This blog post is merely to provide a visual illustration, by way of a map, of the expansion of the California Scrub-Jay across Washington, British Columbia, eastern Oregon, Idaho, and even Montana (one record so far). It is intended to complement my more detailed article, “Tracking Expansion of the California Scrub-Jay Into the Pacific Northwest”, in the Washington Ornithological Society (WOS) News, August-September 2021 edition.
As becomes clear in the article, these are not hard lines. The jays are advancing gradually, not in a solid wave. Typically, a single jay will appear well outside the known range (e.g. Spokane). Within a year or two, there will be several. Then they’ll be breeding. Then they will begin expanding further. Meanwhile, a wave of jays will be backfilling the new territory, with densities increasing annually. The lines in this map are as much art as science, but are intended to show the primary region were jays were “regular and expected”. There were always outliers, pioneer dispersers expanding the range. Records beyond the 2020 line are shown as pale blue dots.
The jay’s expansion, when considered in the context of timing and trends in other species, is likely a function of a warming climate combined with suitable food sources. For more discussion of this, see the WOS article linked above.
It will be interesting to see where the 2030 scrub-jay “contour line” will be. I predict they’ll be on Vancouver Island from Victoria to Campbell River, as well as up the Sunshine Coast, up the Okanagan Valley to Kelowna and possibly Kamloops, and east to Idaho, from Coeur d’Alene in the north throughout the Snake River Valley in the south.
After that, they face some formidable hurdles. The biggest obstacles to their expansion further north and east will be habitat with limited food sources (e.g. high mountains). That said, they’ve already shown some ability to travel up mountain valleys and potentially cross the Cascades north of Mount Rainier.
Researchers from UC Davis collect acorns in arid west Texas to plant on their campus in northern California. They estimate their climate in 2100 will be similar to that of Barstow or even Phoenix today. City staff from a town near Portland, Oregon travel to California and Arizona for seedlings they can take home and plant along their city streets. They are preparing for Portland’s weather to become like Sacramento today.
With these regions breaking new heat records annually – Sacramento just topped 90 degrees for the 110th day (and counting) in 2020—and given that trees take decades to mature, the race is on. Birds can fly, mammals can walk, but trees expand their ranges very slowly. Most acorns from an oak end up within a few hundred yards from their home tree.
Climate velocity, the speed at which ecotones are shifting north, is much faster than that. Our climate is changing ten to one hundred times faster than during a global warming event 55 million years ago known as the Paleocene-Eocene Thermal Maximum (PETM). During that “rapid” spike, palm trees successfully migrated to the Arctic circle, but they had thousands of years to make it there.
While trees can’t walk, they can die. Range contraction of trees along their southern xeric (dry) edge is happening in the American West right with the speed of climate change. Blue oak die-offs are widespread in the southern third of their range. From California to Colorado, conifers such as Ponderosa pine and Douglas-fir are disappearing from lower elevations. To quote Davis et al (2019), “In areas that have crossed climatic thresholds for regeneration, stand-replacing fires may result in abrupt ecosystem transitions to nonforest states.” When people talk about California becoming Arizona, the cleanup hitter in that process may be fire, but the first batters are heat, drought stress, and bark beetles. After fires, decreased soil moisture and increased vapor pressure deficit (VPD) associated with climate change are leading to reduced probability of regeneration (Davis et al 2019). In short, many forests are not coming back.
Researchers have discussed facilitating tree migration due to climate change for over a decade (Aitken et al 2008). For over a hundred years, botanists have recognized regional differences within the same plant species, and simple garden experiments have shown that local varieties do better. The standard rule of thumb has always been that local varieties are best; they are adapted to the local ecological niche. Now that is changing.
Recent research is showing that trees are now in the wrong places; the climate has shifted past them. Valley oaks, white fir, Douglas fir, ponderosa pine, Western hemlock, and lodgepole pine seedlings all do better when removed from their original home and moved north (Aitken and Bemmels 2015).
The local trees are becoming misfits in a world that is changing around them. Many researchers are hesitant to fully embrace assisted migration; introducing non-native species has a horrid track record. But they are beginning to study “assisted gene flow”, moving hardy trees from the southern end of a species’ range to the north end. Cities, on the other hand, are beginning to see trees as more than just aesthetically pleasing; they are critical infrastructure, providing shade and reducing urban temperatures. So the cities and towns are moving faster, boldly cultivating trees from the dry Southwest into the Pacific Northwest.
