St Machar Community Biodiversity Project

Katherine Williams, Education Officer as the Cathedral Church of St Machar, Old Aberdeen is our guest blogger today. Prize winners in our recent Keep Scotland Beautiful pollinator-friendly awards, the pollinator-friendly work in an Aberdeen churchyard could be inspiration for church grounds up and down Scotland.

There has been worship on this site since the 7th century with the Cathedral of St Machar the oldest building still in use in Aberdeen. There are many visitors to the cathedral and many pass by going to Seaton Park or walking back to student halls. It is managed by Aberdeen City Council and is a Scheduled Monument under the watch of Historic Environment Scotland.

A major repair and conservation project was started in 2020 to coincide with the 500th anniversary of its unique Heraldic Ceiling. £1.8 million was needed for the project which included re-slating the roof and cleaning all the stained-glass windows. The National Heritage Lottery Fund grant included funding two posts, Education Officer and Outreach Officer and a three year Activity Plan to raise awareness of traditional skills and attract more people to the site. A Kirkyard Natural Heritage Project was part of this vision.

The aims were to increase the kirkyard biodiversity with a sustainable management system, to enable people to have creative experiences with the benefits of being outside and interpret family stories and increasing awareness of the local built heritage.

In autumn 2020, a presentation was put to the cathedral and with their consent in early 2021 a steering group formed. The group includes the Education Officer, the Outreach Officer, reps from the cathedral, a rep from Friends of Seaton Park, a committee member of Old Aberdeen Community Association, a retired Countryside Officer and the supervisor of the City Council maintenance team.  

Firstly, the group liaised with the maintenance team and the Head of Bereavement Services to come up with a more sustainable management scheme. Beforehand all the kirkyard was cut short between 6-8 times a year and herbicides used on paths and around gravestones. Over the last two years we have worked towards a more nature friendly scheme. In 2020 during the covid-19 lockdowns the grounds were not cut and the grass grew long. This did not please everyone in the locality and the word ‘rewilding’ had to be quickly dropped from any discussions as it was equated with neglect. Some people liked the informal look of the kirkyard at this time, but some families tending graves thought it disrespectful with fears that headstones would be covered over by vegetation.

A balance was needed and a mix of habitats. At the east end of the cathedral the terrain is rougher and the graves older. This area has been left to grow long and only cut at the end of the growing season. It has been planted it with over 100 wildflower plug plants such as red campion, ox-eye daisy, cowslips, herb robert and self-heal.

These were grown from seed by John Malster of Curam Fyvie who uses local seed to protect the biodiversity of this area. Another area was left long by the west entrance door however it drew some criticism. Here the insect-delighting plants of dandelions and ragwort were not always welcomed by brides and their families exiting the west door or passers-by walking to Seaton Park. A more formal approach will likely be adopted here next year where the grass will be cut at least 2 times and a strip all around the area kept short.

On a triangle beside the main footpath to the cathedral entrance we have planted some thyme varieties including red creeping Thyme for pollinators and crocus bulbs to provide early nectar. We have also put in some self-heal, thrift and sea-campion to see how they establish. Early attempts at planting here met with some disappointment as at one point, just before a visit from Prince Charles in 2021. The maintenance team thought that our planting of autumnal hawkbit and self-heal were weeds and pulled them all up!

Also, some Thyme was killed by herbicide use on the path. To help our communications with the maintenance team, we have put up a map of the grounds and a key to the different management areas on the council board to inform them as they work. We also have a yearly site visit with them to discuss the oncoming season and include them in our group meetings and minutes.

To help put our ideas into action we have formed a gardening group. This meets monthly during the growing season, attracting between 3 and 30 each session including young families, students, neighbours and cathedral goers. We have weeded a shady area, planted wildflower plugs, snowdrops in the green and crocus bulbs. We have also been given soil from the council and a local building contractor and have increased soil levels around eroded headstones and reseeded with grass in bare areas. 

Community events include a BioBlitz day on a glorious sunny day in June 2021 organised with NESBReC. They came and helped us record the numbers of fauna and flora (well over a 100 species of wildflowers). We planted wildflowers, listened to stories with Grace Banks and members from the Countryside Ranger team provided activities. We had a summer family day in 2022 with guided wildflower tours, planting and children’s activities but unfortunately the weather wasn’t so kind.

The Education Officer has run biodiversity workshops with primary classes and secondary art classes have come to sketch the kirkyard. One school used the grounds to film some stories from the cathedral’s past. 

Our highlight in 2022 was receiving a Level 3 award in Its Your Neighbour scheme and 2nd place from NatureScot’s Pollinator Friendly Award. This will really help to raise awareness of our work here and hopefully encourage other kirkyards in North East Scotland to become more nature friendly. The award will help us to buy seed to increase our Thyme and sow a woodland wildflower mix in our shady north section with some snowdrops in the green.

We aim to sow seeds that we gathered in the autumn and keep an eye on which wildflowers are establishing in the east end. We’ll also update our maintenance scheme and would like to plan an interpretation panel at the entrance and assess the condition of some of our paths. Finally, we hope in the summer to have a family history day and to offer biodiversity workshops for all ages during the year.

A shift in emphasis

The once cherished routine of mowing great swathes of amenity grassland is slipping away. North Lanarkshire Council epitomises this shift, and has been pressing ahead with the creation of a series of trial wildflower areas within high profile public parks. It’s an idea which has caught the public eye and proved very popular. It’s also great news for pollinators. 

The project covers three well known Country Parks.  At Strathclyde, Drumpellier and Palacerigg the progress has been impressive. This is particularly so when you acknowledge that all three sites are very different in nature, and clearly require individually tailored management techniques.

Just off the M74, at Strathclyde Park, in a site covering around 3.3 acres, the approach advocated was to turn over an area of amenity grassland and with the aid of a local farmer create a fine tilth which would provide a suitable base for sowing a rich meadow seed mix. Conscious that the perception of wildflower meadows in their early stages isn’t always positive the council not only invested in some temporary signage to explain the changes, but retained an unploughed zone adjacent to the path for regular mowing, and in doing so created a zone accessible to local park users who wished to walk or run on a softer surface. 

One benefit of this compromise was that it made acceptance of the suite of changes a deal more likely. The breadth of the zone was also carefully calculated to best suit the cutting width of the machinery the council regularly used to mow grasslands.

