Northward expansion of Northern Cardinal, Carolina Wren, Tufted Titmouse, and Red-bellied Woodpecker

A number of recent academic papers have described northward shifts of bird species in both North America and Europe, driven by climate change. These papers usually present aggregated results from dozens of species; they rarely provide details for any specific species. These maps are intended to offer that.

While there are tremendous species-specific differences, non-migratory resident birds (such as Northern Cardinal, Carolina Wren, Tufted Titmouse, and Red-bellied Woodpecker) appear to be the most adaptable and have expanded their ranges the most. This seems to be primarily driven by warmer winters and, for some species, is further augmented by bird feeders.

I created these maps using eBird, so the usual caveats apply– they don’t necessarily include all records (though many historical out-of-range records are indeed included), and eBird reporting, which became widespread only after 2010, continues to increase dramatically each year. To draw the lines, my intent was to capture the primary range area — and more — but I deliberately excluded the furthest ten to fifteen outliers for each line.


Northern Cardinals (once called Kentucky Cardinals) have been expanding north for decades, but have increased their rate.
Carolina Wren is a classic example of a species knocked back by harsh winters, finding some refuge around bird feeders, and then continuing to expand in warmer winters. See a graph of this at my previous post here.
Like many species, Tufted Titmouse has especially expanded northeast up the St. Lawrence River corridor.
To get a feel for what this expansion actually looks like in one place, see the graphs below from Christmas Bird Counts. Similar graphs could be made for all of these species.

For some examples of western species expanding north from California and southern Oregon into the Pacific Northwest, see this post: The invasion of the Pacific Northwest: California’s birds expand north with warmer winters.

I invite you to join the Facebook group dedicated to this topic: Birds and Climate Change.

Two of the academic papers that report climate-driven range expansions in eastern North America are listed below, along with their abstracts.

Prince, K. and B. Zuckerberg. 2016. Climate change in our backyards: the reshuffling of North America’s winter bird communities. Global Change Biology 21(2): 572-585.

Much of the recent changes in North American climate have occurred during the winter months, and as result, overwintering birds represent important sentinels of anthropogenic climate change. While there is mounting evidence that bird populations are responding to a warming climate (e.g., poleward shifts) questions remain as to whether these species-specific responses are resulting in community-wide changes. Here, we test the hypothesis that a changing winter climate should favor the formation of winter bird communities dominated by warm-adapted species. To do this, we quantified changes in community composition using a functional index–the Community Temperature Index (CTI)–which measures the balance between low- and high-temperature dwelling species in a community. Using data from Project FeederWatch, an international citizen science program, we quantified spatiotemporal changes in winter bird communities (n = 38 bird species) across eastern North America and tested the influence of changes in winter minimum temperature over a 22-year period. We implemented a jackknife analysis to identify those species most influential in driving changes at the community level and the population dynamics (e.g., extinction or colonization) responsible for these community changes. Since 1990, we found that the winter bird community structure has changed with communities increasingly composed of warm-adapted species. This reshuffling of winter bird communities was strongest in southerly latitudes and driven primarily by local increases in abundance and regional patterns of colonization by southerly birds. CTI tracked patterns of changing winter temperature at different temporal scales ranging from 1 to 35 years. We conclude that a shifting winter climate has provided an opportunity for smaller, southerly distributed species to colonize new regions and promote the formation of unique winter bird assemblages throughout eastern North America.

Saunders et al. 2022. Unraveling a century of global change impacts on winter bird distributions in the eastern United States. Global Change Biology

