Species → Moose
Moose
Alces alces
What if it disappeared?
Impact ModerateOn Isle Royale, moose abundance or scarcity can be read directly in the growth rings of balsam fir, which track the cycle in reverse: when moose become scarce, fir growth rebounds sharply — a multi-decade record etched into the wood itself.
DocumentedDetail
McLaren, B.E. et Peterson, R.O. (1994). Wolves, Moose, and Tree Rings on Isle Royale. Science, 266(5190), 1555–1558.
By analyzing balsam fir growth rings on Isle Royale, where wolves and moose have coexisted in a closed system for decades, the authors show a direct link between moose abundance (itself tied to wolf predation pressure) and the browsing that slows tree growth — one of the few records this long of a complete trophic cascade.
Climate itself — through snow depth and wolf pack cohesion — modulates wolves' hunting success on moose, blurring the simple wolf → moose → fir link observed over the long term.
ExtrapolatedDetail
Post, E., Peterson, R.O., Stenseth, N.C. et McLaren, B.E. (1999). Ecosystem consequences of wolf behavioral response to climate. Nature, 401(6756), 905–907.
Years of deep snow favor pack hunting and increase wolves' predation success on moose, which then feeds through to browsing and forest growth. It's the same island, the same trio of species, but an additional factor (climate, via the North Atlantic Oscillation) that modulates the whole system from year to year.
What's missing to confirm it: The exact contribution of climate relative to wolf and moose density alone in the year-to-year variation observed remains debated.
Documentation
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Isle Royale Wolf Population Nears Historic High as Moose Numbers Plummet — Michigan Technological University, Isle Royale Winter Study 2026
Accessed August 10, 2026
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McLaren & Peterson (1994) — Wolves, Moose, and Tree Rings on Isle Royale, Science
Accessed August 7, 2026
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Post et al. (1999) — Ecosystem consequences of wolf behavioral response to climate, Nature
Accessed August 7, 2026
Last verified: August 7, 2026