Motorized recreation impacts wildlife less.

Or at least that's what a review of scientific studies show:

Effects of Recreation on Animals Revealed as Widespread through a Global Systematic Review
Courtney L. Larson, Sarah E. Reed, Adina M. Merenlender, Kevin R. Crooks

-- Non-motorized recreation was ~20% more likely to have negative impacts compared to motorized;
(My own speculation -- fewer corridors and being "warned" by the noise in advance, wildlife may have more time to analyze the situation before reverting to flight-or-fight responses; folks on foot access more areas and surprise wildlife closer and more often.)

-- Snow was worse, with ~30% more negative impacts
(Study's speculation was this was due to increased energy use when wildlife are fleeing human activity)


Here's another article in the same line:

Americans' love of hiking has driven elk to the brink, scientists say

Outdoor recreation has long been popular in Colorado, but trail use near Vail has more than doubled since 2009. Some trails host as many as 170,000 people in a year. Recreation continues nearly 24 hours a day, 365 days a year, said Bill Andree, who retired as Colorado Parks and Wildlife’s Vail district wildlife manager in 2018. Night trail use in some areas has also gone up 30% in the past decade. People are traveling even deeper into woods and higher up peaks in part because of improved technology, and in part to escape crowds. The elk in unit 45, as it’s called, live between 7,000 and 11,000 feet on the pine, spruce and aspen-covered hillsides and peaks of the Colorado Rockies, about 100 miles from Denver. Their numbers have been dropping precipitously since the early 2010s.