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What Works in Conservation 2020

William J. Sutherland
Lynn V. Dicks
Silviu O. Petrovan
et al.

4. Farmland conservation

4.6 Threat: Agri-chemicals

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Leave headlands in fields unsprayed (conservation headlands)

1Twenty-two studies from 14 experiments (including two randomized, replicated, controlled) from five countries found conservation headlands had higher invertebrate or plant diversity than other habitats, twelve studies from ten experiments (three randomized, replicated, controlled) did not. Twenty-seven studies from 15 experiments (of which 13 replicated, controlled) from five countries found positive effects on abundance or behaviour of some wildlife groups. Nineteen studies from 13 experiments (12 replicated, controlled) from four countries found similar, or lower, numbers of birds, invertebrates or plants on conservation headlands than other habitats. Assessment: beneficial (effectiveness 90 %; certainty 75 %).


Reduce fertilizer, pesticide or herbicide use generally

3Thirty-four studies (including a systematic review) from 10 countries found reducing fertilizer, pesticide or herbicide inputs benefited some invertebrates, plants or birds. Twenty-five studies (including seven randomized, replicated, controlled trials) from eight countries found negative or no clear effects on some invertebrates, plants or birds. Assessment: beneficial (effectiveness 100 %; certainty 70 %).


Use organic rather than mineral fertilizers

5Fourteen studies (including four randomized, replicated, controlled trials) from six countries found areas treated with organic rather than mineral fertilizers had more plants or invertebrates or higher diversity. A randomized, replicated, controlled trial from the UK found no effect on weed numbers. Two studies (including a small trial from Belgium) found organic fertilizers benefited invertebrates, a UK review found that in large quantities they did not. Assessment: beneficial (effectiveness 100 %; certainty 70 %).


Likely to be beneficial

Reduce chemical inputs in grassland management

7Six studies (including a randomized, replicated, controlled before-and-after trial) from three countries found stopping fertilizer inputs on grassland improved plant or invertebrate species richness or abundance. Two reviews from the Netherlands and the UK found no or low fertilizer input grasslands favour some birds and invertebrates. Five studies (two replicated trials of which one randomized and one replicated) from three countries found no clear effects on invertebrates or plants. Assessment: likely to be beneficial (effectiveness 90 %; certainty 60 %).


Unknown effectiveness (limited evidence)

Provide buffer strips alongside water courses (rivers and streams)

9Three studies (including one replicated site comparison) from the Netherlands and the UK found riparian buffer strips increased diversity or abundance of plants, invertebrates or birds and supported vegetation associated with water vole habitats. Two replicated site comparisons from France and Ireland found farms with buffer strips did not have more plant species than farms without strips. Assessment: unknown effectiveness — limited evidence (effectiveness 10 %; certainty 15 %).


Restrict certain pesticides

11A small UK study found two fungicides that reduced insect abundance less than an alternative. A replicated, controlled trial in Switzerland found applying slug pellets in a band at the field edge was as effective as spreading the pellets across the field. Assessment: unknown effectiveness — limited evidence (effectiveness 50 %; certainty 5 %).


No evidence found (no assessment)

13We have captured no evidence for the following intervention:

  • Buffer in-field ponds

Evidence not assessed

Make selective use of spring herbicides

14A randomized, replicated, controlled study from the UK found spring herbicides had some benefits for beneficial weeds and arthropods. Assessment: this intervention has not been assessed.


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