A mix of annual and perennial seeds have been sown. The eye-catching annuals are intended in part to deliver ‘a winning show’ in the first year whilst the biennial/perennial mix forms part of a longer-term strategy to give bees and butterflies a ‘get nectar-rich quick’ mix. Yellow rattle seed will be added (as will additional plug plants) to the site to keep potentially dominant grasses in check. This is good news for pollinators and promises a calm oasis for people to enjoy.

For those curious to know what has been sown then it will be of interest to learn that that the more damp sections of the site will include creeping buttercup, swathes of cuckoo flower, meadowsweet, sneezewort and the ever-popular ragged robin. 

At Drumpellier Country Park, near Coatbridge, four areas covering just over four acres are being transformed. The sites here tend to be drier than those at Strathclyde Park and thus a prcentage of ‘dry land’ flower seed was proposed which included kidney vetch, lady’s bedstraw and viper’s bugloss. A lot of the grass is very fine with a high percentage of red fescue. The area is already known to support a number of wildflower species including yarrow, self heal, and creeping buttercup and as at Strathclyde yellow rattle seed will also be introduced to the site. 

Interestingly there is an area directly adjacent to a railway line which is already fairly species rich with occasional young trees. However, the addition of Sessile Oak and Hazel will increase the range and the council’s intention is that the strip is supplemented with various woodland plants including red campion, woodruff, and bluebells.

Plots of land at Palacerigg Country Park are also being tackled. Here an area of rough damp grassland was dominated by the soft rush Juncus effusus. Some careful strimming has created multiple pockets for fresh planting and it looks likely that the council will use pots of wildflowers to ensure they are tall enough to cope within the surrounding ‘towering’ rushes. The majority of the planting will take place near to the path to give greatest visual impact for park visitors. Species will include an attractive mix of meadowsweet, devil’s-bit scabious, flag iris, meadow buttercup, water mint, and marsh marigold.

Trees will feature in the plans here too.  A tree-lined avenue shading the diagonal path running through a drier area of the park will boast a wildflower border below the trees and include primrose, red campion and bulbs such as bluebells, wood anemones, and snowdrops. 

It is often said that transport corridors often offer opportunities to carry out some pollinator friendly planting.  Alongside Cumbernauld’s A8011 Glasgow Road a relaxed mowing regime has been implemented.  The edge of the road will now mirror roadside verges on the M80 where it has been observed that the verges are frequently botanically rich with many sporting ox-eye daisies, meadow buttercups, ragged robin, and cow parsley. Understandably safety concerns remain foremost alongside this busy road, hence all of the plants proposed are low-growing species in order to maintain good sightlines for motorists and pedestrians.

Communicating this shift in sentiments and emphasis in managing greens spaces is important. Changing any local authority grassland management scheme comes with challenges around perception and concern that ‘cost-cutting’ is driving an abandonment of sites and previous management practices.

Temporary signs were employed across the sites explaining the vital benefits of the wildflower meadow for nature. This ensued that the council encountered very little opposition to the meadows, indeed it seems that increasingly residents favour making space for nature in their local patch. Many people stopped to read the signs and discuss the meadows, and enthusiasm for the new steps was high. Without that informative approach the council could have been grappling with anxious resident’s concerns. 

Another smart Lanarkshire move was encouraging the involvement of enthusiastic local volunteers and school children. These relationships have been vital in progressing this work and spreading details of the rationale behind change.  Moreover, involving volunteers and youth should provide a strong foundation for the future.

Recently the UN COP15 summit saw around 200 countries vote to protect 30% of our land and oceans by 2030. Widely featured in the media, it’s an optimistic announcement in the struggle to provide a less erratic outlook for nature. Those global aspirations will ultimately include many local actions, and projects like those in North Lanarkshire’s are both impressive and meaningful. Quick local fixes perhaps, but delivering long term benefits for sure.

A bad gut feeling

By Athayde Tonhasca

In July last year, a group of about 70 enthusiastic and hopeful Americans criss-crossed the slopes of Mt. Ashland, near the Oregon–California border, in the hope of making history: catching sight of the elusive Franklin’s bumble bee (Bombus franklini). Those biologists, landowners, students and other volunteers had a good day out, but came back empty-handed. As did the people engaged in previous searches at Mt. Ashland every year for over a decade.

A meadow near the California-Oregon border, Franklin’s bumble bee habitat © Pacific Southwest Region USFWS, Wikimedia Commons.

An American endemic, the Franklin’s bumble bee has always been rare, with only 94 sightings in 1998, when its monitoring started. All records have been restricted to an area of less than 34,000 km2 between southern Oregon and northern California in localities with altitudes between 160 and 2300 m; this territory represents one the narrowest bumble bee distributions in the world. And something bad happened after 1998, because numbers plunged: 20 bees were recorded in 1999, nine in 2000, one in 2001. After a hopeful recovery in 2002 (20 bees), the negative trend continued. Three bees were sighted in 2003, and one worker was last seen in 2006.

A Franklin’s bumble bee © Colleen Meidt, USDA Agricultural Research Service.

Considering the long run of unfruitful searches, could the Franklin’s bumble bee have gone extinct? Possibly, but rare species are a tricky problem. They are difficult to find because they are naturally scarce, so how can we be sure they are really gone when we look for them? It is unlikely that a species searched for as exhaustively as the Franklin’s bumble bee could remain undetected for so long, but it’s not a farfetched proposition. Among insects, there are many cases of ‘Lazarus species’, that is, species believed to be extinct only to ‘resurrect’ some time later thanks to a fortuitous observation. The downland furrow bee (Halictus eurygnathus) was not seen in Britain since 1946 until rediscovered in 2003; the bone skipper fly (Thyreophora cynophila) was unexpectedly found in Spain in 2010 after remaining unrecorded for 160 years throughout its native European range. Even the largest bee on Earth, the Wallace’s giant bee (Megachile pluto), was not seen for 37 years.

A downland furrow bee and a bone skipper: both species were believed to be extinct until rediscovered ©
Arnstein Staverløkk (L) and Panzer et al., Wikimedia Commons.

So the volunteers who dedicate their time in pursuit of the Franklin’s bumble bee have a reason to be cautiously optimistic. Who knows, one of these secretive bees may yet make its way to the bottom of a collector’s net.

