Providing evidence to improve practice

Individual study: Agri-environment agreements enhance the number of insect species, but do not increase bird densities or plant diversity on farms in the Netherlands

Published source details

Kleijn D., Berendse F., Smit R. & Gilissen N. (2001) Agri-environment schemes do not effectively protect biodiversity in Dutch agricultural landscapes. Nature, 413, 723-725

Background

Agri-environment schemes have been implemented in the Netherlands since 1981. This study compared communities of plants, birds, bees and hoverflies on fields with and without agreements to support species-rich vegetation or wading birds, in nine areas across the Netherlands.

Action

The study involved 39 field pairs, one with a management agreement, the other managed conventionally. Paired fields were within 1 km of each other, similar in size and soil type.

Fertilizer inputs were significantly lower on fields with management agreements than on conventionally managed fields (106 vs 246 kg N/ ha/year for ‘botanical agreements’; 96 vs 277 kg N/ ha/year for ‘meadow bird agreements’).
Effects on birds were analysed only on field pairs with meadow bird agreements, on which mowing or grazing was postponed until June or July. Effects on plants were analysed only on field pairs with botanical agreements, with restricted fertiliser use and/or postponed mowing or grazing dates.
Birds were surveyed during five visits between 22 March and 20 June 2000, with all contacts noted on a map and numbers of territories assessed using methods from the Dutch Breeding Bird Monitoring Project.
Plant species were recorded in up to 20 quadrats (2 x 10 m) along field edges and all species noted around the entire perimeter of each field. Bees and hoverflies were sampled from 1 m-wide transects along field edges, walked for 15 minutes every month from May to August.

Consequences

Plant species richness was not higher on fields with botanical agreements than on conventional fields.

Density of breeding bird territories was not significantly different between fields with meadow bird agreements and control fields, both for all bird species and just for waders. Oystercatcher Haematopus ostralegus, black-tailed godwit Limosa limosa, common redshank Tringa totanus and lapwing Vanellus vanellus were all significantly less abundant on management agreement fields than on control fields. There was no significant difference in the number of territories between field types for three of these species, but oystercatchers had significantly fewer territories on management agreement fields than on control fields (0.13 vs 0.52).

 

There were significantly more species of hoverfly and bee on fields with meadow bird and/or botanical agreements than on conventionally managed fields (averages not given). For hoverflies, the difference was mostly in the May survey, and could be related to vegetation height, because conventional fields were cut earlier. For bees (85% from just three species), vegetation height did not explain the difference in species richness.

 

Note: If using or referring to this published study, please read and quote the original paper, the abstract of which can be viewed at: http://www.nature.com/nature/journal/v413/n6857/abs/413723a0.html.