Plants, people and pollinators

It is one of the most iconic, beautifully green, and superbly relaxing, of Edinburgh landmarks. Some 350 years old, and home to around 100,000 plants, 70 acres, 10 Glasshouses it is of course the capital’s famous Royal Botanic Garden (RBGE).  And it’s home to more than a handful of pollinators.

The famous Palm House in Edinburgh

I was speaking recently to Alex Davey, Science Policy and Impact Officer, about pollinator-friendly projects.

We had a lot of positive subjects to talk about.  Much of the RBGE’s pollinator-related work tends to be around actions to improve pollinator food sources and habitat, two of the key aims in the Pollinator Strategy for Scotland.

Arguably pride of place should go to the eight new meadows (each 10 x 50m) being planted as part of the Edinburgh Living Landscape project. These all incorporate pollinator-friendly plants, and provided new connectivity along what is a heavily developed stretch of Edinburgh’s coastline (one of the successful Biodiversity Challenge Fund bids).

It’s true that butterflies are not our most noted pollinators, but nevertheless they are a key part of our biodiversity, and where they thrive other pollinators often do well too. In a project designed to encourage the rare northern brown argus, the cultivation and translocation of common rock rose is being included in plots called ‘Square Metre for Butterflies’ (which is also an Edinburgh Living Landscape project). This initiative seeks to increase pollinator habitat in the urban environment through creating green roofs and is a fine example of how even in the midst of a thriving, busy, city it is possible to do something positive for pollinators.

On a related theme Alex revealed that there is a survey of green roofs in Edinburgh. These ‘gardens in the sky’ are an approach which acknowledges the role of roof top gardens which are more prevalent, and woven into the fabric of big cities, than we imagine (it’s just that they are not always easy to view). The survey is aiming to compare plant diversity with green roof structure and age, including the occurrence of pollinator food plants, and pollinator visits. This will provide guidance for future design and plantings to have the most impact for pollinator habitat.

There is considerable excitement too around an ongoing volunteer phenology-recording project. This dates back 170 years, documenting annual changes in the development of over 500 plants of 156 species across the RBGE’s own gardens. It helps highlight pollinator-impacting shifts in flowering time as a result of our changing climate. It’s good work and some of that data are incorporated into the International Phenological Gardens of Europe project.

Finally it is impossible to conjure up a visit to the RBGE in 2020 and not acknowledge the sensational ‘Pictorial Meadow’. As well as the annual meadow display bringing a rainbow of hope to visitors, and providing a nectar source for bees, it allows people to think about meadow landscapes. The sheer joy of being immersed in a meadow – surrounded by the fluttering of butterflies, chirping of crickets and the buzz of bees is increasingly rare. You can read a lot more about this fantastic approach on the RBGE website.

A stunning pictorial meadow to savour

For an organisation that began rather humbly with an area roughly the size of modern-day tennis court the RBGE has thrived. Their expertise is unrivalled, and that’s great news for plants, people and pollinators alike.

Serious series

Parliament has Hansard, cricket has Wisden. The world of Natural History has the New Naturalist. This fabulous nature series has strong links to Scotland, for it is wound up in the fortunes of Collins, which began as a printing firm in Glasgow long before evolving into an international publishing house.

The New Naturalist came into being as World War Two ended and has endured for many reasons.  The scientific rigour, the lovingly crafted texts, the often beautiful illustrations. It’s a luxurious smorgasbord of quality.

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First out of the blocks. in a series which now has well over 100 titles, was ‘Butterflies’, which hit the booksellers’ shelves in November 1945. It was an instant success.

With 48 colour illustrations it set a new benchmark for a book of this kind. The series appealed to the naturalist, the scientist, the student, and the book-lover alike. ‘Butterflies’ was an inspired choice as a ‘launch volume’ for the subject has an enduring appeal in Britain and it would be re-published four times – a remarkable testimony to quality.

With the splash made by ‘Butterflies’ the young series was up and running. It was a publishing sensation, and insects and pollination would feature more than once as the series evolved. Evidence came in 1947 when Volume 8 gave us the broad brush approach with ‘Insect Natural History’.

