Press release: launch of study on the effects of pesticides on bird populations in Gelderland, the Netherlands

For immediate release
30 April 2019

High concentrations of pesticides in manure and soil at livestock companies may be an important cause for the dramatic decline of many meadow bird species in the Netherlands. The measured concentrations are higher than expected, even on organic farms. The pesticides enter the environment through straw and cattle feed.

This is one of the biggest conclusions of our and Buys Agro-Services’ study “An investigation into possible relationships between the decline of meadow birds and the presence of pesticides on livestock farms in the province of Gelderland, the Netherlands.

Our water and food safety expert Margriet Mantingh presented the results with research partner Jelmer Buijs on April 12th with an audience of over 100 people. Contributions were also made by Peter Drenth (Province of Gelderland), Frank Berendse (emeritus prof. Nature Management and Plant Ecology), Jan Diek van Mansvelt (emeritus prof. alternative methods in agriculture and horticulture), Miriam van Bree (Bionext) and one of the organic livestock farmers taking part in the research: Jan Dirk van de Voort.

A large number of pesticides and anti-parasitic medicines were measured in animal feed, manure and soil at 24 livestock farms and one tree nursery in meadow bird areas in Gelderland. Nine of the livestock farms do organic farming, 15 are conventional farms. 134 different insecticides, fungicides, herbicides and biocides were found in the samples, in concentrations at which significant effects on the insect fauna can be expected.

The pesticides enter the companies through animal feed, straw and substances that are used to combat pest insects in stables. The toxic substances are spread over the land through the manure.

This study shows a significant correlation between the intake of insecticides via cattle feed and the number of insects in the manure on the land. Insects are usually much more sensitive to insecticides than mammals such as humans. The amount of insects in the grassland has a decisive effect on the survival of meadow bird chicks such as the black-tailed godwit, lapwing and redshank.

Bird counting between 1998 and 2018 shows that the number of meadow birds in the Netherlands has decreased dramatically on all of the investigated farms. The average number of counted breeding birds per average farm has decreased from 69 in the period 1998-2007 to 22 in the period 2008-2018.

Although none of the contributing farmers have exceeded legally allowed maximums of pesticides, the continuing decrease of insects and meadow bird populations illustrate the dangerous effects of these substances on biodiversity. The current regulations are based on effects on human health, insufficient attention is paid to ecological effects. Every year, the Dutch government invests many millions in the protection of meadow birds. When high concentrations of extremely toxic pesticides in soil and grass seriously limit the survival of meadow bird chicks, these investments become a waste of money.

It is therefore very urgent to conduct a national investigation into the presence and origin of insecticides and other pesticides in feed, manure and soil. Furthermore, the effects of these substances on insect fauna and meadow bird populations must be researched more closely. Until the effects are clear, the precautionary principle must be applied.

What is new about this study?

  • This kind of research has never been conducted, in the Netherlands or around the world.
  • The chemical analyses were done with precision that has not been applied in applied research before.
  • Instead of being based on mathematical models, this study is based on analyses of samples from 25 companies: 87 samples were tested for the presence of 664 different pesticides. The manure was analyzed for the presence of 21 anti-parasitic substances.
  • The study researched a correlation between the present pesticides and biocides and the presence of beetles in manure in the grassland.
  • All the substances that were found in in manure, soil and animal feed have been assessed for the possible risks for soil fauna
  • The study included an analysis of meadow bird counts of the past two decades, done by volunteers on the grassland of companies taking part in this study

Download study (Dutch, German, Russian & English)

Six renowned Dutch scientists assisted the two authors in the relevant sections of the 170-page study for correct processing and presentation of the results. The study was conducted by the Buys Agro-Services consultancy firm and by WECF International in the Netherlands with financial support from the province of Gelderland.


  • Jelmer Buijs – Buijs Agro-Services, email: ; tel: 0318 301 880
  • Margriet Mantingh – WECF International in Nederland, email: tel +316 1253 2813

This study has been made possible by financial support from the Dutch Province of Gelderland, and the European Commission in the context of the Make Europe Sustainable for All project. The conclusions of this research are the sole responsibility of Buijs Agro-Services and WECF International and can under no circumstance be seen as the perspectives of the Province of Gelderland or the European Commission.