Shifting spring and its impact on nature

Climate Change and Nature Blog Series No 1

The temperature of spring has always been variable between years: for plants and animals to survive these variable conditions they must evolve mechanisms to hasten or delay their breeding cycle to fit the conditions in any one year. A consistently warm set of springs will therefore result in consistently earlier biological spring, as nature responds appropriately. 

One of the earliest signs (more than 30 years ago), that climate change was already having an impact on natural systems was the observation that biological spring was getting earlier. These now three-decade old studies identified that the timing of bud-burst in the UK and the dates of arrival of certain migrant bird species were getting earlier, apparently linked to warmer spring temperatures. Further research added to this, until a landmark paper was published in 2003. 

This important paper brought together data from over 1700 species to demonstrate a globally coherent ‘fingerprint’ of climate change on natural ecosystems, opening the eyes of many ecologists to the dramatic changes that were already occurring all around. Thanks to the amazing work of 1000s of voluntary citizen scientists, we know that in the UK, the peak migration of 11 of our 14 summer migrant birds has shifted, mostly by more than 10 days compared to baselines from the 1960s. Dates of the first appearances of butterflies are similar and while advances in timing of plant events from bud-burst through flowering to fruit ripening have been rather less, the trend is still evident across Europe. 

There are two ways in which global change impacts on the timing of biological events could result in conservation problems. Firstly, if species don’t have enough inherent adaptability to match future spring advances, and secondly, if timing changes result in a mismatch between different species. Happily, all the evidence suggests we’ve not reached the limits of inherent adaptability in the UK so far. However, there is good evidence that timing mismatches are already occurring for some species, including widespread species like Blue Tits. 

Blue Tits for example, time their breeding to match the spring peak in caterpillar abundance, which is itself timed to match the point when oak leaves are fully unrolled but still poorly defended. Timing of caterpillar peaks and oak leaves have advanced by identical amounts across the UK, but timing of tit nesting has only changed half as much, leading to poorer foraging opportunities at times of peak demand. The even smaller advances by migrants such as Pied Flycatchers have led to greater mismatches in the UK, and may contribute to some of the problems migrants are currently facing.

Monitoring the timing of spring events in your local area is definitely a fun way to measure the impacts of climate change on nature locally to you. Although advances in spring timing are appropriate biological responses to warmer spring, it’s definitely important that we keep an eye on what happens as the situation gets ever more extreme. I’m expecting frogspawn in the garden any day now! 

We will be listing the citizen science projects that you can be involved with, to help monitor spring timing in future Wild Christian blogs.

About the author: Colin is Reader in Ecology at the University of York, where he leads a group of researchers studying spatial patterns in ecology and conservation biology in the UK and globally. He previously worked for A Rocha Portugal and A Rocha Lebanon and is now a trustee of A Rocha UK. As a member of his local parish church, Colin also advises the Diocese of York on environmental matters.

This blog was written for A Rocha UK’s Wild Christian email, February 2021. Sign up here to receive future Wild Christian emails

Read part 2 of our climate change and the UK blog series here.