Keep Davis Water Treatment Ponds wild

The ponds at the Davis Wastewater Treatment Plant have been one of the top birding spots in Yolo County for over 50 years. With 212 species reported via eBird, only two other sites in the county have recorded more (Yolo Bypass Wildlife Area and Davis Wetlands).

Here’s a short video clip from October 2020 illustrating the amazing bird life. A family of Sandhill Cranes walks among thousands of geese, ducks, and shorebirds while the calls of curlews filled the air. A Peregrine Falcon and a Northern Harrier buzzed past. Though the ponds are no longer part of the water treatment plant operations, they still collect rain water and provide habitat. Over 14,000 ducks have been counted on them during the annual Christmas Bird Count. The list of rarities includes everything from Slaty-backed Gull and Arctic Tern to Vermillion Flycatcher.

Earlier this year, the Davis City Council voted 4-1 to lease these ponds to BrightNight solar to convert these ponds into a solar array. Aside from the obvious risk of bird mortality from panel strikes, the project would eliminate one of the best bird habitats in the county. The City Council’s decision has been criticized for its impact on wildlife, for the improper process bypassing the Natural Resources Commission, and for its poor financial terms (the city got ripped off). Gloria Partida, Dan Carson, Will Arnold, and Brett Lee approved it. Only Lucas Frerichs voted against the deal.

But it’s not too late to try to stop it. Here’s what you can do:

1. Call or email each City Council member and ask them to rescind their original vote. Their phone numbers are available here. We need three of them to overturn the original decision. Will Arnold has expressed regret for his vote and Gloria Partida was skeptical at the outset. We also may have an opportunity after the election with new Council member to overturn this decision.

  • Gloria Partida — gpartida@cityofdavis.org
  • Will Arnold — warnold@cityofdavis.org
  • Dan Carson — dcarson@cityofdavis.org
  • Brett Lee — blee@cityofdavis.org
  • Lucas Frerichs — lucasf@cityofdavis.org

2. Call or email Valley Clean Energy Alliance board members and ask them to reject the bid from BrightNight for a new power contract. Their emails are here:

  • Angel Barajas — angel.barajas@cityofwoodland.org
  • Dan Carson — dcarson@cityofdavis.org
  • Lucas Frerichs — lucasf@cityofdavis.org
  • Gary Sandy, Vice Chair — gary.sandy@yolocounty.org
  • Don Saylor — don.saylor@yolocounty.org
  • Tom Stallard, Chair — tom.stallard@cityofwoodland.org
  • Duane Chamberlain, alternate — duane.chamberlain@yolocounty.org
  • Xochitl Rodriguez, alternate — xochitl.rodriguez@cityofwoodland.org

3. Join the effort to increase transparency in City government that would have prevented this travesty. You can see more on that here.

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.  

2020

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.

The invasion of the Pacific Northwest: California’s birds expand north with warmer winters

Birds, because of their mobility, are considered to be fairly adaptable to climate change. They evolved in the aftermath of two of the world’s most catastrophic warming events (the K-T extinction and the Paleocene-Eocene Thermal Maximum), spreading to the Arctic, crossing continents, and evolving along the way. While those warming events took place over tens of thousands of years, the current warming is happening in the space of a couple hundred, with noticeable changes in climate within the lifespan of a single bird.

There will be winners and losers. Generalists, and species that enjoy warmer weather, are likely to be winners. Those with narrow food or habitat requirements, especially those dependent on the ocean or the Arctic/Antarctic, will likely be losers. Although counter-intuitive, it is primarily non-migratory resident species that seem to be more adaptable to a changing climate.

Recent studies

Studies of climate impacts on western North American birds using past data are limited, but some focusing on California were recently published. Iknayan and Beissinger (2018) showed that, over the last 50 years, “bird communities in the Mojave Desert have collapsed to a new, lower baseline” due to climate change, with significant declines in 39 species. Only Common Raven has increased. Furnas (2020) examined data from northern California’s mountains, showing that some species have shifted their breeding areas upslope in recent years. Hampton (myself) (2020) showed increases in many insectivores, both residents and migrants (from House Wrens to Western Tanagers), in winter in part of the Sacramento Valley over the last 45 years. These changes, particularly range shifting north and out of Southwest deserts, is predicted for a wide number of species.

The invasion of the Pacific Northwest

Here I use Christmas Bird Count (CBC) data to illustrate that some of California’s most common resident birds have expanded their ranges hundreds of miles north into Oregon, Washington, and British Columbia in recent years. The increases are dramatic, highly correlated with each other across a wide range of species, and coincide with rapid climate change. They illustrate the ability of some species to respond in real time.

In parts of Oregon and Washington, it is now not unusual to encounter Great Egret, Turkey Vulture, Red-shouldered Hawk, Anna’s Hummingbird, Black Phoebe, and California Scrub-Jay on a single morning—in winter. A few decades ago, this would have been unimaginable. Some short-distance migrants, such as Townsend’s Warbler, are also spending the winter in the Pacific Northwest in larger numbers.

The following graphs, showing the total number of individuals of each species seen on all CBCs in Oregon, Washington, British Columbia, and (in one case) Alaska, illustrate the range expansions. Adjusting for party hours scarcely changes the graphs; thus, actual numbers of individuals are shown to better illustrate the degree of change. The graphs are accompanied by maps showing predicted range expansions by the National Audubon Society, and recent winter observations (Dec-Feb) from eBird for 2015-2020.

These range expansions were predicted, though in some cases the recent trends exceed even projected scenarios under 3.0C increases in temperature.

Let’s begin with the climate. Canada as a whole has experienced 3.0C in temperature increases in winter. British Columbia has experienced an average of 3.7C increase in Dec-Feb temperatures since 1948. The greatest increases have been in the far north; increases in southern British Columbia, Washington and Oregon have been closer to 1.5C.

winter temps in Canada.jpg

Average nationwide winter temperatures deviation from average.

Great Egret

Great Egrets on Oregon CBCs have increased from near zero to nearly 900 on the 119th count (December 2018 – January 2019).