One of the most pressing questions in ecology and conservation centers on disentangling the relative impacts of concurrent global change drivers, climate and land-use/land-cover (LULC), on biodiversity. Yet studies that evaluate the effects of both drivers on species’ winter distributions remain scarce, hampering our ability to develop full-annual-cycle conservation strategies. Additionally, understanding how groups of species differentially respond to climate versus LULC change is vital for efforts to enhance bird community resilience to future environmental change. We analyzed long-term changes in winter occurrence of 89 species across nine bird groups over a 90-year period within the eastern United States using Audubon Christmas Bird Count (CBC) data. We estimated variation in occurrence probability of each group as a function of spatial and temporal variation in winter climate (minimum temperature, cumulative precipitation) and LULC (proportion of group-specific and anthropogenic habitats within CBC circle). We reveal that spatial variation in bird occurrence probability was consistently explained by climate across all nine species groups. Conversely, LULC change explained more than twice the temporal variation (i.e., decadal changes) in bird occurrence probability than climate change on average across groups. This pattern was largely driven by habitat-constrained species (e.g., grassland birds, waterbirds), whereas decadal changes in occurrence probabilities of habitat-unconstrained species (e.g., forest passerines, mixed habitat birds) were equally explained by both climate and LULC changes over the last century. We conclude that climate has generally governed the winter occurrence of avifauna in space and time, while LULC change has played a pivotal role in driving distributional dynamics of species with limited and declining habitat availability. Effective land management will be critical for improving species’ resilience to climate change, especially during a season of relative resource scarcity and critical energetic trade-offs.

Carolina Wren + Climate Change vs the Polar Vortex

Like so many species, the Carolina Wren is expanding northward. And, like many of those species, this expansion started decades ago, before any measurable climate change, but has exploded in the past decades with climate change.

This phenomenon is most obvious – and even dramatic – among non-migratory species and short-distance migrants. The same thing is happening in the West (e.g. Anna’s Hummingbird, Turkey Vulture, Red-shouldered Hawk, Great Egret, California Scrub-Jay, Black Phoebe, Townsend’s Warbler, and others).

The Carolina Wren has been expanding north since the 1800s due to habitat recovery after deforestation (Haggerty and Morton, 2020 – the Birds of North America (BNA) species account). What makes the recent Carolina Wren data so interesting is that we can clearly see, in its expansion into Canada, its battle with winter weather conditions.

The raw number of Carolina Wrens reported on Christmas Bird Counts in Canada. Over 95% of these come from southern Ontario. The cold waves marked on the graph were particularly record-breaking and long-lasting.

The species is known for “decimation… by severe winter conditions” (BNA) at the northern limits of its range. The same account notes that “severe winters have apparently been infrequent enough during the 20th century to allow populations to expand and move northward.” Indeed, one of the key conclusions of an analysis of climate change in southern Ontario was that there has been “a decrease in the frequency of cold temperature extremes”.  While the wren is aided against cold snaps by bird feeders, the climate trend, at least in Canada, is in its favor. The report noted an overall average increase of 1.5C.

eBird abundance map. The Carolina Wren has primarily been a species of edge habitat associated with moist southern forests.

As the wren expanded, certain record-breaking and persistent cold waves knocked the population back, where it restarted. It’s also clear that it is restarting from a higher position each time, thus building its numbers and continuing its expansion.

The cold snaps denoted on the graph were particularly severe in southern Ontario. A more detailed look at weather data may reveal a more complicated pattern and even greater correlation to warmer winters.

Predicted range changes for Carolina Wren by National Audubon under 1.5C scenario. This map is fairly accurate as the bird continues to colonize the St. Lawrence River corridor.
eBird map for December 2021 showing colonization from Toronto to Ottawa and Montreal and nearly to Quebec City.
A Carolina Wren fluffed up against the cold. Pic from National Audubon website.

Mapping the expansion of the California Scrub-Jay into the Pacific Northwest

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.

California Scrub-Jays are often first detected at bird feeders in suburban areas. As aggressive nest predators, jays should not be subsidized by anthropogenic food sources. In short, please don’t feed the corvids. Port Townsend, WA. April 2021.

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 expansion of the California Scrub-Jay mimics that of several other species, mostly non-migratory or short-distance migrants, rapidly expanding from California and Oregon into the Pacific Northwest.

The jay’s expansion has already surpassed that predicted by the Audubon Society’s climate model under a 3.0 degree Celsius scenario, shown here.

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.

They seem to be particularly taking advantage of warmer winters in the lower Columbia River Basin.

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.

