Abstract

The plant phenological monitoring program, Plantwatch, is intended to be a practicable tool for local climate change monitoring using a dispersed network of volunteer “citizen scientists”. The majority of observations have been recorded in the most urbanized areas of Canada, yet little is known about urban influences on plant phenologies. In the present paper, the potential of the program as a climate change monitoring tool was explored by observing the influence of light pollution on floral onset and the degree of small-scale geographic variability of floral phenology in an urban setting. Norway Maple (Acer platanoides) populations of urban Niagara, Ontario, Canada were observed for the onset of first and mid-bloom. Populations exposed to direct artificial light showed significantly earlier floral onset. Geographic variability was not significant for Norway Maple trees across the municipal scale nor for Red Maple (Acer rubrum) trees across a small section of remnant urban forest. Local scale plant phenological monitoring may improve the current Plantwatch program by concentrating efforts and decreasing variability in phenological onset for a given area. However, any volunteer-dependent phenological program must account for anthropogenic influences, including light pollution.