Encouraging insects back into arable land

In Sussex scientists have found that insecticide use has stabilised over the past two decades with an associated stabilisation of some insect groups, write Dr Julie Ewald and Prof John Holland of the Game & Wildlife Conservation Trust. Plus Judith Wright says we should let verges grow

Friday 20 October 2017 18.35 BSTLast modified on Friday 20 October 2017 22.00 BST

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.

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