Relevance
The global climate is changing. According to the UK
Meteorological Office, the average temperature over the first
decade of the 21st century was significantly warmer than any
preceding decade in the instrumental record stretching back over
160 years.
In 2007, the Intergovernmental Panel on Climate Change (IPCC),
concluded that most of the observed increase in global average
temperatures since the mid-20th century is very likely due to the
observed increase in anthropogenic (man-made) greenhouse gas
concentrations.
Phenology is the study of the timing of recurring natural
biological events in relation to climate and such observations
provide year-on-year information on how nature is responding to a
changing climate. This indicator illustrates the stress that one
aspect of climate change (spring warming) can place on biological
systems. Differential responses among species may cause problems
for life cycles (e.g. by increasing vulnerability to extreme events
such as late frosts), disruption of food webs, and changing
the balance of competition between species.
Background
The UK Spring Index is calculated from the
annual mean observation date of the following four biological
events: first flowering of hawthorn (Crataegus monogyna),
first flowering of horse chestnut (Aesculus
hippocastanum), first recorded flight of the orange-tip
butterfly (Anthocharis cardamines) and first sighting of a
swallow (Hirundo rustica).
The four events were chosen for the following reasons:
- Good UK coverage
- Well recognised and easily recorded species
- Good historical data
- Spanning both early and later spring events
- Included plants, a vertebrate and an invertebrate
- Strong phenological response observed
The overall index is compiled by calculating an annual mean
across all sites where all four biological events were recorded.
The pre-1948 data were mostly collected by the Royal Meteorological
Society (RMS). In 1998 the Centre for Ecology and Hydrology revived
the UK Phenology Network (UKPN) in the UK, which was launched by
the Woodland Trust as a web-based project in 2000. The UKPN has
grown since its inception to 29,000 registered recorders in 2008.
In Spring 2005 the UKPN launched the Springwatch survey with the
BBC, the biggest ever survey into the arrival of spring, with
70,000 people logging 157,000 records.
The Index shows a strong relationship with mean March-April
temperature (Figure 12(ii)). There is also a significant difference
in the magnitude of change in the Spring Index at higher
temperatures. The average advance in dates for the Spring Index is
3.1 days per oC below a mean March-April temperature of
7oC and 7.2 days per oC above
7oC.
Figure 12 (ii). Relationship between Spring Index and Central
England Temperature, 1891–1947, 1999–2010
Further development planned
There is a growing body of evidence that some species are
expanding in range as climate changes whilst others will be at risk
of local extinctions as their isolated habitat patches become less
favourable. Whilst at present there is no comprehensive dataset on
the negative impacts of climate change on UK biodiversity, further
development work is likely to focus on identifying data that are
capable of demonstrating the degree of threat to native
wildlife.