Safari West is home to nearly one hundred individual species, each one sporting its own unique set of adaptations. Our cheetahs depend on fleet-footed prey to survive and have adapted to this challenge by becoming the fastest runners alive. Likewise, our many flying birds have adapted to life in the air with rigid feathers, lightweight skeletons, and impressive respiratory systems. Adaptations come in many forms, from the giant ears of the fennec foxes, to the synchronized breeding of the wildebeests, to the defensive social structures of the cape buffalo. Whether physical or behavioral in nature, life excels in adapting to the many and varied challenges of living on this planet.
The adaptations discussed above all have one thing in common. They are the adaptations of individual species. In this edition of Conservation Corner, we’re going to widen our scope. Rather than look at how one species adapts to a particular challenge, we’re going to explore how an entire ecosystem can adapt. Specifically, we’re going to focus on fire adapted ecosystems which, believe it or not, are far more common than you may think. Chances are, you yourself are part of a fire adapted ecosystem.
A primary reason why I want to address this topic is that Safari West is situated in a region famous for frequent and destructive wildfires. The Mayacamas Mountain range contains several fire-adapted ecosystems, including chaparral and oak woodlands, two distinct habitats present inside the fences of Safari West. Last year, the famous valley fire raged through these habitats in the hills just to the east of us, missing Safari West by a matter of miles. The second reason I want to discuss this topic has to do with one of our neighbors. The Pepperwood Preserve shares a border with Safari West and is dedicated to advancing the health of Northern California’s land, water, and wildlife. They are currently engaged in some very interesting fire related projects.
On June 10th, Pepperwood held a prescribed burn. With weather conditions conducive to a safe and controllable burn, the Pepperwood team (in partnership with Cal Fire) ignited a small patch of land in a very specific place on their property and with a very specific goal in mind. In this case, it was to experiment with a novel method of controlling medusahead grass. Medusahead is a famously detrimental invasive which has proven extremely difficult to combat. According to Michael Gillogly, the preserve manager at Pepperwood, the goal was to start this fire just as the medusahead plants were forming seeds. Many of our local grasses have already seeded and become senescent (turned brown and gone dormant). Their dry stalks provide an excellent fuel supply and a resulting fire should ideally have burned hot enough to kill the developing medusahead seeds, thereby preventing next year’s germination and reducing competition for our local grasses.
Later this fall, there are plans in motion to hold another prescribed burn, this one in the Pepperwood Preserve’s oak woodlands. In our particular region of Sonoma County, our oak forests are increasingly invaded and overtaken by stands of Douglas Fir. There is a theory that suggests that in an uncontrolled environment, regular fires would surge through these forests, clearing out the young fir sprouts and saplings and helping to maintain the oak-dominant status quo. The proposed Pepperwood burn will not only serve to test the theory of fire as a naturally occurring stabilizing force but will also clear the understory; the buildup of dead brush and debris that accumulates between fires. This burn will serve to reduce fuel loads, limiting the risk of a more intense, hotter-burning, and likely out-of-control oak-killing wildfire later.
With that in mind, let’s return to the idea of ecological adaptation. We’re well aware that species adapt to meet the needs of their environment. If certain conditions are universally applied to all the member species of an ecosystem, it follows that the ecosystem itself would need to adapt as well. This concept can be readily identified in extreme environments. In deserts, we find plants that are capable of storing tremendous amounts of water and animals that consume those plants rather than waste energy searching for surface water. The interplay of many arid-adapted organisms makes for an arid-adapted ecosystem. Likewise, ecosystems found on mountain tops are generally composed of plants that can bear up under the heavy loads of snow or go dormant beneath it, and animals which either leave the area when winter approaches, or store up supplies to survive it (either in caches or in the case of bears and bats, in their own bodies). The details of fire-adapted ecosystems may be less obvious but in many cases, they are far more fascinating.
Long before humans came on the scene, fires were scouring the landscape. The most frequent sources of ignition were likely lightning strikes although volcanoes, sparks caused by rock slides, and spontaneous combustion can also start fires. In a truly wild environment either without humans or without our ability to fight these fires, they burn unchecked, moving where the fuel supply and wind take them and consuming what there is to be consumed. It’s important to note that naturally occurring fires wouldn’t often have looked like the raging wildfires we’re used to watching on the news. They would have burned less intensely, covered less ground, and in forested areas at least, left much unburnt.
Trees and other plants grow and die at fairly predictable rates meaning that the fuel load of dry plant material in the environment increases at a fairly predictable rate as well. While naturally occurring fires are less predictable, there is still a degree of regularity in their occurrence. This regularity means that while truly devastating stand replacement fires—fires that completely clear a region of standing plant life—would still occur, they would occur less frequently.
