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The heavier than normal rains Napa Valley endured this winter will have beneficial after-effects for plants and animals like birds, fish and the endangered Calistoga popcorn flower.

“Coming off several years of drought, there’s really nothing but a positive from all this rain. The rain flushed out the waterways, cleared the debris, and introduced a great deal of freshwater into the ecosystem,” said Peter Tira, information officer for the California Department of Fish and Wildlife, Regions 3 and 4. Region 3 covers the San Francisco Bay and the Sacramento Delta, while Region 4 covers the Central Valley.

Tira said the fires and smoke in 2017 and 2018 negatively affected pollinators, including bees, moths and other insects. However, this year’s rains provided enough water to support a wealth of grass and other plant life that will increase insect populations. The increase in insects will have a ripple effect extending to birds.

“Insects play a very important role for young birds. When they’re young, they need that protein boost. When birds like turkey and quail are older, they can feed on seeds and grasses,” said Tira.

Surface water on the floodplain also created an abundant food supply for predators.

“The rains forced small animals onto higher ground, making them easy prey for raptors, raccoons, coyotes and foxes,” said Tira.

Napa River fish, fowl, flourish

The rains have also helped freshwater fish that live in and around the Napa River.

“A flow like this moves around wood and stacks up fallen trees in channels. This provides cover for fish. There’s more food for the little bugs that get eaten by salmon, other fish, and birds,” said Jonathan Koehler, senior biologist for the Napa County Resource Conservation District.

However, heavy rains can wash out invasive species like bluegill, bass and catfish.

“They can’t tolerate the big, high flows. Big flows are also bad for beavers because they wash away their dams. People shouldn’t worry about them (however). Beavers always come back,” Koehler said.

Koehler also said heavy rains are critical for maintaining streams and ensuring meadows on the floodplain stay fertile. More vegetation close to the Napa River maintains the health of waterfowl.

“Mallard, teal and other waterfowl use the uplands to nest. More grasses and thicker growth creates more camouflage for hens. Predators will have a harder time finding them. This ensures a better nest result,” said Tira.

Rare Calistoga popcorn flower in bloom

Jake Ruygt, conservation and invasive plant chair for the Napa Valley of the California Native Plant Society, said the increase in frequency and quantity of rainfall is also good news for native plants.

Vernal (or seasonal) pools of water particularly benefit as heavier rainfall generally means that more plants in the pools will germinate.

"If you have really dry years, you don’t get much of a display. When it stays wet longer, you see a higher production of seeds. There is a greater variety of species in bloom,” said Ruygt.

This year, wildflower enthusiasts can expect to see a showy display of sky blue lupines on the hillsides, more goldfields, including the rare Contra Costa goldfields, and several species of popcorn flowers, including the rare Calistoga popcorn flower, Ruygt said. 

"It's named after and limited to two places in Calistoga, in a field near the old gliderport, and in a field off Tubbs Lane. It might be very hard to find plants there, but the habitat is still there," he said. "People often aren't aware of native plants in their area, but it's something to be proud of."

Ruygt added that spots of sediment deposition in the Napa River have created fresh patches of barren ground.

“Spots on sand and gravelbars in the river channel are good places for plants to colonize. You see willows and species that live in gravel pop up, including smartweeds (Persicaria) and willowherbs (Epilobium),” said Ruygt.

Yet heavy rainfall does not ensure that all plants will do well.

“Lupines don’t do well in wet ground. They like a little bit drier weather. The timing of the rain matters. What you may see is a flush of growth for native species early in the spring. They’ll have their moment and then slowly fade in visibility. You’ll see invasive species become more prominent later in the season,” said Ruygt.

The heavy rains coming so soon after the wildfires is likely to promote growth in species that needed space to regrow.

“Some plants dropped their seeds in the ground for decades. The seeds were stored in there, waiting. The fires burned off a lot of the shrub canopy. Last year many plants showed up that had not been seen for many years. Some may return again this year,” said Ruygt.   

Bill Pramuk, a registered consulting arborist in Napa, said the rains may negatively affect older native oaks.

“Older trees have spent many years growing roots where they get the optimal combination of air, moisture, and good soil. They cannot adapt quickly to sudden changes,” said Pramuk.

Pramuk said if you have raised the grade of your property and placed fill around native oaks, you should dig carefully around the base of older native oaks. You should look at the root collar, the place where the trunk flares out into the supporting roots.

“(Excavation can) reveal root fungus beginning to grow on bark buried in wet soil,” said Pramuk.

Treating affected trees is key to help preventing them from falling and causing damage to a home or property.

Green growth aids erosion issues

Tira said biologists hope the rains will offset the heat coming in late spring and summer.

“We want that moisture to hold over into summer as long as possible," he said, explaining that dry periods cause algae blooms to form in stagnant bodies of water, like lakes, and consuming the algae is dangerous for dogs. "Fortunately the heavy rains just cleared all of those out.”

Many natural areas in Napa County are now “greened up,” including Cedar Roughs Wildlife Area east of Rutherford.

“The new growth will hold off erosion. The rise in water will increase flow in seasonal rivers and provide food for wildlife large and small. These areas are going to be regenerated in a way we haven’t seen for a long time,” said Tira.

The Knoxville Wildlife Area has recently reopened after damage from the 2018 wildfires, and is a good place for people to see the aftereffects of the rain. It is located in northeast Napa County about 1.4 miles north of Lake Berryessa, is a 21,500-acre area that is part of the 300,000-acre Blue Ridge/Berryessa Natural Area.

“The Knoxville Wildlife Area was partially closed in 2018," Tira said. "The wildfires went through and wreaked havoc. They burned 6,000 acres. Now all that burned area is lush and green with regrowth.” 

Cynthia Sweeney contributed to this story.

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