The useful interloper

By Athayde Tonhasca

Among the world’s myriad natural habitats, mangroves are not likely to be voted the most beautiful or inspiring. Mangrove forests consist mostly of monotonous swathes of twisted, stunted-looking trees with exposed roots that grow on harsh, muddy, hot shores of tropical and subtropical regions. Mangrove species thrive in these places because they are not put off by oxygen-starved, waterlogged mud; and they are halophytes, that is, adapted to saline or brackish water, conditions that would kill most plants.

A mangrove forest © Leon petrosyan, Wikimedia Commons.

Although mature mangrove plants don’t mind too little oxygen and too much salt, their seedlings would die or develop poorly is such environment. To get around the problems caused by inhospitable nurseries, mangrove species adopted the form of reproduction found in mammals, some reptiles and a few fishes: vivipary, which is embryo development inside the mother’s body. In the case of plants, the seeds germinate and develop into seedlings while still attached to the parent tree, which supplies water and nutrients to its offspring. When the seedlings – called propagules – are sufficiently mature, they drop and take root near the parent tree or float away with the tides to establish somewhere else. You can follow the amazing life cycle of the red mangrove (Rhizophora mangle).

Red mangrove cigar-shaped propagules about to drop into muddy waters © Katja Schulz, Wikimedia Commons.

You may not choose mangroves for a picnic or camping site, but their value should not be underestimated. By hugging the coast, mangroves are barriers against waves, forming a line of defence of increasing importance as the changing climate makes storms and flood surges more frequent and severe (watch a simulation of how mangrove forests protect the shoreline). Their dense, labyrinthine roots filter and purify the water, at the same time creating sediment deposits that reduce coastal erosion. Mangrove roots also act as nurseries for a large number of marine species, many of them vital sources of protein for low-income communities. These apparently impenetrable forests are safe havens for hundreds of plant and animal species, some of them rare and threatened. Although confined to warmer regions, mangroves have a global importance, especially because they absorb and store more carbon than tropical rainforests. Despite their value, mangroves are one of the most threatened habitats on the planet, encroached by coastal development and seafood farms.

Global distribution of mangrove forests © Pinpin, Wikimedia Commons.

Some mangrove species are pollinated by the wind or bats, but most require insects. Bees, ants, flies and butterflies have been identified as potential pollinators in different mangrove regions, but we have a poor understanding of these interactions – with at least one exception:  the European honey bee (Apis mellifera) has proven its credentials as an effective mangrove pollinator. 

The grey mangrove or white mangrove (Avicennia marina) is distributed throughout Africa and south-east Asia, and is the most common and widespread mangrove species found along the Australian coast. Dozens of insects visit this plant, but only the European honey bee has been shown to remove pollen from a flower and deposit it on another one (Hermansen et al., 2013), which are the necessary steps for plant fertilisation. This industriousness created a conundrum for Australian conservationists and policy makers.

Grey mangrove. Native Australians and European settlers use its light but strong wood for construction and boat building © Kahuroa, Wikimedia Commons.

Since its introduction to Australia in the 1800s, the European honey bee has made good use of the country’s favourable climate and extensive areas of native vegetation: it spread out quickly and widely. The bee’s seamless adaptation to its new habitat has created a bonanza for the thousands-strong Australian beekeepers, and for countless farmers who benefit from an efficient and reliable pollination service. But not all was well. 

Trees are the European honey bee’ ancestral habitats; before they became intensively bred and managed, honey bees nested in tree holes and collected pollen and nectar from tree canopies. When swarms escaped into the Australian wilderness, they readily went native by moving into tree cavities and ejecting – and sometimes killing – local residents like cockatoos, parrots, kingfishers, opossums and bats (Western Australia Museum). Feral European honey bees may also outcompete the 2,000 or so native bee species for food and nesting sites, and help spread weeds, pests and diseases. These impacts have been reported elsewhere, but in Australia the data are incomplete or inconsistent (Prendergast et al., 2022). The best we can say is that the interloper may interfere with a flora and fauna that have evolved together for millions of years.

