The effectiveness of the ragweed eradication campaigns in New York City: A 9-year study (1946–1954)

Abstract

1. 1. Approximately half of New York City's ragweed pollen is generated intramurally. The remainder is brought in by brisk western winds from New Jersey, Pennsylvania, and to a lesser degree from upper New York State. Hence, the total eradication of the ragweed within the city can at best reduce its atmospheric contamination with ragweed pollen by one-half. 2. 2. On the basis of the reports of New York City's Health Department, indicating approximately a 50 per cent reduction in the city's ragweed acreage after nine years of “Operation Ragweed,” it may be estimated that the city's ragweed pollen production may have been cut by one-half, thus reducing the pollen contaminating the air of the city by one-fourth. 3. 3. During the nine years of “Operation Ragweed,” pollen surveys were made under standard conditions at 30 stations in and around New York City, covering a total of 98 stations-seasons. The results of these surveys revealed no definite tendency for the pollen index of New York City as a whole, or of any city station, to decline during this period. 4. 4. Comparisons of New York's pollen indices during this period with those of nearby New Brunswick, New Jersey, and Bridgeport, Connecticut, where there have been no elimination campaigns, afford no indication that the course of New York's index in recent years is deviating from that of its neighbors. 5. 5. Pollen counts at the Brooklyn station made with the old counting technique over a period of eighteen years (1937–1954) reveal a 30.6 per cent decline in the average pollen index at this station during the nine-year period (1946–1954) while “Operation Ragweed” was in progress. During this same interval, however, there was also a pronounced decline in Brooklyn's vacant land, probably in excess of 60 per cent. Coincidently, there was, in addition, an inexplicable decrease of 30 per cent in the average incidence of stiff western winds during the active pollinating seasons when such winds contribute heavily to New York's ragweed counts. In the light of these important considerations, it may be estimated that only from one- to two-thirds, or from 10 to 20 per cent, of the 30.6 per cent decline in Brooklyn's index may be attributed to the effects of “Operation Ragweed.” 6. 6. The results obtained in Brooklyn are probably representative of those achived for the city as a whole. 7. 7. New York is a coastal city and easterly and southerly winds blowing into the city on approximately one-third of its circumference are comparatively pollen-free. Inland communities would not benefit in this manner. 8. 8. Since ragweed grows naturally and profusely in the New York Metropolitan Area, there is little likelihood that eradication campaigns, carried out along the lines of those employed at the present time, will succeed either in eliminating the weed completely and permanently from the city or in decisively reducing its pollen index.