1. A computer-implemented method for detecting trees in aerial imagery comprising: training a pixel-level classifier to assign a tree or non-tree label to each pixel in an aerial image; for respective pixels of an aerial image, labeling the pixel as being either tree or non-tree; segmenting tree and non-tree regions based on the labels of the respective pixels; and locating, with a processor-based system, individual tree crowns in the segmented tree regions of the aerial image using one or more tree templates such that the segmenting reduces a number of false positives from the locating step.