Nevertheless, it would be over 20 volumes later before insects were the focus once more, but when they were it was with another searing success. Book number 29 was titled ‘The World of the Honeybee’. Authored by Colin Butler, it was joined by ‘Moths’ in February 1955 – a mere nine months later. The former was admired widely for its content, the later meanwhile made an indelible mark with quite stunning cover artwork.

Volume 36 brought the eager readership ‘Insect Migration’ with an appeal that went well beyond Britain – and in the fullness of time the series would indeed be printed and published in other countries.

May 1959 was a high spot with the publication of ‘Bumblebees’. Again Colin Butler was involved, and once more the cover design earned plaudits all round. This aesthetic detail was by now a much-loved feature of the books, and the 1959 bumblebee wrapper was truly a classic.

Those with an interest in pollinators and pollination had to watch over a dozen volumes come and go before they got another which grabbed their specialist interest –  ‘The Pollination of Flowers’. Time had clicked on relentlessly, the series had endured some ups and downs, and the calendar registered that we were in April 1973.

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‘Ladybirds’, ‘The Natural History of Pollination’, and ‘Moths’ (again) all appeared as the series racked up volume number 90. Moths, Mark II, was a popular repeat in the series.  In March 2006 ‘Bumblebees’ too was given a makeover and the subject revisited under the expert care of Ted Benton.

The artwork of the series by this time had grown to be a popular and increasingly celebrated sideshow. Husband and wife team – Clifford and Rosemary Ellis – were the early stars behind the covers, and they handed over to the equally talented Robert Gillmor.  His artwork on ‘Bumblebees’ (Volume 98) is arguably the finest in the series – but I may be biased!

Gillmor was an astute observer of nature, sold his art for a living (illustrating several Royal Mail stamps), and knew too that some things connected better than others with the public, and certain subjects – such as bumblebees – were good sellers.  As he neatly put it “You’ve got to be very dedicated to buy a picture of a slug.”

Some of the New Naturalist titles are very hard to come by today, some are exceedingly expensive.  A quick search on the internet for some titles is enough to take the breath away. 

The series is explored in detail in this sumptuous volume

Recently an excellent coffee-table book was published exploring this iconic series in considerable detail. Every volume is religiously catalogued, with a small colour picture of the dust jacket for each title, and exhaustive publishing specifics.  There are biographies of all the authors, every artist and their designs, and some humorous tales from collectors of the series, include household names such as Alan Titchmarsh.

The Collins New Naturalist run remains probably the most influential natural history series ever published. And in a series that spans 70 years there is almost certainly something for everyone.

Drones, the derided and suffering warriors

By Athayde Tonhasca

As bad raps go, the one earned by male bees (drones) is hard to beat. Known as freeloading loafers whose single purpose in life is to mate, they have been called ‘flying sperm’, while the Germans have tagged them with the unflattering ‘lazy Willies’ nickname.

But drones deserve better. They do not help in stocking nectar or pollen, but are fundamental for the workings of a bee colony. In the case of honey bees, drones produce body heat that helps maintain the temperature of the hive. Honey bees do not overwinter, so thermogenesis (heat production) is a life or death matter for the colony. Because drones are bigger and chunkier than female workers, their contribution is disproportionately higher. As for bumble bees, their young drones appear to help care for the immature forms, including incubating pupae during their initial development. We don’t know much about the role of male bees because researchers have not given them the attention they deserve. Their reputation as secondary players in a bee colony certainly has not helped.

Whatever input honey bee drones may have in the functioning of a colony, all are dramatically and fatally surpassed when they reach sexual maturity and the moment of copulation arrives. On a warm and sunny day during the mating season, drones fly out of their nest and join other drones 10 to 40 m above ground. These clouds of bachelor bees can be thousands strong, and attract drones from hundreds of nests. After all nearby drones have been gathered, virgin queens leave their hives and join in. Love is in the air.

A honey bee drone © Waugsberg, Wikipedia Creative Commons.

Thanks to its big eyes, a drone spots a queen in the melee. It zeroes in and grabs her. Mating is completed in less than 5 seconds, during which the drone’s endophallus (a penis equivalent) is turned inside out into the queen and inflated by haemolymph (‘blood’) under high pressure. As haemolymph rushes into his endophallus, the drone loses control of his body and falls back, unable to move. Ejaculation happens at such speed and force that it can be heard by people as a ‘popping’ sound. 