Tree migration is also critical for the range expansion of animals. Without the trees and other vegetation, many birds, mammals, and other forms of life have no habitat rungs on the ladder to enable them to move north as well. Anna’s Hummingbirds now winter in Canada and even Alaska, largely due to ornamental plantings. The Oak Titmouse, on the other hand, is dependent on oaks, tightly constraining its ability to expand north. It may be that, in the coming decades, oaks and other tree species planted in cities and towns will provide critical refugia for a wide variety of birds and insects seeking cooler climes.
When climatologists predicted that Sacramento would have Phoenix’s weather by 2100, and Portland would have Sacramento’s, they didn’t explain the ecological implications nor the process. Yet it’s apparent that an awful lot of trees need to disappear for the Sierra to look like the rock, grass, and cacti that make up Camelback Mountain in Phoenix.
A new “new normal” every year
This ecological transformation, the likes of which would normally take a thousand years even during a rapid warming event, is happening, driven by rapid climate change. All those trees are flying away in the form of ashes and smoke.
The process, in human and ecological terms, is brutal. Californians experience a new “new normal” each year, each one stunning in its own right. In 2017 we were shocked when 6,000 homes burned in Santa Rosa, killing dozens as people fled in their bathrobes. Despite decades of fires in suburban California, there had never been anything of that magnitude. Before the year was out, the Thomas fire became the largest in state history as it burned thru Christmas and New Year. The next summer, the Carr fire stunned us with an EF-3 firenado that generated 140 mph winds. A few months later, the past was eclipsed when the entire town of Paradise burned, killing 85 people. That may be the largest climate-induced mass mortality event in history.
After a reprieve in 2019, we arrive at 2020, where acreage burned has exceeded two million and three million for the first time. We keep having to adjust our vertical axes to make room for each new year. Five fires burning at the same time in 2020 qualified for the top 20 largest fires in the history of the state. Three of those, still burning as a write, are first, second, and fourth on the list.
Each year has its macabre highlights. This year, over 300 people were rescued by military helicopters, many at night high in the Sierra. For the first time ever, all 18 national forests were completely closed to the public. The National Weather Service had to create a firenado warning. A dystopian pall of smoke created hazardous air from California to Canada for weeks, forcing people into their homes with all windows shut. And my hometown, Woodland Hills, hit 121 degrees, the highest temperature ever recorded in Los Angeles County.
We have heard for years that, with longer and hotter summers and declining snowpack, fire season has grown by months. In 2006, Westerling predicted such an increase in fires that the forests of the western US would become net carbon emitters. The US Forest Service now plans for fire year-round.
A series of academic analyses lays out the factors and processes of Arizonification. Decreased summer rains, as well as warmer winter and spring temperatures, are creating dry and stressed trees. But that’s not all. Summers that have become 1.4C (2.5F) warmer have led to an exponential increase in atmospheric vapor pressure deficit (VPD). It’s getting drier and, more importantly, vegetation is getting drier. This leads to big fires. Williams et al (2019) noted, “The ability of dry fuels to promote large fires is nonlinear, which has allowed warming to become increasingly impactful.” The Camp Fire, which destroyed the town of Paradise, occurred during some of the lowest vegetation moisture ever recorded. Add to that hot dry winds and vulnerable PG&E transmission lines, and the Paradise disaster looks predictable.
To summarize, slightly warming temperatures, even in winter and spring, and less summer rain lead to an exponential increase in dry vegetation, which leads to an exponential increase in large fires, which leads a conversion of habitat from forest and chaparral to the grass and rock-dominated landscapes of arid desert mountain ranges. Sacramento becomes Phoenix. The Sierra and Coast Ranges become Camelback Mountain.
Arizona State University fire historian Prof. Stephen Pyne calls this a new epoch, the Pyrocene. “The contours of such an epoch,” he writes, “are already becoming visible through the smoke. If you doubt it, just ask California.”
Abatzoglou and Williams (2016) conclude, “anthropogenic climate change has emerged as a driver of increased forest fire activity and should continue to do so while fuels are not limiting.” Williams et al repeat this, “Given the exponential response of California burned area to aridity, the influence of anthropogenic warming on wildfire activity over the next few decades will likely be larger than the observed influence thus far where fuel abundance is not limiting.”
In layman’s terms, it’s going to get worse until there’s nothing left to burn.
Here is a partial list of recent research on the increase of fires in California and the western US.