Humans are the only creatures to cause major modifications to the environment, right? OK, beavers make ponds by building dams, but those are small. And elephants will push trees over, but that’s different. And bison graze selectively and influence the botanical . . . Arrrrrghhhhh!
Actually, non-human animals have caused very large alterations to their physical and botanical environments. It’s just that we don’t see them, because of the time scale involved, or because we entered the habitat after the other animals had modified it.
For example, consider North American beaver (Castor Canadensis). They cut trees for food and to use to make lodges and dams. Those dams have several effects on the stream. First, they slow the flow, reducing peaks and troughs by holding back stored water in a reservoir. By trapping sediment, beaver ponds change the erosion potential of the stream (clean water is hungry water and will dig out more sand, silt, et cetera). Trapping the sediment leads to silting up of the pond, eventually creating a wetland, then a meadow. Beaver also prefer certain types of trees and shrubs, affecting the species composition of the forest within waddling distance of the pond. And beavers have kits, kits become beavers, who move out to start the process over again. Get enough beavers in an area and you will find major changes to the hydrologic system of the streams, and to the plants in the surrounding forests and meadows.
North American buffalo (Bison bison bison) left marks on the landscape of the western plains that can be seen to this day if you know where and how to look. Their dining habits also contributed to the dominance of buffalo grass (Bouteloua dactyloides) in the High Plains.
Buffalo grass and buffalo went together, because buffalo grass can survive short duration, very intense grazing (like happens when a couple thousand hungry bovines show up for lunch). It seeds, as shown above, but also tillers, sending out sideways shoots along the surface of the ground which are much more difficult for grazers to gobble. Other high plains grasses, notably the gramas, do the same thing when stressed by heavy grazing. The semi-arid environment also favored drought-tolerant species, something buffalo grass is.
In areas that have not been plowed, notable part soy the Oklahoma Panhandle and far western Kansas into eastern Colorado (the flat, grassy part of the state), you can still see the faint remains of buffalo travel routes, long stretches of land just a little lower and more compacted than the surrounding soil. They lead to old springs and mark where the long-ago herds crossed the plains. The town of Tascosa, Texas on the edge of the Canadian River in what is now Oldham County was located at a ford and hill gap either heavily used or possibly made by the buffalo herds.
Rudyard Kipling talked about the Sons of Martha, those men destined to do the hard work of blazing the first trails and “piecing and repiecing the wires.” In parts of North America, animals were the first Sons of Martha, treading trails along streams and through wind and water gaps to springs, mineral licks, and grazing. Paleo-Indians followed, then American Indians, and Anglos and Spanish settlers trailed behind.
[Note: During September, this blog will run a series of pieces about non-human animals and how they affect their environments, focusing on the High Plains of North America. It will go into more detail about ideas touched on in this piece.]