Is half the country enough?

 kw: book reviews, nonfiction, land use, agriculture, prairies, restoration, conservation

About 45% of the land area of the "lower 48" is devoted to agriculture. That is about 900 million acres, or 1.4 million square miles. Roughly one third of that was originally prairie, tallgrass, shortgrass, and mixed prairie ecosystems. Most has been converted to agricultural use. Prior to the arrival of the plow, the prairie encompassed

• Tallgrass prairie, 140 million acres, or 220,000 sq mi. All but 1% has been plowed and sowed with crops.
• Mixed-grass prairie, 140 million acres, or 220,000 sq mi. About one-quarter remains unplowed.
• Shortgrass prairie, 250 million acres, or 390,000 sq mi. About one-fifth remains unplowed.

Taken together, prairie grassland once encompassed 530 million acres, but now more than 440 million acres are devoted to agriculture, making up nearly half the total agricultural land in the US. Surveys of the remaining grasslands show that they are ecologically rich, with dozens of species of grass and hundreds of other plant species, hundreds of bird and mammal and other animal species (and of course tons of insects!), and rich soils that have accumulated over ten to twenty thousand years during the current Interglacial period.

Sea of Grass: The Conquest, Ruin, and Redemption of Nature on the American Prairie, by Dave Hage and Josephine Marcotty, chronicles the history of these grasslands that formerly covered one quarter of the contiguous US. Their characteristics are governed by rainfall. The western edge of the shortgrass prairie laps up against the foothills of the Rocky Mountains, and this semiarid prairie is in the deepest part of the mountains' rain shadow. The eastern half of four states, Montana, Wyoming, Colorado, and New Mexico, plus the Texas panhandle, host shortgrass prairie.

Further east, a little more rainfall allows medium-height and some taller grasses to grow. This mixed-grass prairie makes up most of the area of North and South Dakota, Nebraska and Kansas, plus the middle of Oklahoma and Texas. Tallgrass prairie is supported by the more temperate rainfall amounts in Minnesota, Iowa, Illinois, northern Arkansas, eastern Kansas, and a little bit of eastern Oklahoma. The eastern extent of the prairie abutted the deciduous forests of the Midwest, which are now mostly stripped of trees and used to grow corn and soybeans.

The book's three parts cover, with some overlap, the prehistory of the prairie, the progress of its subjugation to agricultural use, and the progress of efforts to conserve and restore portions. The third part includes 40% of the book, and is clearly the authors' aim.

Rather than repeat details that are better stated by the authors, I'll just display the bottom line: Prairie soils are biologically rich, conferring great ecosystem services. These include sequestering large amounts of carbon dioxide, absorbing rainwater runoff which reduces acute flooding, and quickly taking up excess nitrogen from over-fertilization of nearby agricultural fields rather than permitting it to flow into streams and eventually the Mississippi River and the northern Gulf of America. These points are being made in courtrooms throughout the central US, arguing not only that remaining prairie should be preserved and conserved, but that portions of agricultural fields in this area amounting to several percent should be reverted to native grasses to reduce the damaging effects of pervasive monocropping.

Existing primordial prairie is also a treasure to be enjoyed. The image above is like views I've seen in a few grasslands we've visited. In the early 1980's whenever my wife and I went to visit a rancher we knew in central South Dakota, there is a spot along I-90, about seven miles before reaching Wasta, on the plateau above Boxelder Creek and the Cheyenne River, where we always stopped to get out of the car and stretch our legs. In all directions, the only sign of human life was the highway itself, and, of course, us and our car (I note on current satellite images that there are a number of billboards and a new shelter belt in the area now. Sigh.).

Other efforts are discussed, such as researching the best cover crops to preserve soil from erosion after harvest, and finding the "knee" in the relationship between fertilization and crop yields to better select appropriate levels of nitrogen application—I find it amazing that this is still so little known.

In keeping with the importance of the subject, the book is big and packed with information and gripping stories. It is well written and it rewards close reading. Enjoyable.

