When Andrew Skurka published Alan Dixon's 3-part series on hammock camping, there were some claims that the West is less accommodating to hammocks due to lack of trees.
Living in the West and the East, I can attest that the West is more sparse, but I've rarely had a problem finding trees. However, I thought it would be interesting to find an image that showed tree density or coverage across the US to validate some of these claims.
To my delight, I found this intense study that gives a good indication of tree coverage in the world. Where I live in Arizona, there is a nice slice of high tree density, and several patches throughout that are probably mountain ranges.
The worst spots: Nevada and the mid-West. Any Nevada hangers here?
Fig. 11. (a) Per state thresholds at which the area estimate of the 500-m tree cover map matches United States Forest Service estimates. This value is found per state by starting at the highest percent tree cover values in the 500-m map and calculating area totals as the tree cover threshold is lowered. For the 500-m map, the area of tree cover greater than or equal to the threshold value shown yields the same area as estimated by the USFS. (b) Application of weighted mean threshold (35% tree cover) which yields an areal match with the Forest Service data for the lower 48 United States. Gray is tree cover greater than or equal to 35%; black is less than 35%.