European honey bees help sustain populations of grey mangrove in Australia, with substantial economic and ecological benefits; but these latecomers to the Aussie scene may also disrupt other species interactions and processes. Such dilemmas and uncertainties are nothing new in conservation: only hard work and good data can help us learn which way the balance tilts.

Grey mangrove flowers are irresistible to European honey bees © Dave Britton, Australian Museum

Shetland shines

One of the first naturalists to capture my imagination was Bobby Tulloch of Shetland. His tales of otters and snowy owls captivated me, and brought a touch of the northern isles and ‘simmer dim’ into my New Town home in East Kilbride. Tulloch was, to borrow a good old Scottish phrase, a ‘Lad o’ Pairts’, an all-rounder, and his photographs of flowers and ferns suggests he probably had a keen eye for the less obvious and smaller species like pollinators.

A road verge managed for visibility and wildlife. Image courtesy of http://www.austintaylorphotography.com

Few of the actions that help pollinators embrace glitz or glamour. Often the actions that deliver most are cheap and easy, requiring minimal investment. Indeed, in many instances it is simply to manage things differently, to ease back a little, that makes a telling difference. 

Shetland Islands Council has taken a leaf from that book and introduced a few measures which give nature a helping hand.  For example, they have amended their roadside verge cutting policy.  This means verges are often only being cut for safety reasons, for example in visibility splays, at junctions, and where pedestrians require access to the verge so as they can easily step off the road to avoid approaching traffic. It’s a sensible and pragmatic approach.

Another welcome development is very much ‘on the money’ in terms of modern environmental actions. Shetland Islands Council has begun to replace some conventional street lighting with LED equivalents. This has brought a new look to many lamp-posts around Shetland. The new ‘down lighters’ are not only fantastic when it comes to reducing light pollution, but by being deliberately dimmed after midnight they deliver a further aid to local wildlife, especially night-flying pollinators such as moths. This sympathetic action adds a whole new meaning to ‘northern lights’.

Across Scotland altering mowing regimes on public greenspaces is an action that many councils are embracing. In Shetland this has caught hold too, with some large areas of grass, which were previously cut several times during summer months, now being left to grow naturally. It’s another rather simple, basic step, but one which is potentially a fantastic boost for biodiversity. In places the only cutting is beside footpaths, with a narrow edge strip being the only intervention needed. This leaves an extended area that was previously cut on a regular cycle, undisturbed for wild birds, insects and small mammals.

A bumblebee feeding. (c) Austin Taylor

Lerwick is Shetland’s largest community. Just over 7,000 people live in the town and they will have noticed the changes made at Jubilee Flower Park.  Originally waste ground, the park was created by the council in the early 1950s and rapidly became a popular spot. The Council has recently adopted a policy in the park of no chemical use when it comes to eradicating weeds. Instead, these are manually removed by hand and the park is rapidly becoming a sanctuary for wildlife. And that’s not the only change that has been eased in. Around the perimeter of the park, walls and fences are being used for growing a wide variety of climbing plants, which of course will provide shelter and a food source for invertebrates and birds.  On a windy island the walls are much appreciated, by people and nature.

Many will be familiar with the vibrant wildflowers that pepper Shetland, such as red campion and pink sea thrift. When it comes to gardening, however, the challenge is considerable. Yet to visit Jubilee Flower Park is to wander into a scene framed by a range of impressive plants. From elder, hebe and flowering currant, through to lupins, oxeye daisy and poppies there is floral variety that bees and other pollinators will eagerly exploit. 

There is a sense that Shetland is at the start of its pollinator journey, and the actions of today will hopefully be bolstered by increasing steps to help pollinators. With further improvements and refinements the picture should look increasingly rosy.

The Shetland Isles are rightly famed as a nature haven. Understandably there is a big focus on the fantastic bird life, the thrilling marine wildlife, but there is much more besides. Shetland Islands Council is doing its bit to help pollinators in what can be a testing environment. I’m pretty sure Bobby Tulloch would have approved of their efforts. 

Links:

Insects of the Shetland Isles

The bumblebees of Bressay

Crumbling, dusty, ugly – and valuable

By Athayde Tonhasca

‘Picture to yourself everlasting bleak sand dunes with no buildings. Only rabbits find a little nourishment here; they eat a substance which quite unjustifiably goes by the name of grass. It is a sand desert where the wind always blows often howls filling the ears with sand. Between us and America, there is nothing but water a sea whose mighty waves are always raging and foaming. Now you will have some idea of the place where I am living. Without work the place would be intolerable.’  

