of brown and yellow in between. Where the satellite has found chlorophyll. the green areas show a high amount has been detected, the yellow slightly less and so on.

What are the permanently bright green areas?

This is evergreen forest so is most obvious at the start of the animation in the winter months. These areas mainly occur in the uplands of Wales and Scotland.

What are the white areas?

White areas such as London show the satellite failed to record vegetation activity because there is relatively little green space.

Similarly, some highland areas of north England, Wales and Scotland are not visible.  As spring develops, some of these gaps disappear as snow covered vegetation is exposed and the chlorophyll signal intensifies.

What is happening as the animation plays?

To begin with, there is a general decrease in vegetation chlorophyll levels as the map turns browner. This is because chlorophyll is still breaking down as most plants are not actively growing. This is often described as the ‘winter burn’.

Then, as plants begin to grow actively, the browns and yellows disappear and the maps turn progressively into a darker shade of green.

What is the difference between 2009 and 2010?

Look for the dramatic difference in timing when the UK ‘greens up’. If you compare the maps in mid-April for instance, the 2010 greening had still not caught up with 2009. This is hardly surprising as we’ve just had the coldest Dec - Feb period for 30 years.

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