Providing evidence to improve practice

The journal, Conservation Evidence

Our online journal publishes research, monitoring results and case studies on the effects of conservation interventions. All papers include some monitoring of the effects of the intervention and are written by, or in partnership with, those who did the conservation work. It includes interventions such as habitat creation, habitat restoration, translocations, reintroductions, invasive species control, and education or integrated conservation development programmes, from anywhere around the world.

A volume is created each year with peer-reviewed papers published throughout the year. We now accept Short Communications as well as standard papers.

Special issues contain new papers on a specific topic.

Virtual collections collate papers published in the journal on specific topics such as management of particular groups of species.

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Invertebrate management



We tested the effects of herbaceous vegetation enhancement on the abundance and richness of plants and arthropods in a wine-producing vineyard in Israel. We compared the abundance and species richness of plants and arthropods between a plot seeded with local annual plants and an unseeded plot. We also compared soil content and grape quality parameters in seeded versus unseeded plots in the vineyard. Seeding increased plant cover and plant species richness in the spring, but reduced plant cover and did not affect species richness in summer. Arthropods, and especially parasitoids and generalist predators, were more abundant and diverse in the seeded than in the unseeded plots in spring, both on the herbaceous vegetation and on the vine foliage. Arthropods were more abundant in the herbaceous vegetation than on the vine foliage in spring, but not in summer. The soil in seeded plots was richer in ammonium nitrogen and organic matter, while the grapes were smaller and sweeter. Our findings showing a general increase in biodiversity, combined with additional considerations, led the managers of the vineyard to implement these vegetation enhancement practices in 85% of their vineyards.

 

Integrated conservation of bee pollinators of a rare plant in a protected area near Bologna, Italy
Bortolotti L., Bogo G., de Manincor N., Fisogni A. & Galloni M. (2016), 13, 51-56

An integrated approach was proposed for the conservation of the bee pollinators of the locally rare plant dittany Dictamnus albus. Based on previous studies that revealed the most efficient pollinators, we performed three related actions to improve their presence in the area: (i) we provided artificial nests for bumblebees and solitary bees; (ii) we added bee plants to support local populations of pollinators throughout their life cycle, and (iii) we reared and released bumblebee colonies from wild queens collected in the area. Artificial nests were occupied at high rates by cavity nesting species such as mason bees, leafcutter bees and carpenter bees, while we did not observe any ground nesting bees. Artificial nests for bumblebees did not attract any wild queens. The bee plants established at different rates: transplanted adult individuals survived better than seeds directly sown at the site. In three consecutive years we reared and released several colonies of buff-tailed bumblebees, which survived through the flowering season but only one developed new gynes.

 

Bromeliad translocation in Atlantic Forest fragments, Brazil
Melo T.S., Benati K.R., Peres M.C.L., Tinôco M.S., de Andrade A.R.S & Dias Alves M. (2016), 13, 88-92

Habitat loss and fragmentation have negative impacts on the environment, reducing the habitat available to species. In order to minimize these effects we need strategies to enhance the value of refuge areas. Bromeliads are important microhabitats for many taxa during certain stages of their life cycles, and can potentially be readily transplanted. In this study we transplanted terrestrial bromeliads to test their capacity to survive the transplantation procedure over time, and assess whether they are able to maintain their arthropod communities. The experiment was performed between two Atlantic Forest fragments with bromeliads of the genus Hohenbergia. We transplanted 66 plants and monitored them over three years. We assessed plant survival and reproduction as measures of transplantation success, and made comparisons among arthropod communities to evaluate faunal maintenance post-transplantation. All the bromeliads survived the transplantation over the four-year study and conserved their arthropod community. Therefore we recommend this technique as a method for enhancing the value of fragmented habitats, because it both maintains the bromeliad fauna and aids conservation of endangered bromeliads species in the face of environmental change.

 

Translocation of individuals across a barrier which hampers natural colonisation is a potentially important, but debated, conservation tool for a variety of organisms in a world altered by anthropogenic influences. The apollo Parnassius apollo is an endangered butterfly whose distribution retracted dramatically during the 1900s across Europe. In Finland the apollo currently occupies only a fraction of the range of its suitable habitat and is apparently unable to re-colonise other areas. Using eggs collected from wild-caught females from the species’ current Finnish stronghold, a population was reared in order to translocate larvae into an unoccupied, but highly suitable, part of the Finnish archipelago where the species historically occurred until its national decline in the 1950s. In 2009 a restricted number of larvae (1 larva/10 host plants) were released on 25 islands in the inner, middle and outer archipelago zones. In 2010, nine islands situated in all three archipelago zones were (re)stocked with a high density of larvae (1/host plant). In 2011, apollo larval populations were found only on islands in the outer archipelago zone, which were then restocked. The species remained present here in the following two years (2012, 2013) and was hence able to sustain multi-annual population establishment without restocking. Our findings demonstrate that empty suitable habitat may in reality consist of only a few sites where population establishment is possible. Hence, starting the introduction in many sites, which are putatively suitable based on biotic and abiotic criteria derived from species’ existing populations, but then “zooming in” on a smaller set of promising sites showing evidence of successful establishment was key to the success of this translocation.