Thus Alfred Nobel (1833-1896) – of Nobel Prize fame – described to his brother the Ardeer peninsula, the Scottish site chosen to host his British Dynamite Company in 1871. The Scottish tourism board might have looked askance at Nobel’s verdict, but Ardeer was the ideal place for the manufacture of temperamental products such as dynamite and gelignite (blasting gelatine). The peninsula was relatively isolated from skittish neighbours, yet fairly close to Glasgow ports. As a bonus, the site was covered with dunes, which were an abundant source of building material for blast walls that protected life and property against accidental explosions. 

The tip of Ardeer peninsula © Largsnaturalist, Wikimedia Commons.

By 1902, Nobel’s explosives factory was the largest in the world. Manufacture shifted to other products after the plant became part of Imperial Chemical Industries (ICI) in 1926, but production started to dwindle. By the 1980s, most operations ceased:  Ardeer train station, the dining hall, engine houses, boilers, warehouses and countless other buildings were abandoned: a large portion of the Ardeer Peninsula had become derelict. 

Today, a visitor to the once mighty Nobel Enterprises site will find crumbling sheds covered by graffiti and half swallowed by the sand, tracks of weedy tarmac, rusty pipes and barbed wire, and pieces of broken equipment scattered everywhere. Such a place definitely would not qualify as a beauty spot. But these eerie remnants have a significant ecological value.

The remains of Ardeer railway station platform © Dreamer84, Wikipedia.

Land that has been previously built on or developed such as the Nobel factory is classed as a brownfield site – as opposed to greenfield sites, which are land that has never been developed. Some brownfield sites are inhospitable places, layered with tarmac or concrete, and often contaminated with toxic chemicals. But many of these areas are not hazardous; quite the opposite. They are usually populated by patchy, thin vegetation (sometimes because of poor soils and lack of water) comprising weeds, grass and scrub; the landscape is a mixture of bare ground, temporary pools, scattered logs, stones or rubble. These post-industrial sites, old quarries, disused open mines, spoil heaps, gravel pits, and other abandoned enterprises may look like the settings of a Mad Max film, but they are great opportunities for pioneer species – those first to colonize a newly created environment. Ecologically, open ground areas function as habitats in the initial stages of succession – that is, on the way to becoming closed-canopy forests.

Abandonment kick-starts ecological succession, beginning with pioneer species and ending with an old-growth forest © Joshfn, Wikimedia Commons.

Many species benefit enormously from these semi-open spaces that are not yet taken over by strong, dominant competitors. Pollinating insects in particular have at their disposal sunny spots for basking, a variety of wildflowers for nectar- and pollen-feeding, patches of bare ground for nesting, and some solid, sheltered structure such a pile of rubble for hibernation. They have it all. Even better, these sites are mostly free from human interference – people tend to avoid them. Evolving brownfield sites have their own special name: open mosaic habitats. They are sufficiently valuable to biodiversity to be considered a category of UK priority habitats. 

A typical open mosaic habitat © Richard Croft, Wikimedia Commons.

Ardeer is an exemplar evidence of the value of open mosaic habitats. It harbours the most diverse assemblage of bees and wasps in Scotland: 113 species, including many scarce ones such as the northern colletes (Colletes floralis) and the coastal leafcutter bee (Megachile maritima). Beetles, moths and butterflies are also richly represented (Philip et al., 2020).

The hairy-saddled colletes (Colletes fodiens) is common in southern Britain, but with only two records in Scotland, one of them in Ardeer. This bee is considered vulnerable in continental Europe (European Red List of bees, 2015) © Rick Geling, Wikimedia Commons. 

By their very nature as successional habitats, brownfields are ephemeral; in 15-20 years, they are likely to be overtaken by scrub and eventually become woodland. They may not even last that long, as they are prime targets for makeovers; Ardeer itself is being considered to become a housing development, a golf course, a marina, a wind farm, or even a site for a nuclear fusion reactor. The limited aesthetic appeal of brownfields induces few objections to their re-development. But considering their value for biodiversity, their keeping and management to retain their successional nature are equally valid options for their future.

