These pictures were taken from the same spot on the Gateway Arch grounds, looking north toward the Arch. The top photo was taken in October 2014, just before workers started removing all of the rosehill ash trees that lined the walkways. The ash trees were threatened by the emerald ash borer, and for that and other reasons, CityArchRiver, the group that is spearheading the renovation of the grounds, decided to remove them all at once.
They are being replaced by London plane trees, which are said to be much heartier and more disease resistant. The bottom photo was taken last week; the walkways and new paths around the Arch have been reopening in increments, and this area just became available a couple of weeks ago.
It will be a while, though, before the new trees will provide much shade.