Trees ain’t thermometers

I used to work on Mountain Home State Forest in the southern Sierra. MHSF has about 3000 specimen-sized sequoia within its boundaries. Dendrochronolgists often visited to see the stumps from logging in the mid to late 1800s. These were often over 2000 years old when they had been cut.

The Dendrochronolgists were interested in the tree-ring patterns. Trees grow fast or slow in response to many factors and these seasonal factors (light, water, nutrients) created ring signatures or patterns. Certain years might have been favorable for growth with plentiful water, light and nutrients (each favorable year would be marked a large, wide ring) and certain years might have had poor conditions for growth–drought, late spring conditions, early winter–marked by thin (in some cases–microscopic) rings. In general, the wider the ring the more favorable the growing season, the narrower the ring the poor the growing conditions. These ring patterns can be distinctive and can be used to date archeological sites (where wood is present).

Oxford’s Tree-ring Laboratory put it this way:

The way dendrochronology works is relatively simple. As a tree grows, it puts on a new growth or tree-ring every year, just under the bark. Trees grow, and put on tree-rings, at different rates according to the weather in any given year: a wider ring in a favourable year and a narrower ring in an unfavourable year. Thus, over a long period of time (say 60 years or more) there will be a corresponding sequence of tree-rings giving a pattern of wider and narrower rings which reflect droughts, cold summers, etc. In effect, the span of years during which a tree has lived will be represented by a unique fingerprint, which can be detected in other geographically-similar tree-ring chronologies.

Using tree rings as a proxy for temperature however is fraught with caveats and pitfalls.

Mike D.‘s of the Western Institute for Study of the Environment comment (on William M. Briggs’ blog) about using tree ring data as proxies for temperature is an excellent explanation of the problems of using tree ring growth for temperature. He starts with how tree rings are laid down:

Diameter growth on any tree is theoretically a sigmoid growth function. No tree puts on constant radial growth year after year. Trees grow by adding a layer of new wood at the cambium, under the bark. Each year a larger surface area is added. If growth is constant, the rings get narrower. But growth is never constant. There is significant deviation from ideal (model) sigmoid diameter growth in individual trees regardless of the weather. Even when sigmoid growth models are used, the natural variation adds statistical error.

Two sigmoid curves. The taller is the period annual increment for cubic feet; the lower smoother S curve is for mean annual increment of cubic feet.

So as the diameter expands, the amount of material put on would need to be more if the ring’s width was to stay the same as the previous season. Think of a clay disk that you add the same amount of clay to in successive rings. The volume of clay would be the same but the thickness of each new ring would decrease. The ring growth is S-shaped (sigmoid) because initially the tree has little foliage for photosynthesis and often puts its initial years into root development for survival. Then once roots are deep enough the tree puts its growth into height and width.

He then points out that tree-to-tree competition for light, water, and nutrients also affects the ring growth:

Dense stands exhibit narrow rings on individual trees, sparser stands may have wider ring growth, yet both stands may have equivalent gross growth. That’s why only open-grown trees are supposed to be selected for ring studies. But nobody knows what the tree density surrounding an individual tree was 100, 200, 500 years ago. Competitors could have arisen and died without leaving evidence of their presence so long ago. More error.

Besides competition, disease and injury can affect growth.

Trees can sustain injuries that affect growth, such as top and branch damage, that are difficult to detect 200 years later, especially a few feet off the ground where the rings are sampled. There are very few pristine, undamaged trees. I know, having searched for such across broad acreages. Open grown trees at high elevations are always damaged. A heavy winter snow can snap off branches and the tree will exhibit reduced diameter growth for a few years, even if growing season conditions are ideal.

This makes using tree ring data as stand-ins for temperature problematic.

Ring width has all but been abandoned as a temperature proxy. Instead, the latest technique is sampling rings for O18 ratios, under the assumption that O18 varies with temperature. Regardless of the ring width, the O18 ratio is supposed to have recorded growing season temperature. But that theory is fuzzy and mushy, and O18 ratios in living trees correlate very poorly with known growing season temperatures. In other words, it calibrates with much error at best.

Trees are not thermometers, but even thermometers have some serious measurement error problems.

Tree ring studies are a fad akin to phrenology and other discredited pseudosciences that has not dissipated as it should have decades ago.