CLICK ON GRAPHS TO ENLARGE

GREG OR graph.jpg

But their expansion, which took off in the early 1990s into Oregon, is now continuing in Washington, with a significant rise beginning in the mid-2000s. Great Egrets occur regularly in southern British Columbia, but so far have eluded all CBCs.

GREG WA graph.jpg

They have not quite fulfilled the full range predicted for a 1.5C increase, but are quickly on their way there.

GREG maps.jpg

Turkey Vulture

Turkey Vultures began increasing dramatically in winter in the Sacramento Valley of California in the mid-1980s, correlated with warmer winters and a decrease in fog. Prior to that, they were absent. Now, over 300 are counted on some CBCs. That pattern has been repeated in the Pacific Northwest, though about 20 years later. Both Oregon and British Columbia can now expect 100 Turkey Vultures on their CBCs. Curiously, Puget Sound is apparently still too cloudy for them, who prefer clear skies for soaring, though small numbers are regular in winter on the Columbia Plateau.

TUVU CBC graph.jpg

TUVU maps.jpg

Red-shouldered Hawk

Red-shouldered Hawks have increased from zero to over 250 inviduals on Oregon CBCs, taking off in the mid-1990s.

RSHA OR graph.jpgTwenty years later, they began their surge into Washington. It’s a matter of time before the first one is recorded on a British Columbia CBC.

RSHA WA graph.jpg

While their expansion in western Washington is less than predicted, their expansion on the east slope, in both Oregon and Washington, is greater than predicted. This latter unanticipated expansion into the drier, colder regions of the Columbia Plateau is occurring with several species.

RSHA maps.jpg

Anna’s Hummingbird

If this invasion has a poster child, it’s the Anna’s Hummingbird, which, in the last 20 years, have become a common feature of the winter birdlife of the Pacific Northwest. Their numbers are still increasing. While much has been written about their affiliation to human habitation with hummingbird feeders and flowering ornamentals, the timing of their expansion is consistent with climate change and shows no sign of abating. Anna’s Hummingbirds are not expanding similarly in the southern portions of their range. The sudden rate of expansion, which is evidenced in most of the species shown here, exceeds the temperature increases, suggesting thresholds are being crossed and new opportunities rapidly filled.

ANHU CBC graph.jpg

The expansion of the Anna’s Hummingbird has now reached Alaska, where they can be found reliably in winter in ever-increasing numbers.

ANHU AK graph.jpg

The range expansion of the Anna’s Hummingbird has vastly outpaced even predictions under 3.0C. In addition to extensive inland spread into central Oregon and eastern Washington, they now occur across the Gulf of Alaska to Kodiak Island in winter.

ANHU maps.jpg

Black Phoebe 

Non-migratory insectivores seem to be among the most prevalent species pushing north with warmer winters. The Black Phoebe fits that description perfectly. Oregon has seen an increase from zero to over 500 individuals on their CBCs.

BLPH OR graph.jpg

With the same 20-year lag of the Red-shouldered Hawk, the Black Phoebe began its invasion of Washington.

BLPH WA graph.jpg

The figure below illustrates two different climate change predictions, using 1.5C and 3.0C warming scenarios. While nearly a third of the Pacific Northwest’s Black Phoebes are in a few locations in southwest Oregon, they are increasingly populating the areas predicted under the 3.0C scenario.

BLPH maps.jpg

Townsend’s Warbler

Migrant species tend not to show the dramatic range expansions of more resident species – and short-distance migrants show more range changes than do long-distance migrants. Townsend’s Warblers, which winter in large numbers in southern Mexico and Central America, also winter along the California coast. Increasingly, they are over-wintering in Oregon and, to a lesser degree, Washington. This mirrors evidence from northern California, where House Wren, Cassin’s Vireo, and Western Tanager are over-wintering in increasing numbers. These may be next for Oregon.

TOWA WA OR graph.jpg

Townsend’s Warblers are already filling much of the map under the 1.5C warming scenario, though their numbers on CBCs in Washington and British Columbia have yet to take off.

TOWA maps.jpg

California Scrub-Jay

Due to problems with CBC data-availability, I have no graph for the California Scrub-Jay. Their northward expansion is similar to many of the species above. Their numbers on Washington CBCs have increased from less than 100 in 1998 to 1,125 on the 2018-19 count. eBird data shows they have filled the range predicted under the 3.0C scenario and then some, expanding into eastern Oregon, the Columbia Plateau, and even Idaho.

CASJ maps.jpg

Other species

Other species which can be expected to follow these trends include Northern Mockingbird and Lesser Goldfinch. White-tailed Kite showed a marked increased in the mid-1990s before retracting, which seems to be part of a range-wide decline in the past two decades, perhaps related to other factors.

Curiously, three of the Northwest’s most common resident insectivores, Hutton’s Vireo, Bushtit, and Bewick’s Wren, already established in much of the range shown on the maps above, show little sign of northward expansion or increase within these ranges. The wren is moving up the Okanogan River, and the vireo just began making forays onto the Columbia Plateau. Both of these expansions are predicted.

Likewise, some of California’s oak-dependent species, which would otherwise meet the criteria of resident insectivores (e.g. Oak Titmouse), show little sign of expansion. Oaks are slow-growing trees, which probably limits their ability to move north quickly. Similarly, the Wrentit remains constrained by a barrier it cannot cross—the Columbia River.

Call it the invasion of the Northwest. Call it Californication. Call it climate change or global warming. Regardless, the birds of California are moving north, as predicted and, in some cases, more dramatically than predicted.

 

ANHU CBC graph.jpg

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

California’s plan for net-zero by 2045 and net-negative after that

Getting to Neutral cover.jpgIn January 2020, Lawrence Livermore Laboratory released their detailed report Getting to Neutral: Options for Negative Carbon Emissions in California. It provides a detailed plan, with estimated costs, to reach California’s goal of net-zero by 2045, and net-negative thereafter, thus reducing carbon in the atmosphere and potentially returning it to pre-industrial levels.

The plan’s focus is carbon sequestration. For a plan on carbon emissions reductions, see California’s 2017 Climate Change Scoping Plan.

[Note: “ton” always refers to tons of CO2 equivalent (tCO2e).]

