Study
Stream hydrology limits recovery of riparian ecosystems after wolf reintroduction
Marshall, Kristin N.; Hobbs, N. Thompson; Cooper, David J.
Proceedings of the Royal Society B: Biological Sciences, 2013
Willow growth in northern Yellowstone was studied under experimentally crossed treatments: browsing excluded or permitted, and water tables raised by simulated beaver dams or left at current levels. Growth was followed over years.
- Studied in
- Salix, Cervus canadensis, Castor canadensis
- Sample size
- willow plots under crossed browsing and water-availability treatments
Reduced browsing alone did not restore willow to its former stature. Substantial recovery required raised water tables as well — the hydrological conditions that beaver dams had previously maintained.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
Riparian recovery in this system is limited by hydrology as well as by browsing, so reducing elk browsing alone is insufficient.
How NatureHQ reads it
The record that complicates the popular Yellowstone story most usefully, because it does not deny the browsing effect — it shows browsing was not the only thing missing. Beavers had been removed long before the wolves went, and their dams held the water table high. Restoring the predator does not restore the hydrology, and a landscape can pass through changes that are not simply reversed by putting one species back.
- Plot-scale experiment in one part of one park; scaling to the whole system involves assumptions.
- Simulated dams are not beavers, and reintroducing the animals would change more than water tables.
Two things the willows were missing
Wolves returned and elk browsing fell. So why had the willows along Yellowstone’s streams not come back?
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Trophic cascades
In Yellowstone, reducing browsing alone did not bring the willows back. They also needed high water tables — which beaver dams used to supply, and the beavers had gone long before the wolves did.
Beavers
Beaver dams raise water tables, trap sediment and turn running water into standing water across whole catchments. Before trapping they did this across most of a continent — and then they did not.
Published by: The Royal SocietyPublished by the Royal Society.
doi.org/10.1098/rspb.2012.2977
Checked against Crossref on 2026-09-28, and they agree on the title, the authors and the year.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-09-04.