NeighborhoodNewspapers.com is citing a study in which the tree canopy in Sandy Springs increased by 3% since from 2010. This is a big jump in a 3-year period. According to the Wikipedia entry Sandy Springs has 24,142 acres of land area. The report from the study states that the tree canopy in 2010 was 59% and the tree canopy in 2013 was 62%. Using these numbers we would conclude that Sandy Springs had 14,244 acres of tree canopy in 2010 and 14,948 acres of tree canopy in 2013, an increase of approximately 724 acres. This equates to over 547 football fields of new tree canopy! That is a lot of new growth in only three years Furthermore, these calculations assume that there was no loss. A quick look at some of the imagery from the 2010-2013 time period (thanks Google!) shows that there was tree loss in the area due to development. In order to make gains of 3% there had to certainly be an increase of more than 724 acres sq km of new tree canopy over this time period.
|Imagery from 2010. Trees in the red circle were removed over the 3-year period.|
|Imagery from 2012 in which tree loss is clearly visible.|
Based on my quick assessment of the imagery I am inclined to believe that it is more likely that Sandy Springs lost tree canopy over the 2010-2013 time period. In the short term it is far easier to document tree canopy loss than gain as trees are easy to remove but hard to grow. The fact is that based on the available data we don't know if Sandy Springs lost or gained tree canopy over these 3 years, and it is highly unlikely that the 724 new acres of tree canopy appeared in such a short time. Although we have published methods that provide increased precision for mapping tree canopy change, it is very difficult to accurately quantify changes in tree canopy over a short time period, such as was done in this study, without LiDAR. My recommendation is that Sandy Springs wait 5 to 10 years between future tree canopy assessments and use the iTree protocols to analyze historical changes.