Copyright Debbie Miller

Figure 1. Alpine meadows and hillsides may look very different in the future as climate change and nitrogen from air pollution cause changes in plant communities.

Imagine an alpine meadow at the height of wildflower season: a tapestry of blue columbines, yellow buttercups, crimson paintbrush, white phlox, and pink bitterroot contrasting with the deep blue sky of the Rocky Mountains (fig. 1, above). This explosion of color continues to inspire hikers to brave the high winds, low temperatures, and thin air in the high regions of our western national parks during the brief summers that are experienced at those elevations. We know that a changing climate is likely to affect this display (Bowman 2000). A longer growing season and changes in rain and snowfall will alter the alpine environment. Some plants will be displaced and others lost entirely, while some will thrive under new conditions. These changes will occur in addition to those already under way because of air pollution.

Air pollutants containing nitrogen are altering plant communities in many areas of the world because of nitrogen’s fertilizing effect (Bobbink et al. 2010). Vehicles, power plants, industry, and agriculture all emit nitrogen that deposits into ecosystems with rain and snow, fertilizing some plants at the expense of others. Alpine plant communities are particularly at risk, having evolved under low-nitrogen conditions (Bowman 2000). When additional nitrogen from air pollution is available, plants with the ability to quickly assimilate it, including some invasive and nonnative species, gain a competitive advantage (Clark et al. 2007). Current levels of nitrogen pollution are sufficient to induce changes in alpine plant communities in and near Rocky Mountain National Park, Colorado (Bowman et al. 2006). But can we anticipate the even greater changes that are likely to occur as nitrogen pollution interacts with climate change? The Air Resources Division of the National Park Service (NPS) has recently collaborated with U.S. and European scientists to apply the innovative environmental effects model ForSAFE-VEG to help estimate future conditions and answer such questions.