Amphibian Populations Predict Forest Health

The Distribution of Amphibian Assemblages of Zero-Order (Headwater) Catchments and their Relationships to the Landscape Mosaic in the Mill Creek Watershed and Adjacent Parklands in Del Norte County, California

Photo courtesy Save the Redwoods League
Photo courtesy Save the Redwoods League

In a forest of towering redwoods, the small creatures scurrying underfoot and splashing into streambeds sometimes go unnoticed as visitors crane their necks toward distant treetops. We should look down, though, say researchers from the Redwood Sciences Laboratory, who visited several state parks to study the ecosystems that surround and support those mighty trees. Researchers Garth Hodgson and Hartwell Welsh pay particular attention to tiny amphibians such as frogs, salamanders, newts in redwood forests, because published studies suggest they are indicators of forest health.

Welsh and Hodgson are not the sort of researchers who stay at their desks. Instead, they can be found wading in streambeds capturing and cataloguing tiny creatures that hop, slither, and crawl through the forest. In the Mill Creek and Rock Creek watersheds near Crescent City, California, they raked through mud and leaves on the stream banks, swung nets into the water, and used transparent view boxes to detect submerged animals. Their goal: to compare the abundance and diversity of amphibians in logged and unlogged redwood forests.

The League-supported pilot study has unearthed some fascinating results that have bearing on how we conserve redwoods. Their data suggest that destruction of the old-growth forest affected more than trees. The Mill Creek property, a former industrially managed tree farm between Jedediah Smith Redwoods State Park and Del Norte Coast Redwoods State Park was protected by the Save-the-Redwoods League, California State Parks, and a host of other supporters to grow the next generation of old-growth in a strategically located watershed. The Mill Creek property today contains mostly young, very small second growth trees. In time however, the forest giants will reclaim the land, but will the critters also return? Disturbingly, the researchers found less than half as many animals in an hour at Mill Creek than on adjacent parklands containing undisturbed forests. Why does the old-growth forest support more animals?

Welsh and Hodgson think that much of the redwood litter and organic material, in which the slimy creatures live and feed, was lost with the removal of the old-growth trees. While Mill Creek’s streams run relatively clear and support one of the strongest runs of the endangered coho salmon, the upland environments will take time to heal.

California State Parks and the League are working together to create an integrated program of watershed restoration at Mill Creek. Scientific studies like those of Welsh and Hodgson will be pivotal in evaluating whether we are on track. In time, we expect our restoration work will give you and/or your successors an opportunity to see more creatures hopping and crawling through the redwoods.

Garth R. Hodgson and Hartwell H. Welsh’s work was published as a report to the Northern Section of California State Parks in 2007. The funding for this project has been renewed for an additional year.

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