Scorched Earth

Salton Sea, California

All following images are from the book:  Overdevelopment, Overpopulation, Overshoot (OVER)
because climate is only one symptom of the Endocene

This week I had a discussion via email with Guy McPherson about tropospheric ozone, how it directly harms trees, and why that exacerbates climate change in a reinforcing loop.  After I provided him the substantiation he requested, this led to inclusion on his epic list of amplifying feedbacks.   The damage to forests from ozone is now listed as Number Four under the heading, Climate-Change Summary and Update, a link that is prominently posted at his website, Nature Bats Last.  This is quite an honor for Wit's End, so I am very grateful he took the time to consider the evidence.

Number Four on his list reads:

4. Ozone, a powerful greenhouse gas, also contributes to mortality of trees (Global Change Biology, November 2011). Tree mortality reduces uptake of atmospheric carbon dioxide and instead accelerates the contribution of carbon dioxide into the atmosphere. Forest dieback resulting from atmospheric ozone is the primary topic addressed by Gail Zawacki at Wit’s End.

I looked on this exchange as a great opportunity for me to boil down the hundreds of scientific papers and articles I have read to just a few of the most persuasive, and so I'm going to post them below.

Initially Guy had asked me if I could describe exactly how trees dying from ozone increases global warming; and how warming increases ozone.

I reponded as follows:

Ozone is a potent greenhouse gas in itself.

Ozone is causing massive forest dieback.

Trees are a primary mechanism of CO2 removal - their loss will increase the concentration in the       atmosphere, accelerating warming.

More warming leads to more ozone.

Methane is also an ozone precursor, particularly of the persistent background concentration that is so damaging to vegetation, and more warming leads to more methane release.

I added an excerpt from the abstract of a meta-analysis from 2007, which was cited by the EPA in their (failed) attempt to tighten ozone regulations in order to protect forests, and pointed out that like so much else in the realm of climate research, the effects predicted to happen by "2100" are actually already happening, much faster and are much worse than anyone officially anticipates. 

"Modern day concentrations of ground level ozone pollution are decreasing the growth of trees in the northern and temperate mid-latitudes, as shown in a paper publishing today in Global Change Biology. Tree growth, measured in biomass, is already 7% less than the late 1800s, and this is set to increase to a 17% reduction by the end of the century."

"The study is the first statistical summary of individual experimental measurements of how ozone will damage the productivity of trees, including data from 263 peer-reviewed scientific publications...But more importantly, it has the potential to leave more carbon dioxide, ranked as the first strongest greenhouse gas, in the atmosphere by decreasing carbon assimilation in trees...'"

'This research quantifies the mean response of trees to ozone pollution measured in terms of total tree biomass, and all component parts such as leaf, root and shoot, lost due to ozone pollution,' said Dr. Victoria Wittig, lead author of the study. 'Looking at how ozone pollution affects trees is important because of the indirect impact on carbon dioxide concentrations in the atmosphere which will further enhance global warming, in addition to ozone's already potent direct impact.'"

Guy next asked for links to peer-reviewed journal publications, and the EPA findings, in support of my statements so I sent him the following, slightly edited list:

1.  Link to Wittig's paper quoted above.

Other peer reviewed journal articles:

2.  Global Change Biology:  "Tree mortality in the eastern and central United States: patterns and drivers"

From the abstract:  "We investigated 13 covariates in four categories: climate, air pollutants, topography, and stand characteristics. Overall, we found that tree mortality was most sensitive to stand characteristics and air pollutants."

3.  Science Direct:  "Tropospheric Ozone:  A continuing threat to global forests?  From the abstract:

"Ozone (O₃) has a critical role in tropospheric chemistry. It absorbs radiation in the infrared and ultraviolet regions and is very reactive and biologically toxic at appropriate levels of exposure. At the earth's surface, O₃ is subject to long-range transport and is the most pervasive air pollutant affecting the world's forests today. The existence of O₃ has been known since 1840 and smog-induced foliar injury on plants was first identified in the 1950s. Levels were ∼10–15 ppb during the second half of the 1800s, compared with 30–40 ppb measured as the global background today. By 2100, fully 50% (17 million km²) of world forests are predicted to be exposed to O₃ at concentrations >60 ppb. Ozone induces a variety of symptoms and pattern of injury that are dependant upon species, genotype, leaf position on the plant, leaf age, exposure dynamics, and meteorological factors or growth conditions. It is absolutely essential to have knowledge on species sensitivities, O₃ profiles and toxicity concentrations for the species under investigation before diagnosis can be confirmed. Ozone is generally detrimental to tree growth and ecosystem productivity, often through induced changes in patterns of carbon allocation or pre-disposition to insects and disease."

