Global Warming and Walnut Trees: a Case Study in Deception

Guest post by Dr. David Deming

The science of global warming is allegedly “settled.” The American Physical Society has declared that “global warming is occurring” and that the “evidence is incontrovertible.” According to environmentalists and advocacy organizations, unchecked global warming will lead to an environmental disaster of unprecedented proportions. Polar icecaps will melt and rising seas will inundate coastal cities. Species will become extinct. Green pastures and sylvan glades will be transformed into deserts of scorched and desiccated sand.

But the science of global warming is not settled. And there is scarcely any unambiguous scientific evidence that significant future harm will occur to either human beings or the natural environment. People have been systematically deceived by a coalition of environmentalists, governments and institutions that feed off a stream of funding for climate research. This essay documents in specific detail one example of how this deception has been promulgated.

On November 28, 2011, Purdue University issued a press release titled “Walnut trees may not be able to withstand climate change.” Subsequently, the material in the press release was recycled by various media outlets under headlines such as “Walnuts are super-sensitive to climate,” and “walnut industry may crack under climate pressure.” One writer asserted that the genus Juglans could be “pushed to the verge of extinction within a few decades,” explaining “this is the conclusion of a recent study issued by Purdue University.” Walnut trees were vulnerable because “they can’t handle low or high temperatures.”

By now, we’re all used to seeing everything imaginable either linked to, or blamed upon, global warming. The list is long and ludicrous. But I was taken aback by the claim that walnut trees were somehow especially sensitive to climate change. From personal experience, I knew walnut trees to be hardy, not fragile.

I have about half a dozen Black Walnut (Juglans nigra) trees on my property in central Oklahoma (see photo).

Oklahoma has a harsh climate. Record temperature extremes range from a low of -31 degrees F to a high of 120 degrees F. Droughts, heat waves, ice storms, hail, and high winds are common.

According to the Oklahoma State University agricultural extension, “severe weather is a fact of life in Oklahoma” with “storm-related damage a major impediment to maintaining healthy trees.” But my walnut trees thrive under these conditions. And in 2011, my Black Walnut trees survived one of the hottest and driest summers in recorded history.

During the summer of 2011, the southcentral US experienced severe heat and drought. Average statewide rainfall in Oklahoma from October 1, 2010, through July 30, 2011, was 16.7 inches, 14 inches below average. The Oklahoma Climatological Survey described this as an “one of the worst short-term droughts in state history,” the “driest on record.”

The heat in Oklahoma over the summer of 2011 was exceptional. The average temperature for Oklahoma in July of 2011 was 89.1 degrees F, “more than 7 degrees [F] above normal.” It was the hottest July on record for Oklahoma, exceeding the Dust Bowl days of the 1930s. It was also the hottest month ever recorded for any state in the conterminous US.

August of 2011 was also exceptionally hot in Oklahoma. The statewide average temperature for that month was 87.7 degrees F, 7.3 degrees above average, and the hottest August on record for the state of Oklahoma.

Altogether, the months of June, July, and August 2011 were the hottest summer Oklahoma has experienced in recorded history. My walnut trees endured months of drought and extreme heat. The thermometer on my back porch commonly registered temperatures above 105 degrees F and sometimes exceeded 110 degrees F.

Two of my walnut trees compensated for environmental stress by dropping branches. Abscission in walnut is a common response to drought. But the trees survived. And they did more than just survive. They produced a large number of walnuts (see photo).

As a scientist, I understand the difference between anecdotal data and systematic empirical investigations. It is possible that my six trees may not be typical of Juglans nigra specimens in general. According to the US Department of Agriculture’s  Silvics of North America, “Black Walnut contains great genetic variation for growth and survival.” Of course, the very existence of genetic variation in Black Walnut implies that it is not a fragile plant, but a hardy tree capable of enduring and surviving environmental stress.

Contrary to what the press release from Purdue asserted, my experience in Oklahoma over the summer of 2011 suggested that walnut trees were hardy, not fragile. So I decided to do what people rarely do: I read the scientific research article upon which the press release was based. What I found was shocking. The press release issued by Purdue University was not just tendentious and misrepresentative. It was plainly deceptive.

The Purdue press release alleged that walnut trees are especially susceptible to damage from climate change. It stated that “warmer, drier summers and…climate changes would be especially troublesome–possibly fatal–for walnut trees.”

But the research paper read (page 1270) “there is considerable uncertainty regarding the magnitude of potential effects of climate change on walnut. Some studies tend to indicate walnut could be negatively impacted by climate change, while others do not.” Remarkably enough, the research paper also stated climate change could be beneficial for walnut trees. Buried in the text (page 1286) is the statement that there is “evidence suggesting walnut growth and distribution may remain stable or increase in the twenty-first century.”

