A Change is Gonna Come

From the online journal Urban Habitats comes an intriguing study of the flora of the New York Metropolitan area. Using a century of herbarium records, Steven E. Clemants and Gerry Moore discovered a trend of expanding ranges of non-native plants and shrinking ranges of native species. In one of the sobering examples they discuss, native honeysuckles (Lonicera spp. and Diervilla lonicera) all have a negative change index, while their non-native congeners have all increased their range dramatically.

A quick sort of their data, and the species list with the top ten highest change indices reads like a who's who of invasive plants in the Northeast U.S....

• Celastrus orbiculata (Asiatic bittersweet)
• Rosa multiflora (multiflora rose)
• Lonicera morrowii (Morrow's honeysuckle)
• Morus alba (white mulberry)
• Elaeagnus umbellata (autumn olive)
• Aralia spinosa (devil's walking-stick)
• Ampelopsis brevipedunculata (porcelainberry)
• Ailanthus altissima (tree of heaven)
• Acer negundo (boxelder)
• Robinia pseudo-acacia (black false-locust)

...except for boxelder, a native species (though considered a weedy tree in some states). Other native species with positive change index values include Amelanchier canadensis (Canadian serviceberry, one of the more common native shrubs used in landscaping), and Populus deltoides (Eastern cottonwood) and Sassafras albidum (sassafras), two more weedy tree species. Sounds like one hundred years have definitely brought some disturbance to the city that never sleeps.

Thanks to a member of the Yahoo! group ma-eppc for posting a link to the article.