What If Gone

Species → Puma

Puma

Puma concolor

fewer than 50,000 breeding individuals across the Americas, declining…
Extinction risk Least Concern
Apex predatorWaterwayTemperate forest
Puma (Puma concolor)
Photo: Charles J. Sharp, Wikimedia Commons (CC BY-SA 4.0)

What if it disappeared?

Impact High
In Zion, Utah

Where increasing human visitation drove the puma out of a canyon, mule deer became more abundant and grazed more intensively, which reduced recruitment of riparian cottonwoods, increased streambank erosion, and caused a decline in the abundance of terrestrial and aquatic species associated with those wooded banks.

Documented
Detail

Ripple, W.J. & Beschta, R.L. (2006). Linking a cougar decline, trophic cascade, and catastrophic regime shift in Zion National Park. Biological Conservation, 133(4), 397–408.

The authors compare two canyons in the same park: Zion Canyon, heavily visited and practically puma-free, and a neighboring, lightly visited canyon where the puma remains present. The canyon with pumas shows markedly higher cottonwood recruitment, more stable banks, and more butterflies, frogs, lizards, and wildflowers — a paired comparison rather than a simple temporal correlation.

In Yosemite

A similar dynamic is proposed for California black oaks in Yosemite Valley, where the puma's decline under human pressure starting in the early 20th century coincides with a mule deer boom and sharply reduced oak recruitment since the 1920s — but suppression of natural fires over the same period complicates attributing a single cause.

Extrapolated
Detail

Ripple, W.J. & Beschta, R.L. (2008). Trophic cascades involving cougar, mule deer, and black oaks in Yosemite National Park. Biological Conservation, 141(5), 1249–1256.

Unlike the paired comparison at Zion, the Yosemite study relies on a single valley tracked over time, without an equivalent control canyon. The authors themselves present this link as a potential rather than an established cascade, because the fire-suppression policy applied over the same period also independently affects oak recruitment.

What's missing to confirm it: A controlled comparison between valleys with and without pumas, comparable to the one at Zion, would help disentangle the puma's effect from that of fire suppression on oak recruitment in Yosemite.

Documentation

Last verified: August 14, 2026