12 October 2015

Pesticides have a greater impact on invertebrates than climate change, new study reports

Sussex Study areaA new study by the Game & Wildlife Conservation Trust (GWCT), with support from Natural England, has identified that the use of pesticides on cereal fields could be having a greater impact than previously thought and that this impact may increase in the face of climate change. The study, using over 40 years of data collected on farmland on the Sussex Downs, considers the effect on arable insects and spiders of factors including changes in extreme weather events and pesticide use.

This is one of the first studies to investigate the impact such factors have on farmland invertebrates in the UK and it is hoped that the findings will encourage the creation of new measures to mitigate the loss of these organisms. The study utilises the data collected across 100 cereal fields every year from 1970 to 2011. The full suite of data collected in Sussex includes crop management, invertebrates, plants and bird numbers, allowing a comprehensive study of the changes across more than 40 years.

Of the 26 most commonly identified invertebrate groups, 11 were found to be sensitive to extreme weather events such as hot-dry summers or cold-wet winters, although only two (gall midges Cecidomyiidae and fungus gnats Mycetophilidae) took longer than a year to recover. Longer-term trends in invertebrate abundance correlated with temperature and rainfall data obtained from the UK Met Office, consistent with an impact of climate change.

Results suggest that increasing pesticide use has had more of a direct effect on abundance of some invertebrates than temperature change, with the main driver of change in an agricultural environment being human behaviour.

Climate change will, in the long term, cause changes in certain groups of organisms, some of which are cereal pests whose abundance may increase. Any subsequent increase in the use of insecticides will negatively affect the abundance of all invertebrate groups, many of which are beneficial.

This could be mitigated through a shift in emphasis from pesticides as a means of controlling invertebrate pests to the use of conservation headlands alongside beetle banks, which also protect farmland birds, as part of an agri-environment scheme that enhances Integrated Pest Management (IPM).

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Notes to editors

  1. The Game & Wildlife Conservation Trust is an independent wildlife conservation charity that carries out scientific research into Britain’s game and wildlife. We advise farmers and landowners on improving wildlife habitats and we lobby for agricultural and conservation policies based on science. We employ 14 post-doctoral scientists and 50 other research staff with expertise in areas such as birds, insects, mammals, farming, fish and statistics. For information contact: James Swyer, tel: 01425 652381 (direct: 01425 651021), email: jswyer@gwct.org.uk.
  2. The Sussex Study is the longest-running monitoring project in the world that measures the impact of changes in farming on the fauna and flora of arable land. It started in 1968 with an investigation into the causes of the decline in numbers of the grey partridge. The main reason for the decline was determined to be a reduction of chick-food insects in cereal crops caused by the disappearance of arable weeds. This followed the first use of herbicides in the late 1950s, and led to the starvation of partridge chicks. Since 1970, in addition to surveying grey partridges, we have recorded information on crop type, crop disease, arable flora and invertebrates in cereal fields across the 62 km2 of the South Downs between Arundel in the west and Worthing in the east. Information gleaned from the Sussex Study informs all the Game & Wildlife Conservation Trust’s work on farmland.

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