Our pinned mayfly, stonefly and caddisfly specimens are groups of insects that have life cycles reliant on freshwater. Where these insects are plentiful, they are fantastic indicators of water quality.
In my role as an assistant digitiser, I have been working to transcribe some of the Museum’s freshwater insects. Whilst looking at the labels of these specimens a pattern started to emerge around the types of data being recorded and I wanted to find out more.
This International Women’s Day, I want to celebrate the incredible achievements of Grace Mary Crowfoot, a botanist, textile archaeologist, anthropologist, and pioneering anti-FGM advocate and to share her story of breaking biases and fighting inequality for women.
12th February 1832: There has been a little swell on the sea to day, & I have been very uncomfortable Charles Darwin’s diary entry on his birthday 190 years ago.
While on board the voyage of the Beagle, Charles Darwin recorded the journey and mentions notable days like Christmas day and New Year’s day, but although he records each year what he did on the 12th February, he never mentions that it was his birthday.
The UK holds hundreds of millions of natural history specimens of scientific importance. Exactly how many specimens and what those specimens are, is currently unknown. Unveiling the contents of the UK’s collections will open the door to further digitisation and unlock the full scientific potential of UK natural science collections.
Digitising, the process of converting physical information into a digital form, the UK’s natural science collection, opens up a unique and valuable national resource to the world and enable the UK to be part of current and future scientific collaborations to find solutions to the biggest challenges of our time.
Digital Collections support over 1000 scientific papers
The Museum’s Data Portal was launched in December 2014 to provide access to Museum collections and research, enabling to explore, download and re-use these data for their own purposes. Museum collections include specimens collected over the last 200 years, a critical time period, during which humans have had a major impact on the distribution of biodiversity.
Since 2015, more than 1000 research papers have cited data from the Data portal and partner platforms like the Global Biodiversity Information Facility (GBIF), covering topics including agriculture, biodiversity, evolution, ecology, species distributions and human health. This blog looks at just one of the studies using Museum data, PhD candidate Galina Jönsson’s research using data to examine how human activity has impacted butterfly populations over the 20th Century.
Insects are declining at alarming rates, but we do not precisely know why. From wasps to butterflies, Galina is looking for answers in the Museum’s pinned insect collection and extending time series to span the period of accelerating human pressures like agricultural intensification and deforestation. ‘At first glance, my results suggested that British insects fared pretty well, but I quickly realised there is much more to this than meets the eye.’
Blame eccentric Victorians or lazy statisticians?
Natural history collections’ pinned insect specimens have revealed fascinating changes over the last centuries but have rarely been used to map how, and why, some species increase while other decrease. Nearly everything we know about insect responses to human activities comes from survey data collected by national schemes like the UK Butterfly Monitoring Scheme (UKBMS), which was launched in 1976. One of the benefits of using survey data is that it is standardised, meaning that all species at a particular location are recorded in the same way, at the same time of the year, for multiple years in a row. This makes it easy to compare how different species change in population or geographical location over the years. In the UK, which is unusually well-documented, our knowledge from such survey data is limited to the period since 1970. This period falls after most large-scale transformations of the British landscape such as the agricultural intensification of the 1950s with its deforestation and increased pesticide-use. As a result, we find ourselves without baselines reflecting the state of biodiversity prior to major human pressures.
In contrast to survey data, museum specimens do go back much further in time to give us these baselines – but they were not systematically sampled. This challenges conventional statistics. Labels inform us where and when specimens were collected, but not how. Just like millennial houseplant enthusiasts, Victorian bug collectors had individual preferences. Some travelled far to collect one specimen of every species, others collected every tiny variation within their favourite species. Some collectors were working scientists, but a lot of the collection comes from amateurs and those that collected as a hobby, so the type of specimens and data that was recorded also varies due to the collector.
Ambitious digitisation projects are making collections available with the click of a button; and in addition, now, citizen science projects generate enormous amounts of contemporary data in addition to data from collections and systematic surveys. Smartphone applications let anyone submit wildlife sightings in seconds but, just as collections reflect eclectic Victorians, citizen scientists’ preferences introduce their own set of biases to the data. We need new statistical models to extract the valuable yet varied information museum specimens, survey data and citizen science sightings hold, but the models also need to handle their respective biases.
The European hornet (Vespa crabro) and its distribution in the UK over the last 120 years.
