The urban heat island effect is a phenomenon characterized by higher temperatures in
cities, while temperatures in nearby rural areas are lower. Due to the increasing building
density and the heat load in the city caused by human activities, the energy balance
changes and a difference between the temperature in the city and in rural areas arises.
Phenology studies the periodic phenomena in the development cycle of plants and
animals and determines their dependence on environmental factors. Air temperature has
the greatest influence on the phenological phases of plants in temperate latitudes. As the
temperature rises in cities, the dates for the start of the phenological phases change. The
spring phases start earlier and the fall phases later, extending the duration of the growing
season. Other factors such as precipitation, CO2 concentration, general air pollution and
light pollution also have a significant impact on the phenology of plants and other
species. Elevated CO2 concentrations in cities are mainly due to the many sources of
CO2, which translates into a faster onset of the growing season and an extension of the
growing season. The amount of precipitation in combination with temperatures affects
the change in the timing of the phenophases. With higher precipitation, the start of the
vegetation period was earlier, but later in dry conditions. Phenological development is
also influenced by the exposure of plants to pollutants such as nitrogen oxides or ozone,
which affected the delay in the start and end of the season. Nocturnal exposure of plants
to artificial light in cities accelerates the onset of spring phenophases and also has a
significant impact on insect phenology. Phenological shifts in recent years show a strong
correlation with global warming, so studying changing phenological patterns can help
us predict future global climate changes and determine how plants and other species
may adapt to these changes.
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