Trophic level asynchrony in rates of phenological change for marine, freshwater and terrestrial environments
S. J. Thackeray*, T. H. Sparks, M. Frederiksen, S. Burthe , P. J. Bacon, J. R. Bell, M. S. Botham, T. M. Brereton, P. W. Bright, L. Carvalho, T. Clutton-Brock, A. Dawson, M. Edwards, J. M. Elliott, R. Harrington, D. Johns, I. D. Jones, J. T. Jones, D. I. Leech, D. B. Roy, W.A. Scott, M. Smith, R. J. Smithers, I. J. Winfield and S. Wanless
Abstract
Recent changes in the seasonal timing (phenology) of familiar biological events have been one of the most conspicuous signs of climate change. However, the lack of a standardized approach to analysing change has hampered assessment of consistency in such changes among different taxa and trophic levels and across freshwater, terrestrial and marine environments. We present a standardized assessment of 25,532 rates of phenological change for 726 U.K. terrestrial, freshwater and marine taxa. The majority of spring and summer events have advanced, and more rapidly than previously documented. Such consistency is indicative of shared large scale drivers. Furthermore, average rates of change have accelerated in a way that is consistent with observed warming trends. Less coherent patterns in some groups of organisms point to the agency of more local scale processes and multiple drivers. For the first time we show a broad scale signal of differential phenological change among trophic levels; across environments advances in timing were slowest for secondary consumers, thus heightening the potential risk of temporal mismatch in key trophic interactions. If current patterns and rates of phenological change are indicative of future trends, future climate warming may exacerbate trophic mismatching, further disrupting the functioning, persistence and resilience of many ecosystems and having a major impact on ecosystem services.
*Correspondence e-mail: sjtr@ceh.ac.uk
*Correspondence e-mail: sjtr@ceh.ac.uk
Link to abstract: http://www3.interscience.wiley.com/journal/123233053/abstract
Press release:
Press release 2010/03 - Issued by the Centre for Ecology & Hydrology
Will earlier springs throw nature out of step?
The recent trend towards earlier UK springs and summers has been accelerating, according to a study published today (9 February 2010) in the scientific journal Global Change Biology.The collaborative study, involving scientists from 12 UK research institutions, universities and conservation organisations, is the most comprehensive and rigorous assessment so far of long-term changes in the seasonal timing (phenology) of biological events across marine, freshwater and terrestrial environments in the UK.
Led by Dr Stephen Thackeray and Professor Sarah Wanless of the Centre for Ecology & Hydrology, the research gathers together more than 25,000 long-term phenology trends for 726 species of plants and animals. More than 80% of trends between 1976 and 2005 indicate earlier seasonal events. The study considers a diverse array of organisms including plankton, plants, insects, amphibians, fish, birds and mammals. On average, the seasonal timing of reproduction and population growth has become earlier by more than 11 days over the whole period, but change has accelerated in recent decades.
The research shows that there are large differences between species in the rate at which seasonal events have shifted. Changes have been most rapid for many organisms at the bottom of food chains, such as plants and the animals that feed upon them. Predators have shown slower overall changes in the seasonal timing of their life cycle events. However, the seasonal timing of reproduction is often matched to the time of year when food supply increases, so that offspring receive enough food to survive. A key question is whether animals higher up the food chain will react to the faster rates of change in the plants and animals they feed upon, or whether they will fail to do so and become less successful at rearing their offspring.
Dr Thackeray said, “This is the first time that data have been analysed with enough consistency to allow a meaningful comparison of patterns of changing seasonal timing in the UK among such a diverse range of plants and animals.”
Professor Wanless said, “It is important to realise that this analysis doesn't identify which predator-prey relationships are most at risk of disruption due to changes in timing. What it does do is highlight that the recorded changes need urgent investigation, particularly for species with high economic or conservation importance.”
Co-author Richard Smithers of the Woodland Trust said, “Phenology is ‘the canary in the cage.’ The results of this new study make real our changing climate and its potential to have profound consequences for the complex web of life.”
Link: http://www.ceh.ac.uk/news/press/Willearlierspringsthrownatureoutofstep.asp
More:
Will earlier springs throw nature out of step? Q & A with lead author Stephen Thackeray - 9 February 2010
An assessment of long-term changes in the seasonal timing of biological events across marine, freshwater and terrestrial environments in the UK shows an accelerating trends towards earlier UK springs and summers. The new study, published in the journal Global Change Biology, was led by the Centre for Ecology & Hydrology. Lead author Stephen Thackeray gives more details of the analysis:
Oak leaves, photo by Pete Holmes, Woodland Trust Picture Library
Oak leaves
photo by Pete Holmes, Woodland Trust
What are the main findings of the paper?
A major finding of the study is that the timing of seasonal biological events has not only become earlier, but that the change has also been accelerating. It also shows that seasonal events associated with predators have been changing least quickly. This is the first time that either of these patterns have been shown at such a scale. Predatory animals frequently breed within certain periods of the year so that offspring are produced at a time when food is abundant. Since these food plants and animals have changed their seasonality more quickly than the predators then there is a possibility that predators and prey might become desynchronised and that predators might suffer from food shortages.