And in flew century-old butterfly specimens, forming the basis of my PhD research. In the interest of honesty, perhaps I should say ‘in flew iCollections’, NHM’s pilot mass digitisation project that digitised over half a million British butterflies and moths. My current research explores temporal patterns of British butterfly trends across centuries, looking at how the timings of major changes to butterflies coincide with habitat changes, and how species-specific characteristics affect population-level change. There are 59 British butterfly species; another five species have become extinct in the last 150 years. Butterflies are sensitive to temperature and weather conditions, and caterpillars are picky eaters, some accept nothing but one specific host plant. These factors render them particularly vulnerable to, and simultaneously good indicators of, greater habitat and climate changes.
Generalisations hide uncomfortable truths
After a couple of years formulating the perfect model (hint: there is no such thing as a ‘perfect model’), I summarised the trends across all British butterfly species. The preliminary results were surprising. Averaging across species, there has been a 15% decrease since 1900. But we know that humans have extensively altered 75% of Earth’s surface, so this had me wondering – is a 15% decrease over 120 years really that bad?
Next, I grouped species according to whether they are specialists requiring specific habitats (the picky eaters) or generalist wider countryside species that can use a range of habitats. The generalist species nearly doubled since 1900, whilst the specialists had halved. Separating specialists from generalists also showed that the most dramatic changes occurred before the 1970s baseline that many recording schemes give us. Just like the hornets, specialist butterflies started to plummet around 1950, but in contrast to hornets, they did not recover after 1970. It appears that agricultural intensification in the 1950s triggered the troubling subsequent declines (or at least was the straw that broke the specialist’s thorax). Wider countryside species also began expanding in the 1950s, and this expansion continued into the 2000s.
What is wrong with generalists?
Overall, preliminary results show that we’ve lost around 15% of British butterflies since 1900. Specialised species have plummeted, but generalist wider countryside species are making up for the losses. Sometimes people ask ‘what is wrong with generalists?’ – does it really matter which butterfly species are in the ascendant? It all comes down to biodiversity. The diversity of life on Earth, which we need for human well-being, prosperity and ultimately, survival.
Species richness is the number of different species in an area, a way of measuring biodiversity. When the number of species thriving in an area declines or becomes unbalanced, certain species that are doing well can come to increasingly dominate the area. The species that can’t adapt are put under further pressure from the increasing generalist species eating their food or nesting in their areas. A change to the delicate balance of the species in an area can reduce biodiversity and species richness, cause extinctions and dramatically change ecosystems.
The wall butterfly (Lasiommata megera) distribution change over 20th century
However, is it fair to divide all butterflies into either habitat generalist or specialists? And assume that, within each group, every species shows the same long-term trends? Although a habitat-use separation can give useful indications, the reality is much more complex. For instance, the wall butterfly (Lasiommata megera) has suffered worrying declines despite enjoying a variety of habitats. With rising temperatures, the cold-loving wall butterfly has been forced northwards and risks joining the list of butterflies that are extinct in Britain, when it reaches John O’Groats. Biologists often divide species by habitat-use, but the dramatic decline of the wall butterfly shows us that every species has its own particular quirks, extending beyond habitat-use. In addition to temperature-tolerance, species differ in a number of characteristics like their reproduction strategies (for example, many tiny eggs but few survive or a few huge eggs with high survival), the ease with which they find a mate, and how strong flyers they are (which determines if they can colonise new habitats). I am currently using several such species-specific characteristics to identify combinations of characteristics that predispose species to being particularly vulnerable and give others the ability to rapidly expand.
Natural history collections’ specimens are vital to gather the data needed to extend time series of species’ trends to periods prior to extensive anthropogenic pressures and provide important novel insights into our effects on biodiversity. However, most specimens world-wide are relatively inaccessible to research, hidden away in undigitised collections. Mobilising digitisation projects that provide open access to this important biodiversity data will allow us to refine models, produce more accurate future projections, and make effective conservation decisions to bend the curve of global biodiversity loss.
We would love to hear from you if you are using data from data.nhm.ac.uk please get in touch or stay up to date with Digital Collections news by following us on Twitter and Instagram. Keep up to date with our blog posts for more examples of our data in action.
If you are spotting butterflies this summer please log your findings on a recording scheme so that researchers like Galina can make use of your work. You can also follow Galina on Twitter to keep up with her research.
Adults of these species are attracted to the light of a moth trap of course! In this instance I am not referring to the Common Swift bird (Apus apus) that is seen carrying out impressive aerial displays in summer but instead to the beautiful Common Swift moth (Korscheltellus lupulina).