Written evidence submitted by Kent Wildlife Trust (INS0013)

Kent Wildlife Trust is the county’s leading conservation charity. We have over 32,000 members and over 1000 registered volunteers. We manage and protect over 9000 acres of land across more than 80 different sites and nature reserves, alongside 3 visitor centres. We work closely with local communities, landowners and partners to protect and improve habitats in the countryside, coast and town for the benefit of the wildlife and people of Kent. We are working towards creating a better, more sustainable and wilder future.

Topic: The current evidence base for insect abundance in the UK, and the gaps in scientific understanding that require further research.

Here, I am presenting an overview of the Bugs Matter survey and the results, which may have been used to inform the statistic of a 60% insect decline in 20 years, narrated by Sir David Attenborough in the BBC Wild Isles series.

Kent Wildlife Trust (in partnership with Buglife and the RSPB) run Bugs Matter - the National citizen science survey of ‘bug splats’ on vehicle number plates to monitor flying insect abundance. The survey involves participants counting the number of insect splats on their front number plate at the end of a journey, and submitting the count via a mobile app, along with a photograph of the number plate. The journey route is recorded in the app, and by analysing how the measurement ‘splats per mile’ changes over time (years), we can estimate change in flying insect abundance. The method is analogous to the ‘windscreen phenomenon’, a term given to the anecdotal observation that people tend to find fewer insect splats on the windscreens of their cars now, compared to in the past. The survey runs for 3 months from June to August. The survey was piloted in Kent in 2019, then deployed nationwide in 2021 and 2022. The survey was also previously deployed by the RSPB in June of 2004 using the same methodology. A total of 7508 users have signed up to the Bugs Matter app in 2021 and 2022. In 2004, 14,320 journeys were recorded comprising 859,408 miles. In 2019, 519 journeys were recorded comprising 9,122 miles. In 2021, 3,212 journeys were recorded comprising 112,312 miles. In 2022, 4,140 journeys were recorded comprising 124,402 miles.

A comprehensive statistical analysis of the data was performed in 2021 and 2022. First, the dataset was cleaned to remove overseas journeys, journeys outside the survey period, journeys with GPS errors, very short journeys, journeys with unrealistic average speeds, journeys with over 300 splats, and journeys during which rainfall occurred. Zero-inflated negative binomial models were used to determine the change in the number of bug splats recorded between the survey years. A range of independent variables were included in the models to control for their effects on insect splat rates. These included time of day of the journey, calendar date of the journey, vehicle type (car, HGV, SUV, van), daily mean temperature, vegetation greenness (NDVI) within a 500 m buffer of the journey route, and the proportions of each journey that was conducted on ‘primary’, ‘secondary’, ‘tertiary’ or ‘other’ road types.

In 2022, the UK analysis used a dataset of 22191 journeys, and the results showed a 58.4% (95% CI [55.7%, 61.0%]) reduction in the number of insect splats between 2004 and 2021 (34.4%/ decade), and a 63.7% (95% CI [61.5%, 65.8%]) reduction between 2004 and 2022 (35.4%/ decade). The number of journeys which recorded no insects rose from 7.7% in 2004 to 47% in 2022. In England a 67.5% reduction was observed, in Scotland a 40.3% reduction was observed, and in Wales a 74.8% reduction was observed, over the same 2004-2022 time period. In 2004 the survey took place in June, so to maximise comparability only data from June was included, and similar results were obtained. Comparing 2021 and 2022, the results showed an alarming 12.6% (95% CI [5.9%, 18.9%]) reduction in insect splats, which may be partly attributed to the extreme summer temperatures in 2022. All these results were statistically significant.

This dataset is a comparison of only a small number of points in time, and thus the observed reductions do not constitute a trend. There is a chance that insect populations in these years are unrepresentative of the overall trend in insect abundance over this time period. It is therefore crucially important that the Bugs Matter survey continues to acquire data for several more years at least, to provide a robust indication of trends in flying insect abundance. Moreover, an increase in participation by road users across the UK would provide a larger dataset with a greater diversity of journey types, which would reduce noise in the data and enable more accurate regional and county-level analyses. Despite this limitation, there is a good chance that our results do reflect the true trend in insect abundance over this time period, and therefore these results must be taken seriously given the potential severity of the impacts of low insect abundance on the natural world and society. The 2022 reports are available here Bugs Matter (kentwildlifetrust.org.uk).

