Revealed: why spring is coming earlier and earlier each year ...
TOMORROW IS SUPPOSED TO THE FIRST DAY OF SPRING, BUT THE SEASON OF DAFFODILS AND LAMBING HAS BEEN THROWN INTO DISARRAY THANKS TO CLIMATE CHANGE. ENVIRONMENT EDITOR ROB EDWARDS INVESTIGATES Signs spring is coming sooner
SOON the swallows will come swooping back to Scotland from South Africa, a traditional sign that winter has ended. It may seem as if all is as nature intended, but it is not. Swallows are now arriving 20 days earlier than they did in the 1970s – and it’s because of global warming caused by climate pollution.
It’s not just swallows whose habits are changing as temperatures rise. A series of scientific studies have found numerous signs that spring – which officially begins tomorrow with the vernal equinox marking the first day of spring – is coming much sooner than it used to.
Orange-tip butterflies are taking to the air 13 days earlier than they did a century ago, while queen wasps are buzzing about six days sooner. Daffodils at Nethy Bridge in the Cairngorms are flowering five days earlier than they did a decade ago.
Fish and frogs are spawning sooner, trees are budding earlier and lawns are being mowed more often. Insects are appearing two weeks ahead of when they did in 1970, while plants are emerging ten days earlier.
The impacts of rising temperatures are not simple and they can vary, but scientists are clear that most signs of spring are advancing. “A warming climate appears to be disrupting the sequence of events that we have grown up with,” said Tim Sparks, professor of environmental change at Coventry University.
“Early naturalists thought there was a natural order to events. We now know that they were incorrect in this assumption.”
Sparks provided evidence on how the average behaviour of seven selected plants and insects had changed between 1891-1947 and 2000-2016. Horse chestnut trees, for example, were now flowering on April 29 rather than May 6, while hawthorn were flowering on April 29 rather than May 11.
According to the Met Office, the average spring temperature has risen from 7.1 degrees between 1961 and 1990 to 8.1 degrees between 2006 and 2015. Scientists blame the rise on car- bon pollution from vehicles, factories, farms and homes.
One of the UK’s leading experts on shifting seasons, known as phenology, is Dr Stephen Thackeray, from the government-supported Centre for Ecology and Hydrology (CEH) in Lancaster. “Over the last few decades many familiar UK seasonal events, such as flowering, breeding and migration, have shifted earlier in the year,” he told the Sunday Herald.
“Many seasonal events – our traditional signs of spring – have changed in association with changing air and water temperatures. Species have responded very differently over time, and this could affect the way in which they interact with each other.”
Scientists working for the government Joint Nature Conservation Committee (JNCC) and CEH have compiled a “spring index” to show how wildlife is being put under pressure by climate change. It is based on historical data, along with observations by 50,000 volunteers in recent years as part of a major project called Nature’s Calendar.
The index is founded on four events: the first flowering of hawthorn and of horse chestnut, the first recorded flight of an orange-tip butterfly and the first sighting of a swallow. Though timings have Swallow: arrives 20 days earlier than in the 1970s Sand martin: arrives 25 days earlier than in the 1970s Orange tip butterfly: appears 13 days earlier than a century ago Hawthorn: flowers 12 days earlier than a century ago Horse chestnut tree: flowers eight days earlier than a century ago
flowers five days earlier than 10 years ago appears six days earlier than a century ago
spawn earlier than they used to appear 10 days earlier than in 1970 varied over the years, it suggests that since 1999 the annual average dates for these events have been six days earlier than they were in the first part of the 20th century.
The JNCC’s biodiversity indicators manager Dr James Williams noted that the spring index advanced more rapidly when the average temperature in March and April was seven degrees or higher. Complex changes could harm some species, he suggested.
“Differential responses among species may cause problems for life cycles such as pollinating insects emerging out of synchrony with flowers opening in spring,” he said. “This could increase vulnerability to extreme events such as late frosts, disrupt food webs, and change the balance of competition between species.”
Nature’s Calendar has also provided evidence that spring is moving faster from south to north every year. In 2015 spring took nearly three weeks to travel from the far south west of England to the far north east of Scotland, travelling at about three kilometres an hour. Between 1891 and 1947, it moved north at 1.9 kilometres an hour.
Nature’s Calendar is coordinated by the conservation charity The Woodland Trust. “We believe climate change is the biggest single threat to what little remains of our ancient woodland heritage,” said the trust’s spokesman in Scotland, George Anderson.
“The more data we can collect, the more evidence we will have that cli- mate change is a problem, as there are those who still need convincing.”
The more information the trust gathered, the better it could also manage the impact of climate change, Anderson argued.
“Our Nature’s Calendar volunteers make a valuable contribution to understanding climate change and to protecting species from it.”
ROY Turnbull, a naturalist in the Cairngorms, has been charting changes at Nethy Bridge in Strathspey since the 1980s. There, average March temperatures have been rising by 0.7 degrees a decade, he said. Frogs are spawning 1.3 days sooner every 10 years, while bumblebees are appearing 1.3 days earlier and wood anemone flowering two days earlier. Turnbull has seen silver birch leaves growing 7.4 days sooner every decade, and the first daffodils 4.8 days earlier.
Friends of the Earth Scotland highlighted the need to do more to cut carbon pollution. “Nature is sending us very clear signals that the climate is changing and that major disruption is on the way,” said the environmental group’s director, Dr Richard Dixon.
“No one can deny there is a big problem. We need to work much harder to reduce climate change emissions from factories, traffic, farming and homes if we are to save our precious wildlife and, ultimately, our own society.”