Climate change impacts and vulnerability in Europe 2016

Climate change impacts on environmental systems
4.4.3 Phenology of plant and animal species
Key messages
• The timing of seasonal events has changed across Europe. A general trend towards earlier spring phenological stages
(spring advancement) has been shown in many plant and animal species, mainly due to changes in climate conditions.
• As a consequence of climate-induced changes in plant phenology, the pollen season starts on average 10 days earlier
than it did and is longer than it was in the 1960s.
• The life cycles of many animal groups have advanced in recent decades, with events occurring earlier in the year, including
frogs spawning, birds nesting and the arrival of migrant birds and butterflies. This advancement is attributed primarily to
a warming climate.
• The breeding season of many thermophilic insects (such as butterflies, dragonflies and bark beetles) has been
lengthening, allowing, in principle, more generations to be produced per year.
• The observed trends are expected to continue into the future. However, simple extrapolations of current phenological
trends may be misleading because the observed relationship between temperature and phenological events may change
in the future.
Relevance
Phenology is the timing of seasonal events such
as budburst, flowering, dormancy, migration and
hibernation. Some phenological responses are
triggered by mean temperature, while others are more
responsive to day length or weather (Menzel et al.,
2006, 2011; Urhausen et al., 2011). Altitude and the
amount of urbanisation have an effect on temperature
and, consequently, on phenology (Jochner et al., 2012).
Generally, so-called 'spring advancement' is seen in
hundreds of plant and animal species in many world
regions (Peñuelas et al., 2013). Changes in phenology
affect the growing season and, thus, ecosystem
functioning and productivity. Changes in phenology are
having an impact on farming (see Section 5.3), forestry,
gardening and wildlife. Changes in flowering have
implications for the timing and intensity of the pollen
season and related health effects.
Climate warming affects the life cycles of all animal
species. Populations at the northern range margins of
a species' distribution may benefit from this change,
whereas populations at the southern margins may
encounter increasing pressure on their life cycles.
Mild winters and the earlier onset of spring allow for
an earlier onset of reproduction and, in some species,
the development of extra generations during the year.
However, under unfavourable autumn conditions, the
attempted additional generation can result in high
mortality. This developmental trap has been suggested
as the cause for the dramatic decline of the wall brown,
a butterfly with non-overlapping, discrete generations,
in Europe (Van Dyck et al., 2015). In the case of a
phenological decoupling of species interactions in an
ecosystem (e.g. reduced pressure from parasitoids
and predators), certain populations may reach very
high abundances that attain or exceed damage
thresholds in managed ecosystems (Baier et al., 2007).
Desynchronisation of phenological events, such as
shortened hibernation times, may deteriorate body
condition, and interactions between herbivores and
host plants could be lost (Visser and Holleman, 2001),
and may also negatively affect ecosystem services such
as pollination (Hegland et al., 2009; Schweiger et al.,
2010). There is robust evidence that generalist species
with a high adaptive capacity are favoured, whereas
specialist species will be affected mostly negatively
(Schweiger et al., 2008, 2012; Roberts et al., 2011).
Past trends
A variety of studies show that there has been a general
trend for plant, fungi and animal species to advance
their springtime phenology over the past 20–50 years
(Cook et al., 2012). An analysis of 315 species of fungi
in England showed that, on average, they increased
their fruiting season from 33 to 75 days between 1950
and 2005 (Gange et al., 2007). Furthermore, climate
warming and changes in the temporal allocation of
nutrients to roots seem to have caused significant
numbers of plant species to begin fruiting in spring
as well as autumn. A study on 53 plant species in the
United Kingdom found that they have advanced leafing,
flowering and fruiting on average by 5.8 days between
1976 and 2005 (Thackeray et al., 2010). Similarly,
29 perennial plant species in Spain have advanced leaf
unfolding on average by 4.8 days, with first flowering
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