Heat punches

By Athayde Tonhasca

The recent record-breaking temperatures have been welcomed by many of us, deprived for so long of sunny beaches and bright skies abroad. Canadians and Americans, though, have been less thrilled by summer’s temperatures, which have reached life-threatening levels. And it’s not only the sizzling heat: wild fires, power failures, transport disruption and water shortages for people, livestock and crops have added to the summer misery of many in the northern hemisphere. Heat waves are one of the extreme climatic events that seem to have become more frequent, as predicted by those pesky climate scientists.

Heat waves are a growing risk to people, and to bumble bees too. For the last 10 years or so, researchers have noticed accentuated slumps in the numbers of bumble bees in several European countries following a heat wave – which happens when the daily maximum temperature is 5 °C higher than the average maximum for more than five consecutive days, as defined by the World Meteorological Organisation.

Areas of bumble bee scarcity following a heat wave © Rasmont & Iserbyt. 2012. Annales de la Société Entomologique de France 48: 275-28

Bumble bees are cold-adapted animals, and some species live comfortably in harsh alpine and arctic environments. This cold-hardiness is partially explained by their ability to generate internal heat: bumble bees cannot take off until their flight muscles reach 30oC: once they are airborne, their body temperature can go up to 40o C. This energy output may give the impression that bumble bees are heat resistant, but that is not the case. Internal heat is good, external heat is not. High air temperatures interfere with their metabolism, quickly leading to overheating and neuromuscular collapse (heat stupor). 

Unsurprisingly, species from colder habitats seem to be more sensitive to hot spells. And species that reproduce later in the season are also more affected by heat waves because these events tend to occur towards the end of summer. What are the implications of these observations for our bumble bees? Certainly a sombre outlook for species such as the great yellow bumble bee (Bombus distinguendus), Britain’s most endangered bumble bee. Once widespread, this species has been pushed to the northern fringes of Scotland, where it’s active between May and September. As a cold-adapted, late-nesting bumble bee, it could see heat waves added to its woes.

Average heat stress resistance, measured as time (min) before heat stupor, for bumble bee individuals across biotopes © Martinet et al. 2020. Conservation Biology DOI: 10.1111/cobi.13685

Most studies about the consequences of climate change have focused on the gradual increase in average temperatures, and the overall conclusion is that many plants and animals in the northern hemisphere are responding to a hotter world by expanding their ranges northwards and upwards (to higher elevations). However, bumble bees have not been very successful in tracking a changing climate; they tend to stay put, thus becoming increasingly exposed to the risks of heat stress and food shortages. The creation, protection and expansion of suitable habitats can improve species’ endurance and facilitate their escape to better areas, but these mitigation strategies will not be as effective against heat waves and other extreme climatic events. Intense and frequent temperature variations are immediate threats: species may not have enough time to move towards better climatic conditions.

People in Britain will have to adapt to a higher frequency of sizzling summers, destructive floods and paralysing snowstorms. And very possibly, become used to a different bumble bee fauna: some species may be squeezed out of their current area, heat-tolerant species such as the buff-tailed bumble bee (Bombus terrestris) may become much more abundant. The consequences of these changes to pollination services are impossible to predict. 

Although the damage of climate change to people and nature cannot be reversed, it can be contained. But time is running out.

The great yellow bumble bee, a species particularly vulnerable to heat waves © Arnstein Staverløkk/Norsk institutt for naturforskning, Wikipedia Creative Commons

The Thyme is right

When it comes to fragrance and the ability to attract bees you have to hand it to thyme.  One of our most popular herbs, it is both easy to grow and undemanding of space.  No wonder those who want to help pollinators love this little herb.

Herbs are a great option for those who can only have a window box or a container. Garden thyme in particular offers so much.  The leaves have a lovely scent, the flowers are vivid and draw pollinators in good numbers, and when it comes to cooking, it has long been on the top of the herb list. The leaves can be added fresh or dried in a range of dishes. 

When you dig into the reference books to find out more about thyme, you quickly discover that there are many varieties. It is reckoned that our garden thyme originated in the Mediterranean area, and it certainly seems to prosper in well-drained sites and low nutrient soils. 

We are fortunate to have a relative of garden thyme in Scotland. I’ve been seeing it whilst out on hill walks so our species must tolerate cold and wet Scottish winters. Like its garden relative our wild thyme is a magnet for pollinators.

