Watching Ferns in the Redwoods for Signs of Climate Change

Fern Watch volunteers at Purisima Creek Redwoods Preserve.
Fern Watch volunteers at Purisima Creek Redwoods Preserve.
The sword fern, one of the most common redwood forest plants, has become prominent in my life over the past few years. This is mostly due to the League’s Fern Watch project, which monitors the health of sword ferns throughout the redwood range. Even though these ferns are common, little is known about their ecology and how they respond to climatic change.

We know that ferns have been around for over 300 million years, so they were here during the time of the dinosaurs. Worldwide, there are around 12,000 fern species, and redwood forests are home to at least 16. Ferns were some of the first plants to have leaves. They evolved from moss and grew in areas with a lot of water. Having leaves gave the ferns a much broader surface to collect sunlight for photosynthesis, which gave the ferns a big advantage over other ancient plants. Ferns remained a dominant plant until flowering plants came along.

Today, the League is looking at how ferns are responding to our changing climate by monitoring twelve different sites in California. Every year the ferns in our plots are counted and measured. These data are then analyzed to compare different regions of the redwood forest and to see how the ferns are responding to changes in rainfall and temperature.

Fern Watch volunteers at Armstrong Redwoods State Park.
Fern Watch volunteers at Armstrong Redwoods State Park.
Over the past few years, we have seen signs of the drought expressed in the ferns. The plants have reduced the surface area of their leaves by approximately 30%, which means they are making smaller or fewer leaves. We are in the midst of collecting the next season of measurements, and with all the rain we received this year, it will be interesting to see if our ferns have bounced back and increased their growth.

Of course, we could not do this work without the dedicated help of our amazing volunteers, some of whom are completely in charge of data collection in their park and are true scientists at work.

Thank you to all our volunteers for your help in researching these interesting plants. Remember anyone can help with our Fern Watch project through our citizen science app.

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About Deborah Zierten


Deborah joined the League's staff in 2013 as the Education & Interpretation Manager. She brings with her extensive experience teaching science, developing curriculum and connecting kids to the natural world.

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