Like most corvids, California Scrub-Jays are big time cachers, storing extra food for future use. I took this photo in southern California, October 2017, when a family of jays were repeatedly stripping an oak, two acorns at a time, flying over a nearby ridge to cache them, and then returning again and again throughout the morning.

The causes of California’s megafires: Climate change or 150 years of Euro-American mismanagement? Yes and yes.

In a very frank and data-rich webinar, fire ecologist Hugh Safford (USDA Forest Service and research faculty at Department of Environmental Science and Policy at UC Davis) offers “Some ruminations on fire and vegetation trends in California”. He explains the causes of the dramatic increase in megafires and what can be done about it.

A 2,500 year-old tree at Sequoia National Park now needs protection from fires.

The webinar was co-sponsored by the Yolo Interfaith Alliance for Climate Justice and Cool Davis and presented on May 5, 2021.

Safford’s presentation starts at 13:23 of the video. The equally enlightening Q&A session begins at 48:20.

Here is a summary of some of the key points:

  • The annual burned area has been rising rapidly since the 1980s, almost entirely in northern California.
  • This is largely due to fire exclusion caused by the removal of Native Americans as land managers and increased drought and record vegetation dryness caused by climate change.
  • Since 1999, burning over a million acres/yr now occurs regularly; this had not happened before 1999.
  • Pre-EAS (Euro-American Settlement) burning by Native Americans totaled up to FOUR million acres/year (but these were low severity fires that primarily burned the understory and smaller trees).
  • “Euro-Americans, when they showed up in the 1850s, and for that matter today, had no idea how important fire was to the functioning of these ecosystems and they feared it and felt like it was something they needed to stop. After a hundred years of that, it’s really biting us in the butt now because now we have jungles of fuels, we’ve cut most of the big fire-resilient trees out of the system, and when we get the ignitions start we can’t stop the fires anymore. Until about the 1990s, it was easy to put fires out in the forests.”
More mature trees are burning; the acres burned by high severity fires (where more than 90% of trees die) have increased 7x since 2001 in northern Sierra Nevada. 35% of the area of current fires are severe (burn most of the trees); under regular Native burning, this was 5-15%.
  • Pre-EAS forests were at least 40% old growth; current forests are only 6% old growth and highly vulnerable to high severity fires, as they are 4-5x denser than pre-EAS.
  • “Every single fire projection we found in the literature predicts bigger fires, more fires, and more severe fires, basically until we’ve burned so much of California that there actually isn’t much woody vegetation left to burn.”
  • Expect the loss of conifers and an increase in non-native grassland.
  • Changes already underway: loss of blue oak woodland, ponderosa, yellow pine, and subalpine pine; increase in hardwoods. Loss of sage scrub and chaparral in southern California. Many burned areas are quickly invaded by non-native grasses and will not recover. Incense cedar and white fir may become more dominant trees in California forests.
  • Fires in the Coast Range are now destroying chamise and blue oaks with limited evidence of re-sprouting.
  • In the short run, there’s not a lot we can do to manage climate, but there’s a lot we can do to manage fuels.
  • There’s been a huge renaissance, especially among Native tribes, to use controlled burns to manage forests. California’s new fire resilience plan supports the use of controlled burns. Northern Australia has had great success allowing Aboriginies to manage forests. Opportunities are limited, however, because of development.
  • The combination of drought cause megafires in the Sierra to produce “Hiroshima-type landscapes”, burning old growth.
  • How to stop fires: Forest thinning is critical, but it’s not economical to harvest small trees, so the government will have to subsidize it. For example, we can use the cut trees for biomass energy, as it done in Scandinavia. This is the only way to save large old growth trees and healthy forests.  “We have to cut a lot of trees. We don’t have a choice…. We can create forests that can handle large fires, or we can sit around and watch it all vaporize.”

Goodbye California: Reminiscences of a climate refugee

There are a lot of reasons why I’m moving from California to Washington, including family and other personal considerations. But one reason, one big reason, is California’s rapidly changing climate.