It is important to note that multiple independent studies of temporal change in insect abundance show declining trends. In the UK, Fox et al (2013) found that the total abundance of larger moths declined by 28%, the total counts of larger moths decreased by 40%, and 125 species of common larger moths declined by at least 50% between 1968 and 2007. Fox et al (2021) found that the total abundance of larger moths caught in the RIS light-trap network in Britain decreased by 33% between 1968 and 2017. Butterfly Conservation et al (2022) report that 80% of UK butterfly species have decreased in abundance or distribution, with the abundance of specialist species having decreased by over one-quarter (-27%) and their distribution by over two-thirds (-68%) between 1976-2022. Elsewhere in Europe, Hallmann et al (2017) analysed a dataset from Malaise insect traps deployed at 63 German Nature reserves and found a 76% decline in flying insect biomass between 1989 and 2016. Moller (2019) found the number of flying insects squashed on car windscreens in Denmark decreased by 89% between 1997-2017. Hallmann et al (2019) found that larger moths had declined by 61% and ground beetles by 42% in Germany over a 27-year period. In the US, Harris et al (2019) found that the number of beetles captured in traps in New Hampshire had declined by 83% between 1973 and 2017, whilst Wepprich et al (2019) found that butterfly abundance declined by 33% over 20 years in Ohio.

Topic: Additional policy initiatives and solutions needed in the UK and internationally to reduce and reverse the trends in insect decline.

Following implementation of effective policy initiatives and solutions, we require a method to quantify the reduction and reversal of insect declines. The Bugs Matter survey has demonstrated that it has the potential to provide a large-scale indiscriminate (many species) sampling method to quantify long-term trends in flying insect abundance, which could be deployed at a global scale. Governmental support for the project would be welcomed.

The primary driver of insect declines is the conversion of natural ecosystems to human-modified environments which lack the required abundances of species upon which the ecology of many insect species depend. This land-use change, and the industries involved in these changes, bring a cascade of secondary drivers of insect declines including pollution, habitat fragmentation, altered hydrology, introduction of invasive non-native species, and climate change. It is crucially important to recognise that in many locations these conversions started prior to living memory, and restoring the abundance of biodiversity within living memory is not an acceptable target. The restoration of human-modified environments to natural ecosystems, and the strict protection of extant natural ecosystems, is the most effective solution to reduce and reverse insect declines. In addition, natural ecosystems, with their high biodiversity, will sequester carbon and clean water. All policy decisions should be made to favour positive outcomes for nature, which are also the best decisions to make for the future wellbeing of UK citizens.

Stricter policy on the availability and use of pesticides and products containing pesticides would help to reduce and reverse trends in insect declines. There is no high quality, long-term, consistent data from which to quantify trends in pesticide concentrations in UK waterways in the recent past, but evidence shows herbicides and pesticides kill plants and animals as they move through our rivers, soils and oceans. Many insects need healthy freshwater habitats for their lifecycles. Only 3.3% of land is farmed organically in England (Whelan et al, 2022). Perkins et al (2021) detected pesticides used to control companion animal parasites in many English rivers, with levels far exceeding (5.3 and 38.1 times) their chronic toxicity limits. Lentola et al (2017) found Neonicotinoid insecticides in over 70% of plants labelled as “pollinator-friendly” for sale in garden centres.

Fertilizers used in farming change the chemistry and species composition of soils and freshwater ecosystems, with knock-on effects on insect populations and wider biodiversity. Nitrogen often causes algal blooms which reduce light and oxygen and species disappear. Many insects require natural, healthy freshwater environments to complete their lifecycle. Bell et al (2021) found that the amount of Nitrogen and Phosphorus in many UK rivers have more than doubled, and in some rivers increased 10-fold, since 1800.

27 April 2023