Vernal Pools Diverse, Ephemeral

Apr 15, 2019

April 15, 2019 — All over Mendocino County, there are tiny, temporary wetlands that can easily pass for puddles. In a way, that’s exactly what they are. According to Chuck Williams of the Sanhedrin Native Plant Society, they’re just puddles that haven’t been run over by cars.

But before we dismiss the value and beauty of puddles — and before the summer sun dries them out naturally —  let’s take a look at just a few of the vernal pools that are quietly providing a home to tiny sunflowers, polliwogs, salamanders, and Davy’s semaphore grass, to name just a few of the plants and animals that spend key parts of their life cycles in their shallow, temporary waters. We took a field trip with Williams through inland Mendocino County on a warm spring day, to find out what’s going on in these fleeting wetland microcosms.

The pools foster a breathtaking diversity of life. Some are refuge to one or two varieties of water-loving plant, which change throughout the season and from year to year. Others are crammed with Meadowfoam, Blennosperma, reeds, and tiny shrimp or clams. A forty-foot pond could be the equivalent of two different zip codes, if one side is significantly deeper than the other. And two large ponds in the burn zone at the Hopland Research and Extension Center are worlds apart, though they are only a few minutes apart. At Lake Mendocino, there’s a complex of pools that was accidentally created by dam-building and drainage operations.

Vernal pools, which often occur on desirable flat land, are threatened by development, traffic, and voracious invasives, like every other fragile native ecosystem.

And, in the most poignant lesson of all, they can easily be destroyed by efforts to make them permanent.