Sussex Study – long-term insect trends


A conservation headland and a new wild bird seed mix on the Sussex Study. © Peter Thompson/GWCT


BACKGROUND


The GWCT’s Sussex Study is the longest-running cereal ecosystem monitoring exercise in the world. The study has monitored both the cereal ecosystem and the farming decisions on 3,200ha of the Sussex Downs since 1970, collating infor- mation on cropping, pesticide use, cereal weeds and invertebrate abundance. This unique dataset allows us to examine the long-term changes in cereal invertebrates, both in terms of chick-food resources and other service providers. An important reason behind recent declines in the abundance of some farmland birds is a decline in food resources provided by invertebrates in crops. These invertebrates also provide ecosystem services such as pollination and integrated pest control. A knowledge of long-term trends in their abundance is key to understanding changes in both food resources for birds and these ecosystem services.


Figure 1


Overall change in invertebrate numbers (excluding micro-arthropods) on the Sussex Study area


Percentage relative change in abundance Long-term average 1.2 1.0 0.8 0.6 0.4 0.2 0 1970 34 | GAME & WILDLIFE REVIEW 2016 1980 1990 2000 2010 www.gwct.org.uk


The most recent State of Nature report highlighted the effects of agricultural inten- sification and climate change on British biodiversity, while indicating that agricultural intensification seemed to be the strongest driver of negative changes. The GWCT’s Sussex Study is uniquely placed to inform the debate on the relative importance of climate change versus changes in agricultural management on farmland biodiversity. Invertebrate monitoring began on the study area in 1970, after work in the previous two years had identified that a lack of insects was a key factor in the low grey partridge chick survival on the study area. Previous work on the Sussex Study inver- tebrate dataset has highlighted the negative effects of foliar insecticide applications on chick food resources (reported in the Reviews of 2006 and 2014). We have also put the effect of pesticide applications in perspective with that of extreme weather events and long-term changes in temperature and rainfall (reported in the Review of 2015). This showed that foliar insecticide use was associated with the measured declines in several other groups of cereal invertebrates. Our conclusions on the changes that have taken place in the abundance of invertebrates on the Sussex Study have broadly supported those in the 2016 State of Nature report.


1.4


Change in invertebrate abundance (± 1 se)


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