The Greeks must have enjoyed the scent of burnt thyme as it found its way into their religious ceremonies. Indeed its name originates from ‘thymos’, which translates as ‘perfume’.  Others found alternative uses for thyme, for example placing it under pillows in the belief that it would help to fend off maladies ranging from the plague to bad dreams.

There are cultural associations in Scotland too. In some quarters, many moons ago, thyme was associated with fairies and it was viewed as bad luck to bring it into a house. A more pleasant association is found in folk music where the song ‘Wild Mountain Thyme’ has been popular for many years. Indeed in 1965 Joan Baez performed it in Edinburgh, as YouTube will testify.

Thyme is an important element of Scotland’s machair, and, as with many wild plants, cropped up in traditional remedies, such as for settling stomachs and warding off nightmares.  Unconfirmed reports suggested it had antiviral, antibiotic, antiseptic properties, which in this current era of widespread use of hand sanitiser strikes a highly topical note.  Finally, thyme extracts are in some quarters viewed as part of a ‘tonic’ that beekeepers can feed to their honey bees in spring to get them up to strength after a long hard winter.

When I’ve sat down to photograph thyme and watch the insects visiting it, I’ve been impressed by the range of pollinators, which include honey bees, various bumble bees, and solitary bees.

Many of our favourite herbs are great for pollinators.  Lavender, rosemary, borage, sage, fennel, marjoram, mint, chives … the list is endless. Thyme as a member of the Lamiaceae, or mint, family of plants is a worthy addition to that list.

The silent and lethal majority

By Athayde Tonhasca

If you were to stroll around this garden and estimate which insects are most abundant, you may come up with flies, or perhaps beetles. These two groups will indeed be well represented, but chances are they pale in comparison to some other insects you will struggle to even notice: parasitoid wasps.  

We tend to think of wasps as large, social insects like paper wasps and hornets. But the great majority of them are small, solitary (i.e., they don’t live in colonies) parasitoids. A female parasitoid lays her eggs inside or on the surface of a host; the eggs hatch and the developing larvae consume the host, eventually killing it. Like a parasite, a parasitoid requires a single host for its development; but like a predator, it ultimately kills the host.

Parasitoid wasps comprise groups such as Darwin wasps, aka ichneumons or ichneumonids (family Ichneumonidae), braconids (family Braconidae) and chalcids (superfamily Chalcidoidea). These names may sound strange and unfamiliar, and in fact these insects are poorly known. It is hard to tell species apart and few entomologists work with them; trickier still, many species are miniscule and easily overlooked. But parasitoid wasps are one of the most speciose and abundant components of terrestrial ecosystems. Here are some figures to give a proper perspective: it is believed that the 50,000 or so described species represent a small fraction of the total number (for comparison, birds and mammals are in the order of 10,000 and 5,000 species, respectively). Over 6,000 species have been recorded in Britain, which makes up about 25% of all insect species. In a suburban garden in Leicester alone, 455 species were collected in a two-year period.

At 0.15 mm, the parasitoid wasp Kikiki huna is the smallest flying insect. Its name comes from Hawaiian words meaning ‘tiny bit’. © Huber & Noyes, 2013. Journal of Hymenoptera Research 32: 17–44.

Inevitably, such dominance has important consequences. Parasitoid species – wasps and other groups such as flies – keep populations of their hosts under control. Some insects are attacked by 5 to 10 species of parasitoid wasps, so many of them can’t even make themselves noticed because of relentless pressure from their natural enemies. If unchecked by parasitoids, the numbers of some plant feeders would quickly grow to outbreak levels and become agriculture or forestry pests. 

A braconid wasp © Richard Bartz, Wikipedia Creative Commons

We have learned to tap into this biological control potential by rearing large numbers of parasitoid species and releasing them in fields and forests. In West Africa, the cassava mealybug (Phenacoccus manihoti) threatens the production of cassava, a vital staple food. The introduction of Anagyrus lopezi, a parasitoid wasp native to Central America, reduced pest populations by 80 to 90%.

