No abstract

Lawns are considered monocultures and lesser contributors to sustainability than diverse nature but are still a dominating green area feature and an important cultural phenomenon in cities. Lawns have esthetical values, provide playground, are potential habitat for species, contribute to carbon sequestration and water infiltration, but also increase pesticides, fertilization, are monocultures and costly to manage at the same time. To evaluate the potential impact of lawns, whether positive or negative, it is of interest to estimate the total lawn cover in cities and its change over time. This is not a straightforward process, e.g., because many lawns are small and covered by trees. In this study we review the existing literature of lawn cover in cities and the different methodologies used for cover estimation. We found both pros and cons with NDVI and LiDAR data as well as manually interpreted aerial photos. The total cover of lawns in three case study cities was estimated to 22.5%. By extrapolating these percentages to all Swedish cities lawn cover was estimated to 2589 km 2 (0.6% of the terrestrial surface). The approximated total municipal management cost of lawns in all Swedish cities was 910,000,000 USD/ year. During 50 years lawn area almost doubled in relative cover and 56% of them were continuously managed. Since lawns constitute large parts of the urban greenery and are costly to manage it is highly relevant to consider their social, ecological and cultural value compared to alternatives, e.g., meadows with less intensive management.

The aim of this study was to compare the butterfly assemblages in semi‐natural pastures and power‐line corridors and to analyse the effects of vegetation height, occurrence of trees and shrubs and different flowering vascular plant groups on butterfly diversity and abundance. Twelve of 26 analysed butterfly species were more abundant in power‐line corridors than in semi‐natural pastures. Only one species preferred semi‐natural pastures. In semi‐natural pastures butterflies were most common in segments with tall vegetation, whereas butterflies in power‐line corridors were most common in segments with vegetation of short or intermediate height. Short vegetation was sparser in power‐line corridors (mean cover 4%) than in semi‐natural pastures (33%), whereas tall vegetation was more common in power‐line corridors (59%) than in semi‐natural pastures (35%). The amount of flowers was the factor that affected the abundance of most species. Twenty‐one of the 26 species showed positive associations with numbers of flowers of different families. Flowers of the plant families Apiaceae, Caryophyllaceae, Primulaceae, Rubiaceae, Scrophulariaceae, and Violaceae showed positive associations with the abundance of several butterfly species. Vegetation height seems to be a limiting factor in semi‐natural pastures, and less intensive management (division of pastures into grazing pens, late season grazing, grazing every second year, or reduced grazing pressure) would benefit butterflies. In power‐line corridors (dominated by tall vegetation) the opposite would be beneficial for butterflies, for example more frequent clearing of vegetation along the power‐line trails combined with mowing of selected areas.

During the last 50-100 years, large numbers of species associated with seminatural grassland have declined. One reason for this is the considerable reduction of grassland area. Another possible explanation is the loss of historical management practices. This study addresses changes in the timing of management and its implications for biodiversity, and combines historical data on management timing (eighteenth century) with data on reproductive phenology of vascular plants and butterflies. All data are from south-east and south-central Sweden and demonstrate a considerable loss of grassland area, but an even greater loss of historical management practices. Historically, 21-32 per cent of the seminatural grassland area was subject to late season management (from early July University of Virginia Claude Moore Health Sciences Library = username $REMOTE_ASSR = IP address Thu, 16 Jun 2016 03:06:18 = Date & Time A. DAHLSTRÖM, T. LENNARTSSON, J. WISSMAN AND I. FRYCKLUND 386 Environment and History 14.1 onwards) by mowing or late-season grazing. In 2005, management had ceased in 97-99 per cent of the historically managed grassland, and current management was dominated by all-season grazing. 0.2 per cent of the grassland area was managed by mowing in 2005. Historically, at the time of mowing, 50-80 per cent of the butterfly species and 20-95 per cent of vascular plant species had completed their reproductive cycles, the proportions increasing with the later onset of management. The results suggest that the reduced use of late management is a major cause of the observed decline of grassland organisms.

No abstract