Restore or create habitat connectivity

Supporting evidence from individual studies

1. A controlled, before-and-after study in 1998–2001 in two pine plantations in Wisconsin, USA (Kleintjes et al. 2003) found that connecting patches of lupine Lupinus perennis by felling trees increased the abundance of Karner blue butterfly Lycaeides melissa samuelis. Two–three years after felling began, the peak abundance of Karner blue butterflies (26–49 individuals/year) was higher than before felling (32 individuals/year). On an unmanaged site, the peak abundance was lower two–three years after felling at the managed site (16–20 individuals/year) than before felling (46 individuals/year). Within a 1.5-ha, seven-year-old red pine plantation containing 0.25-ha of lupine Lupinus perennis, >400 trees were removed to create openings and connect corridors between lupine patches. In February and March 1999–2001, patches of trees (20 × 20 and 5 × 20 m) were removed with bow saws, and in autumn 2001 additional patches were felled with chainsaws. A 0.9-ha, six-year-old red pine plantation was not managed. From 1998–2001, Karner blue butterflies were surveyed 5–6 times/year (covering both flight periods) on a 953-m transect through the managed plantation, and an 890-m transect through the unmanaged plantation. The highest number of butterflies counted on a single date in each flight period at each site was used as the abundance for that year.

   Study and other actions tested

   Referenced paper

   Kleintjes P.K., Sporrong J.M., Raebel C.A. & Thon S.F. (2003) Habitat type conservation and restoration for the Karner blue butterfly: A case study from Wisconsin. Ecological Restoration, 21, 107-115.

2. A replicated, controlled study in 2000–2001 in eight pine plantations in South Carolina, USA (Haddad and Tewksbury 2005) found that common buckeye Junonia coenia and variegated fritillary Euptoieta claudia butterflies were more likely to move between connected habitat patches than unconnected habitat patches. A greater percentage of common buckeye and variegated fritillary butterflies moved between connected (common buckeye 2000: 5%, 2001: 4%; variegated fritillary 2000: 10%, 2001: 11%) than unconnected habitat patches (common buckeye 2000: 3%, 2001: 1%; variegated fritillary 2000: 5%, 2001: 5%). There was a lower density of butterflies in the corridors (common buckeye 2000: 0.29, 2001: 0.28; variegated fritillary 2000: 0.31, 2001: 0.29) than in patches (common buckeye 2000: 1.18, 2001: 0.93; variegated fritillary 2000: 1.86, 2001: 1.38). Eight 50 ha areas of pine plantation each contained one central butterfly habitat patch surrounded by four patches at a distance of 150 m from the centre. One of the surrounding patches was connected by a 25 m-wide corridor. Connected patches were 1.0 ha each and unconnected patches were 1.4 ha each. Patches and corridors were created by harvesting pines, followed by burning. In June–July 2000 and May–June 2001, mark-recapture butterfly surveys were conducted along 12.5 m-wide transects to cover the entirety of patches and corridors. Each patch was surveyed 23 times in 2000 and 39 times in 2001.

   Study and other actions tested

   Referenced paper

   Haddad N.M. & Tewksbury J.J. (2005) Low‐quality habitat corridors as movement conduits for two butterfly species. Ecological Applications, 15, 250-257.

3. A site comparison study in 2003 in a grassland in Uppsala, Sweden (Söderström & Hedblom 2007) reported that grassland strips providing nectar resources or shelter were each more likely to be used by one of four butterfly species than strips with no resources. Results were not tested for statistical significance. Of 31 pearly heath Coenonympha arcania released on a flower-rich strip with no shelter, 12 flew along it, compared to 4/27 released on a sheltered strip with few flowers, and 5/30 on a strip with few flowers and no shelter. Of 27 mazarine blue Polyommatus semiargus released on the sheltered strip, 11 flew along it, compared to 4/29 on the flower-rich strip, and 5/29 on the unsheltered strip with few flowers. The numbers of common blue Polyommatus icarus and ringlet Aphantophus hyperantus which flew along strips were similar between strip types (see paper for details). Three 30 × 2 m strips of long grass (21–28 cm high) were created in a field. One strip had abundant nectar resources but no shelter, one had nectar resources removed but was sheltered by a plantation on one side, and one had neither nectar resources nor shelter. The surrounding grassland was cut to 2–4 cm. From 27 June–16 July 2003, butterflies were caught in the morning in six grasslands, and transported to the experimental site (<20 km). Each day, 2–4 individuals/species were released, one-by-one, from the north end of each strip. Butterflies were followed for two minutes, and the distance and direction travelled were recorded.

