Shifting seasons: Hedgehogs and Phenology, changing weather patterns, blips and fading winters.
Blog by Jo Farrow
7th March 2019 21:57

Shifting seasons: Hedgehogs and Phenology, changing weather patterns, blips and fading winters.

After our bizarre record-breaking February here in the UK, you may have already noticed wildlife and plants about earlier than usual. Whether they survive/cope with the next few weeks and months could be a different thing. There are already calls to help dozy hedgehogs who have ventured out too early.  Last summer there was the lengthy drought and heatwave conditions and in March 2018 the intense cold and heavy snowfall from the Beast from the East. These could all be labelled as short-term anomalies and extreme events but considering longer-term changes and patterns, there are studies into possible shifts in our seasons. The links to climate change are also being investigated. On a small-scale, observations are being recorded looking at plants, birds and mammal behaviours whilst larger scale studies continue using satellite data to monitor the greening up of vegetation continent-wide.

We can witness these early bursts of warmth and fine weather but if butterflies appear or leaves start to unfold, they can wilt if it turns cold again. It can be a blip in the overall pattern of winter into spring. However, if winter long-term is getting shorter, spring earlier and summers hotter then this will affect many areas of our lives. Farming and water supply stand out in the UK and in low-income countries any shifts can have major impacts on food production and water security. The study of phenology looks at subtle changes; being the study of the timing of life cycle events. Possible changes due to climate change have brought this area into the limelight. It often uses long term records, we are already seeing some of these being digitised for modern day use with calls for volunteers to help. Events being recorded include flowering, leaf fall, hatching and annual migration, also with requests for the public to join in locally.

“Phenology is the study of seasonal changes in plants and animals from year to year, such as flowering of plants, emergence of insects and migration of birds, especially their timing and relationship with weather and climate. Nature’s Calendar volunteers record the dates of certain events which happen to certain species during the changing seasons.”

So, there is a difference in blips of occasional late snowfall, freakish heat in February to the longer-term creep of say leaves unfolding early.

I spoke to Nikki Rogers from AA Salt, to ask her about the gritting season as I’d already heard a few gritting sources mention a gradually shift.

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Nikki "Over the past 17 years, I have noticed that the seasons have become more extreme. So, it's not that winters are getting colder or warmer. It's more that we get extreme blips. Like the Beast from the East versus this February which was an extremely mild period. And the seasons don't get gently colder, peaking in mid-winter then slowly getting milder as we reach spring. The extremes can happen at any point in the winter period. 

We have started gritting in Mid-October in some years but in many, it's not till mid-November. Equally, we seem to be gritting more into the middle of April nowadays."

You might notice blossom on a tree a few days earlier perhaps than last year or frog spawn in the pond. With the advent of things like Facebook memories the comparisons from one year to the next are being thrust in our face.  Over decades, from research in the northern hemisphere, there are suggestions that spring is creeping forward gradually as global temperatures increase. It is the daily maximum temperatures which seem to make the difference. In February, it was still cold by night, with clear skies but by day the maximum temperatures were record breaking across Britain. Just one year but that made nature get a move on regardless of the chilly nights.

It was enough to wake up hedgehogs from their hibernation. The hedgehogs emerged dazed and thirsty, they need lots of water to drink and were thrust into an abnormal time of year and a dry spell. The knock-on effect can be that there aren’t the insects or grubs about that early. This was just one year but tortoises have been struggling over recent years as most winters aren’t getting and staying cold enough for them to sink deep enough into their winter sleep.

“Phenology is the study of the timing of life cycle events at the population level, most often focusing on how they respond to climate change. It often makes use of long-term records and includes events such as flowering, leaf fall, hatching and annual migration.”

This area is being used to research climate change, looking at changes in nature, of behavioural timings. Migrating birds, if they set off at a different time of year can behave differently at feeding sites along the way. The birds have to adapt.

Long distance migrants and hibernating species seem to be especially vulnerable to these changes. The British grape harvest still has a bit to catch up on, the Scottish ski industry hangs on and there are even changes in Alpine resorts. 

If the growing season becomes longer due to a warming climate then there might be more risk of frost within that longer time period. If plants can grow in Feb, rather than March there is still opportunity for spring frosts. 

“In cold and temperate regions, plants generally require the accumulation of a certain amount of heat to trigger spring leaf onset. Several studies also outline the need for plants to endure cold conditions during their dormancy, which defines chilling requirements”

Looking at average temperatures doesn’t seem to be as useful when looking at leaf data as just the temperature maximums. Average temps will include day and night max and mins. Investigations look at temperatures but also consider precipitation and cloud amounts. These are longer-term studies which expect inter-year variance, the blips but are beginning to identify other trends and impacts.

“Phenological changes such as earlier spring leaf unfolding, altered migration timing and changes in flowering onset and duration represent a major mode of ecological response to climate change. These changes may seem small and sometimes even difficult to notice, but the cumulative and interacting effects on ecosystem health and functioning can be very significant indeed." Food and Agriculture Organization of the UN.”

Ideally, we should minimize the amount of climate change but as that continues to hit a global stumbling block or fails to get true high billing on the national political stage, then adaptation is key.

WMO “how to best adapt to a changing climate and manage risks associated with climate variability and extremes.”


Currently, the Woodland trust is advertising its Nature’s Calendar but this kind of recording has gone on for years. 

The Meteorological Society asked people to record the flowering of 13 plants, and the appearance of birds and insects in the late 1800s, early 1900s. By 1938 there was an organisation including national groups covering weather, butterflies, ecology, animals, birds and involved the Natural History museum. There are now phenological databases and networks across North America and a pan European one.

The Woodland Trust with the Centre for Ecology & Hydrology looking at phenology suggests impacts will include:

• Spring events like budburst, leafing and flowering are getting earlier
• Fruiting of trees and shrubs is getting earlier
• Late autumn events such as leaf fall may be delayed

The overall period of active plant growth each year is lengthening. A recent study by the Met Office estimated it to be, on average, a month longer during the past decade compared to the period between 1961 and 1990. It has been calculated that, across Europe as a whole, spring is now advancing by 2.5 days per decade.

Changing phenology is one of the first observed responses to climate change. Eventually, species may also change their abundance, range (i.e. where they are found geographically) and even become locally extinct in areas that are less favourable. So, the science of phenology provides a powerful ‘early warning’ of species that could be ‘winners’ and ‘losers’ as the climate changes.

Plenty of food for thought. Have you noticed any longer-term changes?

WMO “Scientists have been observing changes in the climate that cannot be attributed solely to natural influences. These changes are occurring rapidly, are significant, and will have consequences for this and future generations. Changes in climate variability and extremes driven by human-induced climate change are some of the key challenges facing humanity.”

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