Cocoons of the braconid wasp Glyptapantheles liparidis attached to a gypsy moth caterpillar (Lymantria dispar) © György Csóka, Wikipedia Creative Commons

Caterpillars are the main victims of parasitoid wasps, but bees are not immune to them. Chalcids are a particular headache for solitary bees: they invade bees’ nests and pierce the brood cell walls with their elongated ovipositors. The wasp stings and immobilises the bee larva, then lays her eggs inside the nest cavity. The wasp larvae hatch in one or two days and slowly devour the paralysed host. Monodontomerus spp., chalcid wasps whose big name belies their small size, can be a problem in artificial bee houses, which create unnaturally high concentrations of nests. In these situations, chalcid wasps reproduce quickly and can cause havoc among their hosts. Watch chalcid wasps in action.

Monodontomerus sp., a chalcid wasp © Robert Webster, Wikipedia Creative Commons

In the natural environment, bee mortality by wasp parasitoids is believed to be relatively low, perhaps around 1%. But these tiny creatures are there in the background, shaping the structure of whole insect communities and regulating plant-herbivore interactions. The consequences of this powerful instrument of population control on pollen and nectar production are not completely known, but certainly are not negligible. 

It’s good to talk

Local Authorities are essential to the implementation of the Pollinator Strategy for Scotland. This is good news, as many of them are enthusiastically carrying out pollinator-friendly work. So much so that last month we hosted an online conference to share experiences and learn about one or two challenges.

Scotland’s 32 local councils own about 81,000 acres between them. Their biodiversity officers know their estates well, and are adept at making changes and embedding practices that are good for nature and good for people. 

Below is a summary of what was said over 90 minutes worth of presentations.

Our very own Athayde Tonhasca set the scene with a look at pollinators and pollination with an emphasis on the most significant group – bees. Then, in quick succession, Lindsay Grant, Carol MacLean, and Louisa Maddison gave an insight into how Edinburgh, Glasgow, and South Lanarkshire Councils have made a mark for pollinators. In order to compare and contrast, Phil Sterling, the highly respected and much admired Butterfly Conservation officer from Dorset, and Philipp Unterweger, from Tubingen in Germany, closed proceedings with a view from beyond our own border.

Lindsay Grant, of Edinburgh Living Landscape, gave an insight into Edinburgh’s approaches and techniques to pollinator-friendly public spaces, with an emphasis on community engagement. He revealed how the capital city has gone about delivering a more pollinator-friendly vision. As part of the wider Edinburgh Living Landscape project, a range of approaches and techniques were applied to managing public spaces differently. The role of community engagement was strongly highlighted. Good dialogue can prove a powerful tool in transforming poor amenity grassland areas into something more biodiversity-friendly, especially as the early stages of this work can create an impression of abandonment.

The development of perennial meadows, reduced mowing regimes, use of spring bulbs, and native seeding ultimately proved popular with the public. Trickier was the realisation that, without intervention, perennial meadow areas could become overwhelmed by one or two dominant species. Lindsay spoke too about the required change in machinery and its impact on budgets. 

The mistakes weren’t glossed over, and these included the cutting of some Living Landscape sites, and an initial ‘historic calendar’ approach to mowing rather than ‘site specific’ cuttings. It was a frank look at the objectives, successes, and false steps. 

Carol MacLean, from Glasgow, built on Lindsay’s presentation with a view that having a Pollinator Plan, which dovetailed with the National Pollinator Strategy, had been a welcome move towards biodiversity objectives. Carol also stressed the value of having knowledgeable partners such as Bumblebee Conservation Trust, Buglife Scotland, and Butterfly Conservation involved.

Periodic ecological surveys were seen as essential for the long-term success of meadow creation. Through both a three-year bulb planting project and an ambitious tree planting programme, Carol was able to demonstrate impressive progress. Like Lindsay, Carol emphasised the role of communication and community involvement. The Health and Wellbeing agenda was also central to the works in Glasgow, and green and biodiverse corridors were part of what came over as a cohesive plan of action.

Louisa Maddison was keen to emphasise the value of collaboration and communications too. She rounded off the look at Scottish actions with a report from South Lanarkshire. 

The very title of ‘Pollinators and People Power’ was a taster of what was to come, for  the presentation covered the creation of meadows, thriving community parks, and liaison with community groups. As with Edinburgh and Glasgow, there was an acknowledgement of the role of environmental bodies, and one of the highlights was the role played in helping Buglife Scotland with their B-Lines project. 

Louisa also emphasised how important a few simple, yet explanatory, signs could be in converting the local communities to the value of changes in management practices. When the actions were explained, there was public support. Louisa set the scene nicely for Phil Sterling by ending her presentation with an image that looked at the vital practice of ‘cut and collect’.

