A first approximation of the historical and extant vascular flora of New York City: Implications for native plant species conservation1

Journal of the Torrey Botanical Society, Jul-Sep 2004 by DeCandido, Robert, Muir, Adrianna A, Gargiullo, Margaret B

There are 9 families containing only native species that have been extirpated from New York City: Azollaceae, Eriocaulaceae, Isoetaceae, Juncaginaceae, Limnanthaceae, Najadaceae, Ruppiaceae, Selaginellaceae and Zannichelliaceae (DeCandido 2001). These families are all composed of herbaceous species, and all except for species of Limnanthaceae and Selaginellaceae, are aquatic or amphibious species (Gleason and Cronquist 1991, DeCandido 2001).

Native species in nine plant families have been particularly prone to extirpation with an extirpation rate of 50% or more (Table 5). Of these families, all except for one (Ericaceae) arc composed exclusively of herbaceous species. Even within Ericaceae, most of the extirpations have been of herbaceous species (7 of 12; DeCandido 2001). Of the 481 herbaceous species in these nine families, 274 species (57.0%) have been extirpated. Of 30 known native species of Orchidaceae that once existed in New York City, 24 (80%) have been extirpated.

By comparison, 15 plant families containing only woody species, such as the Betulaceae, Cornaceae, Fagaceae, Juglandaceae, Salicaceae and Ulmaceae, have lost 10 of 89 species (11.2%). Only one woody family (Aquifoliaceae) has lost at least 50% of its species (three of six species). Differences between the rate of extirpation for species in the nine herbaceous families (Table 5) versus species in these 15 woody plant families are significant (χ^sup 2^ = 62.8, P

Staten Island, the least heavily developed borough, has the greatest number of families (154) and largest number of extant species (921) of the five boroughs, including the most native species (621). However, Staten Island has also lost approximately 35% of its native species (334) in the last 70 years (Robinson et al. 1994, Robinson 1999). Of the native plants that were extirpated, 94.6% (316) were herbaceous species. In New York City, Queens has the most extirpated native species (585). Brooklyn has the smallest number of families (109), as well as the lowest number of extant and historical plant species (695). In Brooklyn and Manhattan the number of extant alien species is greater than the number of extant native species. Of the five boroughs, only Staten Island has more native extant species than native extirpated species (Table 3).

Discussion. This study shows both the great diversity of the New York City flora, with 2177 extant and historical species recorded, as well as the great loss of native plant species in the metropolitan area (42.6%; 578 of 1357 native species). New York City has 56.8% of the plant species ever recorded in New York State (2177 of 3835 reported in NYS), and 60.3% of the native species recorded in the state (1357 of 2250). The vast majority of native and alien extant plant species in New York City are herbaceous plants. Of the remaining 1190 extant species in New York City, 65.5% (779) are native. However, in each borough except Staten Island, more native species have been extirpated than can still be found (Table 3). Since 1850 in New York City, native plant species have been significantly more likely to be extirpated than non-native species. Native plants that were extirpated were significantly more likely to be herbaceous rather than woody species. Of the 1357 native species ever recorded in New York City, 134 (9.9%) are currently considered rare, imperiled or critically imperiled in New York State (Young and Weldy 2003).