Animals and Environments 2: The Land and the Bison

Another rerun in the series from 2014. I’m chaperoning again.

Imagine standing on a broad tableland, knee-high grass extending as far as you can see in all directions. The sun has just risen, well on its way north with the shift from spring into summer, and already the southwest wind ruffles the grass and hisses its hot way past. The day will be a warm one. You begin walking north. As you do, you start to see variations in the billiard table surface. Rainwater lakes, the famous playas, form broad, shallow depressions surrounded by taller grasses. Some of the largest playas have sedges, amaranth, arrow leaf, and western wheat grass in their shallows and on the shores. And you discover a faint blue line in the distance, almost like hills, or very, very far away mountains. Continue reading


Animals and Environments Pt. 1: Setting the Scene

February 2, 2019. I’m chaperoning some students today, and had too much to do yesterday to get a post done. This is a rerun from 2014.

[This is the first of a series about how Great Plains and High Plains species affect their physical environment. Sources will be available upon request.]

One of the conceits of popular environmentalism is that only humans cause major alterations to the physical and biological environment. A little research shows that this is far from the case, and while humans have indeed been major shapers of the world, non-human animals played, and still play, important roles in determining the lay of the land and what plants and other animals live on that land.

I’m going to start this series of posts with definitions of certain key terms and landscapes. Then I’ll look at the geology, before narrowing down to certain locations and individual species, notably beaver, bison, prairie dogs, domestic sheep, and domestic cattle on the High Plains. I’ll conclude with an overview of pre-1800 human activity in North America and how it greatly influenced a number of biota, most famously the grasslands of the Great Plains.

One of the terms we need to know is “keystone species.” Think of a Roman arch, how the components are held in place by a key stone. If you remove that stone, the arch loses its integrity and falls apart. A keystone species is one that has a dominant place in determining the composition of an ecosystem during the period of time that you are looking at that ecosystem. Bison and prairie dogs were both keystone species for the High Plains prior to the 1870s, their grazing habits and living conditions determining what other species did better and which fared more poorly. A keystone species is not necessarily the largest or best known animal in an area. Small rodents, if they form the prey base for the next level of animals and if they shape which plants dominate the area, can be a keystone species.

Another term I’ll use is “trophic level.” A trophic level is where on the food chain/ food web an organism lives. Plants are the first trophic level because they don’t eat anything else (pitcher plants and Venus flytraps don’t count). Grazers and other herbivores, of any size, form the second trophic level. That which eats the grazers is the third trophic level. You could argue that bacteria and carrion eaters might form a fourth trophic level, but most textbooks stop at three.

The High Plains refers to the area between the Rocky Mountains in the west and the 20″ isoheyt to the east. That means the 20″ annual average rainfall line, or where short grass steppe shifts to the mixed and tall grass prairies, where pyrophilic grasses become more common. Today, if wheat dominates, you are probably in the High Plains and corn (maize) is the tall grass (irrigation notwithstanding.) The High Plains are a semi-arid belt of short grass ecosystems that extends from the southern end of the Llano Estacado Plateau to the Canadian border. Some books limit the area to eastern Wyoming and Montana, and call the southern stretch the South Plains, but that starts to get very confusing when you look at a smaller scale, so for our purposes, High Plains it is. Why “high?” Because much of the area is over 3000′ in elevation.

Semi-arid refers to the average precipitation and evaporation patterns in the area. Precipitation is strongly seasonal, with most of the rain coming in April, May, and June, with a secondary peak in August-September. The southern part of the High Plains has a very high evaporation rate caused by the dominant southwesterly winds and large amounts of sunshine. The northern areas have less evaporation and more winter precipitation, although it varies from year to year. An average of 20″ of moisture can mean 30″ one year and 10″ the next, as residents of the region know well. Some years are more arid, some lusher. The variation can be striking even over a few miles, depending on where storms form and drop their rain load. I’ve seen pastures on the east side of town withering while two miles west it looks like someone dumped a load of green paint.  Back in the 1800s, the managers of the big ranches had to try and explain to owners “back East” or in Britain how they could get a good rain at the ranch headquarters and still have animals dying of thirst.

Fire plays a role in the Great and High Plains. The Great Plains, while not a truly pyro-dependent landscape, were close. The tall grasses and the associated forbs that grow with them leave a lot of dead material behind over winter, and fires (along with grazing) helped return nutrients to the soil. Fire also keeps the trees and shrubs at bay. Otherwise the eastern woods expand into the prairies. The High Plains are less congenial to trees, in part because the constant wind sucks moisture out of large, fluttering leaves aster than you can say “gush.” However, fires still raced over the land on occasion, set by lightning or by Indians. When rain follows fire, the land turns a rich, lush green that has to be seen to be believed.

Short grasses dominate the High Plains. Knee-high or waist-high at most, buffalo grass, grama grasses such as side-oats, black, and hairy, spartina, and western wheat grass formed clumps and patches. Buffalo grass responds to heavy grazing by sending out side shoots, or tillers, that allow it to grow without attracting attention from hungry bison. It was a rule of thumb that bison and buffalo grass went together, and they did.

To the east, where rain falls more generously, the tall grasses loomed higher than a man’s head. Big and little bluestem, Indian grass, and dozens of other smaller kinds covered the ground. Forbs such as lead plant, compass plant, goosefoot amaranth, and others returned nitrogen to the soil, forming a complete prairie package.

Having laid the cover down over the High Plains, next time we’ll look at the land under the plant roots and animal feet.


The Ghost of a Lake

Once there was a playa, a rainwater lake. It nestled between two low ridges, collecting water from the slopes and the rain and snow. At its fullest, it could stretch over a mile north to south, and as wide east to west. In dry, droughty years it shrank into a puddle, a refuge for water plants and ducks.

Over time, a city grew toward the playa, expanding east to west. The two could not coexist well, and so the city dredged the playa, added plumbing, and turned the remains into a storm water catchment. Houses and businesses, roads and parks covered the old playa bed, leaving only the rainwater catchment to show that once a playa covered the land.

Except… Continue reading

Artifacts, Culture, and Adoption

Last week I came in on the last half of a PBS program about “The Secrets of Stonehenge.” I’d read most of the different bits and pieces, but it was nice to have them all pulled together with attractive shots of Stonehenge and its environs. However, the last ten minutes or so raised my eyebrows and started me wondering… Continue reading

The Longest Night, the Shortest Day

Welcome, Instapunderati, and thanks for stopping by!

The winter solstice has arrived, and the sun has touched its lowest point on the southern horizon for those of us north of the equator.

It took an ice storm for me to understand in my bones why my ancestors back in the Old World so feared and reveled in the end of the longest night. When the sun appeared after two days of night, heavy cloud, breaking trees and cold that crept in as the fires failed, well, I too sang hymns of praise to the sun above. Only sunlight would thin and dissolve the ice, and allow the repairs to begin so that heat and light could return to houses and other buildings. Unlike other, smaller towns, we never lost water, thanks be. Continue reading