The main goal of this study was to experimentally test whether maintaining a fraction of a meadow uncut would create a refuge that can efficiently conserve butterflies in extensively managed meadows registered as biodiversity promoting areas, the most common type of agri-environment scheme in Switzerland. Leaving part of the meadow uncut was expected to benefit butterflies by providing shelter and food resources once the rest of the meadow has been mown. The measure was experimentally applied since 2010 in 12 sites of the Swiss lowlands (Plateau). There were two experimental meadows per site, with one mowing regime applied at random within the pair. One meadow was managed according to the standard regulations for meadows in biodiversity promoting areas, meaning that the meadow was entirely mown at least once a year, but not before 15 June (control meadows). The second meadow was only partially mown, and a grass refuge of 10-20% of its area was left uncut during mowing operations (refuge meadows). In 2013 we conducted Pollard walk surveys to assess the efficiency of the refuge scheme. Results indicate that after mowing the uncut refuges were occupied by butterflies, with much higher abundances than in control meadows. Keeping an unmown grass refuge within hay meadows would be a simple and easy measure to promote butterfly populations within current agri-environment schemes.

 

This study aimed to assess the effectiveness of control measures undertaken by volunteer labour to impede the spread of wild Pacific oysters Crassostrea gigas within the inter-tidal zone of the North East Kent Marine Protected Areas. This was achieved by conducting a one-year field trial during which a small group of volunteers physically reduced the number of oysters towards a pre-determined target. The site contained a large number of oysters and had high levels of annual recruitment, thus posing a threat to native species and biotopes. Comparison of pre- and post-trial data indicated that oyster numbers were considerably reduced at the trial site although they had increased at each of three control sites. The method used had minimal impact on native species and habitats but was labour-intensive, warranting the use of volunteers. This method of control could be used effectively in other similar situations.

 

A small area of ancient woodland in Essex, England was coppiced. Glow-worms Lampyris noctiluca were observed in the cut area in the first four seasons after winter coppicing, whereas significantly lower numbers were recorded in an uncut control. The highest abundance was observed in the second season after coppicing, only for numbers to decline as the area became overgrown with bramble Rubus fruticosus and shading from the maturing canopy occurred. Coppicing may promote the conservation of glow-worms in ancient woodland.

The response of glow-worms Lampyris noctiluca to winter scrub clearance on a sea wall flood defence in Essex, England was monitored. The number of glowing adult females did not show a significant difference in the two seasons (one life cycle) after scrub clearance, or at a control site with no clearance.

The impacts of commercial woodland management on woodland butterfly biodiversity in Morecambe Bay, UK
Taylor D.L., Ramsey A., Convery I., Lawrence A. & Weatherall A. (2013), 10, 10-15

Although the effects on biodiversity in woodland managed for conservation have been studied for a range of species, there is very little empirical data on the potential impacts of commercial woodland management on biodiversity in the UK. This study measured species richness and abundance of diurnal butterflies as a proxy for the habitat quality of three different woodland management techniques in the Morecambe Bay limestone woodland region. Butterflies were sampled at two sites; Gait Barrows and Witherslack, where three woodland management techniques were carried out: low management woodland (woodland with no recent intervention); traditional coppice management for conservation; and commercial woodland management. Both coppice management for conservation and commercial management had significantly higher butterfly species richness and abundance when compared to low management woodland; neither butterfly species richness nor abundance were significantly different between the traditional coppice management for conservation and commercial woodland management. UK Biodiversity Action Plan fritillary species (high brown fritillary Argynnis adippe; pearl bordered fritillary Boloria euphrosyne; and small pearl bordered fritillary Boloria selene) were not significantly different between the traditional coppice management for conservation and commercial management.

Coastal grazing marsh was flooded with seawater in a successful attempt to eradicate New Zealand pygmy weed Crassula helmsii at Old Hall Marshes in 2006. The abundance of Orthoptera and the presence of yellow meadow ants Lasius flavus were broadly similar between the flooded grazing marsh and unflooded ground in 2011 indicating that inundation did not have a deleterious impact on these non-target terrestrial insects. Ant hills in areas of lower ground within the flooded area, which were fully inundated in 2006, had a lower occupancy rate (44%) than those on higher ground (94% occupied), suggesting that unflooded refuges may be important.