Not many people will come away from a Phil Sterling presentation feeling anything other than bowled over by his enthusiasm, clarity, and experience. One of the most interesting elements of Phil’s talk was the realisation that over-zealous mowing is a carbon-related environmental impact as well as a biodiversity problem. He devoted a deal of time to his ‘cut and collect’ philosophy, which ensures low levels of soil nitrogen.  By carrying out repeated short-term cut and collecting in the initial stages, you can expect a huge dividend later, let alone cost savings from reduced mowing.  Phil added a plea to not move soil around needlessly out of habit with the fuel use this entails. 

It was left to Philipp Unterweger of Tubingen, Germany, to bring proceedings to a close with a video that demonstrated the environmental drive embedded in German culture. His talk began with a look at insect losses and a plea that insects should be seen as being more important than nurturing neat lawns and gardens. 

Philipp celebrated the work of students at the University of Tubingen in persuading the university authorities to transform swathes of lawn into flower-rich areas ripe for pollinators and insects in general. This model was rolled out in housing areas too, with considerable success. The paradox of enrichment, in that more nutrition results in lower biodiversity, was covered, as was the importance of communicating change. Indigenous plants and seeds, and taking care of existing meadows, also fell under Philipp’s spotlight.

The insect fix we need isn’t going to be an overnight job, but on the evidence of what we heard last month we are heading in the right direction.

Fungus therapy

By Athayde Tonhasca

About 12,000 years ago, mankind took a mighty leap forward by adopting agriculture; peoples in different parts of the world abandoned nomadic, hunting-gathering existences to take up farming and animal husbandry. Cities multiplied, populations grew dramatically, and civilizations flourished. Not bad for the bipedal primate Homo sapiens, but agriculture was already old news – in fact, at least 40 million years old – for some insects.

Agriculture, or the practice of producing crops, has long evolved as the way of life for about 80 species of leaf-cutter ants, 330 species of termites and 3,400 species of ambrosia beetles: these insects get their food by cultivating fungus gardens. Ants and termites collect plant material to provision their fungi, which convert the vegetable substrate into nitrogen-rich fungal biomass. Ambrosia beetle fungi extract nutrients directly from the host plant. These farming insects propagate and control the growth of their fungi, weed out contaminants and pests and take spores with them to start new colonies. And without their gardeners, these fungi quickly die.

Leaf-cutter queen and workers on their fungus garden © Christian R. Linder, Wikipedia Creative Commons

Recently, a bee was found to belong to this insects’ farming union: the South-American stingless bee Scaptotrigona depilis. Its larvae feed on a fungus in the genus Monascus, bits of which adult bees transfer between brood cells and take to newly founded nests. Without the fungus, few larvae survive. The need to eat a fungus seems puzzling because inside each brood cell, a larva floats in a pool of abundant, nourishing food. The reason appears to be protection rather than nutrition. The fungus may produce chemical compounds that defend the larvae and their food from harmful fungi and bacteria. Monascus fungi are used to preserve meat and fish in Southeast Asia because of their antibacterial and antifungal properties, so the hypothesis is plausible.

A. A Scaptotrigona depilis egg floating on the semi-liquid brood food; B. 1-day old larva: fungal mycelia growing from cell wall onto larval food; C. 3-day-old larva: dense fungal mycelia on cell wall © Menezes, C. et al. 2015. Current Biology 25: 2851-2855

These tropical fungus gourmets may seem of little relevance to our pollinators, but they suggest that cases of insect-fungus symbiosis – from the Greek syn (together) and biosis (living) – are more common and relevant than what we know. Some Aspergillus, Penicillium, Cladosporium and Rhizopus fungi protect the honey bee (Apis mellifera) against diseases such as chalkbrood and contribute to the fermentation of pollen to produce ‘bee bread’ (the main food of larvae and workers, comprising a mixture of pollen and honey). Fungi are known to produce chemicals that work against other fungi, bacteria and viruses. In fact, honey bees that feed on Fomes and Ganoderma mushrooms have reduced levels of infestations of some destructive viruses such as the deformed wing virus and the Lake Sinai virus. We have much less information on beneficial fungi in relation to other bee species. 