Mark Bittman asks, “What Do You Think About Genetically Engineered Food?”

Mark Bittman is asking, “What Do You Think About Genetically Engineered Food?”

Specifically, he wants you to answer four questions for a non-scientific poll:

1. Does it bother you that there are genetically engineered ingredients in most of the foods sold in American supermarkets?

2. Do you want the products that contain genetically engineered ingredients to be labeled “Contains Genetically Engineered Ingredients”?

3. Do you think that government agencies should enact stricter regulations for testing, growing, and marketing of GE crops and other products?

4. If genetically engineered salmon were to come on the market, it would not be labeled according to current policy and would therefore be indistinguishable (visually, at least) from other farm-raised salmon. Would this curb your overall purchasing of salmon?

It probably won’t surprise you that most of people said “yes” to all four questions.

I said “No” to all four.

Gene splicing characteristics is just the latest step in the way we humans have been altering the genetic structures of our food for 10,000 years. It is in many ways safer than natural breeding. After all, natural breeding involves the random mixing of tens of thousands of genes (genes are recipes for proteins) from two parent plants, resulting in entirely new proteins and other plant chemicals never before part of the food supply, but most people find this practice natural and quite acceptable.

Historically, worries about new technology have been wide of the mark. In 1825, Britain’s Quarterly Review howled about “[L]ocomotives travelling twice as fast as stagecoaches!” Some physicians predicted that the incredibly high speeds [nearly 20 miles per hour!] would cause psychological harm. Veterinarians worried that passing trains would cause pregnant mares to spontaneously abort. “We trust that Parliament will, in all railways it may sanction, limit the speed to eight or nine miles an hour,” the Review admonished.” Can’t be too careful, now can we?

A European Union report put it this way, “[A] genome (e.g., all the genes that make up an organism’s DNA) is not a static entity but a dynamic structure continuously refining its gene pool. So, for a scientist in genetics, the act of splicing to generate a transgenic organism is a modest step when compared to the genomic changes induced by all the ‘crosses’ and breeding events used in agriculture and husbandry.” Now, instead of breeding and repeatedly crossbreeding out unwanted traits, agronomists can place a single trait into a plant.

“[T]he environmental movement has done more harm with its opposition to genetic engineering than with any other thing we’ve been wrong about,” says Stewart Brand, leading environmentalist who authored The Whole Earth Catalog. “We’ve starved people, hindered science, hurt the natural environment, and denied our own practitioners a crucial tool. In defense of a bizarre idea of what is ‘natural’…we make ourselves look as conspicuously irrational as those who espouse ‘intelligent design’ or ban stem-cell research, and we teach that irrationality to the public and to decision makers.”

Should you wish to vote, you’ll need to register with the New York Time’s site. Bittman’s poll is here: http://bittman.blogs.nytimes.com/2011/02/15/what-do-you-think-about-genetically-engineered-food/#preview

A warmer and wetter world

I found a link the other day to a government website with global mean precipitation data from 1900 to 2000. Of course, I can’t find the link now (please comment if you have the link, but first see the note at the end of the post).

Anyway, I put the numbers into an Excel spreadsheet and graphed the data and added a trendline. (If you would like a copy of the xls file, please ask for it in the comment section below.) As the world warms it is getting wetter. As Matt Ridley writes in his book The Rational Optimist:

If you take the IPCC’s [International Panel on Climate Change] assumptions and count the people living in zones that will have more water versus zones that will have less water, it is clear that the net population at risk of water shortage falls by 2100 under all their scenarios. (emphasis added)

Global mean precipitation (1900-2000)
10 yr average-global mean precipitation (1900-2000)

Even the EPA cites the IPCC (2007) to say much the same thing:

As global mean temperatures have risen, global mean precipitation also has increased. This is expected because evaporation increases with increasing temperature, and there must be an increase in precipitation to balance the enhanced evaporation (IPCC, 2007). Globally, precipitation over land increased at a rate of 1.9 percent per century since 1901, but the trends vary spatially and temporally. Over the contiguous U.S., total annual precipitation increased at an average rate of 6.1 percent per century since 1901, although there was considerable regional variability. The greatest increases came in the South (10.5 percent per century), the Northeast (9.8 percent), and the East North Central climate region (9.6 percent). A few areas such as Hawaii and parts of the Southwest have seen a decrease.