Alas, these amorous moves will not end well for the lucky suitor. His endophallus breaks off, leaving its extremity inside the queen. The drone dies shortly after. However, his anatomical sacrifice does not guarantee sole paternity. Another drone may remove the piece of endophallus from the queen and mate with her, and the process may be repeated with up to 20 successive drones. 

A honey bee’s everted endophallus © Michael L. Smith, Wikipedia Creative Commons.

We know much less about the mating adventures of bumble bees, but in general they seem to be less melodramatic. Copulation may take up to 45 min, and for many species drones mate more than once before fading away and dying. Sexually mature bumble bee drones leave the nest for a vagabond life. If you have seen bumble bees clinging to flowers at night, sleeping, they are probably drones, who have no home to go to. 

Life has more misfortune in store for our drones. They have no father or sons, although they have a grandfather and grandsons. Such surreal family settings come about because of haplodiploidy. This tongue-twister refers to a reproductive system where females have two sets of chromosomes (just like us), but males have only one. After mating, a queen bee stores sperm in an internal sac called spermatheca. If she releases sperm as an egg passes down her oviduct, the egg is fertilized and generates a female with two sets of chromosomes. If no sperm is released from the spermatheca, the egg will produce a male with a single set of chromosomes inherited from the queen: there is no genetic input from daddy. Sex is determined in a similar way for all Hymenoptera (bees, ants, and wasps), Thysanoptera (thrips) and a few other insects.

The consequences of haplodiploidy are profound. For us humans, offspring share 50% of their genes with their mothers and 50% with their fathers, so siblings share on average 50% of their genetic material: (50% + 50%)/2. Female bees however share 50% of their mother’s genes, but all of their father’s. So they are related by (50%+100%)/2, which is 75%. You can find a detailed explanation of these calculations here. 

This 75% helps solving Darwin’s ‘one special difficulty’, stumbled upon when writing On the Origin of Species.Almost all bees, ants and wasps in a colony are sterile workers whose function is to gather food, protect the nest and help the queen lay eggs; they do not reproduce therefore are not subject to natural selection. How could these social insects evolve?

The answer to Darwin’s conundrum is kin selection: because sister bees are more related to each other than they are to the queen or any daughters they could have, it makes evolutionary sense to pass on their genes by helping their mother produce more sisters, rather than by reproducing themselves. The theory of kin selection involves self-sacrificial behaviour and altruism, including in Homo sapiens. So naturally, it has been controversial and debated for years.

It’s time to get back to our humble drones, who seem always to be lurking in the background, even though the survival and evolution of bees depend on them. In Henry V, Shakespeare vilified The lazy yawning drone. The bard, like many writers since, was too quick to judge.

Perfect for people, pollinators and plants

The coronavirus pandemic has highlighted the importance of quality green spaces and nature for our health. Since lockdown began it has been clear that gardening and spending time outdoors are exceptionally good for mental and physical well-being.

Ninewells Community Garden has long been an advocate of these activities. It lies in the stunning arboretum of Ninewells Hospital, Dundee and the emphasis in this one-acre garden is on promoting physical activity, and healthy living, through community gardening.  In such a magnificent environment it is perhaps no surprise that successful rehabilitation and therapy are often the welcome result.

The garden dates back to 2011, and is an accessible and sheltered haven in a hospital that opened in 1974. It’s free to use for patients, staff, community groups and the general public. Helena Simmons and June Imrie work closely together and are the only paid employees at the garden, sharing a post overseeing the work of a clutch of enthusiastic volunteers. Those volunteers are key to the garden’s success (as indeed are a wonderful Board of Trustees) and without them this remarkable garden simply couldn’t function.  

The work of so many enthusiasts is great news for people and pollinators. Have a look at the online images posted by volunteers and staff at Ninewells and you will see that pollinators are extremely well catered for here. 

Having spent time in the Ninewells Garden during a Butterfly Conservation identification workshop I saw first-hand the amazing array of plants provided for the insects that use this fabulous Tayside resource. But don’t just take my word for it. 

