Leave unharvested crop headlands within arable fields
Overall effectiveness category Awaiting assessment
Number of studies: 1
Background information and definitions
Harvesting crops creates a dramatic change in the farmed landscape, by suddenly and simultaneously removing plants, which may be providing nectar resources to butterflies and moths, from a large area. Even if butterflies and moths are not using the crop itself, harvesting disturbs the structure of the field, and may cause mortality of caterpillars living on other plant species within or around the crop. Leaving unharvested strips, known as headlands, at the edge of fields may provide both shelter and a continued resource availability to butterflies and moths.
Supporting evidence from individual studies
A replicated, paired, site comparison study in 2009–2010 on 24 farms in Champagne-Ardennes and Haute-Normandie, France (Manil & Chagué 2014) found that unharvested alfalfa Medicago sativa headlands had a higher abundance and species richness of butterflies than harvested alfalfa or wheat Triticum spp. fields. In unharvested strips of alfalfa, the abundance (53 individuals/transect) and species richness (4 species/transect) of butterflies was higher than in harvested alfalfa (abundance: 12–15 individuals/transect; richness: 2–3 species/transect) or in conventional wheat fields (abundance: 3–6 individuals/transect; richness: 1–2 species/transect). See paper for individual species results. On each of 24 farms, one alfalfa field was harvested conventionally 4–5 times/year, one alfalfa field had a rotational 7-m strip left unmown during each harvest, and one winter wheat field was managed conventionally. From May–September 2009–2010, butterflies were surveyed visually five times/year on two 200–400-m transects in each field (15–17 farms surveyed/year).Study and other actions tested