Ecologists and conservationists are not surprised by the hard times that befell the Franklin’s bumble bee because this species is naturally rare, therefore particularly susceptible to environmental stresses. But the rusty-patched (B. affinis), the western (B. occidentalis), the yellow-banded (B. terricola) and the American (B. pensylvanicus) bumble bees tell a more alarming story. Once widely distributed in North America, these bees have disappeared from many sites where they were previously common. The decline of the rusty-patched bumble bee has been particularly dramatic: it suffered a range retraction of at least 87%.

A rusty-patched bumble bee © USGS Bee Inventory and Monitoring Lab, Wikimedia Commons.

The possible demise of the Franklin’s bumble bee and the decline of the other North American species must have a reason. Several have been proposed, including habitat degradation, wildfires, climate change, human encroachment of bees’ habitats, pesticides, competition with the European honey bee (Apis mellifera), and introduced parasites and diseases from commercially bred bumble bees. This last possibility came from deductive, detective work. Researchers have noticed that the sharp decline of those species coincided with the collapse of commercial western bumble bee colonies, which were then used to pollinate greenhouse crops. These commercial bees were severely debilitated by the microsporidium (a type of unicellular fungus) Nosema bombi, a gut parasite.

Occurrence records for the rusty-patched (A), yellow-banded (B), and American bumble bees (C), and all bumble bee species (D). Blue points are records from 2000 to 2010, and are overlaid on green points representing records from 1980 to 1990 © Szabo et al., 2012.

According to this scenario, western bumble bee queens shipped to rearing facilities in Belgium in the early 1990s became infected with N. bombi (a known problem in commercial production of bumble bees). When reared colonies resulting from those imported queens were brought to America and distributed to crop producers, the fungus made its way to wild populations of western bumble bees and the other species (National Research Council, 2007. Status of Pollinators in North America).

The evidence for introduced parasites (there are many others besides N. bombi) as the cause of bumble bees’ decline is circumstantial, as it is based on correlation of events. But the hypothesis is compelling. For example, studies have demonstrated high incidence of pathogens (parasites and diseases) in wild bumble bees collected near greenhouses where commercial bees are used – including the common eastern bumble bee (B. impatiens), which replaced the western honey bee in American greenhouses.

Nosema spores from dissected bumble bees. The smaller elongate spores measure 4.5 × 2.0 microns © Bushmann et al., 2012.

Parasites do have the potential for mayhem: the critically endangered Patagonian bumble bee (B. dahlbomii) is believed to be threatened by a protozoan gut parasite that was introduced by commercial bumble bees. But we don’t have a clear understanding of the impact of pathogens on wild bees because these agents are difficult to detect, and some infected individuals are asymptomatic. To complicate matters, susceptibility to N. bombi varies significantly between bumble bee species. So we can’t say with certainty that N. bombi or any other parasite is responsible for the decline of some American bumble bees, but they are likely to be one of the contributing factors. 

Several bumble bees in Britain and continental Europe are also declining. Losses on this side of the Atlantic have been attributed mainly to agriculture intensification and habitat degradation, but parasites and diseases are believed to play their part. And like in North America, commercial bumble bees are likely sources of infections to wild bumble bees, some solitary bees, hover flies and other insects. To make things worse, the European honey bee is also a reservoir of pests and diseases, and a competitor for resources to boot. 

Commercial bumble bees and honey bees make unquestionable contributions to crop production around the world, but they have a dark side. Despite the uncertainties, multitudes of local conditions and conflicting research results, data on the negative effect of these interlopers on wild bees and other pollinators are accumulating (e.g., Mallinger et al., 2017Iwasaki & Hogendoorn, 2022). Addressing the conflicts between crop production and conservation will not be easy, but address them we must for the sake of our wild pollinators.

A: A commercially-reared buff-tailed bumble bee (B. terrestris) with wings crippled by the Deformed Wing Virus; the yellow and white patches are anomalous pigmentation. B: a normal individual © Cilia et al., 2021

Everyone’s a winner

Making space for nature in gardens, allotments, greenspaces and communities is a boost for wildlife and people. Thankfully many agree on this. This was borne out at this year’s Keep Scotland Beautiful ‘It’s Your Neighbourhood gathering when the judges confessed to being spoiled for choice when it came to exploring the many excellent projects competing for NatureScot’s pollinator-friendly awards.

Juliette Camburn, Community Projects Officer at Keep Scotland Beautiful, said: “We’re delighted to have this ongoing partnership with NatureScot, to highlight, recognise and reward community groups across Scotland who are going above and beyond to help our native pollinators and to engage and educate people. As well as the Climate Emergency we find ourselves in, we are also in a Biodiversity Crisis so it is more important than ever for everyone to do their bit to help, no matter how small an action.  Well done and thank you to this year’s winners who are all inspiring, and prove that even simple measures can make a big difference.”

Yorkhill Greenspaces retained their Pollinator-Friendly first prize with another fabulous entry.  Promoting pesticide-free, peat-free gardening & sustainable greenspace management, they complemented these targets by planting pollinator-friendly perennials at Overnewton Park and Cherry Park, including new fruit trees and a sensory garden herb chessboard.

Urban parks are a welcome component of city life. First created in the 19th century, they initially offered a green escape in busy industrial cities. Gradually in some quarters they encountered financial tension and fell from grace, but as work in Glasgow shows the tide is turning. Today our urban parks fulfil a vital role both in terms of social value and in providing wildlife benefits. During the pandemic our parks were a welcome refuge and popular sites for exercise and relaxation. Today urban greenspaces are increasingly recognised as being good for our health and wellbeing. We need greener, healthier cities, and councils are warmly partnering communities to help improve sites.

The list of achievements that Yorkhill Greenspaces can point to is as remarkable as it is impressive. From planting over 100m of native flowering hedging and trees at Yorkhill Park to introducing pollinator-friendly spring bulbs (100 wood anemones, 150 crocuses, 300 grape hyacinths, 750 native bluebells, 145 snake’s-head fritillaries, 377 snowdrops, 350 winter aconites).

Calling on the support of more than 100 volunteers, and 90 pupils from Glasgow’s Gaelic School, the Yorkhill team were able to plant around 2,800 native wildflower plug plants at Yorkhill Park and convert two areas of amenity grass at Overnewton Park to meadow.

Looking ahead, and future-proofing their work, is a big part of what goes on in Yorkhill. The group ran sustainable meadow management and scything workshops and collected yellow rattle seed in Yorkhill Park to sow in new areas.