The stingless bee Scaptotrigona depilis © Cristiano Menezes, Agência FAPESP

Most bees nest and store nutrient-rich food underground, which makes them vulnerable to pathogens and parasites. Many of these bees – and the honey bee as well – are protected to some extent by gut microbiotas, and bacteria are the better known components of these symbiotic fauna. In time, we may find that fungi have a greater protective role than is currently recognized.

Enjoying a natural high

Beinn Eighe is Britain’s oldest National Nature Reserve. It’s also a vast site, covering in the region of 48 square kilometres. Rugged peaks, towering ridges and scree-covered slopes, along with swathes of ancient Scots pinewood, draw visitors year after year.  But now those who like the smaller things in life have an attraction they too can revel in – the Beinn Eighe pollinator trail. 

Increasingly some visitors happen upon Beinn Eighe NNR almost by accident. Often that’s thanks to the North Coast 500, which runs right past the front door at Beinn Eighe’s visitor centre, and what a fantastic visitor centre it is. The road outside the centre is as dramatic as any, rather like Les Corniche on the Côte d’Azur, South of France (which features in the classic film ‘To Catch a Thief’)  mesmerising scenery draws the eye irresistibly.

But whilst our eyes are accustomed to the big views and the grand scenery, the pollinator trail here aims to explain why the very little things in life matter deeply.

Our appreciation of the role of insects in the world is clearly ever increasing. There are plenty of them around Beinn Eighe, and the pollinator trail highlights some of them by tagging onto the Buzzard Trail which starts from right outside the popular visitor centre.

Mind you, that said, walkers, cyclists and motorists will actually spy their first pollinator sign before they have even settled, for it sits on the grass verge immediately outside the visitor centre. This is a wildflower patch that nestles in between the road, the large welcome sign and the centre.  Here the pollinator trail panel ‘Mow less, give more’ explains the benefit of the reduced mowing principle. 

Once you join the pollinator (or buzzard) trail you come quickly to a sign explaining the virtues of helping pollinators. On a lovely, even, path you are soon invited to consider hoverflies, and role of trees and shrubs in helping pollinators.  The information panels are housed in local wood and both sensitive to the special surroundings and easy on the eye.

As the trail meanders beneath the trees the role of deadwood in providing insects with hibernation, shelter and nesting opportunities is followed by a panel that takes a closer look at the early season value of willow as a food source for emerging insects in spring.

Up to this point the trail has been in calming woodland, but things get a bit more dramatic when a series of beautifully laid, and easy to negotiate, steps take the visitor higher up the reserve. When you emerge from the smell of pine trees it is fitting that you quickly come across a sign devoted to another Scottish icon – heather.

Visitors will surely enjoy a sign that celebrates this widespread plant and the chances are they will be equally captivated by the next panel which is intriguingly titled ‘The Hardy Highlander’. It takes a look at the blaeberry bumble bee, also known as the bilberry or mountain bumble bee. It’s a subject you can read more about on our blog.

As the trail gradually descends back into the woodland there is time for one more sign – devoted to the power of flowers. Having something pollinator-friendly in flower from early spring to autumn is crucial for emerging pollinators and those heading into hibernation. 

The trail went out at the start of April, when the primroses were in flower, but it wasn’t feeling very spring-like with snow on the ground. It will stay out over the summer and right through to the end of October, so there is still plenty of time to pay a visit, talk a walk around and pick up some interesting facts. If you are out visiting the pollinator trail be sure to take your camera and submit photos to the Beinn Eighe photo competition that is running over summer to celebrate Beinn Eighe’s 70th anniversary.

The aim of the trail is to raise awareness of species and habitats, and to encourage folk to go home with an idea or two on how they could improve their local patch for bees and other pollinators.

There is of course so much more to see at Beinn Eighe than the pollinator trail. The stunning Mountain Trail, the calming Woodland Trail, and the sheer pleasure of relaxing in such nature-rich surrounds are a fantastic way to spend time. But we are rather taken by reserve manager Doug’s excellent pollinator trail, and – returning our earlier Mediterranean analogy – it surely glitters as brightly as the jewels in ‘To Catch a Thief’.