The plan relies on three main pillars:

  1. Natural sequestration thru improved land management (sequesters 25 million tons/yr);
  2. Biomass fuels made from forestry and agricultural waste, and garbage, with capture and storage of CO2 (sequesters 83 million tons/yr) (and also displaces the use of fossil fuels);
  3. Direct air capture of carbon, sucking carbon out of the air with large machines (sequesters 17 million tons/yr).
  • Natural sequestration

Chapter 2 focuses on natural solutions, which are among the cheapest options for sequestering carbon. However, they are also all limited by the number of acres upon which we can apply them. There are only so many acres of forests, wetlands, etc. By far, the largest (and cheapest) option in this category is changes in forest management.

Changes in forest management

The easiest way to increase carbon sequestration is to change to the way forests are managed. Specifically, those changes include increasing harvest rotation length, maintaining stocks at a high level, and increasing productivity by removing diseased or suppressed trees. Negative emissions are based on ongoing sequestration of carbon, which may include the transfer of harvested carbon to durable wood products. These practices would sequester 15.5 million tons/yr at a cost of $0.80/ton.

Other natural solutions

Other natural options, in order of the maximum amount of carbon they can sequester, are reforestation, tidal marsh restoration, freshwater wetland restoration, and grassland restoration. These are smaller players—more limited and more expensive. The habitat restoration options are especially limited in their potential contributions and very expensive per ton of CO2 sequestered (although restoration provides other benefits, of course). Together, these options can sequester another 10 million tons/yr at costs that range from $16.4/ton (for reforestation) to $440/ton (freshwater wetland restoration).

  • Biomass fuels

Analogous to current ethanol production, Chapters 3 and 4 call for turning leaves, branches, almond hulls, and human garbage into biofuels, but then also capturing the CO2 and burying it in old oil fields. A small part of the plan includes sequestering, rather than releasing, the CO2 produced during ethanol production. In terms of sequestration, this is the largest plank of the plan. It envisions a massive shift from fossil fuels to plant-based fuels, complete with new pipelines to transport and bury the CO2. It relies heavily on the Central Valley’s agricultural sector and old oil fields. The plan assumes existing crops and does not consider planting crops purely to create biofuels; thus, it does not displace food production.

Because biofuels would displace fossil fuels, it would also result in massive reductions of carbon emissions. However, that is not the focus of the report; the focus of the report is to sequester carbon.

Here is where the biomass would come from:

Forest biomass

Slag from logging, sawdust from sawmills, cleared shrub and chaparral. This would sequester 24 million tons/yr.

Municipal solid waste (household garbage)

This would sequester 13 million tons/yr.

Ag residue

  1. Almond hulls and shells (41% of total ag residue biomass)
  2. orchard and vineyard clippings (30%)
  3. other above-ground plant parts after harvesting from other crops (29%).

These would sequester 13 million tons/yr.

Other

Landfill and anaerobic digester gas. This would sequester 6 million tons/yr.

CLICK TO ENLARGE

Fig11.jpg

All this biomass would be converted, thru various processes (gasification, combustion, fast pyrolysis, hydrothermal liquefaction, and biogas utilization) into various products: hydrogen, grid electricity, liquid fuels (e.g. “gasoline”), biochar, and renewable natural gas.

The cost depends on the biomass collection, transport, biofuel conversion process, and CO2 transport for sequestration. All of these will vary in order to provide a suite of biofuel energy needs (e.g. electricity, transport fuel, etc.). Overall, this biomass fuel network would sequester 83 million tons/yr at an average cost of about $60/ton (ranging from $29-96/ton).

  • Direct Air Capture

Chapter 5 of the report goes into detail about direct air capture (DAC) technology, machines that would suck carbon out of the air and store it in underground (primarily around oil and gas fields in the Central Valley). The report highlights DAC’s unlimited potential in sequestering carbon, but also its high energy demands (and thus expensive cost). In the end, they focus on two main options:

  1. Natural gas-based plants located near underground storage sites. These would still be net-negative.
  2. Geothermal plants (primarily around the Salton Sea), which would require the captured CO2 to be transported a long distance to underground storage sites.

They reject solar and wind-powered DAC as requiring too much land for the energy needed. They do not explore nuclear-powered DAC, such as fourth generation thorium reactors.

All of Chapter 6 is dedicated to long-term geologic storage. They conclude that oil and gas fields in the Central Valley offer the greatest promise, and that “these areas will be safe and effective storage sites. At depths below 3,000 feet, CO2 converts to a liquid-like form that has about the same density and viscosity as oil.”

Their initial cost estimates for DAC exceed $200/ton, though they assume, with learning, an eventual cost of $190/ton.

The Whole System

Fig60.jpgChapter 7 dives into the logistical details and infrastructure needed to connect the gathered biomass to the biomass fuel plants and the DAC plants to underground storage reservoirs. Among their main conclusions:

  • Transportation is a relatively small portion of total system cost, between $10 and $20/ton of CO2 removed.
  • Preexisting rail would the most efficient way to move collected biomass to biomass fuel plants, though some short spur lines would need to be constructed, depending on plant location.
  • A CO2 pipeline would need to be constructed along existing pipeline corridors in the Central Valley and to the Salton Sea, but not elsewhere.

Chapter 8 explores technology learning curves and cost reductions over time, mostly with respect to DAC.

Chapter 9 explores total system cost under several scenarios. They note there is “considerable flexibility among the technology pathways and scenario options.” Table 40 offers the optimum combination of technologies, sequestering 125 million tons per year (and avoiding another 62 million tons in emissions avoided) for a total of $8.1 billion/year, which is an a total average cost of about $65/ton.

CLICK TO ENLARGE

Fig77.jpg

The Role of State Government

There is a plan for California; will it be implemented?

The report does not go into specific policy initiatives or economic incentives necessary to jump start, implement, or transition to this plan. I will address that in another post. Their only mention of public policy is with regard to the CO2 pipeline, where the report notes: “industry experts have expressed concern about the costs and legal difficulties of obtaining rights-of-way for new pipelines in California. One power company shared that running CO2 pipelines on existing natural gas rights-of-way requires renegotiating with the landowners because CO2 pipelines are higher pressure and thus are not covered by existing agreements.”