Helena explains some of the help the gardens have had in their quest to provide for people and pollinators, “We were lucky enough to be given wildflower seeds from “Seeds of Hope Scotland” through Bonny Dundee which we planted during lockdown to brighten up the area opposite the main garden gate. We also have been providing online workshops in collaboration with PLANT in Tayport, Strathkinness Community garden and Yellow Wellies Gardening. In the gardening for wildlife workshop emphasis was on the importance of providing habitat and food for the whole lifecycle of wildlife including pollinators.”

If you have a moment I’d thoroughly recommend Ninewells Garden’s blog on Gardening for Wildlife.

In a newsletter update for Keep Scotland Beautiful Helena reflected further on recent activity: “As always there has been lots going on in the garden — bees buzzing, birds feeding, squirrels jumping and a few more volunteers back to the garden each week. We are limiting the number of volunteers in the garden to a maximum of 5 at a time, with volunteers bringing their own drinks and snack and the indoor spaces are still closed. But despite these limitations, everyone is enjoying the time spent in the garden”

“We are still running the online workshops, keep an eye open on facebook @ https://www.facebook.com/ninewellsgarden/  for the next ones and catch up with the previous workshops. The garden is producing loads of courgettes just now, we’ve been able to give them to our volunteers, offer some for a donation and still have had enough to pass on our extra courgettes (nearly marrows) to the West End Community Fridge. 

“Pop into the garden on a Monday, Tuesday, Thursday or Friday to see what we have available by the plant stall or speak to a facilitator. There are also lots of plants available for a donation. If it’s flowers you are after, one of our Trustees has kindly been bringing us sweet peas tied in bunches and will continue to do so on a Monday as long as the sweet peas keep on flowering.”

For the moment things aren’t running along normal lines for the Community Garden. Sadly the quirky leaf-shaped, eco-friendly visitor centre, a particular highlight, is out of bounds.  But despite the loss of that architectural gem (and the cosy fire and tea breaks it hosted) there is still a warm welcome awaiting.

The Garden accepts referrals from GPs and occupational therapists and is increasingly providing support to more conventional treatments. That’s a key element of the good work here, for it is one thing to acknowledge that gardening is good for people, but in doing so the necessary follow up is to have space where people can actually garden. The Community Garden fills that need.

Nobody knows for sure where Covid-19 will take us. However, one thing we can be sure of is that the pandemic has created a new appreciation of the power and value of good greenspaces, of being in nature, and the power of growing.  In 2011 The British Medical Association emphasised their belief that good hospital design should recognise the important therapeutic role of gardens. A clear case of a ‘natural health service’ backing our cherished National Health Service.

The team at Ninewells Community Garden have recognised nature’s healing benefits all along, and their tireless efforts are a welcome boost in challenging times.

40% to Insect Armageddon

By Athayde Tonhasca

Last year The Guardian featured on its front page an academic study claiming that insect numbers are declining at disastrous rates, such that over 40 per cent of the world’s species are threatened with extinction. The piece was picked up and disseminated widely by other outlets, and its reverberations have not abated. As pollination, nutrient cycling, decomposition, food chains and other vital processes are largely dependent on insects and other invertebrates, we must conclude an ecological catastrophe is imminent.

Except that ‘Insectageddon’ is not supported by evidence.

The report comprised a review of 73 studies of insect decline. It was described as a ‘comprehensive review from across the globe’, but the paper was almost exclusively focused on Europe; there were three studies from the Tropics, where the World’s entomofauna is heavily concentrated. In reality, the review covered taxonomic groups already known to be at risk. More troublingly, studies demonstrating stable or growing insect numbers, of which there are many examples, were not included.

There are about 1.3 million described species of insect, but the true number is believed to be much higher; estimates vary from 5 to 10 million, or more. We know virtually nothing about the overwhelming majority. The miniscule and biased selection of examples included in the report simply does not provide evidence for a global decline in insects.

The report also claimed that a third of insect species are endangered. These figures were based on the International Union for Conservation of Nature (IUCN) ‘red lists’. However, fewer than 8,000 species have been assessed (~.05% of the known fauna), and these evaluations understandably focus on species known to be under threat. And yet the authors stated ‘more than 40% of insect species are declining and a third are endangered’.

