Issue 39 Sept 23 - Journal - Page 94
Invertebrates continue
to decline in intensively
farmed landscapes
Terrestrial insects and other invertebrates have continued
to decline in Great Britain over the past 30 years, particularly in intensively farmed areas, a new study has found.
This is despite the introduction of some agri-environment
schemes to try to protect biodiversity, which provides
important services for humans, ranging for pollination to
pest control.
“Changes in agricultural policies and philosophy provide
opportunities to restore invertebrate populations across
the UK, though given current trends, we are facing a
significant challenge.”
The study found:
• Overall, across all species groups, there was an average
5% decline in areas of high cropland cover over the 30year period studied, while in areas of low cropland cover
declines were around 2%.
The study by the UK Centre for Ecology & Hydrology
(UKCEH) found that bees and spiders are the worstaffected invertebrates, possibly because they rely more
heavily on semi-natural habitats for food and shelter.
• The spiders were the group with the most severe
declines - 7% in areas of high cropland cover and 3% in
areas of low cropland cover.
The researchers analysed citizen science data from 19902019 for 1,535 species of bees, hoverflies, ground beetles,
ladybirds, true-bugs and spiders. They divided mainland
Britain’s rural landscape into 1km square grids, each
classified as high-, low- or no- cropland cover. They then
looked at how the proportion of these grid squares
occupied by each species changed over time.
• Bees declined by around 4% in areas of high cropland
cover and around 1% in areas of low cropland cover.
The researchers point out that it is difficult to make comparisons with no cropland areas because these are largely
concentrated in northern Britain, with different climate
and land use.
The study found there were continuing general
reductions in the distribution of invertebrates in Britain
throughout this timeframe but declines were greater in
regions with a high proportion of arable or horticultural
crop cover.
They say that the extent of these declines is significant in
ecological terms if they are part of a continuing trend. It
is likely that reductions in populations were greater prior
between the 1940s and 1990s when there was intensive
agriculture and few agri-environment schemes, though
there are few relevant species data in the post-war years
for comparison.
The way we farm our land has transformed since the
Second World War. Intensive agricultural practices, such
as mechanisation, chemical use and farming land that was
previously wildflowers or hedgerows, have successfully
increased food production to feed a growing population
at relatively affordable prices. But this has come at a high
cost to biodiversity, say authors of the new study, which
has been published in the journal Proceedings of the
Royal Society B.
However, it is possible to reverse these declines. Dr
Mancini points to UKCEH’s long-term Defra-funded
experiment at Hillesden estate in Buckinghamshire,
where 5% of the 1,000-hectare commercial farm was set
aside for wildlife habitats. This resulted in increases in
local bird and butterfly populations without affecting the
farm’s overall food production.
UKCEH ecological modeller Dr Francesca Mancini led
the research, which was funded by the Natural Environment Research Council. She says: “Invertebrates are one
of the most diverse groups in agricultural landscapes but
they are also particularly sensitive to intensive farming
practices. There have been attempts to mitigate negative
impacts since the 1990s and the fundamental question
has been what effect these have had.
“Despite successful conservation at individual farms
where farmers have successfully implemented sustainable
practices, our study shows that more needs to be done to
conserve and restore invertebrate populations at a
national scale.”
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Conservation & Heritage Journal
92