Direct Air Capture: How the fight against climate change will be won or lost

Fifteen years from now, when the Great Barrier Reef is a thing of the past, when downtown Atlantic City, Bangkok, Boston, Charleston, Dhaka, Galveston, Honolulu, Jakarta, Lagos, Manhattan, Miami, Mumbai, New Orleans, Newark, Rotterdam, San Francisco, Seattle, Tampa, and Venice relocate, and when Australia and California burn, everyone — from farmers to stock brokers, peasants to politicians– will be asking the same question: Are the machines working?

DAC.jpg

Those machines will be sucking carbon out of the air and burying it deep in the ground or under the sea. We don’t know exactly where they will be, what they will look like, or even how well they will work. All we know is that we need them (Lackner et al 2013).

Reducing our carbon emissions, which humans have proved incapable of, is not enough now. Even reducing to zero emissions tomorrow is insufficient. We are too far gone in the wrong direction. What’s more, like a ship heading for the end of the world where the water falls off the edge, our foot is still on the accelerator. Slowing down is good, but insufficient to avert disaster; we must turn the ship around and head the other way. We need to not just reduce emissions, we need to reduce the amount of CO2 already in the atmosphere. That means negative emissions– sucking carbon out of the air.

Direct Air Capture vs Flue Capture; Sequestration vs Re-Use

Carbon capture from ambient air, also called Direct Air Capture (DAC), is different from conventional carbon capture at factory chimney flues (i.e. point source carbon capture). First, it’s a lot easier to capture carbon from flues because the CO2 is concentrated. Second, typically the goal of flue carbon capture is to minimize CO2 emissions and often to re-use the CO2 in a process that reduces the need for fossil fuels. If it is re-purposed, you’ve reduced CO2 emissions from fossil fuels, but the CO2 is still released into the atmosphere. This is a process to reduce emissions; it is not net-negative.

There are also plans to capture carbon, from the air or from flues, and use it in a variety of other industrial processes, from putting bubbles in soda to (wait for it)… extracting more oil. These plans are merely meant to reduce emissions and also to incentivize the private sector to capture carbon. But it’s not net-negative.

Feasibility

Back to direct air capture. Here’s the catch: we don’t know if we can do it at the scale needed. Fortunately, humans have been much better at finding technological solutions than political ones. There are more than a dozen pilot projects in Iceland, Switzerland, and elsewhere showing it can be done– on a very small scale. There are a host of questions, but the biggest challenge is sucking it out of the air in an efficient and cost-effective way.

Funding

Feasibility aside, there’s the question of how to pay for it. Suppose we wanted to capture and sequester 7 billion metric tons of CO2 annually, which is the IPCC goal by 2050. Currently we emit 43 billion. Early estimates are that it would cost $700 billion/year (at $100/ton) and require an enormous amount of energy, up to a 12% of annual worldwide energy use. But those are early estimates. Technology gets better and cheaper with time. The Center for Negative Carbon Emissions at Arizona State University thinks it can be done for $210 billion/yr (using $30/ton) and require only 1% of worldwide energy use.

For context, worldwide military spending is $1.8 trillion/yr (or $1,800 billion), nearly half of which is by the US. If the armies of the world ever wanted to save a city, let alone a village, they have the money to do it.

Ultimately, governments will have to pay for carbon capture and sequestration. There is no way to incentivize the private sector to bury a product rather than re-use it. In the near term, we can benefit from private sector carbon capture and re-use because, although it is not net-negative, it can incentivize research into DAC technology. And it does reduce emissions.

DAC on a meaningful level requires international coordination and, of course, cost sharing. The two most obvious models would be to apportion cost share based on current or past CO2 emissions.

Each nation will likely be up to its own to develop their own funding mechanism. A carbon tax is an obvious solution. If DAC costs $100/ton, that translates to 88 cents/gallon at the pump. Other fossil fuel uses would also have to be taxed as well. While this sounds affordable, there are two complicating factors: 1) we can’t just address the gallons of gas we are buying now; we have to address all the gas we have ever bought and all our parents have ever bought; and 2) carbon taxes are regressive, hitting the poor more than the rich (as a percentage of their income). There are ways around that, a subject for another blog post.

The enormity of the task means that technological innovations to lower the cost are critical. This should not be left to small policy initiatives like research grants and tax incentives. This requires the full weight of all the major governments and universities in the world. Progressive governments in Europe and California (where Democrats have super-majorities in both houses of the legislature) could and should embark on DAC projects immediately.

The Free Rider and Moral Hazard Problems

CO2 released anywhere in the world spreads everywhere, and DAC done anywhere reduces CO2 everywhere. This is both good and bad. It means that DAC can be done anywhere, allowing us to select the most expedient locations. For example, a DAC pilot study in Iceland uses clean geothermal energy to capture carbon and inject it into porous volcanic rocks.

But it also means there’s a potential free rider problem, where countries will shirk their obligations in the hopes that others will take care of it for them. One can imagine rogue nations that refuse to pay their fair share and free ride on the public service provided by other countries. The US, whose share would be large by any measure, is a candidate for such recalcitrant behavior. Public support for DAC could overcome this.

It is possible that Republicans would support DAC. The US Congress recently passed a $50/ton tax credit for DAC removal, the most ambitious such incentive in the world. Republican support, however, probably came from the associated $35/ton tax credit for carbon captured from the air and used for enhanced oil extraction. Regardless, Republicans could see DAC as an opportunity to extend fossil fuel use into the future. And therein lies the moral hazard problem. If we’re doing DAC, one could argue that we don’t need to reduce emissions as much. And if DAC became cheap and easy, fossil fuel use (aside from the spill risks and air quality impacts) could arguably continue.

But, like with a penny saved rather than earned, carbon not emitted is carbon you don’t have to capture and sequester. There are two more reasons why reducing emissions must still happen: 1) at the moment, it’s still cheaper to reduce CO2 emissions than to capture it; and 2) we are nearing the edge of the world, when it’s too late even to capture carbon.