Greenhouse Effect – the hidden players

 kw: analytical projects, greenhouse effect, global warming, absorption spectra, saturation

Reading a book about agriculture led me to thinking about the "hidden" greenhouse gases. I am sure almost everyone has read or heard that methane is 80 times as potent as carbon dioxide as a greenhouse gas. I recently learned that nitrous oxide (laughing gas, also a dental anesthetic) is between 250 and 300 times as potent as carbon dioxide. Both of these gases are produced by agricultural activity, so they have increased in the past 200 years as agriculture has been increasingly mechanized, and as chemical fertilizers have been used in ever-increasing amounts. (I generated this image using Leonardo AI; it is free of copyright restrictions)

I researched in several sources to find answers to these questions:

• What were the concentrations of nitrous oxide and methane prior to the Industrial Revolution?
• What are their concentrations now?
• How to they affect global warming?
• Are there other greenhouse gases we should be concerned about?

To simplify the text, I will dispense with formatting the numbers in chemical formulas as subscripts. Thus, CO2 = Carbon Dioxide, CH4 = Methane, and N2O = Nitrous Oxide (Nitrogen has several oxides; only this one is important here).

Here is the connection with agriculture: The middle-American farm belt was created by plowing the prairie and planting grain crops. Today, by far the most important crops are corn and soybeans. The thick, rich prairie soils contained a 10,000-year store of CO2, deposited by the roots of grasses and held there as they decomposed. Plowing the prairie released the CO2 at a pretty steady rate over the past century. It is still going on. Plowing also releases stored CH4.

When I lived in South Dakota in the 1970's and early 1980's, most of the agriculture in the state was cattle ranching, with some grain crops being grown in the eastern third. Since that time seed companies have developed strains of corn and soybeans that can better resist drought, begin growing at lower temperature and ripen faster. South Dakota cattle ranches are being plowed and sown with grains at a steady rate.

Secondly, overuse of nitrogen fertilizer causes much of the "extra" to be converted to N2O. Large amounts also go downstream and contribute to the Dead Zone offshore of the Mississippi Delta.

Thirdly, cattle produce a lot of methane, and the reduction in cattle numbers in the Dakotas is more than offset by continued increases elsewhere; also, plowing the prairie releases CH4, and all this is added to the amount released by fossil fuel production. I have yet to see a credible analysis of all the sources of CH4.

Yet all we ever hear about is the rise in concentration of CO2 alone. This is indeed significant, from about 280 ppm in the 1700's to about 440 ppm today. This "baseline increase" is (440-280)/280 = 0.57, a 57% increase in the past century or so. 

What of CH4 and N2O? Let us first convert them to equivalent CO2. I'll leave out a lot of words and summarize the figures:

1. CH4 as a GHG is 80x as effective as CO2. Current CH4 concentration is 1.9 ppm; times 80 that is equivalent to 152 ppm CO2. In the 1700's, CH4 was 0.72 ppm, or CO2 equivalent (CO2eq)  of 57.6 ppm.
2. N2O as a GHG is ~280x as effective as CO2. Current N2O concentration is 0.34 ppm; times 280 that is equivalent to 95.2 ppm CO2. In the 1700's, N2O was 0.27 ppm, or CO2eq of 75.6 ppm.

Added together, these two gases presently have CO2eq of 247. The preindustrial level was 133. Let's add these to CO2 to see the real picture of the greenhouse effect at these two times:

• Preindustrial: 280+133 = 413 ppm CO2eq
• Today: 440+247 = 687 ppm CO2eq
• (687-413)/413 = 0.66, a 66% increase in CO2eq

The actual increase in CO2eq is greater than the effect of CO2 alone. Suppose we could reduce CH4 and N2O to preindustrial levels. This would subtract 114 ppm CO2eq, for 573. Then (573-413)/413 = 0.39, or 39% increase in CO2eq, compared to preindustrial. To put this in context according to the mental model held by "climate crisis" folks, for CO2 only, a 39% increase over 280 ppm would be 389 ppm. That is about where we stood in 2011; it winds back the clock sixteen years!

