Birds, collateral victims of agricultural intensification in Europe

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The scientific community has been sounding the alarm over the effects of pesticide use on human health and the disappearance of numerous species in agricultural environments for half a century. As early as 1962, Rachel Carson’s pioneering work predicted "silent springs" caused by the decline of birds, the collateral victims of pesticides via the poisoning of environments and the disappearance of insects.

At issue is an agricultural model based on ever-increasing industrialization, with massive recourse to pesticides, in order to remain internationally competitive. This model is increasingly dominant in France, where the number of farms is shrinking (-40% since 2000) and their size is growing (the average surface area has quadrupled since the 1960s).

As a result, the agricultural area covered by farms with high pesticide and fertilizer use has steadily increased. As a result, only 17% of Europe’s soil is pesticide-free. Since 2009, more than 300,000 hectares of often fertile farmland have disappeared under asphalt.

Beyond the worrying observations and prophecies, is there any tangible, unequivocal scientific proof that this model of agricultural production is dangerous for living organisms on a European scale?

The difficulty of experimenting on living organisms in real-life conditions

At first glance, experimentation seems an ideal procedure. For example, feed pesticide-coated seeds to sparrows, and they’ll be in worse shape. So be it. The process is likely to work.

But outside the laboratory, when variables can no longer be directly controlled by the researcher, we enter a complex world where processes are caused by multiple, intertwined factors. In these conditions, how can evidence of the effect of a particular factor on health or the environment be constructed?

To overcome this difficulty, the scientific method can always rely on protocols and control variables. Thus, the effect of substances assumed to be problematic and of all other factors with a potential effect will not be manipulated experimentally, but studied statistically.

For, if it’s already a bit brutal to force-feed pesticides to birds, it’s even more absurd to imagine being able to experiment with everything. Instead, we’ll be able to check whether the use of increasing quantities of pesticides is reflected over time by a drop in the number of insects. In other words, we’ll approach the question from an epidemiological angle.

But there’s a catch. We can always assume that it’s not the pesticides that are to blame, but stress, air pollution, drought or any other variable that has a direct or indirect influence on the system under study.

So we had to give ourselves the means to see more clearly. This is what we did with a team of 50 researchers in an open-air study published in May 2023. Our motivation was to verify whether one pressure dominated over the others, and if so which, to explain the decline in populations of numerous bird species in Europe.

The unprecedented scale of the hecatomb in agricultural environments

First of all, we had to put a figure on this decline. Thanks to the hard work of numerous volunteer ornithologists, who reproduced the same monitoring protocol in 28 European countries each year, an exceptional dataset was compiled, covering the period from 1980 to 2016. This was an essential step: starting from the birds themselves in their habitats, not just from an experiment on a few isolated individuals in a laboratory.

The study tracked 170 different species, with free-ranging populations that are also affected by pollution, climate change, hunting practices, disturbance and the risk of predation.

Far from limiting ourselves to agricultural environments, we were interested in all habitats: forests, towns, mountains, open or not, cultivated or not... In short, we took an unfiltered look at the health of European birds.

Result - Birds lost a quarter of their abundance in Europe between 1980 and 2016, i.e. 800 million individuals over the period, an average of 20 million per year. A hecatomb that comes as no surprise: birds have had to cope with the profound changes in landscapes and lifestyles that occurred over the course of the 20th century.

Not all bird species are affected in the same way.
  • For example, forest birds have lost 18% of their numbers;
  • Urban birds, 25%,
  • What is surprising, however, is the intensity of the spectacular decline in the numbers of birds living on agricultural plains: their numbers have plummeted by 57%!

An unenviable record: one of the most spectacular declines ever recorded on this scale for living organisms.

Proving the link between agricultural intensification and bird decline

We had to go a step further to understand the cause of this decline. We had the ideal data to test whether climate, habitat changes and the industrial agricultural model could be held responsible.

Let’s imagine for a moment that one or more ornithologists have counted the number of birds in a particular place, say at the edge of an oilseed rape field, every year using the same method. And, precisely for this year and this place, we also have available data such as the expansion of intensively farmed areas, changes in temperature, the spread of artificial land, or variations in forest cover.

This process, repeated at thousands of sites in the 28 countries studied over several decades, has enabled us to build the most complete and accurate database ever collected for monitoring wild species in Europe.

This has enabled us to make the statistical link between the fate of birds and these multiple pressures, and to construct a second powerful result: species decline coincides with increasing intensification of agricultural practices. In environments where industrial agriculture is more prevalent, whatever the climate or other conditions, birds decline faster.

We were, however, aware of another possible pitfall: that this link was a mere coincidence attributable to chance. But this is not the case. Our analyses show that we are no longer in the realm of correlation, but of unequivocal connection.

A final result added another brick to our understanding of the situation: species that prefer to feed on insects, which have been eradicated by pesticides, are even more affected than other species.

Global warming and soil artificialization also to blame

Of course, the intensification of agricultural practices is not the only factor behind the observed declines. Climate change, particularly rising temperatures, is a second major pressure.
  • Northern species, adapted to cold environments (such as the Northern Chickadee, which has declined by 79%), are moving northwards and seeing their populations decline sharply as temperatures rise.
  • Conversely, other species adapted to warmer environments (such as the Whimbrel, whose population is increasing) may benefit.

The spread of built-up areas is also at the expense of birds, which are unable to live in mineral and polluted environments, and whose habitat is becoming fragmented.

Even species capable of nesting in urban environments are in decline (such as the Black Swift, whose populations have fallen by 17%), particularly in view of the lack of sites available on modern buildings and the low abundance of insects in these environments.

Finally, the recent return of forest cover in Europe, often through plantations, is not enough to halt the decline of species dependent on natural forests.

Sowing doubt... and buying time?

These results should encourage us to drastically reduce our use of pesticides. But for the defenders of agrochemicals, the level of proof provided by science is never high enough.

A situation reminiscent of asbestos, tobacco and even the actions of fossil fuel producers to delay climate awareness.

All these industries have taken advantage of the difficulty inherent in constructing scientific proof in order to gain time, perpetuate doubt and maintain their reputation and profits. Maintaining doubt has thus become strategic.

So much so, in fact, that manufacturers have now established themselves as the scientific reference for control agencies, particularly in Europe.

It has become irresponsible to minimize the impact of the industrial agricultural model and its pesticides, and to hide behind alleged bias, lack of hindsight or supposed absence of alternatives, which do exist.

The widespread use of pesticides has a considerable social and economic cost, which is not reflected in prices as long as their use remains encouraged and subsidized. In terms of human health, the effects of pesticides are increasingly well documented.

There’s every reason to change this production model. How can we be satisfied with calling "conventional" agriculture incompatible with maintaining the health of humans and non-humans alike?

The necessary changes cannot rely solely on the good will of farmers entangled in an industrial model designed by and for agribusiness, and part of an export model regulated by speculation or the quest for the lowest price.

What’s needed are transformative changes in the way we live, produce and consume. Political tools should be levers capable of initiating this transformation, rather than maintaining an outdated model "whatever the cost".

It’s urgent that decision-makers at European, national and local level finally face up to the ravages of a certain outdated chemical agriculture that destroys life, traps farmers and makes a mockery of consumers.

Science and society are mutually nourishing and mutually beneficial. Research can involve citizens, improve their daily lives and inform public decision-making. This is what the articles in our series "Science and society, a new dialogue", published with the support of the French Ministry of Higher Education and Research, show .

Vincent Devictor , Director of research in ecology, University of Montpellier Stanislas Rigal , Postdoctoral fellow in conservation biology, ENS de Lyon This article is republished from The Conversation under Creative Commons license.

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