Does early spring spell the end of Scotland’s postcard
winters?
Is global warming a reality? And, if so, could plants hold the key to identifying its
advancement? These queries are being tackled by specialists at the Royal Botanic
Garden Edinburgh (RBGE) who aim to lend new weight to ongoing debate through
publication of an annual Edinburgh Spring Index. The first comprehensive
phenological study of its kind, the Index prepares new foundations for research by
combining studies of plant reaction to the weather, in conjunction with wider climatic
recording to accurately gauge whether or not the seasons are changing.
Coordinated by a team of the country’s top botanists and horticulturalists, the
Edinburgh Spring Index sets out to consolidate and advance data which has been
collated at the Garden since the mid 19th century. It focuses on the study of 65 plants
at the Inverleith site and is backed up by information collected at a weather station on
site.
“Ongoing observations suggest spring really is arriving earlier,” explained botanist Dr
Geoffrey Harper. “The results are particularly noticeable for early spring plants, with
an extreme example being the hazel. The first-flowering of one tree has advanced by
55 days in three years, from 21 January, 2002, to 26 November, 2004: that’s 18 days
a year. If the trend continues, this spring-flowering shrub will become an autumnflowering one in the not too distant future. This is almost certainly caused by warmer
temps in late winter and early spring. On this level, climate change is going to affect
how individuals plan their gardens, as different flowers come into bloom together. So,
phenological recording will help the gardeners of tomorrow to design their gardens
more effectively.”
This early flowering can also be expected to have repercussions for the wider
environment, according to horticulturalist Peter Brownless: “When a plant flowers out
of season, everything that interacts with it is affected,” he added. “The various insects
which rely on it must adapt to the changing timescale and this, in turn will affect, for
example, the seasonal feeding habits of birds. From there, the potential implications
are even more wide-ranging. While there is no quick fix solution, it is more important
to study the changing habits of plants, if we are to start addressing the wider issues
of protecting our biodiversity.”
ENDS
EDITOR’S NOTES
Spring Flowering at the Botanics -
(1)
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General
phenological observations have been made at RBGE since 1850 (with
some long breaks);
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(2)
(3)
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observations were re-started in 2002;
since then there has been marked advancement of start of flowering in
early-spring flowers;
e.g. (2004 results) 15-20 days earlier than 2002 in plants flowering up to
end of February; c.10 days earlier in plants starting to flower in March; smaller
effects after that;
quote chosen Earliness-of-Spring Index for 2005 (to be calculated), also for
2004 and 2003 for comparison?
An extreme example – Hazel
first-flowering has advanced by 55 days in 3 years, from 21 January 2002
to 26 November 2004, or 18 days earlier/year;
if the trend continues, this spring-flowering shrub will become an autumnflowering one in a few years.
Flowering season/duration
some plants are extending their flowering season markedly: some formerly
winter-only or spring-only flowers are becoming autumn-winter-spring
flowering;
examples (given as English and Latin names, quoted flowering seasons
from gardening encyclopaedias, ‘now/RBGE’ (meaning recently at RBGE)
followed by our records:
Spurge Laurel Daphne laureola, ‘late winter & early spring’, now/RBGE
September-March;
Wych Hazel Hamamelis mollis, ‘mid winter’, now/RBGE SeptemberFebruary;
Winter Jasmine Jasminum nudiflorum, ‘winter-early spring’, now/RBGE
September-April;
Lily-of-the-Valley Bush Pieris japonica, ‘early-mid spring’, now/RBGE
September-April;
Laurustinus Viburnum tinus, ‘winter & spring’, now/RBGE September-May.
Index values:
2002 – zero (by definition); 2003 – minus 5.8 (21 plants); 2004 – minus 12.6 (22
plants); 2005 – minus 21.4 (21 plants).
By ‘plants’ is meant different kinds of plants (usually species, sometimes varieties if
they are monitored as separate kinds).
The plants used are all those flowering by 15 March in each year, and for which we
have first-flowering dates for 2002. (If you remember from the Provisional Report, 3
of the 68 plants monitored in 2002 were excluded on account of being anomalous or
erratic in flowering behaviour; Stephan suggested including these, but I haven’t had
time to recalculate for each year).
The index is the average number of days difference in first-flowering date in the given
year as compared with 2002; minus values mean earlier flowering. So, on average in
2005, the 21 plants have flowered 21.4 days earlier than in 2002.
Spring has got earlier (by this measure) every year since 2002, but there is no
guarantee that this will continue in 2006 and later.
The Royal Botanic Garden Edinburgh is a scientific research institution with a
world-wide reputation for its expertise in the study of plants and their diversity. As
well as three Regional Gardens – at Benmore, Argyll; Dawyck, Peeblesshire and
Logan, Galloway - it operates several field stations around the world and has
specialists working in more than 40 countries.
For more information, or for interviews and images, please contact Shauna Hay
on 0131 248 2900 or Ellie Cooper on 0131 248 2991.