"In making the announcement, the NPS touted the environmental effects of the new policy, saying the e-bikes can reduce greenhouse gas emissions when used as an alternative to cars and motorcycles and improve poor air quality at national parks by reducing traffic congestion."

Wut. We are talking about trails that are not open to cars and motorcycles. Is the suggestion here that park visitors with e-bikes will use them instead of motor vehicles to get to trailheads?

BTW...PA state parks have this same rule. If it's open to bikes it open to e-bikes. I noticed a few on the Lehigh Gorge Trail, which is a 20+ mile rail trail.