Evaluating the efficacy of a local tree protection policy using LiDAR remote sensing data

This study evaluated the efficacy of a tree removal permit regulation that the city of Lakeway adopted in 2002 to protect trees in private lands by comparing the levels of tree protection in Lakeway with those in the village of The Hills, a neighboring municipality without such a regulation. The level of tree protection was assessed by mean canopy height (MCH) and percent canopy cover (PCC) of a parcel derived from light detection and ranging (LiDAR) data and aerial photography, respectively. MCHs and PCCs were estimated for single family residential parcels where houses were constructed for four years before (1998–2001) and after (2003–2006) the adoption of the tree removal permit regulation by Lakeway. Holding parcel size and vegetation condition before housing construction constant, MCHs of the parcels developed in 2003–2006 were statistically significantly higher in Lakeway than Hills. Because the difference in MCHs was not found in the parcels developed in 1998–2001, it is concluded that Lakeway's tree removal permit regulation has been successful to protect trees in private lands. Unlike MCHs, PCCs between the two municipalities were not statistically significantly different in the parcels developed in each of the two study periods. This result may indicate that PCC is not as accurate in assessing the level of tree protection as MCH due to the inability of PCC to distinguish existing mature trees from young ones planted after construction. Based on these findings, it is recommended that urban planners use LiDAR data to study urban forests.

► A tree removal permit regulation effectively protected trees in private lands.
► Trees were taller in a municipality with a tree removal permit regulation than one without such a program.
► Aerial photography cannot distinguish mature trees and nursery ones planted after construction.
► LiDAR data is more useful to study urban forests than aerial photography.