The first in-depth analysis into the seasonal timing of certain bird and insect behaviours, carried out by scientists at Rothamsted Research, has confirmed that spring is indeed getting earlier each year.
But exactly how much earlier these events now start depends on where in the UK and in which habitat they occur.
The authors of the report have warned that these trends could have serious ramifications for ecosystems, as significant variation between groups of animals in the rates of advance means populations are becoming “out of sync” with the life cycles of their prey.
The fifty-year study into natural cycles of egg laying and migration has also dashed environmentalists’ hopes that shaded habitats such as forests are shielding some populations from the destabilising effects of global warming.
Lead author Dr. James Bell, who heads up the Rothamsted Insect Survey, said: “There was already good evidence that spring is coming earlier each year, but what we didn’t expect to find was that it was advancing as much in forests as it is in open areas such as grassland.
“Equally, in areas where we’d expect to see much greater acceleration, such as urban parkland, the rates of advance appear to be the same.
This all points to a complex picture emerging under climate change, which makes ecosystem responses hard to predict, and even harder for conservationists to prepare for.
An earlier study by the group looking at a 30-year period had shown the average rate of advance varied from about a week earlier for birds and a month earlier for aphids, but this new paper reveals an even more complex picture.
As well as providing more evidence on the effects of climate change, the study also provides the most detailed assessment yet of how many species’ life cycles are determined by geography and altitude.
It shows that, rather than tracking the simple north-south trend of increasing temperatures and earlier onset of spring, the date of key behaviours of many species follow more complex patterns.
So, whilst aphid activity simply becomes progressively later the further north you go, the same was only true for birds and butterflies up to the likes of Northern Ireland, Gretna or Newcastle.
Beyond that point, butterflies become active earlier in the warmer, wetter west than the colder, drier east, whilst for birds laying eggs, the opposite is true.
Dr. Jon Pickup, lead aphid researcher at Science & Advice for Scottish Agriculture (SASA) said: “As pests, it remains a concern that aphid migrations are getting earlier at a dramatic rate, and this piece of work shows us that signal across the UK very clearly.”
