Of Humans and the Environment: Bridges

marce profile flathead lake 2018

Humans may be here to stay. Humans are natural beings, the product of evolution. And we have come to understand that much of our world has been formed by the interaction of humans within and with their environment. But we cannot stay here indefinitely, increasing our industry without destroying the environment that sustains us. This is so obvious, so self-evident that I cannot even begin to understand how some do not grasp this simple concept. I would like humans to stay around for a while in a world we sustain. We will need to change much of how humans live in this world to sustain it in the near and far future, but it is not reasonable to advocate for the removal of all human constructs, those are here to stay, some for millennia to come. Take bridges, for example. Travel, even on a small, regional scale, is difficult without bridges.

Bridges over the Blackfoot River, Montana

A human world without bridges. I have had the fortune to go on adventures, large expeditions in Mongolia to seek out the small hidden wonders of biodiversity. We would cross this amazing, ancient landscape in a caravan of jeeps and vans and one large truck, searching for sampling sites along rivers, lakes, and springs. Our travels often necessitated crossing large rivers, mostly without the aid of bridges. Most of the time we forded these bridges successfully, guided by our competent and knowledgeable drivers, guides, and colleagues. But sometimes we got stuck in mid-river or stuck in the marshes surrounding rivers. And then everyone got out and pushed or pulled. Bridges, safe bridges would have been very welcome during those times.

Jeep stuck while crossing a large river, Mongolia

The art and beauty of bridges. Human ingenuity is most evident in the building of bridges, large suspension bridges, draw bridges, and trussed bridges. These are the bridges we think about, but most bridges are small, spanning small streams and rivers. Here are a few of my favorite bridges.

kaw river under gridge art

Upper, Bridge over the River Kaw, Lawrence, Kansas; Lower, Bridges over the Blackfoot River, Milltown State Park, Montana

Better ways to bridge. So, as long as humans are here using ground transportation, we will need bridges. Bridges can cause environmental degradation, though. Open substrate such as gravel and dirt near bridges increases sediment runoff. De-icing and melting applications to roads during winter enter waterways from bridges. We can mitigate the inflow of these pollutants by stabilizing the substrate near bridges, by creating riparian buffers and terracing the landscape to retain the runoff. These solutions are practical and enhance the beauty of the bridge and the river. Building better bridges is a way to care for the environment, create beauty, and marry form to function to sustain us all. It is just good stewardship.

Wildlife bridge, Flathead Reservation, Montana. Photo from https://en.wikipedia.org/wiki/Wildlife_crossing

For moose and bears. Finally, bridges are being built to reduce wildlife mortality at road crossings. These bridges are covered with vegetation, built to encourage large animals to cross over highways rather than across highways and are an excellent example of how human ingenuity can be a bridge between human endeavors and the environment.

missour r. atchison
Bridge over the Missouri River, Atchison, Kansas

For more reading

Johnson, P.A., 2006. Physiographic characteristics of bridge‐stream intersections. River Research and Applications22(6), pp.617-630.

Mann, C. 2006. 1491. Vintage Books Publishing. 541pp.

Glista, D.J., DeVault, T.L. and DeWoody, J.A., 2009. A review of mitigation measures for reducing wildlife mortality on roadways. Landscape and urban planning91(1), pp.1-7.


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