The study, which is titled Human infrastructure and invasive plant occurrence across rangelands of southwestern Wyoming, USA and is published in the current issue of Rangeland Ecology & Management, evaluates how invasive species follow human development across southwestern Wyoming.
They began with the idea that as people develop a rural area, their actions encourage exotic plant species to move in. People change the original habitat by introducing foreign species and spreading them throughout the area, sometimes unintentionally. These changes stress native plants, making it easier for already aggressive invaders to put down strong roots and further stress native species into a downward-spiraling cycle. This cycle increases the challenge of managing rural lands, the study says.
The study covered 3 million hectares of northern sagebrush steppe in southwestern Wyoming (pictured). The authors targeted infrastructure such as roads, oil and gas well pads, pipelines, and power lines and then created 1,000-m-long sample sites extending outward from these man-made features. They chose sites that reflected climate, soil, geology, topography, and dominant vegetation variations in the region. They then considered both these environmental factors and the distance from man-made features as they sampled invasive plants across the sites.
The authors expected that invasive species would be densest within 50-to-100 m of man-made features and drop steeply as the sample site became less disturbed. This pattern did appear in some cases. However, it was the extent of indirect human influence that most surprised the authors. Instead of finding fewer introduced plants 100 m or more from a road or well pad, they often did not see a decline until 500 or even 700 m out.
More invasive plant species lined informal roads than other human-built features, but all roads, well pads, and pipelines were surrounded by more invasive species compared with semi-remote reference sites. In some cases, these exotic plants spread from man-made features so that the greater the distance, the greater the number of invasive plants in the sample site.