Grasshopper strips (alternate, 1-m wide strips of uncut and cut grassland) are a novel conservation feature in a rural churchyard in the village of Rivenhall (Essex), southeast England.  The effectiveness of these strips in enhancing the abundance of grasshoppers (Acrididae) was investigated during the summer of 2010 using sweep-net surveys.  Two grasshopper species were recorded.  The meadow grasshopper Chorthippus parallelus was significantly more abundant in the cut grasshopper strips than in nearby short grassland (control) plots regularly mown throughout the summer.  The field grasshopper Chorthippus brunneus was contrastingly more abundant in the uncut grasshopper strips than in the controls. The grasshopper strips appear to provide a mosaic of short and tall grassland in close proximity which is required for nymphs and adults of both C. parallelus and C. brunneus.

The mottled grasshopper Myrmeleotettix maculatus is locally rare in Essex, southeast England. To increase the number of populations of this grasshopper in the county, 40 adults (20 female, 20 male) were captured using sweep netting at Colne Point (an Essex Wildlife Trust coastal nature reserve) and transferred to Environment Agency sand dune flood defences at the nearby town of Jaywick in July and August 2009. At least in the short-term, the translocation has been successful; in June and August 2010 at the release site a small number of adult female and male mottled grasshoppers were located indicating that successful breeding had occurred. It is hoped that a new population at Jaywick will establish and spread in the longer-term in adjacent sandy areas recently planted with marram grass Ammophila arenaria.

The efficacy of 'sod removal' as a fenland restoration technique was tested using an experimental approach at Montiaghs Moss Nature Reserve, Northern Ireland, from 2006 to 2008. The site suffered from rank growth of purple moor-grass Molinia caerulea which was out-competing herbaceous species. Soil was removed up to a depth of 15 cm completely denuding vegetation in the experimental plot exposing bare peat. By July 2007, 15.2% of sod-removal areas were revegetated; by October 2008 cover had risen to 64.6%. Of this cover, purple moor-grass accounted for only 9-11% compared to 78-79% on control plots. Cover of other rank-forming grass species was also significantly reduced. Sod removal significantly increased the cover of species characteristic of fenlands including sedges Carex spp., rushes Juncus spp., marsh pennywort Hydrocotyle vulgaris and lesser spearwort Ranunculus flammula. It seems likely that sod removal, which lowered the surface of the peat, restored minerotrophic conditions and exposed the historical seed bank stimulating regeneration of some fenland specialists and pioneer species; this resulted in significantly higher species richness on sod removal plots than control plots two years after treatment. There was no demonstrable effect of sod removal on abundance of devil's-bit scabious Succisa pratensis, the larval food plant of the Annex II listed marsh fritillary butterfly Euphydryas aurinia. We recommend that consideration should be given to artificially seeding devil's-bit scabious soon after sod removal treatment to promote early recolonisation and to increase plant abundance on the site.

 

Created reedbed at Lakenheath Fen (southeast England) supports an abundant and diverse invertebrate population, including rare Diptera and reedbed specialists, just seven years after it was transformed from agricultural land.

Two translocations of silver-studded blue butterflies Plebejus argus (30 in 2006 and 72 in 2007) were made to an area of suitable unoccupied heathland from a nearby donor site. Monitoring of the 2006 release site in 2007 revealed the presence of only four butterflies. Several factors may have accounted for the low numbers. Poor weather (wet and cold) during the flight period may have been partly responsible, but the trend of earlier emergence of silver-studded blues may be a factor; over the last few years, there has been a trend towards earlier emergence and peak counts in June rather than July. Consequently, if the donor butterflies were collected later in the flight period after the peak count as was the case in 2006 and 2007, the proportion of fresh, actively-laying females may have been lower than in previous successful translocations conducted at other localities. In view of this, it is recommended that a further 30 fresh female butterflies are collected early in the flight period in 2008 and are translocated in order to enhance establishment success.

 

Grasshoppers and crickets (Orthoptera) were monitored in the Mardyke River Valley in south Essex in July and August 2007. A standardised transect method was used to count Orthoptera in horse-grazed and ungrazed pastures. Sward height measurements were taken from each pasture. In ungrazed pastures Orthoptera were much more abundant (17.3 individuals/100 m) with greater diversity (7 species) than in grazed pastures (0.8 individuals/100 m; 4 species). The low sward height of the grazed pastures (< 6 cm on average) is considered to have afforded Orthoptera little shelter from inclement weather or avian predators. Based on additional observations, a reduction in the grazing pressure from 3.5 horses/ha (current grazing density to the south of the Mardyke) to less than 2 horses/ha would lead to a more heterogeneous and overall taller sward, which would be favourable for orthopterans and a wider range of other grassland invertebrates.