Let us focus a moment on N2O. By itself, increase in the concentration of this gas is responsible for about 20 ppm CO2eq, the last nine years of increase. This is nearly all due to overfertilization. Guess which industry complex is bigger and has a stronger lobby in DC than oil and gas? Agriculture plus agrichemicals (particularly fertilizer). I have read in more than one place that without artificial nitrogen-based fertilizer, the world's farmland could support no more than four billion people. It is very complex to analyze just how much fertilizer could be reduced to still support the current world population, but reduce nitrate runoff and outgassing of N2O into the atmosphere. For the moment, I just have to leave these thoughts unfinished. If we could come up with a plan, powerful interests would oppose it.

At this point in my analysis I wondered what other greenhouse gases exist, and how they might modify the picture. As it happens, nothing much. Here is a table I worked from for the figures above, which adds six greenhouse gases that, together, are sometimes written about in very scary terms, but have no practical effect at present:

First, ground level Ozone (O3) has a modest Global Warming Potential (GWP: 1.5 x CO2), and exists in the 1-10 parts per billion range, so it is not effectively a greenhouse gas. Then, the industrial chemicals Sulfur Hexafluoride (SF6) and Nitrogen Trifluoride (NF3) have very high GWP, but exist at levels of a few parts per trillion. To totally eliminate them would reduce CO2eq by much less than one percent (see the black text at the bottom of the table)

Various fluorinated refrigerants, those highlighted in brown, have very high GWP, but also exist at levels of a few parts per trillion, so together, they also amount to less than one percent (the brown text). Thus, they present no useful "targets" for ameliorating the greenhouse effect.

My aim here has been to back off a few steps to see a bigger picture. As it happens, this points a finger where none has been pointed before, at farmers. A significant proportion of the increase in CO2eq results from farm practices. In particular, far too many farmers use more fertilizer than their crops really need. There is too much of, "a little more might help." No, it doesn't, it harms. It even harms the farmer, who spends more than needed on fertilizer that isn't helping.

I have a philosophical point to end with. I think that the greenhouse effect will prove to be more beneficial than otherwise. The "father of greenhouse warming", Svante Arrhenius, thought so. Another degree or two of warming is likely to make more of Canada and Siberia amenable to crop production, and let's not forget South Africa and Argentina. On another note, I saw an article recently with a headline, "550,000 will die of extreme heat." The subhead said, "The greatest cause of early death." The article never mentioned that 4.6 million will die from cold. Nine times as many! The subhead is, quite simply, a lie, and the article is utterly one-sided deception. I suspect many of those 4.6 million would love for their home country to be a little warmer.

Tied for the oldest sense

 kw: book reviews, nonfiction, science, olfaction, nose, sense of smell

It is fascinating to watch a motile bacterium such as E. coli in motion. It trundles along, its rear-mounted flagella spinning to propel it in a mostly straight line. If it bumps into something it will back up some distance, tumble, and then move off in a new direction. Frequently, after a short distance, it may reverse course or tumble again to pick a new direction.

The latter action hints at what is going on. How does it pick a direction to go; what is it trying to reach? Of course, like all living things, it is searching for food. It is following a chemical gradient by sensing a chemical of interest in the water around it. If, as it moves along, it senses a stronger concentration, it keeps moving. If the concentration is decreasing it reverses course or tumbles to try a new direction. Its chemical sense can be called either "taste" or "smell" and is one of the two oldest senses. The other is touch. Bumping into something, or alternatively, approaching closely enough for cilia on the cell to touch the something, coupled with the chemical sense telling it, "this isn't what you are looking for," triggers actions such as backing up and/or tumbling. Touch is the other "oldest sense." The two seem to go together, and they work together to guide the cell to a possible source of food.

Strictly speaking, smell is thought to relate to chemical cues carried in the air, so the bacterium, being in a watery medium, must be using taste rather than smell. But at the most basic level these are actually the same. Chemical substances that are smelled first enter a watery layer over the sensory nerves, where they are detected.

