It is with great interest that we read about the long-term decline in the biomass of flying insects on German protected areas (Scientists tell of alarm at huge fall in flying insects, 19 October).
The Game & Wildlife Conservation Trust (GWCT) carries out two long-term surveys of insects on farmland in England – the Sussex Study (1970 to present) and at our demonstration farm in Loddington (1992 to present).
In the Sussex Study, which is one of the first Farmer Clusters in the country, over 100 cereal fields are sampled every year, which has revealed declines of 35% overall in the total number of invertebrates compared with the 87% decline in the biomass of flying insects found by Hallmann et al, with most of the decline in Sussex happening in the 1970s.
However, for insects that are chick-food for declining farmland birds, we found declines of up to 72% from 1970 to 2015, with 45% of invertebrate groups declining significantly.
Analysis on a field-by-field basis indicates that it is insecticide use that is responsible for lower insect numbers, especially those that provide food resources for declining farmland birds.
However, in Sussex, which reflects the case in the UK, GWCT scientists have found that insecticide use has stabilised over the past two decades, with an associated stabilisation of some insect groups.
The GWCT, working with farmers, has developed agri-environmental measures, now available through the current Countryside Stewardship scheme, such as conservation headlands (low-input cereal headlands) and wildbird seed mix. Our research has shown that these can have a positive effect on both arable flora and invertebrate resources in arable land. It is important that governmental support for agri-environment continues post-Brexit.
For more information, visit www.gwct.org.uk/research/long-term-monitoring/sussex-study/
Dr Julie Ewald Head of geographical information systems
Prof John Holland Head of farmland ecology
Game & Wildlife Conservation Trust
• Our penchant for manicuring and trimming every area of grass, along with the wonderful array of machinery available, is surely a major factor in this decline. I believe that in Sweden it is illegal to cut verges – apart from where safety issues demand it – until October, resulting in a much improved biological diversity.
Judith Wright
Darwen, Lancashire
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