| Changes in plant species diversity from 1947--1998 of Pelham Bay Park, Bronx County, New York City were evaluated. In a baseline study of the flora compiled in 1946--47 by Harry E. Ahles (1924--1981), 668 plant species in 108 families were collected. The vast majority of these (477 or 71.4%) were native species, while 188 (28.1%) were non-native (alien) species. In the intervening fifty-one years the plant diversity of Pelham Bay Park (PBPK) significantly changed. By 1998, 792 species from 117 families were documented. Of these, 440 species (55.6%) were considered native and 302 (38.1%) considered non-native. This was a net increase of 136 non-native species (+37.1%) and a net loss of 141 native species (-25.3%). The vast majority of the extirpated native species were herbaceous plants such as wildflowers, grasses, sedges and rushes.; Similar patterns of extirpation have affected parks and other natural areas throughout New York City from 1925--2000. Of the 1,356 native plant species ever documented from New York City, 582 have been extirpated, a loss of 43% of the native flora. Altogether, 91.2% of the plant species extirpated were herbaceous species, primarily from meadow-type habitats. Ten families containing only native herbaceous species have been lost from New York City. By comparison, no families of woody plants, and only 51 total native woody species have been extirpated. Overall, the pattern of plant extirpations in natural areas of New York City and PBPK were similar: native herbaceous species of meadow-type habitats were significantly more likely to be extirpated than native woody species or any type of non-native species. Two primary factors are associated with changes in plant species diversity in natural areas: development including the placement of landfills, parking lots, recreational areas and highways; and to a lesser degree natural processes such as ecological succession. |