Many plants have adapted to this historical fire regime. In our own backyard, we find knobcone pines which depend on these relatively cool-burning and fast-moving fires to reproduce. When the knobcone produces seeds they are contained within a tightly bound pinecone that is coated with a waxy resin. These cones drop to the forest floor where they wait, more or less dormant. Should one of these fast-moving understory fires burn through during the up to half-a-century in which those seeds are viable, several things will happen. Competing for low-level growth will be burned away, adding some fertilizer to the generally poor soil the knobcone thrives in and allowing more sunlight to reach the ground. At the same time, the heat of the fire will have melted away the waxy coating on the pinecone and caused the scales to spread away from one another, releasing the seed into a freshly fertilized and relatively competition-free environment.
In the case of tall, mature pines, they usually sport a thick layer of insulating bark and a tall expanse of the trunk between the understory growth and their lowest branches. Both of these features serve to protect the tree from the semi-regularly occurring low to medium intensity fires. But what about plants that can’t grow so tall or thick? In the chaparral regions of the Sierra foothills, we find many fire-adapted plants of a different type. From the manzanitas, we’re familiar with the back acreage of Safari West, to ceanothus, chamise, and scrub oak, there are numerous plants that are both highly flammable and low growing. Chaparral areas in California often grow so dense and thick we can’t walk through them except on cut trails. Manzanita burns readily and usually to the ground. Ceanothus have beautiful glossy leaves that are coated with a flammable resin. For these plants and their fire-prone and fuel-rich environment, the goal is not to survive fire but to burn away and make space for the seeds left behind. These seeds are often dropped by their parent plants and lie dormant in the soil until a fire burns through. The high heat of the fire wakes the seeds from dormancy and the first spring after a fire will see a surge of new manzanitas pushing through the ash-coated soil. As humans with homes at risk, we tend to think of wildfires as forces of unrelenting destruction but it’s important to recognize that destruction and creation often go hand in hand.
At least under normal circumstances. What happens if that pattern of burning is interrupted? Thanks to well-meaning but misguided fire prevention policies in place over the last several decades, the fire regime in many if not most ecosystems has been disrupted (Smokey the Bear, you may share some blame in this). Well-intentioned, but ill-conceived policies had our fire fighters snuffing out every possible blaze in order to prevent ravaging, expensive, and sometimes deadly wildfires. The problem with this system is that it has allowed a nearly unrestricted buildup of flammable debris. In forest ecosystems, this can be seen in the dense buildup of carpets of pine needles accompanied by fallen logs and the desiccated remains of low shrubs starved of light by overgrown stands of mature trees. In grasslands, this same buildup is present though generally less obvious. Most grazing animals prefer tender green shoots of grass and will avoid eating the dried stalks of senescent plants. Without fire, those stalks compost and decompose but at a slower rate and accumulate in dense mats of highly flammable material. In the long run, the very act of preventing fires raises the near inevitable probability of a catastrophically intense fire occurring later on.
Besides the dangers posed by accumulated fuel, the occasional fire has numerous additional benefits in a fire adapted ecosystem. It tends to restrain the incursions of non-fire-adapted invasive species (an idea being tested with the Pepperwood burn) and recycles nutrients back into the soil. This second point is familiar to those of us from agricultural areas. The burning of fields after the annual harvest is still widely practiced and while there are downsides in the form of air pollution, there are clear benefits as well. As the left over vegetation is rendered into ash, the nutrients extracted from the earth by the growing plants are recycled and reintroduced into the soil. If you’ve ever stumbled into a recent burn area a few months after the fire, you no doubt noticed the eruption of greenery pushing through the ash. Sudden sunlight reaching freshly fertilized soil triggers abundant growth. That sudden growth attracts wildlife; herbivores to nibble the succulent shoots and carnivores to stalk the herbivores.
Humanity has a long, involved history with wildfire. Many if not most tribes of native Americans have a history of prescribed burning. The fires started by these pre-Columbian civilizations were used for many reasons, among them to improve soil for crops just as we do today, but also to drive game, clear trails, fireproof settlements (by clearing the land around them), and create areas of sprouting greenery that attracted deer, elk, bison, and other animal sources of food. For thousands of years, human beings have understood the importance and utility of fire in the environment. The mistake of the last century has been to treat every fire the way we treat those sparked by a discarded cigarette of fallen power line.
When the Pepperwood Preserve sparked their fire June 10th, they added new data to our increasing understanding of the role of fire in our ecosystem. We’ve come a long way from the days of viewing fire as intrinsically and exclusively destructive, but the science still has a long way to go. As Californians, we have a tense and anxious relationship with fire. While the occasional catastrophic fire will undoubtedly occur just as they did in the pre-human world, a few simple changes in practice and policy can both reduce their occurrence and increase the health of our fire adapted ecosystems. Fires caused by humans, those started by a car crash or neglected campfire, those should be fought and brought under control. Fires that we had nothing to do with, the lightning started fires that typically occur when winds are low and humidity is high, those we should let burn unless there’s undue risk to life and property. Difficult though it may be to watch a stand of trees burn or to witness a herd of panicked antelope fleeing a brush fire, the trade off is the beauty of a forest reborn and the site of those same antelope nibbling on bright green shoots a month or later. Fire, not always our friend, is nonetheless and ally in keeping our ecosystems healthy, stable, and viable.