Monitoring continues to be a strong suit for this group. They expertly fused monitoring and awareness-raising classes in their parks with contributions to the City Nature Challenge, Big Butterfly Count, and POM Scheme FIT-counts. 

The imagination of St Machar Biodiversity Community Group caught the judges eye. Their use of church grounds sets a wonderful example of how opportunity exists in almost every walk of life. 

A project which started in 2020 is now a joint partnership between St Machar’s Cathedral and Aberdeen City Council. The aims were to increase biodiversity whilst balancing the needs and expectations of families visiting graves, tourists and wildlife. A small steering group with representatives from Old Aberdeen Community Association, the Cathedral, Friends of Seaton Park, Aberdeen City Council Maintenance team and a Countryside Ranger was formed to keep things on track. 

A grass maintenance scheme was conceived which allowed for a variety of habitats in the graveyard by using different cutting schedules. There is now no herbicide use around graves and less strimming with some areas only cut once a year. 

It’s a real community effort with a variety of people including older residents, families and University students taking part. Tasks include propagating, and planting, low growing Thyme borders, and introducing a wide range of wildflower plugs (Ox-Eye Daisy, Cowslips, Red campion, Herb Robert and Bird’s Foot Trefoil) into long grass areas. 

An added extra came in the shape of family bio-blitz events diligently recording flora and fauna, popular pollinator ID sessions, and fun seed bombing with local primary schools. 

The folks at St Machar don’t intend to rest on any laurels. They have plans in place to increase their beautiful Thyme border, by division and growing more plants, as well as intentions to plant a shade tolerant wildflower mix on the north of the cathedral whilst reviewing their grass maintenance scheme annually.

Another fantastic entry from Bonnie Dundee, who excel in both pollinator-friendly planting and engaging with their community

There was an award too for the energetic team at Bonnie Dundee.  The sheer breadth of their approach draws admiring comments from everyone who hears about their work. In 2022 Dundee ‘Flowering Dundee’ became a Beautiful Scotland city project and the group’s drive through planting, erecting notices, and hosting a range of engaging events clearly demonstrates that there can be so much more to helping pollinators than growing flowers. 

Last year the group threw a welcome spotlight on solitary bees and an exploration of the opportunities to use bee houses. As ever the planting by Bonnie Dundee was very pollinator-friendly and included apple orchards underplanted with wildflowers, seasonal planting from early bulbs such as snowdrops and alliums through to summer shrubs, perennials, and annuals with provision made to include late flowering species.

But really in a gathering of this kind everyone’s a winner, and pollinators are major beneficiaries.  Congratulation and thanks go to FARE Lochend Community AllotmentFriends of Starbank ParkHazlehead Outdoor Nursery, and Inchview Care Home for fantastic entries too. All of our entries have been sent a NatureScot community seed pack to help them keep up the good work.

Looking up for pollinators

By Athayde Tonhasca

The sycamore (Acer pseudoplatanus) is a robust, fast-growing tree that tolerates strong winds, salt spray, frost, pollution, and poor soils. Its versatility makes it popular with urban planners as a street tree, especially in coastal areas, and a component of parks and large gardens. Sycamore is highly attractive to aphids, so motorists who park under it may find their cars covered with sticky honeydew that drips from the canopy. Some conservationists join forces with grumpy car owners in opposing the planting of sycamore because it is not a native to Britain. Alien it may be, but this tree is believed to be an archaeophyte, that is, a plant that was introduced and became naturalized before 1500 (this cut-off date has a reason: it marks the start of the Columbian exchange, which was the widespread transfer of plants and animals between the Americas and Eurasia following Christopher Columbus’ 1492 voyage).

A sycamore tree in Dalry, UK © Rosser1954 (Roger Griffith), Wikimedia Commons.

So for better or worse, the sycamore has long become part of the British landscape. And many species take advantage of it: birds and mammals eat its seeds, caterpillars of many moth species feed on the foliage, and humans use its good quality wood for kitchen utensils, furniture, flooring and musical instruments. The sycamore has more to offer: its flowers produce sucrose-rich nectar and protein-rich pollen, resources not left to go to waste by some bumble bees (Bombus spp.), mining bees (Andrena spp.) and other pollinators. 

Sycamore is one of several trees that contribute significantly to the food stores of wild bees in urban settings: related maple species (Acer spp.), horse chestnuts (Aesculus spp.) and lindens (or limes; Tilia spp.) are also sources of abundant nectar with high concentrations of sugars, especially sucrose. Maples and oaks (Quercus spp.) supply pollen to the red mason bee (Osmia bicornis) and other mason bees. These species are important pollinators of several crops and wild flowers, and many of them rely on trees to provide pollen early in the season when flowers are still scarce in the landscape. Mining bees are also big fans of tree pollen: maples, beech (Fagus spp.), oaks and chestnuts are important sources.

An ashy mining bee (Andrena cineraria) and a tawny mining bee (A. fulva), two species that rely on maple trees for pollen © Orangeaurochs and gailhampshire respectively, Wikimedia Commons.

Trees are good for food quality, and also for quantity. A single tree produces thousands of flowers, so in a given area, they can supply much greater quantities of nectar and pollen than herbaceous species.  This aspect should be considered when planting for pollinators, especially in situations of limited space such as small parks and along streets.

Flower densities reproduced onto visible planes from a flowering strip and a tree © Donkersley, 2019.

Interestingly, these arboreal pollen suppliers are predominantly wind-pollinated. Could they benefit from their many insect visitors? Entomophily (insect pollination) is the main mode of reproduction in angiosperms – plants that produce flowers and fruits – but anemophily (wind pollination) occurs in about 10% of the species. We don’t know with certainty, but it appears that many wind-pollinated plants are also pollinated by insects, a system labelled ambophily. That seems to be case for most willow species (Salix spp.), even though some species are largely entomophilous while others are mostly anemophilous.

Willows can be pollinated by the wind, by insects, of by both © AvLieshout, Wikimedia Commons.

Ambophily adds another layer to the relationship between pollinators and their host plants. By protecting and planting selected tree species, we would help pollinators with food, especially during times of scarcity. At the same time, we could be improving the means for trees to reproduce. A truly symbiotic relationship. 

Madrid’s pollinator push

I recently enjoyed a short break in Toledo, the Spanish not the American version. On the way home I found myself with time to kill in Madrid, so opted to visit the Botanic Gardens, which are handily placed for the sprawling Atocha railway station. Even lugging a suitcase around wasn’t going to stop me wallowing in these fabulous gardens.