Find out more about Beinn Eighe National Nature Reserve

Einstein’s bees, sound bites and vitamins

By Athayde Tonhasca

If you have been following the news about bees’ decline in the newspapers and social media, you’ve probably come across variations of this quote, attributed to Albert Einstein: “If the bee disappears from the surface of the earth, man would have no more than four years to live.” This insight from one of the greatest scientist who ever lived seems to corroborate another mantra: “one in every three bites of food we eat depends on bees”. So the message from these sound bites is clear and dire: bees’ extinction would lead to food shortages, widespread famine, and ultimately the extinction of mankind.

Considering the seriousness of the matter, we may feel a bit disappointed by Einstein’s vagueness: did he mean the honey bee alone as humanity’s saviour, or the other 20,000 or so known species as well? But don’t blame Einstein for this taxonomical oversight because the quote is a myth: he never said it. Which is not surprising, really; would it be reasonable to expect the man who revolutionized our understanding of space, time, gravity and the universe, to have the time and knowledge to lecture us about bees as well? Probably not. Could the eminent evolutionary biologist Richard Dawkins offer new insights about the Special Theory of Relativity? Probably not. Authority has boundaries, and experts generally know their limitations.

Einstein’s prophecy belongs to the extensive list of fake quotes attributed to him and the likes of Abraham Lincoln, Mark Twain and Winston Churchill. But at least we know that one of every three bites of food we eat depends on bees. Or do we?

The 1 to 3 ratio could be read as the amount of food we eat by weight or by volume, or the proportion of food items in our diet. The latter is the usual interpretation of the quote, which originated from a misinterpretation of a 1976 report by the American Department of Agriculture.

But here are the data. Nearly 90% of the world’s caloric intake comes from rice, maize, millet, barley, sweet potatoes, bananas, wheat, sorghum, rye, potatoes, cassava and coconut. Only the last crop may require some insect pollination. About 60% of global food production comes from crops that do not depend on animal pollination: they are wind-pollinated, self-pollinated or propagated asexually. 

But how about the number of food items? Around three-quarters of the world’s main crops benefit from animal pollination (insects, birds, bats, etc.). But ‘benefit from’ is a far cry from ‘depend on’; pollination is not an all-or-nothing scenario. Crops have diverse degrees of reliance on pollination (see figure), which does not necessarily reflect on yield, but sometimes on product quality or shelf life. Only about 12% of the main crops depend entirely on pollinators to produce the food we consume.

Level of dependence on animal pollination of the main crops produced in 200 countries. Data from Klein et al. 2007. Proc. R. Soc. B 274: 303-313

The ‘1 in 3’ formula ignores meat in our diet. It’s difficult to evaluate the contribution of pollination to meat production considering the range of animal species and production systems. But it is safe to say that the bulk of animal protein originates from plants that don’t need animal pollinators such as grass, maize, and soybean. 

The proportion of animal-pollinated food of course depends on cultural backgrounds, dietary preferences and economic status, but it is not likely to be that great. You can check it for yourself: make a list of non-meat items on your dinner plate and look it up as to whether they are pollination-dependent (you may exclude the pizza and fish & chips dinners).

None of the above undermines the importance of pollination. This ecological service is estimated to account for around 10% of the world’s annual agricultural output; we could expect losses of 5 to 8% in total crop production in the absence of animal pollination. In the EU, 15% of crop production involves pollination, which generates around 31% of the income from crops. These figures are far from inconsequential. And the importance of pollination stretches way beyond yields and income: nearly 90% of the world’s flowering plants require animal pollination, so the whole functioning of the planet is linked to pollinators.

Like any good sound bite, “one in three bites” is memorable and catchy; but as it is often the case with sound bites, it is unclear, inaccurate and simplistic. It also distracts us from pollination’s real contribution to food production, which is the quality of our diet.

Most of the vitamins A, C, and E we need come from animal-pollinated plants such as vegetables, nuts, seeds, and fruits. The same is true for a large portion of vital minerals such as calcium, fluoride and iron. A decline in pollination services would decrease the supplies of these crops, which inevitably would result in higher incidence of diet-related illnesses such as heart diseases, cancer and diabetes. Fewer animal-pollinated fruits and vegetables in our diet would also contribute to the ‘hidden hunger’, which is a form of malnutrition caused by a lack of vitamins and minerals in the diet. Close to 2 billion people worldwide suffer from ‘hidden hunger’; this figure could be brought down by the addition of minerals and vitamins to staple foods, and by protecting pollinators that provide this public health service for free.

