Submitted to: Journal of Allergy Clinical Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 16, 2002
Publication Date: February 1, 2003
Citation: Ziska, L.H., Gebhard, D.E., Frenz, D.A., Faulkner, S.S., Singer, B.D., Straka, J.G. 2003. Cities as harbingers of climate change: common ragweed, urbanization and public health. Journal of Allergy Clinical Immunology. 111(2):290-295.
To date, all known data which has examined the response of plants to future climate change scenarios have relied on artificial systems (greenhouses, growth chambers etc.) to simulate future temperatures and/or carbon dioxide concentrations. As a means to evaluate whether urbanization already provides a future, hotter, higher carbon dioxide environment, we monitored climate along a urban-rural transect from western Maryland to Baltimore city in 2000 and 2001. We used observed changes in temperature and/or carbon dioxide along this transect to determine in situ changes in the growth and pollen production of common ragweed, a species which affects public health. Average daily (24 h) values of carbon dioxide and air temperature within the urban environment were about 30 and 31% and 1.8-2.0 oC (3.4-3.6 oF) higher relative to the rural site for 200 and 2001, respectively. Ragweed at urban locations grew faster, flowered earlier and produced significantly greater above ground biomass and ragweed pollen relative to the rural location. These data indicate that climate change at the urban level is already occurring, and that such change may have significant consequences with respect to the growth and distribution of common ragweed, an agronomic and public health nuisance.
To evaluate the impact of climate change on plant species that affect public health, we tested whether urbanization provided stable increases in carbon dioxide concentration and/or air temperature that could be used to monitor the in situ response of common ragweed, the principle Fall allergen. For 2000 and 2001, average daily (24 h) values of carbon dioxide concentration and air temperature within the urban environment were about 30 and 31% and 1.8-2.0 oC (3.4-3.6 oF) higher relative to the rural site. Ragweed at urban locations grew faster, flowered earlier and produced significantly greater above ground biomass and ragweed pollen relative to the rural location. These data indicate that regional, urban-induced climatic change may already have public health consequences; and suggests that urbanization per se, may provide a low-cost alternative to current experimental methodologies evaluating plant responses to climate change.