Miljøprojekt, 1172 – Randzoner og andre pesticidfrie beskyttelsesstriber i dyrkede arealer - en udredning

Randzoner og andre pesticidfrie beskyttelsesstriber i dyrkede arealer - en udredning

Summary

Unsprayed field margins, beetle banks and flower strips etc. are different structures, though with a major aim in common: the diminishing of the negative influence of agricultural intensification. This includes pesticide effects and in particular effects of the very widely used herbicides and effects of the very toxic insecticides. The tackeling of these problems also link up to the structural problem of the modern field landscape in which the small non-cropped habitats (e.g. water logged spots and ditches in between fields) are very few. Establishment of field margins and banks/strips may counteract losses of such habitats.

The reasons for establishing field margins and banks/strips are improvement of biodiversity, protection of neighboring habitats (water, hedgerows etc.) and natural regulation of insect pests. The literature on field margins and “strips” is voluminous but the aims, the methodologies and the effects found are highly variable. That variation also includes the lack of a coherent terminology, why this report includes a terminological overview, including some new definitions. “Field strips” for example, are used as the common denomination for all elongate structures placed within the field. Despite all the variation it can be concluded that field margins and strips generally improve the biodiversity assessed using plants, arthropods and birds. Despite the variation in dimension and status it is clear, that buffer margins may be too narrow (1.5 m) and that at least some bird species improve with increasing dimensions of buffer zones.

The question of increasing beneficial effect and hence yield improvement is much related to field strips but coherent results are few. Thus it cannot be concluded how much benefit that can be obtained by a particular quality of field strip in terms of reduced pest attacks and maybe also increased yield.

In a number of countries in EU, economical compensation can be obtained by establishing particular types of buffer zones but published reasons for specific initiatives are missing. Furthermore the targets of different member states are either obscure or missing and generally the effects of buffer zones are not assessed.

In a broader perspective some investigations in other countries demonstrate that field margins and field strips increase the heterogeneity of the landscape (habitat and ecosystem diversity), particularly in uniform landscapes with intensive agriculture. It can therefore be concluded, that a general improvement of biodiversity is the most obvious goal for the establishing of extensive field margins and field strips. Still it cannot be neglected, that this may also imply an improved natural regulation with some reflection in yields.

Overall there is a need for more coordinated research due to lacking knowledge on biodiversity effects related to dimensions and status of margins and strips as well a need for developing markers /indicators for specific levels of biodiversity. This includes buffer margins as well as field strips which also need to be compared in terms of biodiversity benefits and as a potential tool for improving natural regulation of pests. In relation to the biodiversity aspects it would de desirable, on a longer time scale, to investigate the potential of margins and strip as means of coherence in larger fragmented landscapes.

A last under-researched area is the perception / acceptance and economic consequences of such structures: the perception / acceptance of people in general, farmers in particular, and for the society the cost effectiveness of different types and approaches.