Increased pesticide and fertiliser use driving bird declines across Europe

An increase in the use of pesticides and fertilisers on farmland has been identified as the main cause for declines in most bird populations across Europe, according to a major new study.

The collaborative research, published today [15 May] in the science journal PNAS, used the most comprehensive dataset of its kind ever assembled to understand what drives population change in European birds. It looked at how 170 bird species have responded to major human-induced pressures, including climate and land use changes, with research carried out at 20,000 monitoring sites across 28 countries over 37 years, and including data from the UK.

Over the study period (1980-2016), common bird species in Europe have shown a general decline in abundance of around a quarter (-25.4%). 

Numbers of farmland species have more than halved over the same period, amounting to a decline of some -56.8%. Reductions were also noted in woodland birds (-17.7%), urban dwellers (-27.8%), among northern, cold-preferring birds (-39.7%) and southern, warm-preferring bird species (-17.1%). 

One of the study's key findings is the negative impact modern intensive farming practices have had on bird species across Europe, including the UK. Researchers found that intensification, measured by the high use of pesticides and fertilisers, has led to the decline of many populations. Birds that rely on invertebrates for food, including Common Swift, Yellow Wagtail and Spotted Flycatcher, have been hardest hit.

Insectivorous species such as Yellow Wagtail have declined drastically due to the excess use of insecticides (Paul Bateson).

Richard Gregory, lead author for the RSPB, said: "While many studies have tried to figure out what has driven bird declines in UK and Europe, this is the first to look at the major, man-made drivers in one go, using the best data available. The results are compelling. They show the power of citizen science and co-operation across borders to better understand the natural world and what must be done to turn things around." 

Along with the impact of intensive farming, researchers also uncovered direct relationships between declines in bird populations and three other widespread pressures linked to human activity – a change in forest cover, urbanisation and climate change (focusing on temperature) over the last decades. Unlike intensive farming, these pressures tended to have a greater impact on specific bird species. 

James Heywood, the National Organiser for the BTO/JNCC/RSPB Breeding Bird Survey, data from which contributed to this study, said: "The decline of farmland birds across the Europe is one of the standout observations from this study, in particular just how widespread they are. What is also highlighted is just how little woodland the UK holds compared to our neighbours on the continent. That said, the study makes clear that a simple increase in forest cover can mask other changes, particularly in the quality and nature of forests; the planting of managed forests won't produce the same benefits for birds as old-growth forests or ancient woodlands, for example. This very much a problem that we are facing with in the UK."

The RSPB said the report underlines the need for nature-friendly farming to become the norm, for UK governments to support farmers in reducing pesticide use and adopting nature-friendly principles, and at the same time improve testing and understanding of exactly what chemicals are being used on the land.

Alice Groom, RSPB Head of Sustainable Land Use Policy England, commented: "Increasing our reliance on pesticides and fertiliser has allowed us to farm more intensively and increase output, but as this study clearly shows, at a huge cost to our wildlife and the health of the environment. Yet we also know that the loss of nature, alongside climate change presents the biggest medium to long term risk to domestic food security. 

"Without farmers we haven't a hope of tackling the nature and climate emergency, but they need the right policies and support in place if they are to produce healthy food while helping to reverse wildlife declines and restore the environment.

"The UK and devolved governments should ensure agri-environment schemes reward nature-friendly farming practices such as flower rich margins and herbal leys that are proven to enable farmers to produce good food whilst supporting progressive reductions in the use of pesticides and fertilisers."

Common Swift is declining across many parts of its European breeding range (Steve Cribbin).

Many farmers and land managers across the country are already adopting such practices, moving towards a nature-friendly approach that is helping nature to rebound, producing healthy food and profits, and contributing to climate-change goals. 

In order to fully monitor and test the impact of a range of these measures, in 2000 the RSPB purchased Hope Farm, a 181-ha arable farm in south Cambridgeshire. The adoption of nature-friendly farming practices has resulted in a 177% increase in the number of farmland breeding bird territories on site, while winter species have risen even more sharply – nearly 15 times higher. Butterfly numbers have increased by 398%.

Despite taking more than 10% of the farmland area out of cropping for nature, and moving away from conventional production since 2000, the business has maintained a similar profit level, while nature has recovered and bounced back. Additionally, in 2019 Hope Farm went insecticide-free but saw no significant reduction in yields comparing to previous years when comparing to national averages.

A comprehensive review of studies looking at the harmful effect of pesticides on wildlife in the UK, the RSPB's Pesticides and Wildlife report, was published in June 2022. It found more than 150 different pesticides are used across the UK's countryside every year in a combined quantity that could cover all UK farmland ten times over.