Written evidence submitted by Butterfly Conservation (INS0018)

The House of Commons Science and Technology Committee

Inquiry into Insect decline and UK food security

Butterfly Conservation is the UK charity dedicated to saving butterflies, moths and our natural environment. Founded in 1968, we are a leading authority on the conservation of these beautiful creatures – key indicators of a healthy ecosystem– and we have achieved numerous successes for them locally, nationally and internationally.

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

Butterfly Conservation collects and uses millions of records to inform all of its research and recommendations. Increasing the recording and monitoring of the UK’s butterfly and moth populations is vital to document wider biodiversity change, understand its causes, help develop and measure effective solutions, and to engage people in citizen science.

Survey and monitoring

UK butterflies are among the most comprehensively monitored insects in the world, with spatially extensive data on species’ distribution and population abundance dating back to the 1970s. These citizen science data have mainly been contributed by volunteers, thanks to a long tradition of natural history study and recording, that is more popular in the UK today than it has ever been. This incredible effort is encouraged and channelled through two main recording schemes, the UK Butterfly Monitoring Scheme (UKBMS) and Butterflies for the New Millennium (BNM), which gather data on species’ abundance and distribution respectively. Sampling methodology differs substantially between these two schemes, requiring separate data analysis techniques. Ultimately, however, the schemes provide equally useful, important and complementary information on how each species is faring.

The UK is fortunate in also having a long history of large moth recording undertaken by skilled amateur naturalists as well as the most comprehensive data on moth abundance in the world from the Rothamsted Insect Survey (RIS). The RIS data allows for analysis of data trends for over 50 years (since 1968) The more recent National Moth Recording Scheme (NMRS) collates present distribution (occupancy) trends based on sighting. In both cases, the trends presented are for Great Britain (i.e. England, Scotland and Wales) plus the Isle of Man. Utilising these two different data sources provides separate but complementary insights into how species of larger moths have fared.

Results

Butterflies[1] - In the UK, long-term trends show that 80% of butterfly species have decreased in abundance or distribution, or both since the 1970s. On average, UK butterflies have lost 6% of their total abundance at monitored sites and 42% of their distribution over the period 1976-2019.

Most habitat specialist species, that is those restricted to particular habitats such as flower-rich grassland, heathland and woodland clearings, have declined dramatically in the UK. As a group, their abundance has decreased by over one-quarter (-27%) and their distribution by over two-thirds (-68%) since 1976.

Moths[2] - The total abundance of larger moths caught in the RIS light-trap network in Britain decreased by 33% over 50 years (1968–2017). Losses were greater in the southern half of Britain (39% decrease) than in the northern half (22%).

Long-term abundance trends were calculated for 427 species of which 41% (175 species) had decreased and only 10% (42 species) increased, with the remaining 49% (210 species) having trends that did not show statistically significant change. Thus, four times as many moth species decreased in abundance than increased.

Distribution trends revealed a different picture. Of 511 larger moth species for which

long-term trends could be calculated from NMRS data, 32% (165 species) decreased in distribution and 37% (187 species) increased, while 31% (159 species) had non-significant trends. More moth species increased in distribution than declined.

Habitat destruction and deterioration remain pressing concerns, driven by land-use change and chemical pollution. Artificial light at night has negative effects on moth development and behaviour, but links to population-level decline are yet to be proved. Climate change is the principal driver of range expansion, but there is also growing evidence of negative impacts, particularly on moths that are adapted to cooler conditions in northern, western and upland Britain.

Gaps in knowledge

The majority of research into pollination has concentrated on honey bees and wild bees with some investigation of other diurnal pollinators. More recent work has investigated both the breadth of invertebrates that are part of the pollination ecoservice as well as the day/night processes.

For example; Knop et all[3] looked at pollination on a weedy grassland showed that activity of flower-visiting insects never dropped to zero over 24-h. During the day, non-syrphid Diptera and Hymenoptera (flies and bees) were the most abundant, and species-rich groups of flower visitors, Lepidoptera and Coleoptera (moths and betles) during night. While two of the seven most frequently visited plant species were most likely to be visited during the day, five also had a high likelihood to be visited during the night.

Anderson et al (2023)[4] isolated an individual species of plant (bramble)to assess pollination rates and showed that while 83% of all flower visits were undertaken during the day, pollen deposition rates were significantly higher at night. Diurnal pollination was from a variety of taxa compared to the almost exclusively moth pollination at night. No relationship was detected between pollen counts and flower visitation rates, suggesting that moths are more efficient pollinators of bramble compared with diurnal insects.

Increasing our understanding of the complexity of pollination offers both a better understanding of threats as well as the potential for increased solutions.

Dicks et al (2012)[5] looked at the top 35 knowledge needs for evidence-based conservation of wild insect pollinators, as scored by conservation practitioners or scientists. There was general agreement in priorities identified by these two groups; understanding the economic benefits of crop pollination, basic pollinator ecology and impacts of pesticides on wild pollinators emerged strongly as priorities, as well as a need to monitor floral resources in the landscape. Many of these priorities remain the same today, in particular the top 4:

1. How important is the diversity of pollinator species to the resilience and reliability of the pollination service?
2. What are the relative contributions of wild and managed pollinators to crop yield (for a few crop models)?
3. What are the costs and benefits of maintaining and restoring the pollination service in farmland and how are they linked to farmers’ evaluation of pollinators?
4. What are the sub-lethal effects of chemicals (pesticides and other environmental pollutants) on wild pollinators?