Dappled shade in Real Jardín Botánico

The Real Jardín Botánico turned out to be a bit of an insect haven. For a Scot in November it was lovely to see a variety of insects on the wing; bees and wasps were aplenty. 

Particularly active were beautiful glossy Carpenter bees. With their shimmering blues and glinting purples these sizable solitary bees are a delight. Ponderous perhaps, but focussed and methodical as they worked their way around a wildly blooming salvia. The deep buzz as they languidly shifted from flower to flower was strangely soothing. I’d seen them a few days earlier in Toledo but on that occasion they were too high in the plants for me to get a photo. This time, in the heart of the Spanish capital, they were obligingly at eye level.

Carpenter bee in Real Jardín Botánico

The sound track to the Real Jardín Botánico doesn’t just rely on bees. Dashing overhead, in what seemed like mock outrage, noisy Parakeets made for both a colourful and raucous backdrop. Some appeared to be carrying nesting materials, and they all had the uncanny ability to entertain in abundance, and in so doing render the antics of the many magpies tame by comparison.

One of the many bumblebees making the most of the garden’s floral resources

Bumblebees were about too, perhaps not surprising in a country well-endowed with interesting insects. It is reckoned that Spain has in the region of 1100 wild bee species.  The bumblebees were moving lazily, much slower than the carpenters, so much so that occasionally I had to hang around to see if they were indeed alive. Madrid’s Botanic Garden clearly cherishes insect visitors and in amongst the impressive vegetable section I spied a bee hotel, perhaps new for not a single cell was occupied.

This part of Madrid appeared pretty well-heeled, and amongst the impressive properties lies the world-famous Prado Museum, sitting adjacent to the Botanic Garden. It is an area of good real estate for urban pollinators too. Across the road from the Botanics lies the expansive Parque de El Retiro and within its vast boundaries are a range of habitats for insects.

Toledo

In 2019 a draft national action plan for the conservation of pollinators in Spain was published, hot on the heels of a report prepared by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). The IPBES study had stressed the value of pollinators in not only influencing the yield and quality of many crops but in providing multiple benefits for people.

The last I heard Spain was inching towards a pollinator strategy and looks set to taking a series of actions to help protect pollinators and their habitats. This will cover many of things we are familiar with and includes creating good habitat, promoting more research, action to reduce risks from pests, pathogens and invasive species, encouraging a reduced use of pesticides, and ramping up research to fill knowledge gaps around pollinator conservation.

For urban settings a stated aim was to ‘increase the availability of, or maintain, floral resources’. It was delighted to read that staff at the Botanic Gardens in Madrid had supported a citizen science project called SOS Polinizadores. Run in partnership with the Spanish National Research Council it sounds rather like our FIT-Counts in the UK, and students monitor wild pollinators in the green spaces of Madrid and post observations on the Natusfera citizen science recording platform.

Parque de El Retiro in Madrid

My visit to Madrid was all too brief, but in sampling the delights of the Real Jardín Botánico and Parque de El Retiro on a sunny Sunday afternoon I got a sense that Spain increasingly has an eye on pollinator-friendly approaches. 

Further reading:

EU Pollinator Initiative informed by EU Member States initiatives: successes and gaps

Pollinators and their misandrist bacteria

By Athayde Tonhasca

Bacteria are single-cell organisms found practically everywhere on the planet: your body alone harbours millions of them, mostly living quietly on your skin and inside your gut. But bacteria from the genus Wolbachia* have a specific niche: they spend their lives inside the cells of insects and other arthropods and are transmitted exclusively through the female germline, that is, the cells that pass on their genetic material to the progeny. 

*Insect-living Wolbachia comprise ten phylogenetic groups, and there’s no consensus as to whether they are lineages or species. So they are usually considered collectively: Wolbachia. The green dots show Wolbachia distribution in the tissues of some invertebrates © Pietri et al., 2016.

That’s a good strategy for those bacteria living inside a female host because they are transferred to her offspring via the eggs’ nutritious and protected cyto­plasm (the gooey solution that fills each cell). But bacteria in a male host are virtually doomed: they have little chance of being transmitted because sperm cells have almost no cytoplasm. For the Wolbachia‘s perspective, male hosts are a dangerous prospective. But these bacteria deal ruthlessly and efficiently with the problem: they make males irrelevant, or just get rid of them. 

Wolbachia bacteria (bright spots) inside an egg of the parasitic wasp Trichogramma kaykai © Merijn Salverda & Richard Stouthamer, Microbe Wiki.

For some flies, beetles, wasps, moths, mites and isopods (woodlice relatives), Wolbachia-infected males mating with uninfected females are incapable of reproducing because the bacteria interferes with the paternal chromosomes, resulting in embryonic death. Mating with females carrying the same Wolbachia strain is not affected. The consequence is that Wolbachia-free females have lower chances of reproduction, while infected females spread the bacteria through the population. This process, known as cytoplasmic incompatibility, is the most common effect of Wolbachia. But there’s more. For some butterflies, true bugs (Hemiptera) and isopods, the bacteria turn genetic males into infertile or functional females by inhibiting the production of hormones that trigger the development of male sexual characteristics, a process known as feminisation. Interestingly, feminisation can be ‘cured’ by antibiotics that kill Wolbachia (e.g., Narita et al., 2007). 

Wolbachia’s cunning has no end: they take advantage of the reproductive system of Hymenoptera (bees, wasps and ants), where fertilized eggs contain two pairs of chromosomes and develop into females, whereas non-fertilized eggs contain one copy of each chromosome and develop into males. In some parasitic wasps, the number of chromosomes doubles in infected male egg cells. So voila, those eggs develop into females that reproduce asexually, giving origin to a new generation of infected female clones. And just like feminisation, asexuality can be ‘cured’ by treating wasps with antibiotics or heat, which kills the bacteria. In the laboratory, antibiotic ministrations over several generations induces wasp populations to revert to a sexually reproductive mode (e.g., Stouthamer et al., 1990).

A tiny Trichogramma dendroliti wasp laying eggs inside a moth egg. Some species in the genus are entirely female © Victor Fursov, Wikimedia Commons.

Last but not least, Wolbachia may resort to outright homicide: infected males of some beetles and butterflies are killed during embryonic or larval stages, resulting in populations heavily skewed towards females.