Arable field margins were established by natural regeneration or sowing with a legume seed mixture in 2001 on farmland at Romney Marsh in Kent. Establishment of bumblebee Bombus spp. forage plant species was monitored using frame quadrats from 2001-2004. Monitoring showed that the natural regeneration margins had low species richness of forage plants, and a sward dominated by creeping thistle Cirsium arvense or bristly ox-tongue Picris echioides, 'weed' species, which are unlikely to be favoured by the farmer or used extensively as forage plants by bumblebees. In the sown margins, the abundance of red clover Trifolium pratense and alsike clover T.hybridum was extremely high one year after margin establishment (almost 100% ground cover combined), but declined rapidly for T.hybridum two to three years after sowing. The subsequent invasion of the clover-dominated margins by perennial grass species in 2003 and 2004 suggests that legume swards may need to be re-sown every three years due to the poor persistence of Trifolium spp.

The netted carpet moth Eustroma reticulatum is one of the rarest moths in the UK where it now occurs only in a few sites in The Lake District of northwest England. In the late 1990's there was a decline in its larval foodplant, touch-me-not balsam Impatiens noli-tangere; a highly isolated netted carpet colony at Derwentwater almost certainly became locally extinct because of the extreme food shortages. Subsequently the balsam recovered and an attempt was made to reintroduce the moth to this locality by translocation of 30 larvae in September 2006. However, in September 2007 the site was surveyed for larvae, but none were found. The procedure was repeated (40 larvae translocated) in September 2007 but at an alternative site at this locality where the foodplant was more abundant and conditions were considered more favourable. In September 2008, surveys revealed four netted carpet moth larvae, considered progeny of the previous year's introduction; in order to bolster this initial success, a further 150 larvae were translocated. This movement of larger numbers of larvae was possible because of their unprecedented abundance found in the actively managed donor site. Monitoring is ongoing to ascertain the longer-term success of the translocations.

 

Thinning of the woodland canopy by selective tree felling and removal of humus and nutrient-rich soil by scraping are techniques being used as a first step to regenerate heathland vegetation and associated insect assemblages at Norton Heath Common in southeast England. Two years subsequent to initial restoration activities, there has been germination and establishment of two heathland plant species, gorse Ulex europaeus and sheep's sorrel Rumex acetosella, in the tree-cleared and soil scraped areas, whilst the warmer microclimate created by tree felling has led to higher thermophilous insect species richness, particularly of butterflies. It is hoped that the continuation of felling and soil scraping will lead to the return of other characteristic heathland plants, especially heather Calluna vulgaris, and rarer species such as lousewort Pedicularis sylvatica.

In an attempt to enhance breeding habitat for the grizzled skipper Pygus malvae at a site in central England, a low drystone wall was laid to create egg-laying habitat in a herb-rich grassland. During subsequent egg searches, it became apparent that the butterflies preferred to lay eggs on the leaves of creeping cinquefoil Potentilla reptans which were growing over stones in the wall. The relatively high egg density found one year after the wall construction suggests that this habitat is now more suitable than a nearby, traditionally used, coppiced ditch habitat.

During experimental trials, it was discovered that 'bracken bashing' (mechanical damage) to control Pteridium aquilinum on an annual basis is not a suitable form of habitat management for the nationally vulnerable heath fritillary Mellicta athalia. It was in fact found to be detrimental to promotion of growth of desired vegetation, with lower cow-wheat Melampyrum pratense (the larval food plant of heath fritillary) and bilberry Vaccinium myrtillus cover than that considered necessary for the habitat to be in suitable condition for the butterfly. Consequently, bracken bashing was halted after 2005, but monitoring of these plots continued. Mechanical damage is a viable option for heath fritillary habitat management in the future but on a less frequent basis. Spraying plots with Asulox in 2002 (commonly used in bracken control) appeared beneficial. Bracken spraying produced favourable ground cover of bilberry and cow-wheat by opening up the previously dense bracken canopy, with bracken itself persisting at lower densities which afforded favourable micro-climate conditions for growth of these plants and shelter for butterflies. Past evidence suggests that livestock grazing is an effective and also a more sustainable management option in the longer term for control of both bracken and invasive woody species, and it is envisaged that other characteristic heathland flora and fauna will also benefit. Livestock have been introduced onto Halse Combe; grazing will be combined with rotational burning and post-burn bracken control (including spraying and mechanical damage) to maintain suitable habitat for heath fritillary in the future.