It was late February in the Coast Range of northern California when I was wearing shorts and a t-shirt. Dust swirled around my car in the dirt parking lot at Cold Canyon. The car thermometer, warmed by a sun that felt imported from Palm Springs, said 87 degrees; it was actually only 77. A hint of ash, omnipresent since The Fire last summer, remained in the air.

Its oaks torched with little hope of return, Putah Creek Canyon is quickly resembling a sun-scorched canyon in Arizona. Until 2018, only one fire in the area had burned more than 15 square miles. Then the County Fire burned 140 square miles. In 2020, the LNU Complex Fire burned 570 square miles.

The hillsides were green with the new growth of non-native grass, which was responding to a recent heavy rain. That was deceptive. More than half the rain we’d had in the previous eight months came in that single event. We had six inches of rain in all of 2020. Looking beyond the grass, nearly every tree – blue oaks and gray pines – on the hillsides was dead, burnt black and orange monuments to a previous era. For our local blue oak woodland, that era ended last year and, given that recruitment of saplings is unlikely due to heat, fire, and cattle, it was an era that will never return.

Massive die-offs are eliminating blue oaks from the southern third of their range. Black oaks are marching up the Sierra, displacing Ponderosa pine, which are marching up, displacing firs. Everyone is on the move. Oak woodlands are becoming oak savannahs, oak savannahs are becoming grasslands, grasslands are becoming rocky high deserts. Arizonification is happening quickly, thru heat, drought, and ultimately, thru fire.

Virtually all of the east slopes of the Coast Range between San Francisco Bay and the Trinity Alps has burned in the past ten years. In the Sierra, one can practically predict where the next fire catastrophe will happen, because it hasn’t burned yet (hint: Lake Almanor, Placerville, Arnold).

The Fire, the LNU Complex Fire, was part of 2020’s 4.3 million acres of scorched earth. The LNU Fire exceeded the total acreage of all previous fires that impacted my county over the last 50 years combined.

It was a beautiful day—for April. But February has become April, April has become May, and June, July, August, September, and even October and November have become unrecognizable. Every year more heat records are broken. Hottest summer, hottest month, most days over 100, most days over 90. The list goes on, each year breaking the records set the previous year. Weather data is normally highly variable; now it is a straight line—warmer and warmer. And smokier.

My cape honeysuckle and bougainvillea, both planted with a degree of optimism outside their recommended zone, used to die back so badly in the winter that each spring I was tempted to declare them dead and pull them out. Now they bloom year-round, looking like they’re in a courtyard at a hotel in the tropics. We haven’t had a real freeze in seven winters.

The songs of lesser goldfinches on my street are a depressing warning. I can’t take two steps outside without seeing or hearing a bird that reminds me that our climate has seriously changed. Western tanagers, house wrens, and turkey vultures are regular in winter now. The lesser goldfinches have come out of the arid hills and are quickly becoming one of the most ubiquitous nesting birds in Davis. (I know this definitively because one included an imitation of a canyon wren in its song.) What’s more, at least four Say’s phoebes, essentially a high desert species, are scouting for nests in town now. A fifth arrived on my block last week, singing as if on territory. They’ve been doing this for a few years and their numbers are growing.

The graphs of acres burned in California (and in other western states) and the expansion of some bird species into the Pacific Northwest (in this case, Anna’s hummingbirds in winter), are strikingly similar.

I’m leaving. I’ve lived in California fifty-five years but it’s no longer the state I grew up in.

We’re headed to the Olympic Peninsula in Washington. We are fortunate to be able to do so.

Besides the cooler summers, one of the best things about moving to a new place is that I won’t be reminded of climate change on a daily experiential basis. Because the ecosystem will be new to me, I won’t know what’s different, what is changing, except maybe for the brown boobies, a tropical seabird, that are now showing up in Puget Sound each year. Or the family of California scrub-jays that have just established residence on my new street. Like Anna’s hummingbirds, black phoebes, great egrets, red-shouldered hawks, and people like me, scrub-jays are moving north. I expect more of California’s birds to follow me, just as I follow some of them. Yes, lesser goldfinches are coming north too; they’re already established southeast of Tacoma.

