Butterflies, hedgehogs and bats are at risk as the unseasonably mild weather has disrupted hibernation in the UK and is causing spring flowers to bloom in January. Climate change is disrupting the seasons, and this year the winter has been especially mild, with trees not dropping their autumn leaves and others bursting into fresh leaf and bloom months early. This New Year’s Eve is expected to be the mildest on record, with temperatures predicted to hit 15C in some parts of the country – double the average temperature for this time of year. This could have devastating effects for creatures that depend on the rhythm of the seasons for survival. While a low-pressure system is behind the unseasonal warmth, experts say background temperature rises caused by climate change are exacerbating the issue. Grahame Madge, a climate spokesperson for the Met Office, said: “The unseasonal warmth that will be a feature of the new year period is caused by a low-pressure system drawing up warm air from further south in the Atlantic. Although this would have always created relatively much warmer conditions compared with average, with around 1C of background warming, it is possible that climate change will bring the event to a point that challenges previously held records.” He said this could cause butterflies to be killed off as they emerge from hibernation too early before sufficient food is available, especially as a deadly later cold snap could hit. Madge said: “Abnormal warm spells during winter can encourage species out of hibernation. Butterflies such as red admirals and small tortoiseshells and other insects can be particularly challenged as they can emerge largely without access to life-saving food sources like nectar. If the warm spell is followed by a return to colder conditions, the hibernating individuals will have used up valuable energy reserves without being able to replace them, possibly with disastrous consequences.” The unseasonably warm weather has been confusing for hibernating mammals, which have been emerging from their slumber early. This could be fatal for creatures including hedgehogs, which are waking without sufficient food to sustain them until spring. Kathryn Brown, the director for climate action for The Wildlife Trusts, said: “Our climate is changing, which is having an impact on whole ecosystems as well as individual species. The warming climate is affecting breeding cycles, the availability of food, and behaviours including hibernation. Unusually mild temperatures mean that some species can temporarily emerge from hibernation more often in winter, which is problematic if there is insufficient food to make up for the extra energy used. We know that hedgehogs are at increased risk, and we need more research to understand the effects on other hibernating species such as bats and dormice.” Horticulturalists have noticed that roses have been in bloom all winter, much like in more Mediterranean climes, and colourful spring flowers are already bursting into bloom across British gardens. Matthew Pottage, the curator of the Royal Horticultural Society’s Wisley garden, said: “There are both pros and cons related to the current mild weather for plants and gardens. Out-of-season plants such as roses will, for example, continue to flower, and spring plants like magnolia will likely begin to bloom earlier than normal, which will bring a welcome bit of colour into gardens from early next year if the mild weather continues.” Gardeners and farmers have greatly missed the frosts that kill off pests. Certain fungi and insects now thrive all year round. Pottage said: “The lack of a cold snap will enable exotic plant varieties to continue to flourish but the downside is gardeners will continue to experience some garden pests until significant frosts arrive to kill them off.” Experts at the Botanical Society of Britain and Ireland (BSBI) are asking gardeners to chronicle unusually early blooms in their garden. This has become a growing phenomenon as the seasons become more muddled. Louise Marsh, from the BSBI, said: “We have seen reports on social media of plants in bloom at the moment that have raised a few eyebrows … I expect we will see a similar pattern to previous years – hundreds of species in bloom.” “It isn’t, however, a straightforward story of everything coming into bloom early. We usually find that about half the species in bloom are ‘autumn stragglers’ that have managed to keep on flowering because they haven’t been knocked back by hard frosts; around a quarter are all-year-rounders (typical urban “weeds” such as groundsel, shepherd’s purse, dandelion and daisy) and a few winter specialists such as winter heliotrope; around a quarter are those spring flowers, such as primrose and lesser celandine, blooming early.” There are concerns about the impacts on pollinators if the flowers bloom before they have a chance to take advantage of the nectar, and on migratory birds that feed on fruit and have not yet arrived.