The mechanisms used by Wolbachia to manipulate their hosts remain largely unknown and speculative, even though this is a hot research topic. By whatever device, Wolbachia take control of their hosts’ reproduction for their own benefit, so they spread quickly throughout the population wherever they are introduced.

That male-hating feeling: populations of the two-spot ladybird (Adalia bipunctata) and the Asian corn borer (Ostrinia furnacalis) are overwhelmingly females because most males are killed and feminised, respectively, by Wolbachia © Entomart (L) and Kembangraps, Wikimedia Commons.

You may think that such male-bashing shenanigans are oddities; you would be wrong. It is estimated that 40 to 60% of all arthropod species are infected by Wolbachia. These are remarkable figures, considering that these bacteria were unknown until 1924, when Wolbachia pipientis was first identified. And they are only one of the many microorganisms causing sexual aberrations in insects.

These facts and figures sound alarming; could Wolbachia be a risk to invertebrates? Highly distorted sex ratios could threaten populations or even whole species. But data from a variety of studies suggest that these bacteria are symbionts, that is, they have established a close and sustained relationship with their hosts. And as improbable as it sounds, these female chauvinistic bacteria can be good: there are instances of increased fertility, fitness and resistance against certain viruses in Wolbachia-infected hosts. Wolbachia may even be a factor in insect speciation (when populations evolve to become distinct species). If two populations become infected with different types of Wolbachia, males from either population may be unable to fertilize females from the other; with time, these two populations split into different species (Campbell et al., 1994).

The effects of these bacteria on their hosts have been used for our benefit. Viruses like dengue, Zika, chikungunya and yellow fever have hard times multiplying inside Aedes aegypti mosquitoes infected with Wolbachia. So researchers and mosquito control organisations are breeding Wolbachia-carrying mosquitoes and releasing them into areas of mosquito-borne diseases. Tests with modified mosquitoes have shown significant reductions of dengue incidence in Singapore, Brazil, and Indonesia. The potential for the management or control of other pests is enormous.

When infected male Aedes aegypti mosquitoes mate with wild females that are Wolbachia-free, their eggs will not hatch © Singapore National Environment Agency.

Considering the prevalence of Wolbachia, one would not expect pollinators to go unscathed. Indeed, honey bees, bumble bees, several solitary bees, wasps and hoverflies harbour the bacteria. Data for these groups are still scarce, but 66% of Germany’s native bees may be infected (Gerth et al., 2011). We have the vaguest understanding about the implications of Wolbachia infections for pollinators, but we can assume they are susceptible to the same effects found in other invertebrates, i.e., cytoplasmic incompatibility, feminization, induced parthenogenesis and male killing. So many characteristics of our pollinating species such as sex ratios, biology, ecology, behaviours, distribution and phylogeny (their evolutionary history) could have been shaped or at least influenced by some bacteria whose workings we are just beginning to understand. Wolbachia is a good example of the vast area of known unknowns in the field of natural sciences.    

A female Nasonia parasitic wasp. © M.E. Clark, Wikimedia Commons. The American species N. giraulti and N. longicornis infected with Wolbachia cannot breed with each other, but when both species were treated with antibiotics, interspecies mating produced hybrid offspring. This result suggests incipient speciation: reproductive isolation is already apparent, while genetic barriers have not yet been formed (Bordenstein et al., 2001). 

Wider benefits

We’ve gained a lot from connections with Sweden. Think Carl Linnaeus, Abba, Fika, Henning Mankell, Ikea, and Spotify, to name but a few, and you get the picture.  We could perhaps add to that list a UK pollinator project with an interesting Swedish connection. The work to reintroduce Bombus subterraneus – the Short-haired bumblebee – to these shores has certainly brought wider benefits than perhaps initially envisaged.

Short-haired bumblebee (c) Bumblebee Conservation Trust

That great bee observer Frederik Sladen noted the Short-haired bumblebee in 1912 as being common in the east and south of England, but over time even that concentrated hold loosened. It was last seen Britain in 1988, and twelve years later it was declared extinct on these shores.

Why had it disappeared?  The loss of so many of our wildflower meadows hit B. subterraneus especially hard. Here was a bee which thrived on a diet of kidney vetch, red clover and knapweed. The significant reduction in the availability of these food sources proved disastrous. 

Brown-banded carder worker in a wild flower meadow (c) Bumblebee Conservation Trust

It wasn’t always thus. Britain used to have loads of hay meadows – an estimated 7 million hectares around 100 years ago. Yet by the end of the 20th century it was reckoned we had lost an eye-watering 97 per cent of our wildflower meadows, which for nature was pretty catastrophic. Lose great swathes of habitat crammed with flowers and by extension you are going to lose great numbers of bees which relied on this source of food. 

A ray of hope emerged soon after the 2000 extinction announcement. As the world of reintroductions evolved there appeared to be an opportunity to reverse that loss. The Short-haired bumblebee fell under the reintroduction spotlight and thus began a story with an unexpected geographic twist.

The short-haired bumblebee project10th anniversary gathering with volunteers and project partners. (c) Bumblebee Conservation Trust

It was recalled that farmers in New Zealand had, around the end of the 19th century,  imported bumblebees from the UK.  Puzzled that red clover, an important fodder crop, wasn’t setting seed, one enterprising entomologist aired his suspicion that it was the lack of bumblebee pollination that was the nub of the problem.  So a call went out to send bumblebee queens from England to New Zealand. Four species, including the Short-haired bumblebee, were despatched on refrigerated ships and soon adapted to life on the other side of the globe.

What if come the 21st century that process was turned on its head and bees were sent in the other direction?  If the process was reversed, and queens brought back to England, could the Short-haired bumblebee perhaps be re-established in the UK?

However, those bumblebees in New Zealand were not the ideal solution initially imagined. DNA studies revealed genetic weakness in their population due to inbreeding (comparisons with museum samples held in the Natural History Museum bore this out) and this was compounded by a problematic six-month difference in seasons between the UK and New Zealand.

Undaunted, and fired by the hope reintroductions offered, the project to bring the Short-haired bumblebee back to these shores turned to Sweden. Not only did the Scandinavian nation have the bumblebee in question, but genetic studies revealed them to be a better match than their Antipodean counterparts.