Positive Feedback Loops

This brings us to the gremlins in the room– positive feedback loops. These are additional sources of global warming that are caused by the current global warming. They are force multipliers, accelerators, that can make global warming much worse very fast. It’s hard to predict when they will kick in. If they do, our job will become much much harder. We will lose ground, a lot more ground (read human suffering) before we win. They put victory in doubt.

Some positive feedback loops, such as increased water vapor in the air and dark seas and mountains exposed from melting ice and glaciers, have been accounted for in climate models. More pernicious are the more unpredictable “time bombs”, such as permafrost melt and massive wildfires.

Melting permafrost is the proverbial elephant of the gremlins in the room. Research suggests that rapid methane releases from melting permafrost may have been the final driver in runaway climate change that led to past mass extinction events, including the End-Permian Extinction in which 97% of all life on earth perished. This effect is already happening. NOAA recently reported that melting permafrost now contributes as much as net 0.6 billion tons of carbon (equivalent to 2.2 billion tons of CO2) to the atmosphere each year; “the feedback to accelerating climate change may already be underway.”

Forests are normally carbon sinks, taking in CO2. However, in 2006 Westerling et al warned that “forests of the western United States may become a source of increased atmospheric carbon dioxide rather than a sink, even under a relatively modest temperature-increase scenario.” Since then, wildfires have increased dramatically.

These positive feedback loops are like an increasing current threatening to pull the ship over the falls. If we are waiting for technology to save us, we may have waited too long.

Controlling the Climate

In the long run, Homo sapiens might eventually hopefully maybe win the climate battle and be able to capture and sequester enough carbon to return the earth’s atmosphere to normal conditions. But there will be suffering in the short-term, for the next two hundred years, thru sea level rise, heat waves, droughts, powerful hurricanes, and agricultural disruption. The poor will suffer most. Turning the climate around is like turning a cruise ship. There’s a lot of lag time between cause and effect. That’s why humans have found themselves in the current crisis. Only the scientists saw it coming. Nobody felt the impacts until now, and now it’s too late to avoid them. The same is true regarding corrective measures. A lot of sea level rise, caused by ice melt in Greenland and Antarctica, is already built into the system. It is coming and coming at an increasing and exponential rate. We may have to actually cool the planet beyond the recent historic level to stop it. And that may take 150 years. In the meantime, hundreds of coastal cities will go under water. This appears inevitable, even under the most optimistic scenarios.

The graphs below present the most wildly optimistic scenario, achieving the Paris goal’s peak emission in 2020 (this year), DAC of 7 billion tons of CO2 per year by 2050, plus optimistic net removal thru reforestation and new soil management practices, all of which help to get us to net-zero emissions by 2050, another Paris goal. After that, we remove more than we emit; we are net-negative, returning the earth to under 400 ppm.

It would be great to just use natural approaches to sequester carbon (e.g. reforestation and soil management). But the numbers just don’t add up fast enough. During past global warming events (e.g. the Paleocene Eocene Thermal Maximum), it took the earth’s natural processes tens of thousands of years to restore balance. We have put so much carbon up so fast thru industrial processes that we need the same kind of speed sucking it back in. Nevertheless, looking at the graph below, reduced carbon emissions are still the biggest player, followed by DAC and the natural processes. We need it all to the maximum extent possible as soon as possible.

But this wildly optimistic scenario still has us peaking at 510 ppm in 2050, high enough to hit 2.0 Celsius warming, which is perilously close to unleashing enough carbon and methane from permafrost and other positive feedback loops to launch us toward 3 or 4 or 5 C warming and create another mass extinction event  (which we know from the past the world will recover from, re-evolving new life forms, in a few million years).

DAC chart1.jpg

The graph of CO2 levels below is derived from the assumptions regarding CO2 emissions and removal above. This is a best case scenario.

DAC chart2.jpg

But suppose humanity gets past this. Successful implementation of carbon capture and sequestration would mean that Homo sapiens can control the earth’s climate. That brings with it a host of other questions. At what level do we set atmospheric CO2? Do we return to 300 ppm or lower? Who decides? Because carbon released or captured anywhere affects everywhere, who will police it? These are questions for our children, if they are fortunate.

Modern climate change is 10x faster than historic global warming mass extinction events

There have been several mass extinction events in the history of the earth, most of them caused by global warming due to “sudden” releases of carbon into the atmosphere, and it only took an increase of 4 to 5 degrees Celsius to cause the cataclysm. The current carbon emissions rate is 10 to 100x faster than during those events. And we’re already a quarter of the way there in terms of warming.

CLICK TO ENLARGEemissions rate

The current warming trends, RCP 8.5 and RCP 4.5, refer to estimates of carbon emissions under high and moderately low projections by the International Panel on Climate Change. The straight lines on the extinction events are approximate; there may have been episodic spurts and stops as different thresholds, positive feedback loops, and other natural events occurred. But these lines connect the dots we have.

The earth is 4.5 billion years old. Land animals with backbones didn’t really evolve until 300 million years ago (mya), so we’ll start there.

The most massive mass extinction event in the history of the earth was the End-Permian extinction event (also known as the Permian-Triassic extinction event or the Great Dying) 252 mya. It was caused by a massive release of carbon. The equatorial regions, both on land and in the ocean, were too hot for most life forms, including plants. The cause of the warming event is debated, but was most likely due to a series of volcanic eruptions from the Siberian Traps that lasted two million years. The extinction occurred during an initial 60,000 year period, which is “sudden” in geologic terms. Recovery of the ecosystem, basically a whole new evolutionary period to create new animals, took 2 to 10 million years.

The End-Triassic extinction event came next, 201 mya. It was also associated with volcanic activity and the massive release of carbon, this time from the mid-Atlantic ridge. It probably triggered a positive feedback loop, with melting permafrost releasing tons of methane. The extinction period, affecting plants and animals, lasted about 10,000 years and paved the way for the rise of the dinosaurs.

The dinosaurs dominated after that, until all but the avian dinosaurs (the ones that evolved into birds) were wiped out by another mass extinction event 66 mya. This may have been caused by a comet or asteroid striking the earth, or by extreme volcanic activity creating global warming similar to the other events here (8 degrees Celsius over 40,000 years). This one is not shown on the graph.

