Post-fire resiliency & recovery in the Putah Creek watershed
The LNU Complex Fire, which started in August and grew to be the fourth largest in California history, devastated wildlife in the upper Putah Creek watershed. However, the oak woodlands in this region have evolved with fire and, with natural resiliency and a little support from local agencies, recovery is expected.
Ignited by lightning, the LNU Complex Fire charred 363,220 acres, destroyed 1,491 structures, and claimed five human lives. But the tragedy wasn’t ours alone. The fire’s impact on nature has been less publicized.
Putah Creek Council executive director Kenny Liner witnessed such undocumented loss while fighting to save structures alongside Putah Creek’s inter-dam reach. “The fire leaves visible scars on the landscape, but the impact to wildlife can sometimes go unseen. During the fire, I won’t soon forget the deer running to escape the flames or seeing the many birds dead on the ground from the smoke. It was a jarring scene.” Recently, Forbes and ABC News covered unexplained deaths of thousands of birds in the southwest, both suggesting that smoke from CA wildfires may be the culprit.
Days after the fire, a paddle upstream from Solano Lake reveals still smoldering beaver lodges, gasping Western Grebes, and ash-covered deer crowded into narrow riparian strips where a few green shoots survive. Charred and toppled trees line the upper reaches of the creek, creating competition among raptors for remaining perches. Ash smothers the landscape, a black blanket speckled with white patches where fire burned hottest.
Putah Creek Streamkeeper Rich Marovich described other less visible impacts a large fire has on ecosystems. Importantly, winter rain run-off poses a long term threat. “Past fire events have resulted in significant surges of ash and sediment that impacted benthic micro-invertebrates (small aquatic animals and insect larvae that live on the stream bottom ) and buried spawning habitat.”
The California Department of Fish and Wildlife concurs in its “Bio in the Region” report of fire impact on fish: “Fish are directly impacted by wildfires when the heat from a fire increases the water temperature. Fires can also negatively change the water chemistry by increasing phosphorous and nitrogen when plants are burned. Increased phosphorous and nitrogen can cause algae to bloom. Algal blooms…remove oxygen from the water.…Wood ash is very alkaline and can raise the pH of water.” Bald eagles, just beginning their annual sorties downstream in anticipation of the salmon smorgasbord Fall provides, may find their feast wanting this year.
Clearly, the impact of fire lasts well beyond the heat from its last ember. But nature is resilient, and with a little help from local agencies, will recover sooner than the current apocalyptic view would suggest.
California oak woodlands, like the one cradling Putah Creek, have evolved with fire. The subterranean biomass of all oak trees, protected from fire by soil, is greater than what we see above ground. Oak trees can regenerate basal shoots from this root base. This adaptation is especially important to oak species with thin bark, as damage to their essential cambium layer is more likely. Oaks with thicker bark, which protects their cambium layer, push out new leaves in their canopy. Additionally, as a result of the fire, many oaks drop their acorns. The charred landscape, cleared of competing shrub and grass vegetation, allows more light and water to reach these acorns, helping them grow into new oak seedlings. An added bonus of this acorn drop is that it provides a nutrient rich food source for deer, whose browse has been destroyed by flames. The unsightly ash also provides nutrients, enriching the soil for many native plants that quickly begin to re-emerge. According to Putah Creek Council’s native plant manager, Brian Keeley, “The oak woodland should be viewed as a huge, interconnected organism in and of itself. It will never be exactly the same after a fire, but it will recover, adapt and continue to thrive in its new form.”
Dr. Seuss-like clumps of native grasses that line the creek, verdant hippy-hair wigs, became blackened lumps. Yet, only a week after the flames, new green shoots extend from each wig, promising future waterfowl nesting sites once again.
An iconic sight along Putah Creek is playful otters. Because of their varied diet and water-loving lifestyle, fire has less affect on their immediate survival. The fresh blanket of ash along the banks creates an irresistible fur-care treatment, and they can be seen log-rolling in ash piles until sooty from nose to tail. However, otters suffer in polluted water conditions. So the threats to them, and wild salmon that spawn in Putah Creek, are related to post-fire erosion.
Fortunately, creekside land owners and local agencies such as Solano Irrigation District, Solano County Water Agency, and Putah Creek Council, are currently instituting emergency erosion mitigation measures to prevent excess silt and debris from polluting the creek during eventual seasonal rains. Fallen debris is being cleared from feeder creeks along the watershed. Strategically placed boulder vanes, curved lines of large boulders, are installed to trap silt in pools and deflect currents away from sharp turns in the creek where flooding incurs excess erosion. Rice straw, preferred because of its lack of invasive weeds as a result of its aquatic origins, is placed on slopes to help control sheet run-off. Water chemistry is monitored on a continuing basis. This triage care by humans may be able to reduce unnecessary damage and possibly even speed recovery of the Putah Creek “ecosystem organism.”
Meanwhile, popular recreation areas along the creek such as Cold Canyon, Solano Lake Picnic Area, and Solano Lake Campground remain closed while nature recovers.
Fire seems devastating at first, but since most fires do not burn everything, life quickly begins to emerge from the soil, spill out from unburned “habitat islands,” and drift or fly in from surrounding regions to begin repopulating the ecosystem. In time, the landscape will shed its current ashen blanket and snuggle into one of vibrant wildflowers.
Submitted by Leslie Allen, Putah Creek Council member and wild lands enthusiast.
Photos were taken by Leslie along the inter-dam reach of Putah Creek, post LNU Fire. The boulder vane photo was taken at the confluence of Pleasants Valley Creek and Putah Creek.