Nevertheless, as many a weary conservationist will confirm, the waters don’t always run smoothly in the reintroduction world, particularly in the early stages. If you have followed beaver and sea eagle reintroductions you will know that the path can be littered with misunderstandings and spats. The prospect of 100 queen Short-haired bumbles being removed from the Skane province of Sweden soon created a mini-storm. There were fears in some quarters that this was unsanctioned and would threaten the bee in southern Sweden, and it took a series of meetings to allay public concerns that the project could herald the demise of this popular species.

As is so often the case it transpired too that a communication issue was afoot. The  project to remove the queens had indeed been vetted and approved.  With some relief the Swedish Board of Agriculture, Swedish Environmental Protection Agency, and the Swedish Threatened Species Unit, as well as the local County Administrative Board of Skane, were all confirmed as supportive.

Moss carder bumblebee (c) Bumblebee Conservation Trust

Nikki Gammans of Bumblebee Conservation Trust led the project aiming to ease the Short-haired bumblebee back into the UK.  Her story takes the reader back to 2009 when she devoted considerable energy to laying the groundwork for the reintroduction project. Firstly she diligently persuaded farmers in and around Dungeness in Kent of the merits of the project, and the role they could play in creating flowery-meadow habitat in advance of a release of bumblebees acquired in Sweden.

Mention of a specific site such as Dungeness perhaps makes this project sound rather narrow and local. In fact it was a project conducted at landscape scale, as it relied on building a network of farms supporting wildflower meadows. That connectivity was crucial if enough suitable habitat and forage was to be provided.  Management and maintenance methods which enhanced the prospects for flower-rich meadows were enthusiastically encouraged. Grazing regimes, field margins, cutting cycles, suitable seed mixes and rotation of stock were all employed in a way which would enable significant and effective habitat changes.

The groundwork laid, it was then a nervous time as, for five consecutive years, batches of Swedish queens were released in Kent. There was a disappointing initial failure in 2012, when it was reckoned a very wet summer did the damage. 

Ultimately Nikki’s project ran from 2009 to 2022 and is a remarkable testimony to her commitment and ability to work in partnership with a wide range of partners.  Thanks to her persuasive work with many farmers and other landowners, swathes of flower-rich habitat were established not only around Dungeness but across the Kent Marshes and beyond into East Sussex too.

Habitat green hay work party day with volunteers (c) Bumblebee Conservation Trust

The project has delivered considerable benefits for bumblebees generally. These range from an increase in other rare bumblebee species, through to landscape scale habitat improvements and the recruitment of over 65 volunteers committed to helping bumblebees. Nikki and her Bumblebee Conservation Trust colleagues continue to engage with the local community and between 2,000 and 3,000 people per year.  

Nikki is honest in her assessment of the reintroduction scheme. “Unfortunately, we don’t think the reintroduction has been successful,” she concedes, “For the years of release, we saw evidence of establishment but no confirmed sightings since they ended. We will continue to look though.

“Around 2,600 hectares of flower-rich meadows and 100 miles of B roads are to this day being actively managed to help the bumblebee. Other species have certainly taken advantage of the new habitat. Ruderal and Brown-banded carder bumblebees have increased as a result of the projects interventions, and the moss carder is stable where the project works but decreasing outside of this area.”

Bombus ruderatus (c) Bumblebee Conservation Trust

Not one to give in, Nikki still looks ahead with some optimism.  “From March 2022 we have been working on Bee Connected, the legacy project of the Short-haired bumblebee project. This project brings an increase in 40% of the project area extending further across Kent and into East Sussex. Our main aims are giving advice to farmers and other landowners, recruiting volunteers, conducting outreach such as identification days, and undertaking practical habitat management. We have a new 12 month trainee beginning in January and are currently recruiting a 24-month project officer.”

Britain is home to 24 species of bumblebee, and in addition we have over 250 species of other bee, mostly some quite small and easily overlooked.  In the wider world there are estimated to be around 20,000 species of bee.  Those numbers perhaps sound impressive but beneath them lies a story peppered with extinctions and declines.  Loss of habitat has hit our bees hard, the work of Nikki and her team in connection with the Short-haired bumblebee deserves our attention and advocates a strong focus on habitat restoration.

Further reading:

Nikki’s report on the project  

Chapter One of Dave Goulson’s highly readable A Sting in the Tale’ delves into the background to short-haired bumblebees in New Zealand.

With sincere thanks to Nikki Gammans of Bumblebee Conservation Trust (project manager for Bee Connected) for all her help in the compilation of this article.

Bobby bright buttons

Some plants have delightful nicknames. Amongst them surely is devil’s-bit scabious, which enjoys the catchy alternative of Bobby Bright Buttons. A stalwart of many a meadow, this is a plant that captivates by looks as well as name.

Devil’s-bit scabious. ©Lorne Gill/SNH

Devil’s-bit scabious has an attractive flower head in a striking blue/purple colour.  It appeals to many species of butterfly and is also very popular with bees. It’s pretty robust, and you will easily find it between midsummer and early autumn (and later in the year in parts of southern England). It favours meadows and damp pastures.

Arguably one of its claims to fame is being the main foodplant for the marsh fritillary caterpillar. The marsh fritillary is giving cause for concern as numbers of this attractive butterfly sink dangerously low, so we should be grateful that devil’s-bit scabious is so robust. There is a lovely passage in Jane Smith’s beautifully illustrated homage to Oronsay, ‘Wild Island’, in which she talks about the joy of spending the first truly warm day of the year going out to look for the caterpillars of the marsh fritillary on devil’s-bit scabious.  Good news that that marsh fritillary features in Scotland’s Species on the Edge project.

Speaking of going outdoors looking at plants. If you feel the notion and fancy some fun then why not join in the Botanical Society of Britain & Ireland’s (BSBI) New Year plant hunt?  You would be helping them build a clearer picture of how our wild and naturalised plants are responding to changes in autumn and winter weather patterns. Their  twelfth New Year Plant Hunt will run from New Year’s Eve until Tuesday 3rd January 2023. You can find out more on their website.

Bumblebee feeding on devil’s bit scabious. ©Lorne Gill

This strikingly colourful devil’s-bit scabious is surely one of our easier flowers to identify. The round globe-shaped flower head sit exposed at the end of a stalk that can be up to half a metre tall and has so many tightly packed flowers that it is said by some to resemble a ‘busy’ pin-cushion (although I can’t actually remember the last time I laid eyes on a pin-cushion, and I suspect younger readers are frantically googling pin-cushion as we speak). You are unlikely to confuse it with any plant other than the field scabious which has pinker, paler flowers. I’m wary, however, as the distinction between a deep pink and light purple often catches me out.

