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The Research Triangle area’s population has almost tripled since 1980. Some of the development accompanying this growth has replaced forests and created smaller forest patches separated by roads, parking lots and housing developments. During three summers, doctoral student Bianca Lopez focused on the impact of urban development on plants within 50 Research Triangle forest sites next to streams. Lopez found no difference in the number of plant species within urban and rural forests; however, urban forests have more introduced species (such as ornamental plants introduced by the horticultural industry) and fewer species native to North Carolina than rural forests. She also discovered that urban development appears to alter the plant species composition of forests, primarily through changes in local environmental conditions (particularly warmer temperatures) and less movement of seeds among forest patches.

Former doctoral student Liz Matthews, Ph.D., had documented plant species composition at the best remaining examples of forest situated near streams. By comparing urban forest sites to these reference sites, Lopez found that many rare species found in reference sites are absent from urban forests. Native species whose seeds travel only short distances are also found at lower frequencies in urban forests than in reference sites. These results suggest potential challenges for maintaining and restoring native plant biodiversity in urban areas.

Lopez has identified plant species that are highly affected by urban development and those that are resilient to this process. Her study findings indicate the need to set aside larger forest patches for conservation to encourage seed movement and buffer the effects of warmer urban temperatures. She plans to share her information with city and state officials to inform forest conservation and restoration policies.