Human activities are definitely affecting some species and taxonomic groups: habitat loss, agricultural intensification, urbanisation and pesticides are the main culprits of these insect losses. But this is a far cry from concluding that insects as a whole are on the path to extinction in a few decades.

Manu Saunders, from the University of New England, Australia, offered this analysis: ‘From a scientific perspective, there is so much wrong with the paper, it really shouldn’t have been published in its current form: the biased search method, the cherry-picked studies, the absence of any real quantitative data to back up the bizarre 40% extinction rate that appears in the abstract (we don’t even have population data for 40% of the world’s insect species), and the errors in the reference list. And it was presented as a ‘comprehensive review’ and a ‘meta-analysis’, even though it is neither.’

Similar criticisms about the report’s methodological flaws and conclusions have been reiterated in the academic literature, but largely ignored by the press. The misleading, unproven and sensationalist claims continue to be parroted, including by people who should know better.

Fake news rushing to the press by Frederick Burr Opper, 1894. Image in the public domain.

In the age of fake news, climate change denialism, anti-vax movements and Chloroquine pills, we need to be particularly protective of scientific evidence. Overstating findings to entice support is counter-productive, because exaggerations and deceptive conclusions sooner or later will come to light. But then public trust will be eroded, thus undermining efforts to address true conservation problems and priorities.

May the Force be with the bee

By Athayde Tonhasca

If we are asked how a bee finds a flower, we think of smells, colours, shapes and textures. These are important sensory signals, but there is another one whose relevance is just beginning to be understood: electricity.

It has long been known that the platypus, some fish and amphibians, as well as some ants, cockroaches, mosquitoes and fruit flies have the ability to detect external electric forces. However, vertebrates need water as a conductive medium, while most insects respond only to unusually strong electric fields such as those generated by high voltage power lines. Bumble bees however have a sparking story to tell. 

We do not notice it, but our planet is an immense electrical circuit. On a calm day, the air is positively charged, while the ground surface has a negative charge. Now and then the equilibrium of charges is disturbed by lightning bolts or a minor shock from a car door, reminding us we are surrounded by electricity.

The negative charges accumulated on the planet’s surface extend to any object connected to the ground, plants included. So flowers have a slight negative charge in relation to the air around them. As a bee buzzes along in search of food, electrons are stripped off its body by friction with the air, leaving the bee positively charged. When the bee lands on a flower, some of the negatively charged pollen grains stick to the bee, sometimes jumping from the flower even before the bee makes contact. So electrostatic forces are a great aid to pollination.

An electrifying encounter: a positively charged bee approaches a negatively charged flower. Images in the public domain.

Pollen clinging to a sweat bee. © Pixabay.

But flower power reaches shocking levels for the buff-tailed bumble bee (Bombus terrestris), and probably for other bumble bees as well: they are able to sense the weak electric field around a flower. No one knows exactly how they do it, but mechanoreceptive hairs must be involved. These special hairs are innervated at their base, so they detect mechanical stimuli such as air movement and low frequency sounds. Apparently, the flower’s electrical field moves the mechanoreceptive hairs of an approaching bee, similar to the way a rubbed balloon makes your hair stand on end. This hair movement is processed by the bee’s central nervous system and gives information about the shape of the electric field. It is as if the bee ‘sees’ the flower’s electrical aura. 

Bumble bees’ hairs provide thermal insulation, collect pollen and help bees sense air motion, sounds and electricity. ©Kevin Mackenzie, University of Aberdeen. Attribution 4.0 International (CC BY 4.0).

But bumble bees’ capacity to detect electric forces may go beyond recognising flowers’ sizes and shapes: they could use the information to maximise foraging trips. Once a positively charged bee lands, the flower’s electric field changes and remains changed for about two minutes after the bee leaves. Researchers believe that an altered field warns the next bee that the flower is temporarily depleted of nectar; it’s like turning off a ‘we are open’ neon sign. So the next bee may as well buzz off to another flower with sufficient negative charges and a decent volume of nectar. 

