Have you noticed spring arriving earlier?

The Met Office and UK National Parks have teamed up with Nature’s Calendar to better understand how climate change is altering the seasonal rhythms of nature across the UK's Protected Landscapes.

By combining long-term observations from Nature's Calendar with high-resolution Met Office temperature records, we find that warmer years are already associated with earlier flowering, budburst and the arrival of wildlife across many of Britain's iconic species. The scatterplots below show two examples - Horse Chestnut budburst and Holly Blue butterfly emergence - where the downhill trend illustrates this relationship. We can also use these historical relationships to estimate how the timing of these events may change with future warming. The slope of the trend line tells us how many days earlier an event occurs per degree of warming. For the Holly Blue butterfly, this works out at around 7 days earlier with 1°C of warming, and 14 days earlier with 2°C.

Note that these estimates are based on simple linear relationships fitted to historical data. Real phenology is also influenced by day length, rainfall, and cold-spell timing, among other factors, and the response to warming may not stay linear as the climate changes further. Therefore, these projections are best read as an indication of scale and direction, not a precise estimate.

These changes are not just shifts in the calendar; they also change the geography of spring. As the climate warms, spring in northern Britain begins to resemble the spring we experience further south today. Under 2°C of warming, the emergence of the Holly Blue butterfly would be earlier than anything currently experienced anywhere in the country in the last 25 years.

As shown in the timeline image, this pattern is seen across many species. The average timing of several trees, flowers and butterflies in the southeast occurs 9 – 19 days earlier and beyond the range of normal conditions from the last few decades. Note that, these projections are based on average temperatures - individual years could be even earlier during exceptionally warm springs. How far these events can ultimately be pushed, and where their limits lie, is still an open question in the research. One complicating factor is winter chilling: many species need a period of sustained cold to trigger spring growth, and as winters themselves warm, that chilling requirement may be met later - which could slow the pace of these shifts over time.

Why does this matter?

Nature depends on timing. Trees, insects and birds have evolved to be synchronised with one another. If spring arrives earlier for some species than others, these relationships can become disrupted. For example, insects may emerge before the birds that rely on them to feed their chicks, or flowers may bloom before their pollinators are active.

Understanding these changing seasonal rhythms helps us anticipate the impacts of climate change and provides valuable evidence to help National Parks conserve the wildlife and landscapes that make these places so special.

How can you help?

Become a citizen scientist and record your own observations!

Record your observations

Nature's Calendar relies on volunteers to record seasonal events. Every first butterfly, flowering tree or birdsong you record becomes part of a growing picture of how the UK's seasons are changing. Together, these observations help scientists, conservationists and National Parks understand and prepare for the impacts of climate change.

We gratefully acknowledge the generous funding provided by Estée Lauder Companies UK & Ireland and the South Downs National Park Authority, whose support has made this collaborative research possible.