I feel like a frog in a boiling pot. I’m getting out. I’m saying goodbye to California, but I feel it has left all of us without saying goodbye to anyone.

The view from Point Wilson, a mile from my new home in Port Townsend, which has had only a few nights below freezing all winter. Climate change is occurring there too, but remains well within temperate ranges.

I do believe that Homo sapiens may ultimately win the climate battle and bring atmospheric CO2 back down to 300 ppm or something. But that’s a hundred years off. And there’s no guarantee we can stop the tide of Greenland and Antarctic ice melt to prevent sea level rise. In the meantime, in the next 50 to 100 years, it’s going to get a lot warmer. And we may ultimately lose New York City, Singapore, Mumbai, and every other low-lying coastal city. My new home is fifty feet above sea level. Well, probably forty-nine and a half now.

The song of the Lesser Goldfinch: Another harbinger of a warming climate

As the climate warms, different thresholds are crossed for different species at different times. For the Lesser Goldfinch, that time seems to be now—both in the core and northern edges of its range, where the species is increasing, and in some parts of the southern arid regions, where it is decreasing.

As I prepare to migrate myself from Davis, California to Port Townsend, Washington, I’m serenaded by Lesser Goldfinches every time I step outside. This is a new thing, a warning of coming heat and smoke brought by a beautiful voice. A more open and arid country version of the American Goldfinch, until five or ten years ago, Lesser Goldfinches were sparse breeders in Davis. I would get a few of them mixed with Americans at my feeder in winter, but I’d have to go west to the more arid edges of the Sacramento Valley, or up into the hot dry foothills, to find them in the breeding season.

They arrived in my neighborhood as nesters about five years ago. This year, 2021, they seem to be the most ubiquitous singing bird, setting up terrorities throughout the town. Friends in Sacramento have reported the same. This comes after several years of record heat and lack of rain (only 6″ in all of 2020).

Here’s what the eBird data says. For comparison, Northern Mockingbird, one of the most common birds in town, is reported from about 20 eBird locations in Davis each June (ranging from 16 in 2015 and 14 in 2016 to 18-22 in the more recent years as eBird users and reports increased). Using mockingbird as a metric for Davis, it’d be fair to say that 20 sites represents close to 100% presence throughout the town, and that number was probably 25% lower (i.e. 15 sites) in 2015. Lesser Goldfinches have increased from reports from four sites in June of 2015 (representing about 20% of the town) to 17 sites in June of 2020 (representing 85% of the town). It feels like it will be 100% this year.

They are not the only arid-country species increasing in Davis as a breeder. Nesting Say’s Phoebes have expanded up from the south, with multiple pairs in Woodland each year (and it’s looking like Davis this year as well).

As with so many less-migratory species, Lesser Goldfinches are expanding north into the Pacific Northwest and beyond.  Their colonization of the Columbia River Valley began in the 1950s, with the first state of Washington record in 1951; they are now established around Portland, The Dalles, and in the vicinity of Clarkston on the Idaho border. They remain rare elsewhere, but increases in records have been dramatic in recent years. In the northern Puget Trough region (Chehalis north thru Puget Sound to Canada), June records have increased from 1 in 2015 and 2016 to 10 in 2020 (as reported on eBird). While they have clearly gained a toe-hold in Olympia and Puyallup in the South Sound region, in 2020 they made appearances in Victoria and Vancouver, Canada (not shown in the data because these records were in May, not June).

Lesser Goldfinches in British Columbia were limited to four scattered records until 2007. Since then, they have become nearly annual, with most records between January and June.

This is a pattern seen in other resident and less-migratory species. Many of those that were already growing before detectable climate change (around 1985) have expanded noticeably since then. Anna’s Hummingbird is the most dramatic example.

Further east, Lesser Goldfinches are moving due north from Yakima and Kennewick into the Okanagan Valley. June records in this region have increased from zero in 2015 to eight in 2020.

All this is predicted. The National Audubon climate prediction map for Lesser Goldfinch, under the 2C warming scenario, describes much of what we are witnessing.