Finally, there was the Paleocene-Eocene Thermal Maximum (PETM) and associated extinction event 56 mya. Likely caused by a combination of carbon and methane releases, this global warming event is the most recent, offers the most evidence and information, and is most analogous to climate change today. The continents were in roughly similar positions as today. The warming, 5 degrees Celsius in about 5,000 years, wiped out much benthic marine life, pushed the tropics to Wyoming and alligators to the Arctic Circle, warmed oceans to 97 degrees, and made the equatorial regions too hot for many species. The PETM is well-studied, with hundreds of papers available on-line, plus quite a bit of media coverage.

The high temperatures lasted for about 20,000 years. Eventually, the Arctic Ocean became covered with algae. These algae slowly absorbed CO2. When it died, it sank, taking the carbon with it to the bottom of the sea, lowering the carbon in the atmosphere and cooling the earth back to normal. This process took 200,000 years.

Climate change during these past events, considered rapid in geologic time, would have scarcely been noticed by animals on the ground. Animals didn’t go extinct by dropping dead; they just had a lower reproductive rate such that their populations slowly declined until none were left. Also, they evolved. In fact, there was a pulse of evolution during the PETM, producing, among other things, the first primates.

The current warming is 10 times faster than during the PETM. It is noticeable within the lifespan of an individual animal. Adaption thru evolution is not an option. Scientists mince no words:

“We conclude that, given currently available records, the present anthropogenic carbon release rate is unprecedented during the past 66 million years. We suggest that such a ‘no-analogue’ state represents a fundamental challenge in constraining future climate projections. Also, future ecosystem disruptions are likely to exceed the relatively limited extinctions observed at the PETM.”  – Zeebe (2016)

The PETM raised average earth surface temperatures 5 C. We’re at 1.1 C now, with probably up to 2 C already built into the system, meaning we’ll reach that even if we stop all carbon emissions tomorrow. We’re likely to reach 2 C even if we dramatically reduce emissions and successfully implement Direct Air Capture of ambient CO2 in the atmosphere. Assuming business as usual, we may reach PETM levels in 140 years.

Note: See hyperlinks for sources.

Magic from Isla Mocha: Pink-footed Shearwater conservation thru soccer and children’s theatre

PFSH1Many think of Pink-footed Shearwaters as a relatively common bird on West Coast pelagic trips. I like to call them the “photographer’s shearwater” because they invariably offer great photo ops off the back corner of the boat. But they are considered endangered by Chile, threatened by Canada, and vulnerable by the International Union for Conservation of Nature (IUCN). They could easily be called the Chilean or even Isla Mocha Shearwater, as the entire world’s population comes from just three islands off the coast of Chile, 85% from Isla Mocha, and the remaining 15% from Santa Clara and Robinson Crusoe Islands in the Juan Fernandez group.

The very limited breeding range of the Pink-footed Shearwater is actually pretty typical of seabirds. To use some other West Coast species as examples, about half of the world’s Ashy Storm-Petrels come from one hillside on Southeast Farallon Island, 95% of the world’s Black-vented Shearwaters come from Isla Natividad off the Pacific Coast of Baja, and 99% of the world’s Heermann’s Gulls come from tiny Isla Rasa in the Sea of Cortez.

PFSHmigration

New research (Felis et al 2019), following 42 satellite-tagged birds, describes their seasonal movements from their breeding colonies in Chile. The new paper focused on threats at sea, especially bycatch by purse seine and drift net fisheries in Peru and Chile. CLICK TO ENLARGE.

And, typical of most seabirds, Pink-footed Shearwaters face some daunting challenges at their breeding colonies. At Santa Clara Island, non-native European rabbits denuded native vegetation, caused erosion, and kicked the shearwaters out of their burrows. When the rabbits were eradicated in 2003, the number of shearwater pairs went up 40% in three years. Native plant revegetation continues. On Robinson Crusoe Island, cattle trampled burrows, but a fence installed in 2011 now serves to keep them away from the colony. Shout out to Oikonos (a non-profit based in California, Hawaii, and Chile) and the Chilean national park service (called Corporacion Nacional Forestal or CONAF) for these projects.

 

But the real conservation challenge is at the shearwater’s main colony on Isla Mocha. Here, the local fishing community of 800 people are accustomed to harvesting shearwater chicks from their burrows. They’ve done so since the community began in the 1930s. And each pair lays only one egg a year. Chick harvesting has been illegal since 1998, but enforcement within a small community where everyone is friend or family is difficult.

PFSHcup

Opening ceremonies of Copa Fardela soccer tournament.

Usually seabird restoration on breeding islands means restoring habitat or, more often, eradicating non-native rats, cats, mice, donkeys, you name it. But on Isla Mocha, Oikonos and CONAF have used another approach: outreach and education designed to reduce chick harvesting. The creative part is the strategy; the goal is for the islanders to identify with the shearwater as a symbol of their unique home, and thus want to protect them. Importantly, the project is led by a local Mochano, tapping into local values and local styles of communication. Thanks to the outreach efforts, school kids now flap their wings and enact dramas of the birds returning home. Adults play in the annual Copa Fardela (Shearwater Cup) soccer tournament.

This 48 minute video (in Spanish) documents the project. The Copa Fardela opening ceremonies, which features a children’s drama showing the shearwaters returning from the sea and producing a chick, begins around 42:00.

The fardela blanca, as they call it, is becoming their shearwater.

PFSH2

Three-acre beach restoration project produces first nesting Snowy Plovers in nearly 70 years

SMbeach2

Pilot study area after three years of protection and restoration. Plant cover has gone from zero to 5% coverage, which offers enough cover for plover nests.

Sandy beach restoration is simple and effective. A three-acre pilot project at Santa Monica Beach by The Bay Foundation has lead to the first nesting by Snowy Plovers in Los Angeles region in nearly 70 years. This was in 2017. Since then, plovers have remained in the area but not yet re-nested.

SMbeach1

This tiny project demonstrated “restore it and they will come.”