Did the research look at global warming?
A number of studies have highlighted that warming is likely to be a predominant driver of changes in the seasons. However, this study focused purely upon assessing patterns of change in the timing of natural seasonal events and comparing these changes among different groups of plants and animals. The paper does not explicitly relate data to patterns of warming across the UK but this is one of the major questions that must be addressed next so that comparisons between changing seasonality and warming can be made soon.
Why was the period 1976-2005 chosen for the study?
Simply because this is the period for which the most comprehensive data set of changes in the timing of seasonal events could be assembled, for a wide range of plant and animal species. Each of the monitoring programmes that contributed to the analysis has data from a different time period, and the period 1976-2005 was an effective compromise.
Which particular species may suffer as a result of these changes?
A major finding of the study is that the timing of seasonal biological events that are associated with predators has been changing least quickly. In the study the predators are birds, fish, amphibians, insects such as dragonflies and marine invertebrates. Predatory animals frequently breed within certain periods of the year so that offspring are produced at a time when food is abundant. Since these food plants and animals have changed their seasonality more quickly than the predators then there is a possibility that predators and prey might become desynchronised and that predators might suffer from food shortages. However, this study is very large-scale and shows only that the conditions that could cause these problems are becoming apparent. We cannot, at this stage, say which species would be adversely affected. Various co-authors of this work are currently involved in more detailed analyses of particular species, to look for evidence of adverse effects.
Which parameters were studied for rates of change?
Rather than just giving an average figure for rates of change in the seasons the study tried to identify whether rates of change varied with particular attributes of species. One parameter studied was thermal physiology. It might be expected, for example, that species for which body temperature is set by the external environment (such as insects, fish and amphibians) would be more strongly affected by warming than species that internally control their body temperature (such as birds and mammals).
Generation time is a measure of the time between an individual being born and producing its own offspring. So this tells you something about lifecycle length. Currently, an important issue in climate research is whether plants and animals are responding to climate through some form of evolution. Evolutionary processes happen over generations so it might be expected that if generations pass more quickly, organisms are more able to adapt quickly to the changing climate by altering the seasonal timing of their activities.
Food chain position was also looked at. Scientific studies show that changes in the timing of seasonal activities such as breeding can be different for predators and their prey. However, these studies have often been carried out at just a single location e.g. for different bird species in a particular woodland. The new research looked for large-scale evidence for this kind of pattern, across all of the major UK environments.
How well do these findings reflect the global picture?
There have been some studies that have taken a global perspective to changing seasonality and these also show evidence that, on average, seasonal biological events have been occurring earlier in recent decades. So these findings are in agreement with such studies. However, in those previous studies inconsistencies in analysis methods made it difficult to compare changes for different groups of plants and animals. This latest study uses more consistent methods but, as yet, a similar approach has not been used at a global scale. So, as yet, it cannot be said whether the patterns observed among species in the UK are similar to those observed at a global level.
Why is the rate of change increasing?
The study observed that the fastest changes in the timing of seasonal events have occurred in decades which have been, on average, warmer. It is tempting to conclude that the acceleration of change in the biological seasons has been brought about by increases in temperature but this has not yet been explicitly tested using this dataset. However, trying to understand the links between warming and the accelerating change in the UK is clearly a priority for future study.
What is likely to happen in the next 10-20 years?
Much research effort has been spent in trying to understand how changes in the seasons might impact upon the functioning of ecosystems. Analysis of data from the past has suggested that changes in the seasons might have adverse effects on populations of some species, typically predators. It has been suggested that this occurs due to the desynchronisation of predator breeding times and the timing of peak food availability. However, it still isn’t clear how widespread and severe these effects might be. There is a need to develop models that can be used to project possible future consequences.
How much have changes accelerated?
The acceleration has been very pronounced across all major environments but varies among species of plants and animals. Between the mid 1970s and mid 1980s average changes were of the order of just 1-2 days per decade earlier. Following this, rates of change have been at least three times that value for marine species and up to five times that value for freshwater and terrestrial species.
Is the pattern of change different in different environments?
The study examined whether the acceleration in rates of change and the differences throughout the food chain varied across marine, freshwater and terrestrial environments. The analysis would suggest that patterns of change have been consistent across all of these environments.
Which species shift fastest?
Of the groups examined, it would seem that terrestrial plants and aphids have shown particularly rapid advances in the timing of seasonal events. They also show strong acceleration of change over time. Between 1976 and 1985 they show little or no evidence of earlier seasonal timing, whereas changes in the timing of flowering and leafing and aphid flight dates advanced by over 10 days per decade after 1986. A key challenge now is to try to understand the key attributes that make some species more susceptible to changing their seasonal behaviour.
Are changes different in different parts of the UK?
These data cover the length and breadth of the UK but so far the analysis has not explicitly considered how patterns of change in the seasons vary with latitude and longitude. Separate analyses of some of the datasets included in the study do show that the timing of seasonal biological events can differ across the UK and so it would be interesting to compare the spatial variations in the seasons among different plants and animals using the full dataset.
Link: http://www.ceh.ac.uk/news/news_archive/2010_news_item_04_qanda.html
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