Q. The effects of pesticides, such as neonicotinoids or other agricultural control methods on insects including pollinators and their impact on UK food security

Neonicotinoids

The scientific evidence has been steadily building for some time that neonicotinoid pesticides are having a widespread impact on bees, other pollinators including moths and butterflies as well as birds and other wildlife. Godfray et al (2014) set out the evidence base for the impact of neonicotinoids on pollinators[6] At Butterfly Conservation we became convinced that the evidence, despite some uncertainty, was sufficient to call for a ban several years ago, in part because of the extremely worrying link between rates of neonicotinoid use and the decline of widespread butterflies.

The pesticides are taken up by wild plants growing in field margins and therefore both adult butterflies drinking contaminated nectar and caterpillars feeding on plant tissues are exposed.  Essentially, butterflies, a non-target group of widespread insects not generally found in cropped fields were being contaminated in the general countryside, the very field margins we have been encouraging and even paying farmers to create and manage for wildlife for years.

The 2015 study[7] published by researchers from the Universities of Stirling and Sussex, the Centre for Hydrology (CEH) and Butterfly Conservation clearly showed correlation with the rate of neonicotinoid use on farmland and declines in butterfly indices. This research came on the back of other studies that were showing even quite low rates of contamination could have serious negative impacts on the health and behaviour of bees[8].

Butterfly Conservation considers that recent scientific evidence is now sufficiently compelling that the current EU wide neonicotinoid pesticides ban should be expanded to cover all agricultural uses as a precaution (not just the ban on use in gardens and in flowering crops where there might be a high exposure to bees and other pollinators, as is currently the case). This ban should be reviewed regularly and lifted only if clear evidence becomes available that they cause no harm to non-target insects and other wildlife, or that alternative crop management practices might be more harmful.

Pesticide regulation

The National Pollinator Strategy is ten years old and was written while we were still members of the EU; a key plank of the pesticide impact on pollinators is based on the “tough regulatory regime” governed by EU law. The UK government has taken the decision to move away from the EU direction in a number of recent decision in particular on granting permission for neonicotinoid use on sugar beet. England does not have a Food Security Strategy.

Butterfly Conservation believes that there remains an urgent need for a major improvement in the regulation of all pesticides including thorough screening and independent research into their impact on biodiversity before they are approved for use. This research should include field trials of their use in practice as well as laboratory studies of direct mortality on a wide range of native, non-target invertebrate species.

Q. The extent that biodiversity initiatives, such as creating reservoir populations, are addressing insect decline and whether there is sufficient co-ordination with the UK food system

Sites of Special Scientific Interest were introduced in the 1949 National Parks and Access to the Countryside Act 1949. Agri-environment schemes were introduced in 1987.  Both the nature conservation designations and the agri-environment support schemes worked on the principal that protecting the core species and habitats would enable long term sustainable populations to continue.  And yet, as our monitoring data demonstrates, both species and habitats have decreased in extent and range since the introduction of these schemes. The Lawton review (2010)[9] reported that despite the important contribution designated sites have made, England’s wildlife habitats have become increasing fragmented and isolated, leading to declines in the provision of some ecosystem services, and losses to species populations. The recent Defra Environmental Improvement Plan has recognised the need to tackle the continuing decline in quality of SSSIs with a target for all sites of special scientific interest (SSSIs) to have an up-to date condition assessment; and for 50% of SSSIs to have actions on track to achieve favourable condition by 31 January 2028[10].

Targeted conservation action works. There have been significant success stories of nature recovery across all taxa. Butterfly Conservation targeted conservation actions have been able to turn around the fortunes of threatened butterflies and moths at site, landscape and national levels – for example restoring March Fritillary meta-populations on Dartmoor[11]. However, the resources currently available for such work are woefully inadequate to address the scale of the task and to stem the ongoing decline of the UK’s wildlife.

Agri-environment spending in England is approximately 20% of the overall agriculture budget[12] and yet has some of the best long-term outcomes both in economic and environmental appraisals[13]. Investment in nature friendly farming is proven to help maintain and even improve yields. One study showed that organic systems have the potential to produce yields up to 40% higher than conventional systems in times of drought[14]. Another study demonstrated that managing 8% of a farm for nature helped to maintain and even enhance yields of some crops and led to no loss in economic or nutrient value[15].  On the contrary, a 30% decline in pollinator numbers over 10 years would cost more than £188m per year in lost crop yield[16].

Relying on creation and maintenance of reservoir populations to maintain an effective pollinator population will no longer work. Nature is in crisis and insect populations are suffering significant declines, we need to act at a much more widespread basis. The Welsh Government has recently recommended that under their new Sustainable Farming Scheme farmers will need to actively manage at least 10% of their land to maintain and enhance semi-natural habitats[17]. Actions like these may be needed if we are to ensure pollinator populations in the future. The development of the new Environmental Land Management schemes in England will be an essential part of delivering on the public money for public goods rhetoric but it needs to further than just within the higher tier options and be fully embedded within all agricultural support.

Butterfly Conservation believes that there is evidence for both the need for, and benefits of, a significant increase in resources for agro-ecological support which works at an all-farm level as well as the continued support for targeted actions for at risk species and populations.

28 April 2023