Current warming and likely future impacts - Climate Change: Biological and Human Aspects - page 271

Table6.1 Somephenologicalevidenceofadvancesinspringevents(fromWaltheretal.,2002)

Taxon Location Changes Period observed

Many plant
species

Europe Flowering and leaf unfolding

1.4-3.1 days per decade
earlier

Past 38-40 years

North America Flowering and leaf unfolding

1.2-2.0 days per decade
earlier

Past 35-63 years

18 Butterfly
species

UK Earlier appearance by 2.8-3.2

days per decade

Past 23 years

Amphibians UK Earlier breeding Past 25 years

Numerous bird
species

Europe, North
America

Earlier spring migration by
1.3-4.4 days per decade and
breeding by 1.9-4.8 days per
decade

Past 30-60 years

for every degree Celsius rise in temperature. However, species do react differently.
For example, oak ( Quercus spp.) responds twice as fast as ash ( Fraxinus spp.) to an
increase in temperature.
European and North American phenological sets have predominantly reflected
changes that are probably associated with climate change, especially with regards
to earlier spring phenology (Table 6.1). But there is also some indication of later
autumnal events, which again would be expected in a warmer world; however, these
are less marked. Indeed, birds that show an earlier migration arrival do not show as
late an autumnal departure. Autumnal leaf colouring is even more ambiguous within
regions. On a long timescale, European autumnal leaf colouring has shown to be
delayed at a rate of about 0.3-0.6 days/decade, whereas the length of the thermal
growing season (TGS) has increased by 3.6 days/decade over the past 50 years. This
correlates well with independent satellite data.
Here it is worth emphasising that although a warming world may be a dominating
driver of current phenological change, as mentioned in the previous subsection, a
number of the major climate-related oscillations have a phenological effect. In 2002
Gian-Reto Walther and a small group of mainly European scientists published a
review of ecological responses to climate. They reported that an analysis of 50 years
of data on 13 plant species in 137 northern hemisphere locations revealed responses to
the North Atlantic Oscillation in 71% of the data. Early-blooming herbaceous species
showed greater response to winter warming than late-blooming and woody plants.
Knowledge of regional climatic cycles is fundamentally important when studying
biological response to climate change.
Then (as mentioned in the previous section with regards to plankton) there are the
physiological affects of changing seasons on species. In 2010 Arpat Ozgul, Dylan
Childs, Madan Oli and colleagues, based in Britain and the USA, demonstrated that
the earlier emergence from hibernation and weaning of young of a North American
rodent, the yellow-bellied marmot ( Marmota flaviventris ), led to a longer marmot
growing season and a larger body mass before hibernation between the years 1976