The proportion of food production that is dependent on pollination for vitamin A (a) and iron (b) © Chaplin-Kramer et al. 2014. Proc. R. Soc. B 281: 20141799

Pollinators do not contribute significantly to our caloric necessities; the number of bites of food that depend on bees is relatively small. But these few bites are essential for our nutrition and consequently to our health. In a country where 1 in every 4 adults and 1 in every 5 children are estimated to be obese mostly because of poor diet and lack of exercise, reducing the number of bites we eat should be a national priority. But improving the quality of those bites is equally important, with more fruit, vegetables and nuts on our plates: here’s where pollinators make their greatest contribution to our wellbeing.

Sunshine on leaf

Living walls, or if you prefer green walls, are a great urban solution when horizontal space is tight.  By using the vertical options a great deal of space can be used to maximum effect.  And green walls deliver many benefits – they can insulate buildings, they can cool buildings down, they can remove polluting particles from the air, they are a boost for biodiversity, and being good to look at they improve our health and wellbeing whilst making areas more attractive.

However, they aren’t a plant and walk away solution, there is a maintenance commitment

We’ve certainly found that out at Battleby, where you might at first glance reckon we don’t need a living wall.  But hold fire.  What we have just outside Perth is a great demonstration site, and as we seek to tackle climate change and biodiversity loss the Battleby example gives a fascinating insight into one booming urban solution.

Now there have been a few challenges with our living wall. It hasn’t been all sweetness and light, there have been moments of anxiety and moments of bewilderment. So in the interest of helping others contemplating this journey here are a few of the challenges we have faced.

Water.  Now you wouldn’t think this would be a great problem in Scotland. But small pockets of plants need to be watered regularly. Our wall’s planted side faces roughly south, and it gets a lot of sunshine. And being a wall it isn’t always catching the prevailing drift of any rain. A drought is amplified by the small amount of soil involved, so care needs to be taken to avoid things drying out.  We thought we had this cracked with our water pipes running from the Battleby mains to the wall, controlled by a timer device dictating when watering began and stopped several times a day. “Simples”, I hear you say.

But there was a catch, this was all battery controlled. One hot Friday evening the batteries gave up, by the time we spotted this it was a few days later and the plants were stressed.  

On another occasion too much water was an issue. Our controller device sat beneath a manhole adjacent to the underground water pipes. Housed behind the Living Wall this all seemed very convenient and sensible. All went well for a couple of years and then we had a storm of near biblical proportions and the recess under the manhole was completely flooded – cue another timer issue, this time a fatal issue as the electronics, as well as the batteries, succumbed.

The solution was to relocate the timing device three or four feet off the ground in a metal, water-tight box. This meant getting the plumber in to reconfigure the piping.  The solution has worked well to date; we no longer have to peer down a hold to adjust the timer settings. And as Jim and I advance in years the delights of hanging upside down in a manhole recess won’t be missed!

Plants. We planted with the best intentions and good advice. However, nature is fickle. Some plants did well, some struggled, and some gave up the ghost after a year or so.  Almost three years in we elected to restock, basing our new selection on the proven experience of what had thrived and what had rather inconveniently failed.  Here’s what we added to our wall – geraniums, chives, water avens, yarrow, marjoram, lamium, tellima, orange hawkweed and red campion. Seeds of hardy annuals such as pot marigold & love-in-a-mist were added in May. Some of the great survivors have had the equivalent of a horticultural haircut, some have been moved lower down or higher up the wall.

The learning curve probably isn’t over, but with power, watering, and plants on a new course we should enjoy a few years without any headaches.  Now, how’s that for tempting fate?

Wave upon wave of colour

By Therese Alampo with images from Pauline Smith

The conditions at St Cyrus NNR make it an absolute haven for a diverse range of pollinators, and spring, summer and autumn are a fascinating time for anyone who wants to delve into the buzz and hum of this world.

The climate at St Cyrus NNR, low rainfall, the shelter from the cliffs and dunes create a unique microclimate which supports a breath-taking variety of flowering plants some found at their Northernmost limit or very uncharacteristic of the area.  These plants do a season round Mexican wave of colour and scent offering up a veritable smorgasbord of pollen and nectar to the invertebrates on the reserve.

Early in the season the pussy willow offer pollen for the big fat queen bumblebees to delve into, turning them into buzzing yellow powder puffs!  They have been in torpor all winter and emerge hungry and needing to find food and a nest site for their developing eggs and brood.

