When grey wolves returned to Yellowstone National Park in 1995-96 after a 70-year absence, scientists expected a reduction in elk numbers; however, what they didn’t expect was the recovery of vegetation that followed. According to a 2025 synthesis published in Global Ecology and Conservation , average willow height on Yellowstone’s northern range increased from 92 cm in 2001 to 192 cm in 2020, while willow crown volume expanded by approximately 1,500%. Notably, researchers argue that the recovery represents a strong documented trophic cascade, underscoring how restoring a top predator can reshape an ecosystem from the top of the food chain to plants growing along streams.
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