Beavers Still Active
New Channel is Old Channel
Sept. 23, 2016
An anonymous reader who lives on Buffalo Bayou wrote in to give us a report on beavers and some history on the new channel cut through a sandy point in Memorial Park.
The channel isn’t new at all, the reader pointed out. During the extended high waters following record rains last spring, the bayou cut across a sandy point on the north bank and settled back into the course it used to take back in the 1930s. This is based on property maps from that era, wrote the reader, who lives on the south bank.
Bayous and streams tend to do that: seek out their historic channels, amazingly even when concrete blocks the way. They have a memory. Houston historian and Buffalo Bayou chronicler Louis Aulbach tells the story of the time during Tropical Storm Allison in 2001 that the bayou broke through a concrete retaining wall in Tranquility Garage underneath the Wortham Center in downtown Houston. The bayou may have been seeking out its former natural channel, which was filled in and the bayou rerouted in 1927-28. The Wortham Center now stands on top of the original channel, and the garage beneath it would actually be in the old channel.
Aulbach is the author of the fascinating book Buffalo Bayou: An Echo of Houston’s Wilderness Beginnings.
Big Trees Had Fallen
In our State of the Bayou report Sept. 2, 2016, we stated wrongly that residents on the south bank had cut down trees on the sandy point. In fact, according to our reader, the trees had fallen during the Memorial Day 2015 high waters. First to go was a live oak, and then a large cottonwood further downstream. Beavers had stripped a ring of bark almost all the way around the trunk of the cottonwood, says the anonymous property owner, cottonwood bark being a favorite meal of Texas beavers. The tree, undermined by the high waters, fell eventually, blocking the channel, and the property owner cut it and dragged it out of the way. This is why the stump looked cut, he says.
Note to property owners: trees falling in the woods or into the bayou are sad and even dangerous events. But fallen trees are a vital part of the natural system. Fallen trees should be dragged out of the way but left on or near the bank where they provide fish habitat and trap sediment to rebuild and reinforce the banks.
Ecological Benefits of Beavers, a Keystone Species
The cottonwood stump, previously on the north bank, is now on south bank of the new channel. But did the beaver kill the cottonwood?
Beavers are controversial. They are very efficient at cutting down young trees. Our anonymous reader writes that some his neighbors “would shoot them on site if they were able” but that personally he is “thrilled that we have beavers living in the middle of Houston.”
Beavers have an important ecological function, which is why they are called a “keystone species.” Wildlife specialists estimate that at some point in their lives, 85 percent of all wildlife in the American West depends on the ponds and riparian habitat that beavers create.
Beavers on the prairies create wetlands, which capture carbon and filter pesticides and other pollutants from the water. Alas, it has been the policy of the Harris County Flood Control District to remove beavers and destroy their lodges, according to a district employee who spoke at an urban stream conference in Austin last year.
Beavers in the bayou and other rivers behave differently from prairie beavers. Bayou beavers burrow underwater into the banks, creating their dens underground but above the water level. And because they cut down young saplings, it would seem improbable that this activity actually has an ecological benefit. But it does!
According to one authoritative publication about living with beavers, “riparian plant communities (willow, cottonwood and alder) thrive amongst beaver activity. Beaver cuttings cause dense vegetative growth and each cut willow stem can lead to three to four new stems.” (p. 6)
Protecting Trees from Beavers
Because of the extended high flows that came in the spring when beavers were having babies, we were concerned that many beavers on Buffalo Bayou had been flooded out of their burrows and their kits drowned.
But our anonymous source says beavers have recently been active in his neighborhood. Too active for some. But our source says he has no qualms about their foraging. “That’s what beavers do,” he notes.
“It’s easy enough to wire wrap the trees I want to keep and leave the others as a food source. In fact, and this observation is confirmed by other persons, on trees greater than four inches in diameter these local beavers typically do not ring the entire tree but leave just enough of the bark on one side to allow the tree to survive – if only humans were as careful!”
His advice for protecting trees: “For small trees, it is very easy and cheap to use a light gauge wire mesh (Home Depot or any hardware store) and wrap one layer (loosely to allow room for the tree to grow) around the lower 24 – 30 inches of the tree. Heavy gauge wire is not necessary and light gauge seems to work fine as a deterrent – the belief is that although they could easily chew though the lighter gauge, that they stop and move on when they taste or otherwise sense the wire. I have not had any attempted chewing on trees that were wire wrapped with this very simple protection.
“It’s also apparent they do not like the bark of sycamores – I’ve not noticed any full cut trees and have only witnessed two chew marks on a sycamore – as if they did not like the taste and moved on to sweeter samplings.”