How Intensive Farming Practices Are Wiping Out Europe’s Wild Birds

by techlowdown · 29 May 2023

The widespread use of pesticides, herbicides and synthetic fertilisers by modern agriculture is the biggest cause of the dwindling number of wild birds throughout Europe

There are many factors contributing to the widespread decline of wild bird populations, including cat predation, hunting, urbanization, habitat destruction, light pollution, wind turbines and climate change, to name a few. This multitude of causes is rather overwhelming and has resulted in widespread inaction because many of us have lost hope.

But a large collaborative team of more than 50 ornithologists, zoologists, biologists and ecologists from across Europe have stepped up to declare that the main cause of dramatically declining bird populations in Europe is the intensive use of pesticides, herbicides and synthetic fertilizers by farmers.

“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”, said one of the lead authors, Richard Gregory, Head of Monitoring at the Royal Society for the Protection of Birds (RSPB) Centre for Conservation Science, and an Honorary Professor at the Centre for Biodiversity and Environment Research (CBER) at the University College London.

“The results are compelling”, Professor Gregory continued. “They show the power of citizen science and cooperation across borders to better understand the natural world and what must be done to turn things around.”

To do this, the team assembled and examined the most comprehensive dataset ever amassed to identify the main driver of population declines in 170 European bird species. The study analyzed climate and land use change data gathered from 20,000 monitoring sites across 28 countries during the past 37 years (1980 to 2016). During this period of time, the study found that common bird species throughout Europe have declined by 25.4%, generally. This stunning decline in wild bird numbers not only reflects a reduction in bird numbers but also a reduction in overall bird diversity.

But when these birds were examined by ecotypes, the researchers found that farmland bird species fared the worst: their numbers were reduced by more than half (-56.8%). Declines were also noted in woodland birds (-17.7%), urban birds (-27.8%), amongst northern, cold-preferring birds (-39.7%) — and declines were even prevalent amongst southern, warm-preferring bird species (-17.1%).

F I G U R E 2 | Anthropogenic pressures for countries participating in the PanEuropean Common Bird … [+] Monitoring Scheme (PECBMS) (n = 28, non-PECBMS countries and countries with no available data in gray). For each country and each pressure, the color represents the mean and the black line corresponds to the time series. (A) High-input farm cover (% of total cultivated area covered by high-input farms), period covered by data 2007 to 2016. (B) Forest cover (% of the country’s surface), 1996 to 2016. ( C) Urbanization (% of the country’s surface), 2009 to 2016. (D) Temperature (°C), 1996 to 2016. (doi:10.1073/pnas.221657312)

doi:10.1073/pnas.221657312

Not only did the team confirm earlier studies that reported enormous declines in almost all bird species throughout Europe, but they also pointed to pesticides in particular, as well as herbicides, used by farmers as the main contributors. These chemicals harm wild birds by directly poisoning and killing them, or harming their health and indirectly through starvation by killing the insects they feed on or feed to their growing chicks.

This study reported that birds that feed on invertebrates experienced the largest drops in their populations. Once again, farmland species were the hardest hit of any species groups, but urban bird population numbers dropped as did woodland bird populations.

F I G U R E 3 | Relationship between anthropogenic pressures and bird trends and time series. (A) … [+] Relative effects of high-input farm cover, forest cover, urbanization, and temperature and their trends on bird trends (1996 to 2016, 141 species) obtained by partial least square regression (PLS). Bias-corrected and accelerated CIs are displayed. (B) Distribution of the strength of the influence of pressures (scaled S-map coefficients) on bird time series. The number of species with negative and positive mean S-map coefficients is shown. (doi:10.1073/pnas.221657312)

doi:10.1073/pnas.221657312

“Invertebrates represent an important part of the diet for many birds in at least some development stages”, the authors wrote in their study. “They are particularly crucial during the breeding period for 143 species among the 170 studied species for which, for instance, a reduction in food availability is likely to impact reproductive success by modifying parental behavior and nestling survival in addition to direct contamination by seed consumption and trophic accumulation with sublethal effect.”

This study reports that agricultural intensification, with its use of pesticides, herbicides and fertilizers, is the main culprit in the decline of many bird species present in both agricultural and non-agricultural areas.

“The tremendous negative impact of agricultural intensification on birds has long been reported in particular for farmland and insectivorous birds, but our study provides strong evidence of a direct and predominant effect of farmland practices at large continental scales”, the authors elaborated in their study.

Only “the rapid implementation of transformative change in European societies, and especially in agricultural reform” could save the continent’s bird populations, the researchers warned.

F I G U R E 4 | Results of the partial least square regression between each pressure influence on … [+] species time series and species traits. Nonsignificant effects are shown in gray, negative effects are shown in light red, and positive effects are shown in blue. The magnitude of the effect is displayed by the line width, scaled for each pressure.

doi:10.1073/pnas.221657312

But not all hope is lost. The RSPB purchased Hope Farm, a 181-hectare farm in south Cambridgeshire in 2000 to monitor and ground-truth various nature-friendly farming practices. So far, they’ve found a 177% increase in the number of farmland breeding bird territories on the site, while winter species have risen even more sharply – nearly 15 times higher. Butterfly numbers have increased by 398%.

Further, despite taking more than 10% of the farmland area out of cropping and leaving it to nature, and moving away from conventional production since 2000, Hope Farm has maintained a similar profit level, whilst nature is recovering. It’s very interesting to note that Hope Farm went insecticide free in 2019 but saw no significant reduction in yields comparing to previous years when comparing to national averages.

“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”, said Alice Groom, the Senior Policy Officer at RSPB and head of sustainable land use policy in England. “Yet we also know that the loss of nature, alongside climate change presents the biggest medium to long term risk to domestic food security.”

“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.”

Source:

Stanislas Rigal, Vasilis Dakos, Hany Alonso, et al. (2023). Farmland practices are driving bird population decline across Europe, Proceedings of the National Academy of Sciences 120(21):e2216573120 | doi:10.1073/pnas.221657312

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