Pollution and phenology

The most alarming of all man's assaults upon the environment is the contamination of air, earth, rivers, and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable; the chain of evil it initiates not only in the world that must support life but in living tissues is for the most part irreversible. - Rachel Carson

The above quote is taken from Carson's Silent Spring, published in 1963 but sadly still relevant today. Arguably, climate change has overtaken pollution as a concern for the environmentalism movement.

I was wondering about other environmental changes associated with urbanisation which led me to consider the effect of car exhaust fumes on phenology. Vehicular emissions are the major source of air pollution in urban environments (Brophy et al. 2007). These are mostly made up of nitric oxide (NO) and nitrogen dioxide (NO₂).

Car exhaust fumes. Source: the times

Honour et al. (2009) simulated air pollution in roadside, urban environments using a diesel generator fumigation system to see the effect it would have on some herbaceous plants. Their fumigation system emitted lots of different chemicals, not just one or two, which made it like pollution in a real urban environment. Their study was carried out for 3 years. Overall, they found that senescence was brought forward and flowering was delayed compared with the control group.

Hieracium pilosella. Source: wikipedia

Traffic is also a major contributor to heavy metal contamination in soils in urban and roadside environments (Zereini et al., 2007). Ryser and Sauder (2006) found that heavy metal contamination of soils delayed flowering phenology in Hieracium pilosella. They found that flowering phenology was highly sensitive to metal contamination, being affected at very low levels.