All aflutter with Citizen Science?

Citizen Science can produce valuable scientific results but is an asset rather than replacement to conventionally collected data.


A Peacock butterfly. Credit: M Paulus

It is rather a bucolic way to do science; sitting in your garden on a sunny July day, counting butterflies that dance past in a 15-minute window. As fieldwork goes, it is infinitely preferable to wading through thick mud on a windy saltmarsh and, perhaps more importantly, it is accessible to all.

The Big Butterfly Count (BBC) is an excellent example of the rise of Citizen Science (CS) projects in recent years. Established in 2010, it asks volunteers up and down the country to sit outside for 15 minutes on a sunny day and record their count data for 20 common species of Lepidoptera (butterflies and moths). It takes place during a set period in July/August and the data is then uploaded via their website or app to an interactive map where it can be viewed. In the 2017 count, 550,000 individual Lepidoptera were observed by over 60,400 volunteers. That’s a lot of data.

Lepidoptera are far more than pretty faces; they are also a useful indicator of how an ecosystem is doing. They are a well-recognised indicator taxon for both habitat change and climate change[1] but also a fairly easy taxon to observe and identify.

For many Lepidoptera in the UK, they are at the current northern most edge of their European range and should therefore benefit from climate change and expand northwards. Conversely, northern or upland species may well be pushed out during the coming decades. However, even the butterflies and moths that are predicted to benefit from climate change in the UK, will likely be severely negatively affected by habitat loss and degradation[2]. Not an ideal combination really.

Based on comparison studies of British Lepidoptera records in the last few decades, scientists believe that, at the moment, habitat loss is a more important factor than climate change. A team of scientists looked at data for 46 species of butterflies that were known to be at the northern edge of their range and should thus benefit from climate change. Soberingly, they found that three quarters of the 46 species had declined since the 1970s; pointing the finger at habitat loss[3].

meadow brown

A Meadow Brown butterfly. Credit: M Paulus

The importance of butterfly records is well-established but are mass participation schemes like the Big Butterfly Count actually useful to science? The BBC did not require any specialist knowledge or lengthy protocols so how good is the data?

Scientists from the BBC and other partner organisations have attempted to quantify the quality of the data obtained by the Count in relation to the UK Butterfly Monitoring Survey (UKBMS).

The UKBMS is a long running, standardized annual survey of the UK’s butterflies and is recognised as an important and reliable dataset. They found that there was a good correlation between the two datasets with the BBC showing the same trends as the UKBMS dataset. The BBC data tended to underestimate the magnitude of some of the trends but misidentification does not seem to be a massive issue given the correlation.

This is a relief as, when doing my own count, I misidentified two individuals but only realised after I had submitted my observations thus illustrating one of the pitfalls of CS.

Where the BBC does fall down is on phenological data. Phenological data is data relating to the timing of natural events, e.g. when the first daffodils appear in spring. The timing of butterflies emerging is very dependent on weather and long-term phenological records of butterflies are a useful proxy for the effects of climate change. Because the BBC is a snapshot of a few specific weeks in summer, it can’t provide us with phenological data. It is also difficult to tell if there are lower counts of butterflies because they are suffering from habitat change or whether because they all emerged earlier in the spring.

However, this becomes less of a significant issue if the BBC data is analysed in the context of other data that does contain phenologies. In their own analysis, the BBC concluded that the dismal performance of certain species was likely to be because they had emerged 2 weeks earlier than last year and so had already peaked by the time the count started. By itself, the BBC data does not give us any phenological records but, when used in context, it can be further evidence of changing phenologies in response to climate change.

Perhaps just as importantly, citizen science projects like the BBC have a fantastic effect on engaging the general public with nature and biodiversity conservation. It can boost enthusiasm, increase scientific literacy and deepen the relationship and concerns that the public have about the environment and its health[4].

The science is important but so are the positive effects of public engagement. It can also generate a huge dataset that otherwise would not be practical to collect. The Global Biodiversity Information Facility has over 7,700,000 Lepidoptera records globally submitted by 49 CS projects[5] and that doesn’t include data from the BBC or other surveys that report their data elsewhere.

Therefore, whilst Citizen Science should not replace systematic long-term records collected by experts, it does certainly have a place in modern science. It’s fun, scientifically useful and probably here to stay. Find out how to get involved here.

With thanks to Richard Fox of Butterfly Conservation for further information on BBC data.

[1] Bates et al., (2013) Assessing the value of the garden moth scheme citizen science dataset: how does light trap type affect catch? Entomologia Experimentalis et Applicata. 146:386-397.

[2] Fox et al., (2014) Long-term changes to the frequency of occurrence of British moths are consistent with opposing and synergistic effects of climate and land-use changes. Journal of Applied Ecology. 51(4):949-957

[3] Warren et al., (2001). Rapid responses of British butterflies to opposing forces of climate and habitat change. Nature. 414(6859):65-69.

[4] Bates et al., (2013) Assessing the value of the garden moth scheme citizen science dataset: how does light trap type affect catch? Entomologia Experimentalis et Applicata. 146:386-397.

[5] Chandler et al., (2017) Contribution of citizen science to towards international biodiversity monitoring. Biological Conservation, 213:280-294.  



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