   Study and other actions tested

   Referenced paper

   Söderström B. & Hedblom M. (2007) Comparing movement of four butterfly species in experimental grassland strips. Journal of Insect Conservation, 11, 333-342.

4. A before-and-after study in 2002–2011 in an area of woodland, heathland and grassland in South Wales, UK (Hobson and Smith 2012) reported that after tree felling to create habitat connectivity, along with coppicing, scrub control and grazing, the number of high brown fritillary Argynnis adippe and small pearl-bordered fritillary Boloria selene increased. Results were not tested for statistical significance. In 2002, prior to felling, an average of seven high brown fritillary adults/hour were recorded at the site, and seven years after felling began 14 adults/hour were recorded. Small pearl-bordered fritillary also increased in number between 2003 and 2011 (numbers not given). From 2003–2011 large trees were felled to increase connectivity between patches of bracken Pteridium aquilinum in the Alun Valley, a 254 ha landscape comprising woodland, heathland and grassland. The area of tree felling was not provided. Coppicing of hazel Corylus avellana and gorse Ulex europaeus (1999–2011), scrub clearance (2003–2011), and sheep grazing (start date not given–2011) were also conducted in areas of the site. Adult butterflies were counted annually from 2002–2011.

   Study and other actions tested

   Referenced paper

   Hobson R. & Smith R. (2012) High Brown Fritillary in the Vale of Glamorgan: saving the last site in Wales. Pages 52-57 in: S. Ellis, N.A. Bourn & C.R. Bulman (eds.) Landscape-scale conservation for butterflies and moths: lessons from the UK. Butterfly Conservation.

5. A before-and-after study in 2005-2010 in two pastures in Devon, UK (Plackett et al 2012) reported that in areas with tree felling to create connectivity corridors between habitats, along with scrub and bracken Pteridium aquilinum control and livestock grazing, marsh fritillary Euphydryas aurinia populations increased. Results were not tested for statistical significance. Of two pastures where trees were felled, along with scrub and bracken control and livestock grazing, one had one marsh fritillary population in 2005 and in 2010, after management, had two populations, and the other had no population in 2005 but did have a population in 2010. In 2005–2010, small areas of woodland on two pastures were felled, western gorse Ulex galli, willow Salix spp., soft rush Juncus effusus, greater tussocksedge Carex paniculata and bracken were controlled, and there was some livestock grazing. In 2005 and 2010 surveyors conducted timed adult marsh fritillary counts during their flight season and caterpillar web counts in the autumn.

   Study and other actions tested

   Referenced paper

   Plackett J., Bourn N.A. & Bulman C.R. (2012) Restoring Marsh Fritillary metapopulations on Dartmoor. Pages 6-9 in: S. Ellis, N.A. Bourn & C.R. Bulman (eds.) Landscape-scale conservation for butterflies and moths: lessons from the UK. Butterfly Conservation.

6. A study in 2014 in a restored grassland and oak barren landscape in Indiana, USA (Shuey et al. 2016) reported that regal fritillary Speyeria idalia were found across a restored, connected grassland landscape. Results were not tested for statistical significance. Eighteen years after restoration began, the abundance of regal fritillaries in the restored area peaked at 12–19 butterflies/30-minute transect, compared to 12 butterflies/transect on remnant prairies, and 0 butterflies/transect in an agricultural field. In addition, fritillaries were present in ≥17 habitat patches ≤16 km from the restoration area. Prior to restoration, authors reported that regal fritillaries were only found at three small sites in the landscape. Beginning in 1996, over 3,240 ha of agricultural land was restored to native grassland and oak barrens by planting seed mixes containing over 620 native species, to reconnect remnant grasslands and oak barrens. In addition, seeds and plugs of arrowleaf violet Viola sagittata and bird's-foot violet Viola pedata were planted as host plants. The area was managed to control invasive species and, once established, patches were burned on a three-year rotation. From May–September 2014, butterflies were surveyed every two weeks on 30-minute transects at nine sites across the landscape: five restored sites, two remnant prairies, one old field, and one site still in agricultural production. In 2014–2015, suitable habitat surrounding the restoration area was searched for regal fritillaries.

   Study and other actions tested

   Referenced paper

   Shuey J., Jacquart E., Orr S., Becker F., Nyberg A., Littiken R., Anchor T. & Luchik D. (2016) Landscape-scale response to local habitat restoration in the regal fritillary butterfly (Speyeria idalia) (Lepidoptera: Nymphalidae). Journal of Insect Conservation, 20, 773-780.