Then the hoverflies start arriving, across the sea from Continental Europe to join in the buzz, the mining, mason and leafcutter bees join in the party soon after.  

Then to the lepidoptera. We have over 500 species, many of which are important pollinators, the moths are my favourite and with names like Merville de jour, gold spangle and Hebrew character who could resist the intrigue.

These species are key to our survival on this planet, how lucky are we to see a slice of the planet so rich in pickings and them enjoying every bit of it.

When you step foot on the main path into the reserve you are confronted with a scruffy haven, just stopping and looking at the umbel (flower head) of cow parsley or sweet scicily on the way past offers up a comedic clutter of hover flies, soldier beetles, bumblebees and others all head down and bottoms up.

Even offering a little information about a few key pollinator species in the form of a simple pollinator trail helps to connect people to the importance of pollinators, and can spark so much interest!  Everyday we see people stopping to read the information on the short trail, capturing an audience that may just be on the way to the beach.  I love people’s reactions to the trail and the fascination, particularly to the wasp panel, “really, wasps are useful I never knew that”!

It’s complicated

By Athayde Tonhasca

Himalayan balsam (Impatiens glandulifera) was brought to the British Isles in 1839 as an addition to Kew Gardens’ collection of ornamental plants. As usually happens with introduced species, Himalayan balsam escaped into the wild, causing consternation ever since. It has spread throughout damp woodlands and along rivers, flourishing in thick stands up to 2 metres high that overshadow the local vegetation. This plant does well in a variety of climatic conditions and soil types, and has a tremendous capacity to spread.

So nobody likes Himalayan balsam. Nobody but pollinators.

Himalayan balsam © MurielBendel, Wikipedia Creative Commons
Himalayan balsam © MurielBendel, Wikipedia Creative Commons

This invasive is a nectar factory. Each flower produces about 0.5 mg of sugar per hour, a rate far higher than any European plant; flowers of most species yield less than 0.1 mg/h. And because the plant flowers late in the season, nectar it available at a time when other sources start to become scarce. So naturally, bumble bees, honey bees and wasps go for it with gusto. And there is something in store for hoverflies as well; they feed on the copious amounts of pollen produced by these flowers. Predictably, the number of bumble bees and other insects increase in areas invaded by Himalayan balsam. 

This abundance of food could have undesirable side effects. Many bees get the proteins, carbohydrates, lipids and amino acids they need from a variety of pollen sources. But thanks to the plentiful and readily available pollen from Himalayan balsam, bees stick to this easy option: in some situations, up to 90% of the pollen collected by honey bees comes from this plant, with unknown consequences to bees’ development and health. The profusion of pollen and nectar could also indirectly harm other plants: if native species receive fewer visitors, their pollination could be compromised. But the evidence for such outcomes is contradictory. Some studies suggest that Himalayan balsam reduces flower visitation and seed production of native plants; others have demonstrated no differences, or a ‘magnet effect’: Himalayan balsam attracted pollinators to itself and to plants nearby. 

A marmalade hoverfly (Episyrphus balteatus) and a common carder bee (Bombus pascuorum), two Himalayan balsam beneficiaries © Charles James Sharp (L) and André Karwath, Wikipedia Creative Commons
A marmalade hoverfly (Episyrphus balteatus) and a common carder bee (Bombus pascuorum), two Himalayan balsam beneficiaries © Charles James Sharp (L) and André Karwath, Wikipedia Creative Commons

Alien species are a hot and controversial topic among conservationists. Some highlight the damage caused by introduced species to the native fauna and flora, habitats, the economy and even human health. But other conservationists point out that alien species may have neutral or positive impacts: that is, they are alien but not necessarily invasive. The invasiveness of Himalayan balsam has been well documented, but there are mitigating factors in its favour: in some situations, this plant had no effect on local species composition, or at worst it only replaced a few ruderal species (plants that colonise areas that have been disturbed). And its presence may check the spread of harmful alternatives such as the giant hogweed (Heracleum mantegazzianum).

Assessing the impact of alien species is important because a great deal of money and resources have been spent on controlling or eradicating them, quite often unsuccessfully. It is usually assumed that invasive plants are bad for pollinators, but there isn’t much evidence to support this assumption. Like many aspects of species’ ecology, data are scarce, results are often contradictory, and generalisations are risky. In summary: it’s complicated.