Bees and other insects detect ultraviolet and polarized light, and use magnetic fields for navigation. Sensing electricity is one more way their world is experienced radically differently from ours.

How to sow a wildflower meadow

We dip into the archives today and go back two years when we carried an article on how to sow a wildflower meadow.  In his guest blog, John Frater, of Scotland’s Rural College, summarised a talk he gave at the InverclydeBuzz conference in July 2018 looking at creating wildflower meadows.

If the following basic principles are grasped then you could be looking forward to a lovely meadow. It’s not rocket science, it just needs careful planning and of course maintenance.

Site Analysis: There are various kinds of wildflower meadow. Is it wet, dry, lowland, upland, acidic or basic.. etc? Some sites can be a combination of several of these. Walk over your site and look out for wet depressions, or areas where it is particularly dry, or the soils are particularly thin. Establish the pH of the soil and how fertile it is. Once you have a good sense of the conditions on the site you are more likely to select species for your meadow that will thrive there.

There are generic ‘wildflower meadow’ seed mixes on the market but I’d avoid these. There is a large proportion of grasses (often 80%) in these mixtures and the species in them are not selected to suit your conditions. However, where a mixture is sold as ‘wet meadow mix’, or ‘clay soil meadow mix’ then you are on safer ground. If budget allows I would recommend sowing a mix that is 100% wildflowers — this assumes that grasses will find their own way in eventually. Doing this ensures a higher establishment rate of the forbs (grasses germinate faster and earlier).

Composing the Seed Mix: It is possible to design your own mixture. This does involve a bit of maths and a spreadsheet! It’s not that grim really – if you take a look at the wonderful new book, by James Hitchmough of Sheffield University, ‘Sowing Beauty’ you will be guided through the steps: https://www.goodreads.com/book/show/30754004-sowing-beauty

Design Tips: There are some design principles worth bearing in mind as well. Firstly, the simplest and most important of these is to do with the relative amounts of plants from different height categories. A good looking meadow has a variety of structure – rather than just being a flat topped expanse. Below is a good rule of thumb when thinking about structural variety:

1. Tall ‘emergent’ species.(900-1500+mm)
2. Medium height species. (300-600mm)
3. Low growing species. (50-200mm)
4. 5-15% emergent species.
5. 30-40% medium height species.
6. 50% low and ground cover species.

Secondly, you want some variety over time. Often meadows in nature have flowering combinations that come in waves. Two or three species flowering at any one time, followed by another two of three species. So think about the flowering times of the species you select to ensure a spread over as long a season as possible.

Site Preparation and Sowing: The crucial thing here is to clear the site of all perennial weeds. This means either spraying with herbicide, or scraping off the existing vegetation. If perennial plants are left in the soil (perhaps just ploughed in, for example) then they will quickly cover the site again and prevent the germination of your seeds.

Some cultivation is required – approximately 25mm deep is sufficient unless there is known to be a lot of compaction. With a reasonable tilth cultivated you are ready to sow. Your seeds need to be mixed with a ‘carrier’ such as moist sawdust. You’ll need 2 handfuls of sawdust per square meter. Mix thoroughly the seeds with the sawdust. Then walk in rows giving each square meter a handful of the seed/sawdust mixture. Once the whole area is covered repeat but this time walking in rows at 90 degrees from the original rows. Once the seeds are broadcast, rake with a wooden pegged rake and then roll the surface.

Maintenance: Essentially this involves establishing a cutting regime that will have the effect of controlling the vigour of the grasses. Grasses left unchecked will gradually edge out the forbs. The following gives a general idea of what to do:

There has to be one summer ‘hay cut’ in late July or early August at the latest (to 40-75mm).

• This removes nutrients from the site – steadily reducing fertility (over many years).
• Doing this main cut in sections over several weeks on a large site helps support diversity.
• Then cut throughout the winter. On a fertile site you might cut it 4 more times.
• However, leaving small patches to stand all winter is valuable for over wintering insects.
• One cut in spring – some time in April – will take out the first flush of the grass growth and make space for the forbs – which are usually slower into growth than the grasses.

Scotia Seeds are a well established Scottish producer with a variety of mixes to choose from.

Emorsgate Seeds are a good source for seeds and further information.