There is a rule now: https://www.pennfuture.org/Blog-Item-Philly-Tree-Fund-Bill-A-Significant-Step-in-Protection-of-Tree-Canopy

Trees must be replaced depending on the size of the tree, or money must be paid into the Tree Fund to pay for the replacement elsewhere. It's a step in the right direction but needs to be stronger. It's anywhere from 10-20° cooler in tree-filled NW Philly than it is in treeless concrete hellscape South Philly on hot summer days, and it's only getting worse with Parks and Rec cutting down hundreds of mature trees in FDR Park.

Our own Parks system under Kathryn Ott Lovell with the help of the Fairmount Parks Conservancy under Maura McCarthy singlehandedly undid the benefits of years of street tree planting in one fell swoop this summer.

Kind of a joke to worry about what developers are doing when the city isn't subject to the same restrictions.