For air-dwelling creatures, smell is a more long-range sense. Chemical substances travel through the air faster than they do through water, although both aerial and fluid currents can bring them from far away. But diffusion in still air is faster than in still water. Furthermore, when two senses work together, smell precedes touch, while taste follows contact.

The title of Jonas Olofsson's book, The Forgotten Sense: The New Science of Smell and the Extraordinary Power of the Nose led me to think, "Why didn't he call it The Neglected Sense?" No matter. He reveals the neglect that smelling has undergone through the centuries since it was placed by Aristotle at the bottom of the list of useful senses, an error compounded when Paul Broca divided animals into "osmatic" and "anosmatic": those like the dog for which smell was primary and those like humans (he thought) for whom smell was definitely not worth much. I guess that neither Broca or old Ari stopped to consider how he would detect a bad lot of wine or olive oil if he plugged his nose. Tasting without smelling could be a risky business!

I was most fascinated by an analysis to which the author refers, "Human and Animal Olfactory Capabilities Compared," by Matthias Laska in the 2017 Springer Handbook of Odor. Humans and a number of medium-sized and smaller animals were tested for their sensitivity to a few dozen scented substances. Animals tested included rats, dogs, vampire bats, a couple of monkey species…twenty species in all. The only animal with a nose more sensitive than ours was the dog!

Earlier studies that compared the size of an animal's olfactory bulbs to its brain were misleading because it is the absolute size of the bulb that matters. The roughly 60 mm³ volume of human olfactory bulbs is a tiny fraction of the brain's volume, about 1/20,000th. In relative terms, the olfactory bulb of a mouse is enormous, about 1/16th of the total brain. However, its actual size is less than half that for a human: 25 mm³. An ordinary dog (not the tiny breeds or pug-nosed ones) has an olfactory bulb six times larger than a human, which gives it a huge advantage, as was shown clearly by the sensitivity tests. I wonder if they could give a similar test to an elephant, with an olfactory bulb volume of 11,000 mm³ ?

Technical issues aside, a big section of the book relates the emotional effects that smells can mediate, such as a whiff of salty air evoking a favorite memory of a seaside vacation, or the comfy aroma of a morning coffee and bowl of blueberries. 

This also introduces the subject of smell gone wrong: COVID-19 introduced millions around the world to a life without smells, at least temporarily. An interesting consequence of the sudden loss of smell for many people was that they began to wonder how they could tell if their own smell was offensive to others! Another was the loss of interest in food, because most of what we call the taste of many foods is actually a combination of smell and taste. We can taste but five qualities: sweet, salt, savory (umami), sour, and bitter; we can smell thousands or hundreds of thousands of different qualities. So many that we can seldom describe any of them to someone else.

Loss of smell is called anosmia. In some ways, a distorted sense of smell, parosmia, can be even worse. Imagine one day finding that your morning cuppa smells like rotting onions! This can also be caused by viral infections, but there are other causes, including a hard bump on the head. Some people with parosmia can't stand to eat favorite foods, though some are able to eat enough to stay healthy by putting on a nose clip. There is a long section describing ways of desensitizing and retraining the sense of smell. Sadly none of the methods is effective in all cases, but it can be a lifesaver for many.

A side note: There is a reversible distortion of taste I have experienced, caused by an Asian spice called Tiger Claw, related to Star Anise. The seed pods are used whole to flavor soup. They aren't supposed to be ingested. Biting into one causes a shift of taste, such that water tastes like battery acid and nothing seems edible; it lasts several hours. I have numerous Chinese friends, and I wound up mostly fasting during a potluck lunch…

The author is a scientist of the sense of smell. He first wrote the book in Swedish, then translated it into English himself. His and his colleagues' work just might elevate our understanding of the sense of smell, from a "neglected" sense to one that is equally essential. And in time perhaps we'll attain added vocabulary to help us describe our favorite (or otherwise) aromas.