The Purdue press release claimed that walnut “has an extremely narrow range.” But it doesn’t. The genus Juglansis found worldwide. The range of the species Juglans nigra alone extends over most of the eastern US. According to Silvics of North America, the natural range of the Black Walnut extends from Florida north to Massachusetts, Michigan, and Minnesota. Juglans nigra is found on the east coast of the US westward to the states of Kansas, Oklahoma, and Texas.

A genus or species with a wide geographic range must have an inherent ability to withstand the climatic variations found within its range. The wider the range, the hardier the tree. If a person wanted to portray a tree as fragile or especially susceptible to climate change, they would necessarily have to describe its range as limited.

The text of the press release asserted that “almost all climate change models predict that climates will become drier.” But the text of the research paper stated (page 1285) that “in North America and northern Europe, mean annual temperature and precipitation are expected to increase.”

The Purdue press release described walnuts as being “sensitive to cold.” This is partly correct. Like many other trees, walnuts can be damaged by late spring frosts. But spring frosts are a symptom of global cooling, not global warming. And Juglans nigra is remarkably resistant to winter cold. It can withstand winter temperatures as low as -45 degrees F. It survived the Pleistocene Ice Ages. The very fact that the genus Juglans is not extinct is evidence that these trees have survived all the climatic variations and extremes that have occurred on the planet Earth since their evolutionary origin about 60 million years ago.

Purdue’s press release stated that “walnuts would have difficulty tolerating droughts.” My experience over the summer of 2011 was anecdotal, but demonstrated that at least some Black Walnut trees could shrug off droughts, even extreme ones. One reason that Juglans nigra is resistant to drought is foundSilvics of North America. The root system of Juglans nigra is described as “deep and wide spreading, with a definite taproot…[and the tree is] able to rely on the deeper soil layers for survival during times of drought.”

Critical information was omitted from the press release. The text of the research paper stated that carbon dioxide and global warming may actually prove to be beneficial for the walnut tree. But these statements were completely absent from the press release.

Carbon dioxide fertilizes trees. Trees grow faster and larger when the concentration of carbon dioxide in the atmosphere increases. The research paper reported (p. 1280) that “a five-fold increase in CO2…generated growth increases of 70%.” The authors concluded (p. 1286) that “productivity gains associated with increased atmospheric CO2 in walnut appear to be greater than average.”

The research paper also stated (p. 1286) that global warming could benefit walnut trees by extending their range. “Milder winters may actually increase walnut establishment,” and “areas that are currently considered cold for walnut growth may see increased establishment and growth.” But the press release stated that climate change could be “fatal” for walnut trees, not beneficial.

The press release from Purdue repeatedly emphasized the economic value of walnut trees. Purdue was right. Walnuts and walnut wood are valuable. If you want people to give you money to conduct research on walnuts you have to convince them that there is a crisis at hand, and that you’re going to save them from it. You can hardly state that climate change is likely to benefit the walnut. You have to convince the public that there is some tangible benefit to be derived from the money they are giving you. So the propaganda you want politicians and the public to read is placed in a press release while the truth is buried in the scientific literature. After all, hardly anyone reads the scientific literature other than a handful of specialists.

It is not difficult to understand why people and institutions exaggerate the potential dangers of global warming and omit any mention of the probable benefits. There are billions of dollars available for climate change research. Obama’s 2011 budget allocated $2.6 billion for the “global change research program.” This stream of cash has created a monstrous industry that produces junk science that feeds demands for even more money. It is a scam.

In summary, this is a sad example of how money and ideology have corrupted contemporary science. Everything has to be tendentiously linked with climate change in order to obtain money. The public is being swindled, and the respect people have for science and scientists is being eroded. I feel especially sorry for the gullible activists who have a sincere concern for environmental quality. They’re being played for fools.

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David Deming is associate professor of arts and sciences at the University of Oklahoma. His book, Black & White: Politically Incorrect Essays on Politics, Culture, Science, Religion, Energy and Environment, is available for purchase on Amazon.com.

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I add this to Dr. Demings essay. The black walnut is common throughout California, even perrenially dry southern California. The Wikipedia entry on the tree says:

Juglans californica, the California black walnut, also called the California walnut, or the Southern California black walnut, is a large shrub or small tree (up to 30 feet tall) of the Juglandaceae (walnut) family endemic to California.

J. californica is generally found in the southern California Coast Ranges, Transverse Ranges, and Peninsular Ranges, and the Central Valley. It grows as part of mixed woodlands, and also on slopes and in valleys wherever conditions are favorable. It is threatened by development and overgrazing. Some native stands remain in urban Los Angeles in the Santa Monica Mountains and Hollywood Hills. J. californica grows in riparian woodlands, either in single species stands or mixed with California’s oaks (Quercus spp.) and cottonwoods (Populus fremontii).

It seems development is a bigger threat than drought/heat.

English Walnuts are also widely cultivated where I live, and they routinely experience 110F + temperatures in the hot summer of the Sacramento Valley.