In fact, only two acres were actively restored thru not much more than a sand fence to build up sand hummocks and the distribution of native plant seeds to encourage dune vegetation. Add a key final ingredient: the absence of people and “beach grooming” (raking by trucks dragging large rakes). The third acre, on the ocean side of the restored section, was left un-groomed, a rarity in southern California. This leaves the “seaweed” (aka beach wrack), home to invertebrates and food to shorebirds. The cessation of beach grooming  has already been correlated with an increase in shorebird foraging.

Furthermore, a new native plant species, or possibly a rare variant, was discovered at the site, having germinated on its on. For a very detailed report on the project, see the project website.

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Snowy Plovers, a state and federally listed species, nest on sandy beaches, often putting them in conflict with human recreation.

 

Predicting winter irruptions: Correlating Red-breasted Nuthatch, Pine Siskin, and Red Crossbill winter invasions with previous years’ snowfall

I can almost do it; I’m just wrong this year.

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Pine Siskins in fall 2015 during the “superflight”. Davis, California.

Boreal seed-eating birds are notoriously unpredictable in their winter wanderings. Unlike a certain distinctive Dark-eyed Junco that once returned to my small apartment patio in Davis, California several winters in a row, these birds of the northern forests have no such allegiance to any patch of land. A Pine Siskin once banded in winter in Quebec turned up in California during a subsequent winter; other Pine Siskins banded in winter in New York and Tennessee spent a later winter in British Columbia; an Evening Grosbeak banded in winter in Maryland spent a later winter in Alberta; a Eurasian Siskin banded in winter in Sweden was later found in Iran; a Common Redpoll once wintered in Belgium, and later in China; another Common Redpoll banded in winter in Michigan was found during a later winter in Siberia (Newton 2006). In other winters, they hardly migrate at all. While up to 90% of band recoveries for many winter-banded species are pretty much where they were banded, that rate fall to about 1% for irruptive boreal species (ibid).

There’s a rich literature focusing on cone crop failure and irruptions of crossbills, redpolls, Clark’s Nutcrackers and other species (Reinikainen 1937, Lack 1954, Svardson 1957, Davis and Williams 1957 and 1964, Ulfstrand 1963, Evans 1966, and Eriksson 1970). To quote Newton (2006), “Clear evidence has emerged that major emigrations follow periodic crop failures.” Most recently, Wilson and Brown (2017) confirmed that Red-breasted Nuthatches are not fleeing bad weather nor are they attracted to specific food elsewhere; they are spreading across the land “because of failure of conifer seed production on the breeding grounds.” They are famine refugees. Other research has shown that, “despite the presumed benefits of irruption as an adaptive response to food shortage when population levels are high, negative population consequences can ensue.” Large irruptions are correlated with smaller numbers on Breeding Bird Surveys the following summer; they don’t all make it back (Dunn 2019).

Another factor, however, is high population densities of the birds (Bock and Lepthien 1976). Koenig and Knops (2001) reached some specific conclusions when they examined 30 years of Christmas Bird Count (CBC) data, focusing on multiple species, and compared it with data on cone crops. They found that Red-breasted Nuthatch, Black-capped Chickadee, Evening Grosbeak, Pine Grosbeak, Red Crossbill, Bohemian Waxwing, and Pine Siskin irruptions were “correlated with a combination of large coniferous seed crops in the previous year followed by a poor crop.” In short, a good year causes a pulse in reproduction, followed by a lean year which causes the expanded population to suddenly roam in search of food. There was some variation, with the good year or the bad year playing a more dominant roll for different species, but for most species, it was both. (And for Purple Finch, it seemed to be neither.) They concluded that “seed crops of boreal trees play a pivotal role in causing eruptions for a majority of boreal species, usually through a combination of large seed crop resulting in high population densities followed by a poor seed-crop, rather than seed-crop failure alone.”

RBNU Davis 10-12-15

Red-breasted Nuthatch, also in Davis in fall 2015.

A year previously, Koenig and Knops (2000) studied just the trees, and concluded that various tree species often boom and bust in sync. They noted that “the large geographic scale on which seed production patterns are often synchronized, both within and between genera, has important implications for wildlife populations dependent on the seeds of forest trees for food. In general, resident populations of birds and mammals dependent on mast are likely to be affected synchronously over large geographic areas by both bumper crops providing abundant food and, perhaps even more dramatically, by crop failures.” Newton (2006) reported synchrony in boreal conifer seed production in forests 1000 km apart. Strong et al (2015) links Pine Siskin irruptions to continent-wide winter climatic patterns.

With synchronized cone crop failures, one would expect synchronized irruptions across bird species. The literature on this is supportive but mixed. Bock and Lepthien (1976) provide nice annual maps by species illustrating “generally synchronous” irruptions in many (but not all) years. Koenig (2001) offers the most comprehensive analysis, exploring synchronous irruptions among all combinations of 15 species, including multi-year lagged effects. (Here it’s important to understand correlation coefficients, or Pearson’s r. For guidance in interpreting r, 1.00 would be a perfect match, 0 would mean no correlation, and -1.00 would mean they do the exact opposite of each other.) Koenig’s highest correlation coefficients between two species were generally between 0.30 and 0.50. He also shreds an earlier assertion from Bock (1999) that there is strong correlation between Common Redpoll and Pinyon Jay irruptions; there was, but it didn’t last long.

Here I examine 49 years of CBC data (1970-2018) for Red-breasted Nuthatch, Pine Siskin, and Red Crossbill from the northern Central Valley of California, centered around Sacramento. I used data from eight CBCs: Caswell-Westley, Folsom, Lincoln, Marysville, Rio Cosumnes, Sacramento, Stockton, and Wallace-Bellota. I didn’t have any data on cone crops, but I assumed they might be correlated with precipitation the previous year, so I looked at snowfall. In short, I find some support for Koenig and Knops, but I wouldn’t bet more than a beer on it in any given year.