In the Mojave Desert, Lesser Goldfinches have declined. Iknayan and Beissinger (2018) reported them from only 43% of 61 study sites, compared to 68% historically. This is part of a massive avian community collapse in the Mojave Desert, as extreme aridity is pushing many species beyond their limits.

The renewable diesel revolution: How California is reshaping world oil markets

Despite all the attention on the new Biden Administration’s efforts to combat climate change, one state, California, is reshaping the world’s oil markets through its progressive climate policies.

Most dramatic has been the state’s shift to renewable diesel (RD). Unlike its green cousin, biodiesel, RD is molecularly identical to conventional ultra-low-sulfur-diesel (ULSD), making it a “drop-in” fuel. No modifications to engines, gas stations or pipelines are needed. It can be mixed with conventional diesel seamlessly. It is made from bio feedstock such as vegetable and animal oils such as canola, soybean, and corn oil, used cooking oil, tallow, and even municipal solid waste; the exact recipe varies. Current production methods reduce carbon emissions 50 to 85% compared to conventional diesel. RD burns cleaner than conventional diesel, producing 30% less particulates. In addition to less air pollution, this also means less wear on engines.

A 20% RD mixture is called R-20. The ferry boats in San Francisco Bay are running on R-100. UPS, Amazon Prime, and Cherokee Freight Line trucks are now switching to RD, at least in California where the fuel is available. Internationally, cargo vessels with diesel-electric engines are adopting the fuel.

Many cities in California – Oakland, San Francisco, Sacramento, San Diego – now exclusively use RD in city-owned heavy-duty trucks, buses and equipment.

Renewable diesel already accounts for 20% of California’s diesel supply and is projected to grow well beyond 50% by 2024, expanding to include jet fuel, where it is called “sustainable jet fuel”. Renewable propane is also produced during the refining process. Renewable gasoline, unfortunately, is still not economically feasible.

California’s RD comes from a variety of sources. It is imported from Singapore (Neste) and North Dakota. At the latter, the Marathon refinery in Dickinson, North Dakota, originally built to refine fracked Bakken oil, has converted to taking soybeans to make RD for the California market.

The California Energy Commission has identified enough proposed RD projects to supply all of the state’s needs in the future.

Increasingly, refineries in California are ramping up to produce RD from local feedstock. Two of the state’s largest refineries, Phillips 66 and Marathon in the Bay Area, are currently closed, using the Covid downturn to retrofit their operations into making RD. They will each produce 20% of the state’s diesel in the form of RD; they will completely cease using crude oil as an input. Other smaller refinery conversions are underway in southern California.

The California Energy Commission (CEC) projects that the state’s overall oil use, already down 20% due to the pandemic, will scarcely rebound and then continue declining in the future.

Washington and Oregon are taking steps to increase RD supply in their states. (Phillips 66 had originally sought to convert their Cherry Point refinery near Bellingham, WA, to RD production but ran into permitting problems. They are now trying again.) [Note: Phillips 66’s “Green Apple” plan to convert the Cherry Point refinery ran into permitting obstacles with the WA Dept of Ecology over – wait for it – carbon emissions. After an EIS was required, Phillips pulled their plans.]

This conversion to non-petroleum-based fuels is being driven by a combination of federal and state laws. The federal government already offers a $1/gallon tax credit for conversion to renewable fuels. Since the credit is bankable and tradeable, it’s essentially real cash. The program is set to expire at the end of 2022 but is likely to be extended with bipartisan support.

At the state level, California’s ever-lowering cap of tradeable permits under the AB32 cap-and-trade program is finally biting hard enough to change incentives. Carbon credits are now yielding about 30 cents/gallon and is likely to rise. Because this comes from traded permits, it is not a direct payment from government funds.

Combining federal and state incentives, a refinery converting from conventional to renewable diesel reaps an additional $1.30/gallon. If the Phillips 66 project goes to its full 800 million gallons/year, that’s at least a billion dollars each year in subsidies – from tax credits and tradable carbon credit sales.

