The influence of pollution on phenology may lead to a failure of
fingerprinting climate change. Generally, phenology is regarded as
an excellent bio-indicator for climate change, since air temperature
is able to explain a huge amount of the variability in phenological
onset dates of temperate species in spring (Menzel and Fabian,
1999). However, the associations with air pollution found in our
study might also be attributable to other environmental conditions
that are statistically correlated with pollution. Although we
excluded the influence of air temperature on phenological onset
dates in partial correlation analyses (Table 3), there might be other
factors (e.g., radiation, soil nutrients) that are altered by pollution/
urbanization.
In general, delays in phenology affect a range of ecological
processes such as the start of CO2 uptake via photosynthesis and
the start of pollination which is also important for human health
when allergenic plants are considered.