59
• Pollution, including air, water, soil and other forms of pollution, on various spatial and temporal scales.
• Weather events, including drought or extreme rainfall, wind gusts, thunderstorms
and any kind of extreme micro- and macro-meteorological effects.
• Land use changes, land management, habitat fracturing and moving to the north
because of global warming.
Plant phenological traits (like flowering, leaf and bud formation, fruit and pollen
production) are well known to be very sensitive to environmental stress and especially to temperature variability. This is particularly true for flowering and pollen
production (e.g. Damialis et al. 2011; Menzel et al. 2006; Parmesan and Yohe 2003).
There have been strong indications that plants produce more pollen, and earlier,
when temperatures are higher, that is, at urban locations, lower elevations or southern exposure slopes, or during warmer years (e.g. Damialis et al. 2011; Fotiou et al.
2011). Higher rainfall prior to the inflorescence production and pollen formation
and liberation also favour increased pollen and flower production (Damialis et al.
2011). However, the implicated processes are excessively complex and influence of
many other factors is involved, for example microclimatic conditions in the examined site. Likewise, temperature seems to have a direct effect on allergen release, as
revealed by the inter-annual variability in a study on birch pollen in Germany
(Buters et al. 2008).
Air pollutants are also responsible for higher biomass production (including
flower and pollen production). Wan et al. (2002) and Wayne et al. (2002) experimentally found that, especially in combination with elevated air temperature,
increased carbon dioxide (CO 2 ) did not alter pollen production per se, but increased
plant biomass in Ambrosia artemisiifolia and, consequently, individual plants produced more pollen. Ziska et al. (2003) studied the same species but in real-life
conditions in a gradient simulating different climatic scenarios and, likewise, found
that plants exhibited higher biomass, pollen production and earlier flowering dates.
Ziska et al. (2003) additionally concluded that plant expansion rates and regional
abundance may also increase with increasing CO 2 , thus increasing allergenic pollen
exposure rates on a wider spatial scale.
Air pollution and climate change do not only affect plant growth, pollen and
flower production, and duration of the whole pollen season, but can also display
more direct health effects by increasing the amount of allergenic proteins of the pollen (Zhao et al. 2016, 2017). According to Zhao et al. (2016), elevated levels of
certain pollutants, like nitrogen dioxide (NO 2 ), which is traffic-related and hence
more prevalent in urban locations, increase overall pollen allergenicity, thus also
increasing the relevant allergy risk for sensitised individuals. El Kelish et al. (2014),
as well as Zhao et al. (2017), showed that elevated pollutants change the transcriptome of ragweed pollen; therefore, under global change scenarios, the allergenic
potential of pollen is also expected to change. Vehicular-exhaust pollution has been
reported to influence the allergenicity of ragweed pollen: pollen along high-traffic
3 Climate Change and Pollen Allergies
• Pollution, including air, water, soil and other forms of pollution, on various spatial and temporal scales.
• Weather events, including drought or extreme rainfall, wind gusts, thunderstorms
and any kind of extreme micro- and macro-meteorological effects.
• Land use changes, land management, habitat fracturing and moving to the north
because of global warming.
Plant phenological traits (like flowering, leaf and bud formation, fruit and pollen
production) are well known to be very sensitive to environmental stress and especially to temperature variability. This is particularly true for flowering and pollen
production (e.g. Damialis et al. 2011; Menzel et al. 2006; Parmesan and Yohe 2003).
There have been strong indications that plants produce more pollen, and earlier,
when temperatures are higher, that is, at urban locations, lower elevations or southern exposure slopes, or during warmer years (e.g. Damialis et al. 2011; Fotiou et al.
2011). Higher rainfall prior to the inflorescence production and pollen formation
and liberation also favour increased pollen and flower production (Damialis et al.
2011). However, the implicated processes are excessively complex and influence of
many other factors is involved, for example microclimatic conditions in the examined site. Likewise, temperature seems to have a direct effect on allergen release, as
revealed by the inter-annual variability in a study on birch pollen in Germany
(Buters et al. 2008).
Air pollutants are also responsible for higher biomass production (including
flower and pollen production). Wan et al. (2002) and Wayne et al. (2002) experimentally found that, especially in combination with elevated air temperature,
increased carbon dioxide (CO 2 ) did not alter pollen production per se, but increased
plant biomass in Ambrosia artemisiifolia and, consequently, individual plants produced more pollen. Ziska et al. (2003) studied the same species but in real-life
conditions in a gradient simulating different climatic scenarios and, likewise, found
that plants exhibited higher biomass, pollen production and earlier flowering dates.
Ziska et al. (2003) additionally concluded that plant expansion rates and regional
abundance may also increase with increasing CO 2 , thus increasing allergenic pollen
exposure rates on a wider spatial scale.
Air pollution and climate change do not only affect plant growth, pollen and
flower production, and duration of the whole pollen season, but can also display
more direct health effects by increasing the amount of allergenic proteins of the pollen (Zhao et al. 2016, 2017). According to Zhao et al. (2016), elevated levels of
certain pollutants, like nitrogen dioxide (NO 2 ), which is traffic-related and hence
more prevalent in urban locations, increase overall pollen allergenicity, thus also
increasing the relevant allergy risk for sensitised individuals. El Kelish et al. (2014),
as well as Zhao et al. (2017), showed that elevated pollutants change the transcriptome of ragweed pollen; therefore, under global change scenarios, the allergenic
potential of pollen is also expected to change. Vehicular-exhaust pollution has been
reported to influence the allergenicity of ragweed pollen: pollen along high-traffic
3 Climate Change and Pollen Allergies