4.  Excerpt from "Global Alert", a book by Dr. Jack Fishmann, student and then colleague of Paul Crutzen, and Susan Solomon (you can see his lecture Dec. 2013 "Are We Creating a Toxic Atmosphere?" at the Max Plank Institute here):

"The earth is an enclosed system, with a wonderful proclivity to cleanse itself, but it is being taxed to the limit by the sheer number of humans and their waste products in the form of gases and manufactured chemicals. This is not speculation; it is already happening. These are the signs: In the autumn of 1988 the NYTimes published a story about the Jamaican palm trees in the southeastern United States being decimated by a disease known as yellowleaf fungus. The species may disappear from America by the turn of the century. Although the cause of the disease is a known fungus, the underlying cause is the increased ozone levels in the air, which, by placing the trees under stress, pave the way for the attacking fungus…Forest in parts of Germany are suffering from “early autumn” syndrome: they lose their leaves by late August and early September. The cause? Increased ozone levels in the air…During the sumer of 1988 American farmers lost between $1 billion and $2 billion in crops. The drought was a factor, but a sizable fraction of the losses from lower crop yields can be attributed to increased ozone in the atmosphere."

p. 18  "Increased ozone levels are destroying our forests, diminishing our crops, and adding to the global warming trend."

Posted with more transcribed excerpts here.

5.  From published research by Andrew Bytnerowicz re: the San Bernardino Mountains

"In the 1970s, when the first reliable measurements of O3 started, peak concentrations could reach 600 ppb (National Academy of Sciences, 1977), and national and state air pollution standards were exceeded during most of the photochemical smog season (http://www.arb.ca.gov/ html/brochure/history/htm). During that time it was also determined that the mysterious ‘‘X’’ disease killing thousands of sensitive ponderosa (Pinus ponderosa) and Jeffrey (Pinus jeffreyi) pines in the SBM in the 1950s was caused by high O3 concentrations in combination with frequent drought stress and severe bark beetle attacks (Miller et al., 1963; Taylor, 1999).This was the first worldwide evidence of a large-scale decline of coniferous forests caused by ambient O3 (Mackenzie and El-Ashry, 1989)."

"In the early 2000s, a widespread dieback of trees in the SBM started to take place due to prolonged drought, over-stocking of forests caused by long-term fire suppression, air pollution, and bark beetle infestation that eventually resulted in a death of 4.6 million trees (Christensen et al., 2007). Such enormous amounts of dead biomass caused a very serious risk to the remaining forests and to the local population. The 2003 fires in the SBM (Keeley et al., 2004) showed that a very high probability of catastrophic fires exists in southern California mountainous forests." 

 

6.  Regarding EPA, research by the USFS indicates that human health standards ("primary") are not enough to protect vegetation, so that stricter, "secondary" regulations should be implemented.

  

"The EPA has concluded that the primary NAAQS based on an hourly average concentration and used to protect human health is inadequate to protect sensitive ecosystems, and has proposed a new secondary standard that is targeted to protect non-urban and non-crop natural vegetation and ecosystems. The EPA has specifically indicated that a strengthened primary standard for ozone will not adequately protect sensitive tree species in higher elevation Western ecosystems where little O3 data are available."

Directly from EPA Secondary Ozone NAAQS Evaluation:

"Exposure to ozone has been associated with a wide array of vegetation and ecosystem effects in the published literature (U.S. EPA, 2006). These effects include those that damage or impair the intended use of the plant or ecosystem. Such effects are considered adverse to the public welfare and can include reduced growth and/or biomass production in sensitive plant species, including forest trees, reduced crop yields, visible foliar injury, reduced plant vigor (e.g., increased susceptibility to harsh weather, disease, insect pest infestation, and competition), species composition shift, and changes in ecosystems and associated ecosystem services.

"Specifically, plants may become more sensitive to other air pollutants, or more susceptible to disease, pest infestation, harsh weather (e.g., drought, frost) and other environmental stresses, which can all produce a loss in plant vigor in ozone-sensitive species that over time may lead to premature plant death. Furthermore, there is evidence that ozone can interfere with the formation of mycorrhiza, essential symbiotic fungi associated with the roots of most terrestrial plants, by reducing the amount of carbon available for transfer from the host to the symbiont (U.S. EPA, 2006)."

"Ozone impacts at the community and ecosystem level vary widely depending upon numerous factors, including concentration and temporal variation of tropospheric ozone, species composition, soil properties and climatic factors (U.S. EPA, 2006). In most instances, responses to chronic or recurrent exposure in forested ecosystems are subtle and not observable for many years. These injuries can cause stand-level forest decline in sensitive ecosystems (U.S. EPA, 2006, McBride et al., 1985; Miller et al., 1982)."