Here are the results.  CLICK TO ENLARGE.

irruptiongraph

First, there are no units for the vertical axis. That’s because the units I used for the birds is basically an index. I converted them all to natural log (ln) because the numbers of siskins, which often occur in large flocks, dwarfed the nuthatches and crossbills. Converting to natural logs put them all more on a level playing field. What you’re seeing is the natural log of total individuals across all eight CBCs each year. (In most years, most birds were in the Sacramento CBC.) The blue circles are the water content (in inches) of the deepest observed snowpack from winter snow surveys at Upper Carson Pass from the previous winter. For example, the large irruption (or “superflight”) in 2015 occurred in the fall and winter of 2015-16, and the very low blue circle on that column is associated with the snowpack from the winter of 2014-15. In general, the snow surveys occurred in Jan-Apr and the CBCs in December of the same year.

A few quick observations from the chart:

  • Red Crossbills only occurred in six of the 49 winters, but 4 of those were during nuthatch/siskin irruptions. The only large crossbill irruption occurred in 2015, on top of the largest combined nuthatch/siskin invasion. The 2015 superflight also coincided with the lowest snowpack the previous winter, which came at the end of a four-year drought. So 2015, as an extreme event, tells us a few things. Previous snowpack is important, and correlation across species does occur.
  • Most of the other highest irruption years (1981, 1987, 1992, 2012) all came after low snowpack years, and all had higher snowpack the year before that, exactly what Koenig and Knops would predict.

And now for some math:

  • The correlation coefficient between nuthatches and siskins is 0.32, so they do tend to irrupt together-ish, but not always and certainly not in the same magnitude. Koenig writes, “For Red-breasted Nuthatch and Pine Siskin, synchrony over different 10-year periods varied from a high of 0.82 (1965-1974) to a low of 0.24 (1987-1996).” His sample included eastern North America, which he showed follows different patterns than the West.
  • I then looked at correlation between the cumulative nuthatch/siskin/crossbill irruptions (in natural log, so the full blue, yellow, and red columns in the graph) and a variety of other parameters. Here are the results:
    • Correlation with previous winter’s water content from snowpack (the blue circle): -0.44.
    • Correlation with water content more than 5″ below average: 0.41.
    • Correlation with multiple years of drought: 0.37.
    • Correlation with a 10″ drop in water content from the year before that (thus going from a good year to a worse year): 0.38.
    • Correlation with the same 10″ drop in water content, but only if the recent year was below average (thus, going from a good year to a bad year): 0.40.

So these correlations all lean in the right direction, supporting Koenig and Knops’ notion that bad years are bad, and bad years after good years are even worse. I would also add that bad years after bad years (a drought) are also bad.

These correlations come with some caveats. First, the correlation between snow water content and cone crop is imperfect. Koenig and Knops (1999) state that, while recent precipitation is indeed an important variable, it’s not the only one. Spring and summer temperatures play a role in cone development, as well as previous seasons. After a really good year, trees need a break, regardless of rainfall, and will produce less. An example might be 1984, where there was an irruption after an average snow year, but two really heavy precipitation years preceded that.

Another source of noise in the data is that our birds, especially the siskins, may be coming from much further afield than Tahoe. (I deliberately left out Evening Grosbeak because call types from our last invasion suggested the birds were brooksi from Washington state or somewhere up there.)

Donner Jan20-2015

Donner Pass without snow. January 20, 2015.

While it may seem that the data on irruptions and snowpack tell a compelling story, let’s not forget the present. It’s fall 2019 and we’re in the midst of a significant Red-breasted Nuthatch irruption (and I’ve seen one siskin as well). This year is not on the graph above, but we do already have the snowpack data from earlier in the year. It was way above average. Thus, we’ve just gone from an average snowpack year in 2018 to above-average in 2019, the opposite of what should prompt an irruption. If you bet me a beer, I’d owe you one.

References

Bock, C.E. 1999. Synchronous Fluctuations in Christmas Bird Counts of Common Redpolls and Piñon Jays. The Auk 99: 382-383.

Bock, C.E. and L.W. Lepthien. 1976. Synchronous eruptions of boreal seed-eating birds. American Naturalist 110: 559- 571.

Davis, J. and L. Williams. 1957. Irruptions of the Clark nutcracker in California. Condor 59: 297–307.

Davis, J. and L. Williams. 1964. The 1961 irruption of the Clark’s nutcracker in California. Wilson Bulletin 76: 10–18.

Dunn, E.H. 2019. Dynamics and population consequences of irruption in the Red-breasted Nuthatch (Sitta canadensis). The Auk 136.

Eriksson, K. 1970. Ecology of the irruption and wintering of Fennoscandian redpolls (Carduelis flammea coll.). Annals Zoologica Fennici 7: 273–282.

Evans, P.R. 1966. Autumn movements, moult and measurement of the lesser redpoll, Carduelis flammea. Ibis 106: 183–216.

Koenig, W.D. 2001. Synchrony and Periodicity of Eruptions by Boreal Birds. The Condor 103: 725-735

Koenig, W.D. and J.M.H. Knops. 2000. Patterns of annual seed production by Northern hemisphere trees: a global perspective. American Naturalist 155: 59-69.

Koenig, W.D. and J.M.H. Knops. 2001. Seed-crop size and eruptions of North American boreal seed-eating birds. Journal of Animal Ecology 70: 609-620.

Lack, D. 1954. The Natural Regulation of Animal Numbers. Clarendon Press, Oxford.

Larson, D.L. and C.E. Bock. 1986. Eruptions of some North American seed-eating birds. Ibis 128: 137-140.

Newton, I. 2006. Advances in the study of irruptive migration. Ardea -Wageningen 94: 433-460.

Reinikainen, A. 1937. The irregular migrations of the crossbill, Loxia c. curvirostra, and their relation to the cone-crop of the conifers. Ornis Fennica 14: 55-64.

Svardson, G. 1957. The ‘invasion’ type of bird migration. British Birds 50: 314-343.

Ulfstrand, S. 1963. Ecological aspects of irruptive bird migration in Northwestern Europe. Proceedings of the International Ornithological Congress 13: 780–794.

Wilson Jr., W.H. and B. Brown. 2017. Winter Movements of Sitta canadensis L. (Red-breasted Nuthatch) in New England and Beyond: A Multiple-scale Analysis. Northeastern Naturalist 24.