Crops may flourish with warmer climes and more CO2. There is some indication that in California some trees are increasing their ranges in response to this change. While increasing temperatures do have their downside, they also have positive benefits as well.

Continue reading “A warmer and wetter world”

Plants moving to lower and warmer elevations in a warming world

A news release out of the University of California at Davis says, “study shows plants moved downhill, not up, in warming world.”

In a paper published last month in the journal Science, a UC Davis researcher and his co-authors challenge a widely held assumption that plants will move uphill in response to warmer temperatures. It turns out that plants respond more to moisture. The results are based on historical data collected by the U.S. Forest Service since the 1930s

Between 1930 and 2000, many California plant species moved downhill an average of 260 feet.  Jonathan Greenberg, an assistant project scientist at the UC Davis Center for Spatial Technologies and Remote Sensing said, “While the climate warmed significantly in this period, there was also more precipitation. These wetter conditions are allowing plants to exist in warmer locations than they were previously capable of.”

While the news release does not mention it, let me conjecture that increased CO2 availability may have played a role in the plants ability to move downhill despite warmer temperatures encountered at lower elevations. Plants do not need to open their stomata as much or as often for CO2 intake and therefore do not lose water through transpiration.

Many forecasts say climate change will cause a number of plants and animals to migrate to new ranges or become extinct. That research has largely been based on the assumption that temperature is the dominant driver of species distributions. However, the new study reveals that other factors, such as precipitation, may be more important than temperature in defining the habitable range of these species.

The findings could have global relevance, because many locations north of 45 degrees latitude (which includes the northernmost United States, virtually all of Canada and Russia, and most of Europe) have had increased precipitation in the past century, and global climate models generally predict that trend will continue, the authors said.

The study is titled “Changes in climatic water balance drive downhill shifts in plant species’ optimum elevations.” Greenberg’s co-authors are: graduate student Shawn Crimmins (the lead author), assistant professor Solomon Dobrowski (a UC Davis alumnus) and research analyst Alison Mynsberge, all of the University of Montana; and assistant professor John Abatzoglou of the University of Idaho.

Weekend Postcard: Carquinez Strait

This weekend’s postcard is from Benicia, California’s third capital (1853-1854).

This Super Bowl Sunday is warm and sunny in California. The rest of the country may be seeing snow, ice, and winter. It’s 75F as I post this. Last Sunday poured rain. This Sunday pours sunshine. Ah, California.

The picture was taken from the north side of the Carquinez Strait where Benicia sits.

Run for your lives! It’s lunchtime at Dr. Strangefood’s

One evening, during the drearily sodden summer of 1816, Lord Byron and his friends read Fantasmagoriana, (a French translation of a German book of ghost stories—they were intellectuals after all) in his Villa Diodati in Switzerland (they were rich intellectuals). Afterward, Byron suggested they all write a horror story. Everyone did except Mary, the wife of his friend, Percy. She kept demurring, saying she had not yet thought of anything suitable. Then one night they discussed the rumor that Erasmus Darwin had electrically “galvanized” a piece of a worm; an electric current had made the vermicello twitch. Mary Shelley began writing a moral cautionary tale of what happens when arrogant science meddles with nature: “Frankenstein.”

In 1816, the Industrial Revolution had just begun. Dizzying technological advancements such as the spinning jenny displaced workers from their livelihoods. Angry bands of men, calling themselves Luddites, smashed machines, murdered industrialists, and fought with the military.

Today we are experiencing the biotech revolution. The human genome [e.g., all the genes that make up an organism’s DNA]  has been mapped. Genes from one species are being placed into other species. Genetically modified E. coli bacteria now produce much of our insulin and GE yeast produce vaccines for us. About one-half of the acres planted in the United Stated are with genetically modified crops that resist insects or herbicides. The result is less soil erosion (the primary reason for tilling is weed control) and pesticide usage; one estimate puts the amount of pesticide (active ingredients only) not used at more than 100,000 tons and climbing.

