Yellowstone's Destabilized Ecosystem

Abstract

Historical accounts, park records, and biologists' observations indicated that wintering elk in Yellowstone's northern range were present in low numbers prior to and at park establishment in 1872; increased to 20,000-35,000 by the early 1900s when they heavily impacted the northern-range ecosystem; and declined to 3,172 censused animals in 1968 due to park control efforts. In 1967, the park announced a politically coerced natural-regulation policy terminating park control; and in 1971 posed a natural-regulation ecological hypothesis stating that northern-range elk had been numerous prior to 1872, had not risen to 20,000-35,000 in the early 1900s, and would stabilize at moderate numbers following recovery from control efforts without significantly affecting the northern-range ecosystem. Archaeological and historic evidence, park records, and censuses begun in the 1920s indicate a northern herd of ~5,000-6,000 in 1872, increasing to ~20,000-35,000 in the early 1900s, declining to a censused number of 3,172 in 1968 in response to control efforts, increasing to a census-based number of 21,071-25,920 in the 1980s and 1990s, then declining somewhat after 2000. This book reviews critically the published and unpublished records to test the natural-regulation hypothesis and propose a conceptual model of the northern-range ecosystem with inferences from system changes associated with the four stages of elk abundance, inside-outside exclosure comparisons, and system comparisons inside and outside park boundaries.

The role of large predators in maintaining riparian plant communities and river morphology

“…Adapted from: Ripple and Beschta, 2006a. from elk herbivory following extirpation of wolves in the 1920s have been widely documented (Bailey, 1930;Rush, 1932;Grimm, 1939;Kay, 1990;Chadde and Kay, 1996;Singer, 1996;Ripple and Larsen, 2000;Kay, 2001;Barmore, 2003;Beschta, 2005;Wagner, 2006;Beschta and Ripple, 2009). Additionally, the loss of functional willow communities in the northern range led to abandonment of beaver dams during the 1920-30s with stream incision, unprecedented in the last two millennia, occurring within two decades (Wolf et al, 2007).…”

Intended and unintended consequences of wolf restoration to Yellowstone and Isle Royale National Parks

“…The most pressing issue inside the park was elk population fluctuations without a robust predator community and no human control. Since about 1923, following dramatic reductions in predators, elk were culled (e.g., killed or shipped to other locations) by the NPS inside and Montana hunters outside the park because of perceived damage to the vegetation (Houston, 1982; Wagner, 2006). How would wolves affect this situation inside the park and what would they do to game outside park boundaries was a crucial question.…”

Can large carnivores change streams via a trophic cascade?

“…With the effective dismantling of YNP's large carnivore guild in the early 1900s, herbivory of Rocky Mountain elk ( Cervus elaphus ) in Yellowstone's northern ungulate winter range or “northern range,” began increasing with resulting impacts upon plant communities (Grimm, ; Keigley, ; Wagner, ). One consequence of increased ungulate herbivory for young deciduous woody species was that the number of seedlings and root sprouts capable of growing into tall saplings and trees (i.e., recruitment) began to decline over time.…”

“…spp.) was almost completely absent during the last half of the 20th century (Beschta, 2003(Beschta, , 2005Kay, 1990;Painter, Beschta, Larsen, & Ripple, 2014;Ripple & Larsen, 2000;Wagner, 2006). Elk herbivory similarly impacted other woody species such as willows (Salix spp.…”