BBC News - Crane ride high above the forest canopy:
How do you accurately measure the heights of some of the world's tallest trees?
Scientists from Colorado State University and Nasa are compiling a unique satellite map that details the heights of the forests - which they say will help them build an inventory of how much carbon they store, and how much is recycled back into the atmosphere.
At the same time, botanists on the ground are tagging and measuring trees to establish an inventory of woodland areas in specific locations. One of these is the Gifford Pinchot National Forest in south west Washington.
At the Wind River Canopy Crane Research Facility scientists from the University of Washington are following the life cycles of trees such as the Douglas Fir, many of which are over 500 years old. They are using an industrial crane that lifts researchers over 60 metres in a gondola, to above the tree canopy.