 

Scrapes totalling 0.2 ha were dug and the excavated material used to create windbreaks in an attempt to enhance silver-studded blue butterfly Plebejus argus habitat at a quarry in southern England. Populations of silver-studded blue and small blue Cupido minimus butterflies increased over the next two years; however, it is unclear whether management alone and/or recent favourable weather in winter and spring was responsible for these increases. The scrapes led to re-colonisation by black ants Lasius alienus and an increase in the silver-studded blue's food plant, bird's-foot trefoil Lotus corniculatus.

Artificial macrophytes have been suggested as a means of improving water quality by providing zooplankton refugia. Plastic brushes provided a short term reduction in phosphates as they were absorbed by the periphyton growing on the brushes. They also provided a refuge for invertebrates. After two years, the brushes became colonised by sponges, which greatly reduced their long term usefulness as invertebrate habitat.

The grassland at Witch Lodge Field, Somerset has been cut annually since 1979 using a brush cutter to maintain butterfly habitat. Despite management, many butterfly species have declined on the site including several species of conservation concern. These declines may be attributable both to the increase in the proportion of grass in the sward and grass 'greening'.

 

Nylon Italian cobweb brushes were added to Alderfen Broad to provide a refuge for zooplankton and other invertebrates. These were colonised quickly, initially largely by chironomids but then by a greater diversity of taxa. In the second year, there was a vigorous build-up of sponges.

 

A core heath fritillary Mellicta athalia breeding site had become dominated by bracken Pteridium aquilinum. Following bracken control by burning and herbicide spraying there was a considerable increase in common cow wheat Melampyrum pratense (the larval food plant) and a 10-fold increase in fritillary numbers. There had also been grazing and trampling by red deer Cervus elaphus, which might have also improved the habitat quality. Two other burnt and sprayed areas did not show an increase in butterfly numbers, perhaps because at higher elevation and therefore constituting less suitable habitat.

Hay and cuttings rich in red clover Trifolium pratense, were added to five former arable fields and established well in four of them (present in over 10% of 2 x 2 m² quadrats).

Despite initial concern, a haylage cut of herb-rich meadow in mid-June 2006 did not reduce the numbers of common blue Polyommatus icarus butterflies. Red clover Trifolium pratense flowered later in the cut area and attracted up to eight clouded yellow Coleas croceus butterflies. July 2006 was exceptionally hot and this undoubtedly benefited the second generation of common blues in that year.

Totals of 67 Middle Island tusked weta Motuweta isolata were released on Red Mercury Island and 80 on Double Island between 2000 and 2003. In 2005 surveys located 11 wetas on Red Mercury and 4 on Double Island. Juvenile wetas were found on both islands in 2004 and 2005 showing that successful breeding had occurred.

Juvenile flax snails Placostylus ambagiosus experience high mortality from introduced predators. Snails were kept in a terrarium with constant high humidity, regular moisture and a relatively constant temperature. Leaves, especially from karaka tees Corynocarpus laevigatus, were provided as food but the juveniles also fed on the algae allowed to build up within the terrarium. They eventually bred successfully and grew faster than in the wild.

 

Two hundred wooden refuges were provided for the Auckland tree weta Hemideina thoracica. Within six months over half were used, 52 weta were transferred to Korapuki Island by plugging then translocating these refuges. After five years, there were over 500 individual tree wetas present on Korapuki.

 

Scrub and trees were removed from overgrown clay pits at a nature reserve in southern England. Prior to management the maximum counts of southern damselfly Coenagrion mercuriale was 40-70 adults annually, but this increased to around 150-200 adults after management opened up the pools.

At a nature reserve in central England, after failure of smaller pools dug to provide long-term white-faced darter Leucorrhinia dubia breeding habitat, a larger 7 x 7m pool was created in 1992. Breeding by white-faced darters was confirmed in 1995 and they have since bred annually with 54 individuals recorded in 2003.

At a National Nature Reserve in the Norfolk Broads (eastern England), between 1986 and 1998, 1,600 m of new dykes were excavated in the winter months. Seven of these 12 dykes were subsequently colonised by Norfolk hawker Aeshna isosceles dragonflies (a species of conservation concern in the UK).

 

 

Four shallow bays, each about 3 x 5 m, with a rear vertical face of 30 cm, were dug to attract ground-nesting bees and wasps. All four were colonised in the first year and 80 solitary bee and wasp species have been recorded to date (2004). Two scarce heathland mosses also colonised the site and the bays were frequently used by common lizards Lacerta vivipara for basking.