The scientific name for this wiry plant, Succisa pratensis, reveals a link to a medicinal use in bygone days. It was sought out as a solution for certain skin conditions, including scabies and eczema.  The devil element of the common name nods to the legend that the roots of the plant were shortened as they had been bitten off by the Devil, who had taken umbrage at the supposed healing properties of the plant. The Latin word succido, means ‘cut-off below’.

It isn’t just in Scotland that the plant is popular, in 2007 the Jersey Post Office issued a set of wild flower stamps and one of those featured was devil’s-bit scabious. So there you have it. An interesting, native wildflower, popular with pollinators and people. How could you not love a plant that looks like a pom-pom and goes by the name of ‘bobby bright buttons’?

The sweet smell of success

By Athayde Tonhasca

Flowering plants – the angiosperms – underwent a rapid and profound diversification during the Cretaceous period (145 to 66 million years ago), so that they became the most diverse group of land-based plants. Their abrupt and rapid rate of species radiation puzzled and bothered Charles Darwin because the scale of transformation suggested an uncomfortable and significant exception to his deeply held belief in natura non facit saltum: nature does not make a leap. Angiosperm radiation occupied much of Darwin’s thoughts, and he referred to the problem as ‘a most perplexing phenomenon’, ‘nothing… more extraordinary’, and an ‘abominable mystery’, which became one of his most memorable quotes.

Timeline of plant evolution and the beginnings of different modes of insect herbivory © L. Shyamal, Wikimedia Commons.

Despite all the data accumulated since Darwin, the abominable mystery lingers on; for one thing, palaeontologists and molecular biologists don’t always see eye to eye about interpreting the evidence. But whatever the explanation for the radiation of angiosperms, insect pollination (entomophily) is believed to have much to do with it: flowering plants and their pollinators depended on each other for reaching their level of species richness, making it the most celebrated case of coevolution.

The success of the flowering plant-pollinator relationship depends on plants’ ability to attract insect visitors, which is achieved by a variety of flower advertisements such as size, corolla shape, orientation, colour, and scent. Of these, scent must be the least understood of flower lures; the development of gas-chromatography techniques started changing that.

Floral scents are complex mixtures or volatile organic compounds (VOCs) emitted by the petals and other tissues. Some of these chemicals mimic insect pheromones that dupe pollinators into coming to the flower hoping to find a mate, a place to lay their eggs, or to feed. But most VOCs are the ‘flowery’ types, scents that are pleasant to us such as benzyl acetone, which is one of the most abundant attractants in flowers (you are likely to have smelled it from cocoa butter, raspberries, soaps, perfumes, etc.).

A woman making potpourri, a source of benzyl acetone © Herbert James Draper (1863–1920).

Even though VOCs are metabolically costly and may attract unwanted visitors such as herbivores, many plants produce an array of complex scent blends that often appeal to particular pollinators. We know little about how insects distinguish specific chemicals in these mixtures, but they are quite good at it. Their olfactory sensitivity has profound consequences: any tweak in floral chemistry can change completely the character of visitors. This was demonstrated experimentally by Shuttleworth & Johnson (2010) for pineapple lilies (genus Eucomis) from Africa. These plants are difficult to tell apart based on flower appearance: they all look alike with a greenish-white colour, and their nectar is comparable. But plants containing two sulphur components in their floral aroma are visited by carrion flies (families Calliphoridae, Muscidae and Sarcophagidae); those that do not are visited by spider wasps (family Pompilidae). And here’s the thing: the addition of these two chemicals to wasp-pollinated flowers provoked an immediate shift to fly pollinators: the ‘missing stink’ was found. This result suggests that a radical shift of pollinators is one short step away, with no need of sweeping changes in a plant’s other properties.

The autumn pineapple flower (E. autumnalis) is pollinated by spider wasps, which are replaced by carrion flies when flowers are laced with sulphur compounds © Ton RulkensBernard Dupont and Toby Hudson, respectively. Wikimedia Commons.

In South America, petunias (Petunia spp.) also comprise species with distinct pollinators. The large white petunia (P. axillaris) has white flowers with long, narrow tubes and produces abundant scent: this plant is pollinated by nocturnal hawk-moths. The rare, endemic and threatened P. exserta has a bright red corolla and no scent. As one would expect from a plant with colourful and scentless flowers, it is pollinated by hummingbirds. Klahre et al. (2011) observed that the ability to produce scent or not for these two petunias depends only on two genetic loci (specific positions on a chromosome). This relatively simple genetic characteristic suggests that loss or gain of odour properties – and therefore of pollinators, just like the pineapple lilies – can happen with relative ease, for example by hybridisation.

Large white petunias © Magnus Manske, and the endangered P. exserta © scott.zona, Wikimedia Commons.

Sometimes the plant itself takes care of changing its aromatic profile for the sake of self-defence. In the south-western United States, the flowers of coyote tobacco (Nicotiana attenuata) usually open at night (18:00-22:00 h) and release benzyl acetone. This chemical draws in the five-spotted hawk-moth (Manduca quinquemaculata) and the tobacco hawk-moth (M. sexta), who pollinate the flowers. But there’s a catch: the larvae of these moths feed on the plant, sometimes extensively. Kessler et al. (2010) noticed that high numbers of five-spotted hawk-moths induce the coyote tobacco to open its corollas between 06:00 and 10:00 h, and to reduce the production of benzyl acetone. Day-time flowers with a weak scent are no longer that attractive to hawk-moths, but they are fine for hummingbirds, especially the black-chinned hummingbird (Archilochus alexandri). Why then doesn’t the coyote tobacco stick to day-flowers and save energy by doing away with benzyl acetone? Probably because hawk-moths are better pollinators, since they are attracted to scent over large distances.  

A coyote tobacco with its trumpet-shaped flowers (ideal for long-tongued pollinators), a five-spotted hawkmoth and a male black-chinned hummingbird © DcrjsrMuséum de Toulouse and Mdf, respectively. Wikimedia Commons.

These observations and experiments highlight the importance of scent for pollination services, and the potential for radical changes in plant-insect relationships caused by apparently minute twists in floral chemistry. Nature takes care of these modifications, but geneticists have noticed the implied opportunities for plant selection.  

Benzyl acetone, the sweet smell of success ©Edgar181, Wikimedia Commons.