California has already reduced greenhouse gas emissions 15-20% since the peak in 2004. This has been achieved during a period of significant economic and population growth; emissions per gross domestic product are down about 45%. Because the transportation sector has been among the most challenging for reducing emissions, the RD revolution will go a long way to helping California reach net zero by 2050. The Biden Administration is using California’s carbon reduction measures as a model for the nation.

The RD revolution is a transition to more dramatic decreases in oil use due to electrification of the vehicle fleet.

Mojave Desert bird populations plummet due to climate change

Two recent papers concluded that many breeding bird species in southern California and Nevada deserts have declined dramatically due to climate change.

In their abstract, Iknayan and Beissinger (2018) summarized, “We evaluated how desert birds have responded to climate and habitat change by resurveying historic sites throughout the Mojave Desert that were originally surveyed for avian diversity during the early 20th century by Joseph Grinnell and colleagues. We found strong evidence of an avian community in collapse.”

They re-surveyed 61 sites originally surveyed by Grinnell teams in the early 20th century (primarily between 1917 and 1947).

Of 135 species assessed (which included some wintering and migrating species, as well as breeding species), 39 had significantly declined; only one (Common Raven) had increased. This was in stark contrast to similar assessments they conducted of Sierra and Central Valley sites, where more species had increased than decreased and there were no overall declines (not to say there weren’t winners, losers, and range shifts within those regions).

Figure 1B from Iknayan and Beissinger (2018). Every study site had fewer species than previously– on average each site had lost 43% of their species.

Detailed analyses suggested less rainfall and less access to water was the primary driver. Habitat change only affected 15% of the study sites and was of secondary importance. They found no evidence of expansion of species from the hotter, drier Sonoran Desert (e.g. Phainopepla, Verdin, Black-throated Sparrow) into the Mojave Desert.

Consistent with a community collapse, declines were greatest among species at the top of food chain — carnivores such as Prairie Falcon, American Kestrel, and Turkey Vulture. Insectivores were the next most impacted, and herbivores the least. But the declines affected both common and rare species, both generalists and specialists.

Figure 1B from Iknayan and Beissinger (2018), which I’ve augmented with species labels from the database available in the supplementary materials. Other significant losers (red dots), in order of degree of decline, included Western Kingbird, Western Meadowlark, Black-chinned Sparrow, Lawrence’s Goldfinch, Bushtit, Ladder-backed Woodpecker, and Canyon Wren. The yellow dots are newly invasive species: Chukar, Eurasian Collared-Dove, Eurasian Starling, and Great-tailed Grackle.

A follow-up study by Riddell et al (2020), also involving Iknayan and Beissinger, focused on the thermoregulatory costs — the water requirements to keep cool — for the declining species. They found that “species’ declines were positively associated with climate-driven increases in water requirements for evaporative cooling and exacerbated by large body size, especially for species with animal-based diets.” Larger species get much of their water from the insects they eat. They estimated larger species would have to double or triple their insect intake to meet their water needs, though insect abundance is lowest July thru September.

American Kestrels were among the biggest losers in the study, struggling to meet their cooling needs.

Intriguingly, they found that 22 species had actually declined in body size over the last century, consistent with Bergmann’s Rule, and had reduced their cooling costs up to 14%. These species fared better. Current climate change, however, is at least ten times more rapid than any previous warming event, during which many species evolved. They estimated cooling costs have already increased 19% and will reach 50% to 78% under most scenarios, far outstripping any species’ ability to evolve through the current rapid warming.

These results stand in stark contrast to the Pacific Northwest, where many of the same bird species (e.g. Anna’s Hummingbird, Turkey Vulture, Northern Mockingbird) are increasing. This is consistent with projections which generally show individual declines along species’ southern edge and expansions at the north edge of their range (see Audubon climate projection maps for individual species).

Iknayan and Beissinger conclude, “Our results provide evidence that bird communities in the Mojave Desert have collapsed to a new, lower baseline. Declines could accelerate with future climate change, as this region is predicted to become drier and hotter by the end of the century.”

Helping forests migrate: Planners race to plant trees adapted to the future climate

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.

