Altitudinal range shift detected through seedling survival of Ceiba aesculifolia in an area under the influence of an urban heat island

Oscar Valle-Diaz, Arnulfo Blanco-Garcia, Consuelo Bonfil, Horacio Paz, Roberto Lindig-Cisneros

This paper explores the link between the Urban Heat Island effect and the altitude range of Ceiba aesculifolia near Morelia, Mexico. (The Urban Heat Island effect is essentially the increase in temperature observed around urban areas due to a decrease in reflectance of the built environment.) As climate change progresses, the heat island effect is expected to increase temperatures by approximately 8 degrees C by 2050, compared to a rural equivalent.

This dramatic increase in temperature will likely have impacts on surrounding vegetation, particularly in mountainous regions where plants' ranges are governed by altitudinal gradients. It is therefore logical to assume that species will shift upward in their range to compensate for increased temperatures. This paper essentially documents that these expected range shifts are already occurring. The authors found highest survival rates of planted seedlings at altitudes above the historical elevation range of the species.

From this discovery, the authors suggest that sensitive plant communities will need human assistance if their natural migration rates are unable to cope with the increased pressure from climate change. While this is not exactly ground-breaking news, I think it's important to document proof of altitudinal shifts in plant populations in response to increased temperatures, particularly those of urban areas. I also think it's an important issue to consider when planning urban restoration projects.