Just as the Industrial Revolution triggered riots, so has today’s biotech revolution: vandals have uprooted genetically engineered (GE) crops and burned research facilities. Recently, Marie Mason, who said she was acting on behalf of the Earth Liberation Front, was sentenced to 22 years for torching the Michigan State University’s Agriculture building. She told the judge, “I meant to inspire thought and compassion, not fear.”

That humans have been altering the genetic structures of their food for 10,000 years gets lost in the shouting. As an example, the wheat we use for bread came about from the crossing of at least three different species of wild grasses from two different genera. This new food had new proteins and chemicals that were never, ever part of the food supply before. One European Union report put genetic engineering this way, “(A) genome is not a static entity but a dynamic structure continuously refining its gene pool. So, for a scientist in genetics, the act of splicing to generate a transgenic organism is a modest step when compared to the genomic changes induced by all the ‘crosses’ and breeding events used in agriculture and husbandry.”

Consider this: natural breeding involves the random mixing of tens of thousands of genes (genes are recipes for proteins) from two parent plants, resulting in entirely new proteins and other plant chemicals never before part of the food supply, but anti-GE advocates find this practice totally natural.

Now, instead of breeding and crossbreeding, and then breeding again to breed out unwanted traits, agronomists can now select and place a single trait into a plant.

GM products are as safe as any other food products. The World Health Organization (WHO), the U.S. Centers for Disease Control, and food agencies in the United States and Europe say GM foods currently on the market pose no health risk. The WHO says on their website, “No effects on human health have been shown as a result of the consumption” of GM foods.

“[T]he environmental movement has done more harm with its opposition to genetic engineering than with any other thing we’ve been wrong about,” says Stewart Brand, leading environmentalist who authored The Whole Earth Catalog. “We’ve starved people, hindered science, hurt the natural environment, and denied our own practitioners a crucial tool. In defense of a bizarre idea of what is ‘natural’…we make ourselves look as conspicuously irrational as those who espouse ‘intelligent design’ or ban stem-cell research, and we teach that irrationality to the public and to decision makers.”

“After 14 years of cultivation and a cumulative total of 2 billion acres planted,” writes Pamela Ronald, Professor of plant pathology at University of California, Davis. “GE crops have not caused a single instance of harm to human health or the environment.” Two-thirds of the processed food in our nation’s food system is GE.

Pamela Ronald has been slurred ‘a shill for industry’ in a recent letter to the Lake County Record-Bee’s editor. I suspect the writer had no idea that Professor Ronald is married to a certified organic gardener. Together they have written a book called “Tomorrow’s Table.” She has developed rice that can withstand two weeks of inundation, which will help poor farmers in Asia survive the monsoons. By the way, note the use of the term “poor farmers”: about ninety percent of farmers growing biotech crops are small and resource-poor farmers in developing countries, the majority of them in China.

It’s not Frankenfood; it’s just food, like we have been eating for thousands of generations, and it holds the promise to feed those most in need. “You people in the developed world are certainly free to debate the merits of genetically modified foods,” says Dr. Florence Wambugu of Kenya, “but can we please eat first?”

Nearly 200 years after fabulist Mary Shelley raised Romantic objections to science, some have labeled GM food as “Frankenfood.” Greenpeace, the Sierra Club, and other environmental organizations hold that we are playing god and meddling with forces that we cannot possibly understand. Yet, historically, predictions often end up quite wide of the mark.

About two hundred years ago, Britain’s Quarterly Review howled about “[L]ocomotives travelling twice as fast as stagecoaches!” Some physicians predicted that the incredibly high speeds (nearly 20 miles per hour) would cause psychological harm. Others predicted that passing trains would cause pregnant mares to spontaneously abort. “We trust that Parliament will, in all railways it may sanction, limit the speed to eight or nine miles an hour,” the Review admonished.” Worries about new technology have often proven to be overblown.

Let’s eat, and not confuse the product with the process.

Sunday funny

I wrote recently that Mick Hume over at Spiked-online had a thoughtful post on the “shocking” revelations that a British undercover cop, Police Constable (PC) Mark Kennedy has gone native and offered to give evidence for the defense. Now Josh at Cartoons by Josh has added humor. He worries “it might not play on the US as I think the policemen there have ‘Night sticks'” In our law enforcement training we called them ‘batons.’