For decades, bats have defied scientists’ best ideas for keeping track of individuals, which is crucial to wildlife research. Banding (either legs or forearms) can result in injury, and banded bats are seldom recaptured anyway. Tattoos take too long. Holes punched in their wings are only visible for 5 months.
Tree canopy cover is a vital but impermanent urban asset. “Urban tree canopy” is the extent of the outer layers of leaves (or canopy) of a tree or group of trees. Tree canopy can increase dramatically in a year with excellent growing conditions, and just as dramatically it may disappear in a single season in the face of insect infestations or drought or a change in land use.
If you are old enough and grew up far enough away from Ohio, where Dutch elm disease was identified in the 1930s, you may remember a canopy of mature American elm arching above your street. Today that image exists only in photographs; Dutch elm disease long ago eliminated mature American elm from the city streets and northeastern forests of their native range.