EPA Welfare Risk and Exposure Assessment for Ozone Second External Review Draft Executive Summary:

RISK TO VEGETATION AND ECOSYSTEMS - In this welfare REA, we quantified the impact of O3 exposure on two categories of ecological effects: (1) relative biomass loss for trees and crops, and (2) visible foliar injury...cosystem services most directly affected by biomass loss include: (1) provision of food and fiber (provisioning), (2) carbon storage (regulating), (3) pollution removal (regulating), and (4) habitat provision for wildlife, particularly habitat for threatened or endangered wildlife 

note:  In this welfare REA, we do not quantify insect damage resulting from O3 exposure. In the next Section, Risk to Ecosystem Services, we briefly discuss the ecosystem services associated with insect damage on tree stands and timber production, including the overlap of areas with higher W126 concentrations and risk of bark beetle infestation. 

EPA:  Integrated Science Assessment of Ozone and Related Photochemical Oxidants (Final Report)

Chapter Nine refers to ozone's impact on ecosytems (as opposed to human health)

(citation to Wittig, the first excerpt I sent, is on p. 9-186)

As to how ozone killing trees is an amplifying feedback effect to climate:

1.  More trees means lower temperatures because when moisture evaporates from leaves it cools the air.  Loss of trees leads to higher temperatures.

"Air Pollution Removal and Temperature Reduction by Gainesville's Urban Forest" publication from the University of Florida:

2.  Higher temps also cause leaves to close stomata, meaning they take up significantly less pollution, leaving more in the air, creating more heat (and damage to people and plants):

"It's not just the heat, it's the ozone:  Hidden heat wave dangers exposed" - title of an article in ScienceDaily about a paper called:  "Scorched Earth: how will changes in the strength of the vegetation sink to ozone deposition affect human health and ecosystems?"

Vegetation plays a crucial role in reducing air pollution, but new research by the Stockholm Environment Institute (SEI) at the University of York shows that they may not protect us when we need it most: during extreme heat, when ozone formation from traffic fumes, industrial processes and other sources is at its worst.

The reason, explained lead author Dr Lisa Emberson, is that during heat waves -- when the ground is especially dry -- plants become stressed and shut their stomata (small pores on their leaves) to conserve water. This natural protective mechanism makes them more resilient to extreme heat and high ozone levels, but it also stops them from absorbing ozone and other pollutants.

"...we know that pollutants such as ozone and its precursors can carried around the globe," she says.

The research can also inform public-health responses, Dr Emberson says. For example, people may mistakenly believe that as long as they get out of the city, they are not at risk from poor air quality, so it is important to raise their awareness."

3.  Higher temperatures from climate change lead to even more ozone formation:

From the report by the Union of Concerned Scientists, titled "Rising Temperatures, Worsening Ozone Pollution"

"Given the strong dependence of ozone formation on temperature, a changing climate can make ozone pollution worse. As temperatures increase in a warmer world, days that are conducive to ozone formation are likely to be more frequent...

...What this means is that climate change is likely to complicate the challenge of reducing ozone pollution. Although emissions of ozone-forming pollutants are currently declining, temperature increases associated with climate change are likely to work against this trend. As a result, even to maintain today’s ozone levels may require a greater reduction in precursor emissions. Also, there could be a positive-feedback effect; because increasing temperatures would correspond to greater electricity demand for air conditioning during hot summer months, emissions of ozone-forming pollutants from fossil-fuel power plants would probably increase further."

I didn't add this one, but it's worth mentioning that scientists who have been studying the death of plant species for over a decade in China now believe that the nitrogen emissions in smog - the precursors to ozone - are threatening to "massacre" the world's forests.  An article about their study said the following:

Thick smog could kill off most southern China's natural forests within decades and threatens trees around the world unless nations take action, say scientists.

A 13-year study by Chinese scientists has revealed strong evidence to show the danger is being caused by nitrogen emissions in the atmosphere.

"It is a silent massacre," said Dr Lu Xiankai, associate researcher at Chinese Academy of Sciences' South China Botanical Garden in Guangzhou and a lead scientist of the project.

At one observation point in Dinghu Mountain, Zhaoqing , more than a dozen plant species growing below an old tree had died off until only one or two were left, and the tree could be next to go if the "nitrogen fallout" from smog continued, Lu said.

"Immediate measures must be taken to reduce air pollution, especially nitrogen emissions," Lu said.

"If the situation remains as it is, most forests in southern China will be destroyed within decades. But the impact is not limited in China. The problem will have a ripple effect around the world."

The study, published in this month's Environmental Science and Technologyjournal, run by the American Chemical Society, said the scientists took more than a decade to find solid evidence that smog is killing off trees.

Nitrogen is one of the most important causes for the formation of smog. Many human activities, such as industrial production and vehicle exhaust emissions, pump large quantities of nitrogen into the atmosphere.

Episode 10 of Extinction Radio with my weekly Dispatch from the Endocene is now available for listening!  Thanks to all the hardworking doomers who put the show together.