The range of Arizona oak. For one town near Portland, Oregon, the list of potential future street trees includes this species, as well as California buckeye, California laurel, and silverleaf oak.

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.

Dead blue oaks in Fresno County, California. They experienced excessive mortality during the 2012-16 drought. These hills may revert to grassland. Researchers want to use the genes of the survivors as stock for the future in the north. For a full presentation of blue oak gene-assisted migration see this presentation by the California Department of Fish and Wildlife.

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.

Ponderosa pines are disappearing from lower elevations of the Sierra in California. This has been documented in Colorado as well.

Range expansion of trees northward has been documented, but the pace is anemic, insufficient to keep up with the changing climate. One study in the east found that ranges in adult trees expanded north less than 150 yards per year (Sittaro et al 2017). They concluded, “our results add to the body of evidence suggesting tree species are mostly limited in their capacity to track climate warming…”

Recent mega fires include many of the drought-killed conifers in the southern Sierra. Research suggests regeneration may be imperiled due to a warming climate.

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.

This photo from Aitken and Bemmels (2015) shows a series of Sitka spruce, all eight years old, planted together in British Columbia. The trees from the south, adapted for a warmer and drier environment, are out-competing the locals.

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.

Becoming Arizona: How climate change is transforming California thru fire

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.

Camelback Mountain near 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.

California under smoke, September 9, 2020.

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.  

In 2019, the media reported that Oregon firefighters make an annual trek to California to provide mutual aid. In 2020, that changed. A quarter of the west slope of the Cascades from Portland to Medford appears to be on fire. One out of eight Oregonians are evacuating. The media is filled with horrific stories of grandmothers and teenagers burned alive while the father asks a badly burned woman along a roadside if he’s seen his wife. “I am your wife,” she responds.

Eugene, Oregon on the morning of September 8, 2020.

The process

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.

Northern California, being at western North America’s southern edge of the low elevation temperate forests, is especially at risk. As documented in the Verdugo Mountains near Los Angeles, high fire frequency converts forest and chapparal to weeds and rocks. That southern edge is pushing north. Forests are migrating north; so are deserts. (So are bird populations.)

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.

The future

Nearly the entire east side of the northern Coast Ranges have burned since 2018. Much of the southern Sierra forests died during the recent drought; most of those have yet to burn.

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.

The annual area burned in California has increased fivefold from 1972 to 2018 (Williams et al 2019). Several individual fires in 2020 exceed the average from 1987-2005. The point shown here for 2020 is still increasing.

Academic papers

Here is a partial list of recent research on the increase of fires in California and the western US.

Abatzoglou and Williams (2016). Impact of anthropogenic climate change on wildfire across western US forests. PNAS 113 (42) 11770-11775.

Goss et al (2020). Climate change is increasing the likelihood of extreme autumn wildfire conditions across California. Environmental Research Letters 15(9).

Haidinger and Keeley (1993). Role of hire fire frequency in destruction of mixed chaparral. Madrono 40(3): 141-147.

Holden et al (2018). Decreasing fire season precipitation increased recent western US forest wildfire activity. PNAS 115 (36) E8349-E8357.

Kitzberger et al (2017). Direct and indirect climate controls predict heterogeneous early-mid 21st century wildfire burned area across western and boreal North America. PLOS One.

Lareau et al (2018). The Carr Fire Vortex: A Case of Pyrotornadogenesis? Geophysical Research Letters 45(23).

Seager et al (2014). Climatology, variability and trends in United States 2 vapor pressure deficit, an important fire-related 3 meteorological quantity.

Swain (2020). Increasingly extreme autumn wildfire conditions in California due to climate change. Weather West Blog (related to Goss et al 2020 above).

Syphard et al (2019). The relative influence of climate and housing development on current and projected future fire patterns and structure loss across three California landscapes. Global Environmental Change 56: 41-55.

Williams et al (2019). Observed Impacts of Anthropogenic Climate Change on Wildfire in California. Earth’s Future 7(8): 892-910

Westerling et al (2006). Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity. Science 313(5789): 940-943.