An interesting article came across my desk recently. Entitled, “Ecological homogenization of urban USA,” it presented some recent research on landscape structure within some of the major US cities, compared to their surrounding ecosystems. In general, there is a great similarity among neighborhood landscapes, whether they are in Phoenix, Baltimore, Miami, or Boston. The “idealized” American landscape consists of a lawn, a few shrubs, and some tall trees.
Of course there are some differences, but those differences actually had more to do with socioeconomic status than local biome characteristics. In other words, affluent neighborhoods in Boston tended to resemble affluent neighborhoods in Baltimore more than they resembled poor neighborhoods in Boston.
This alteration of the native landscape that occurs with human development also affects the wildlife that live among us. Animals respond to the changes in habitats near human dwellings, with some attracted to our carefully cultivated plantings, or perhaps the bugs attracted to the plants, and while others are attracted to the changed structure, for example, the opening up of woodland near our eastern cities, or the addition of tall trees in the desert. Some animals don’t care to live near people and move away; others we don’t tolerate, so we remove them.
The change in habitats and habitat structure that occurs in and near cities also affects the soundscape. I’m not talking about the cars, trains, planes, and lawnmowers. I’m talking about the wild sounds. I’m reminded of this every day when I walk out the door. I’m almost always greeted with the sounds of Great-tailed Grackles from my neighbors pine trees, and House Sparrows nesting in a nearby Saguaro cactus. The grackles are native, but they like trees and moister habitats, so they were pretty unusual in the Sonoran desert before urbanization came along. The House Sparrows are not native at all. According to the Cornell Lab of Ornithology’s All about birds website, “You can find House Sparrows most places where there are houses (or other buildings), and few places where there aren’t.” It is native to Europe and Asia, but has now been introduced to most of the world, and is considered one of the most widely distributed bird species. Eurasian collared-doves have recently moved in, too, adding another voice to the soundscape.
Things get more complicated in the suburbs and exurbs, those areas that have a mix of native and introduced vegetation and wildlife. I live in an exurban area to the east of Tucson, Arizona. It is not an affluent area, and very few of my neighbors have lawns and only a few have tall trees. “Landscaping” consists of mostly native mesquite trees, creosote bushes and a huge variety of cactus, including the iconic Saguaro. I put landscaping in quotes, because the yards could really be considered “feral” rather than “landscaped.” Some of the lots have been cleared for corrals for horses and burros, but most are pretty much neglected, maintaining native habitat for a wide variety of wildlife from tarantulas to bobcats. Yet even with all of the native vegetation, the soundscape in my neighborhood has changed since it became developed. Here is an example I recorded on a recent morning:
In early March, a friend and I went camping out in the middle of the Sonoran Desert, near Ajo, Arizona, searching for a “wild” Sonoran desert soundscape. On a remote stretch of BLM land, we pulled off and camped for a couple of nights, and I recorded the dawn choruses. Although many of my neighborhood birds were there (Gambel’s Quail, House Finches (which, unlike house sparrows, are native and not tied to houses), Phainopepla, Northern Cardinals, Curve-billed Thrashers, Mourning Doves, Cactus Wrens, Verdins, and Gila Woodpeckers), lacking were the grackles, House Sparrows, Eurasian Collared-doves, and the crowing of my neighbors roosters.
The Sonoran desert near Ajo, Arizona.
Same desert, but with less human alteration:
It’s an interesting take on biodiversity, which we normally assume to be lower in urbanized landscapes. In this case, the addition of a few tall trees and some water (and tons of bird seed) has substantially increased the avian biodiversity. A growing body of research is looking at the impacts of housing developments on local and regional biodiversity. In general, increasing housing density results in a loss of native species, across a wide range of taxa from birds to butterflies to carnivores, and an increase in exotic and weedy species. In some cases, like in my exurban neighborhood, low density housing is accompanied by an increase in biodiversity – with much of the increase coming from non-native species. What that means for the long-term ecological health of the surrounding environments has yet to be determined. We’ve affected the cast of characters in our local environments, and have also affect the soundscape. Recording the soundscapes can provide another way to monitor changes in our local environments.
Recordings made with a Sony PCM-M10 and Audio-Technica AT2022 mic with a Felmicamps SK3.5 preamp. Recordings subject to amplification and equalization.
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