Impact of rewilding, species introductions and climate change on the structure and function of the Yukon boreal forest ecosystem

Abstract

Community and ecosystem changes are happening in the pristine boreal forest ecosystem of the Yukon for 2 reasons. First, climate change is affecting the abiotic environment (temperature, rainfall and growing season) and driving changes in plant productivity and predator–prey interactions. Second, simultaneously change is occurring because of mammal species reintroductions and rewilding. The key ecological question is the impact these faunal changes will have on trophic dynamics. Primary productivity in the boreal forest is increasing because of climatic warming, but plant species composition is unlikely to change significantly during the next 50–100 years. The 9–10‐year population cycle of snowshoe hares will persist but could be reduced in amplitude if winter weather increases predator hunting efficiency. Small rodents have increased in abundance because of increased vegetation growth. Arctic ground squirrels have disappeared from the forest because of increased predator hunting efficiency associated with shrub growth. Reintroductions have occurred for 2 reasons: human reintroductions of large ungulates and natural recolonization of mammals and birds extending their geographic ranges. The deliberate rewilding of wood bison (Bison bison) and elk (Cervus canadensis) has changed the trophic structure of this boreal ecosystem very little. The natural range expansion of mountain lions (Puma concolor), mule deer (Odocoileus hemionus) and American marten (Martes americana) should have few ecosystem effects. Understanding potential changes will require long‐term monitoring studies and experiments on a scale we rarely deem possible. Ecosystems affected by climate change, species reintroductions and human alteration of habitats cannot remain stable and changes will be critically dependent on food web interactions.

Demography of snowshoe hare population cycles

“…However, food supplementation experiments revealed that supplemental food had little or no effect on snowshoe hare reproduction, survival, or population growth (O’Donoghue and Krebs , Krebs et al , Krebs et al ). Furthermore, winter shrub biomass in Kluane has been increasing because of climate change over the last three decades (Boonstra et al ); however, there has been no concomitant improvement in hare reproductive output during this period. Second, chronic stress due to predator chases could potentially depress reproduction during the decline and low phases.…”

Impact of climate change on the small mammal community of the Yukon boreal forest

“…The harvest of Canada lynx, grizzly and black bears, moose, caribou, and thin-horn sheep are co-managed by First Nations and other governments with a conservation objective. Given the problems that large mammals face in most parts of the Earth, our area is again a contrast at present (Ripple et al 2014;Boonstra et al 2018) because none of these large mammal species are under threat.…”

“…Winter temperatures (November to April) have been increasing on average since 1970 by 0.47 °C per decade (see Fig. 2 in Boonstra et al 2018). Summer temperatures during the growing season are increasing more slowly, at 0.26 ºC per decade ( Fig.…”

“…This cycle affects many, but not all, species in the food web and has been reviewed extensively in Krebs et al (2001Krebs et al ( , 2018a. We concentrate here on the small mammal community, only one part of the boreal forest fauna described in Krebs et al (2001) and in Boonstra et al (2018).…”

Population cycles in voles and lemmings: state of the science and future directions

“…). Earth's climate is changing; climate change will inevitably affect the distribution and abundance of many plant and animal species via changes in the abiotic environment, primary productivity and species interactions (Boonstra et al. ). There exists some evidence that climate change may dampen the dynamics of some cyclic rodent populations (e.g.…”