Derelict sites: dumping grounds, eyesores, a waste of space – and hotspots of biodiversity © Graham Horn, Wikimedia Commons.

Travelling into a green future

We know more than ever about how to help pollinators. Sure, there is still much to learn, concerns about the speed of change linger, but when it comes to pollinator-friendly actions we have a bank of informed and successful actions we can implement here and now.  Around Scotland’s transport network, old and new, confidence in adopting pollinator-friendly actions is taking hold.

Speaking to Nicole Tyson, Sustainability Manager, at ScotRail you get a sense that our national rail provider has met the challenge head on.  Scotrail Station Adopters have used packs of wildflower seeds (many provided by NatureScot) to improve the options for pollinator around their stations. As commuters stream in and out of stations they will increasingly catch a glimpse of pollinator-friendly steps being taken. These come in many guises, from reduced mowing regimes, and signage to explain the benefits of changes, through to banks of flower-festooned containers … these are all good news in the battle to help our hard-pressed insects. 

At stations such as Kelvindale they have taken advantage of the proximity of Dawsholm Park to improve options for insects, the installation of bee hotels near to a newly sown wildflower meadow being a fine example of trying to build a suite of actions. That juxtaposition of food and nesting sites is a sound idea and all part of the strategy to increase biodiversity across their estate. Around Pollokshaws West the removal of invasive non-native plants has been gathering apace. And at Pollokshaws, adjacent to the popular Pollok Country Park there is a feeling that another push could result in making connections that would create an extended resource for pollinators.

Speaking of connections, working with local schoolchildren is another goal at Scotrail has, and this is taking shape in helping to facilitate STEM sessions (STEM being sciences, technologies, engineering and mathematics subjects). Nature is arguably the greatest adventure playground of them all, and combining fun with learning about pollinators is an investment in our future.

Monitoring too is something that ScotRail have increasingly grasped. A recent deadwood survey, carried out with help from TCV, being a shining example.  

It’s a similarly impressive picture over at Scottish Canals.  If you have followed NatureScot’s Green Infrastructure Fund you will know that around Canal and North Gateway in Glasgow a raft of biodiversity advances have been made.  

I remember being introduced to Robert Alston, one of the driving forces in the local community, and he told me “Nature is coming back onto this site. When the initial works here were carried out we had to remove about 300 trees, but we’ve since replaced them with more than double that number, and we are going to plant more. We’ve surveyed the wildlife living here, and we’ve got deer, a range of interesting birds such as coot, moorhen, swans, heron, sparrowhawk, jays, as well as rabbits and foxes as well as various insects. In an urban context these are great for people to enjoy, and we get a sense that we have really made space for nature.  I’m particularly proud of the trees. Not only were they planted by local communities, we had the local school and nursery come and help us. That’s the way of it, and now anything we do we aim to get the local community to help us.”

But that’s just one element of a wider picture that Olivia Lassiere, Environment Manager at Scottish Canals, can proudly point to.

“Enhancement of the canal network has increasingly seen the management of vegetation to favour pollinators,” she explains. “Changes implement include the creation of wildflower-rich grasslands alongside the towpaths, and the planting and filling out of hedgerows and orchards.”

Around lowland canals visitors will have noticed that the towpath-side meadows aren’t planted and forgotten, they are supported through pollinator-friendly revised mowing regimes. There is also an aesthetic element to work around some of Scottish Canals’ network in the Central Belt which will improve pollinator provision and the look and quality of sites. That latter direction is important as it improves sites for people and contributes to growing demands for better, more attractive, neighbourhoods and increased access to nature.

In Inverness there has been a burst of activity on the banks of the Caledonian Canal. Native hedgerow and wildflower planting has complemented the grounds of the recently completed, and architecturally impressive, Treehouse community centre. Low-intensity mowing regimes to favour pollinators are increasingly a feature of canal path management on the canal banks stretching out from Inverness.

Meanwhile in Argyll users of the Crinan Canal will have been impressed by a new mowing regime which deliberately favours wildflowers. Amongst the success stories here is recognition of how to better protect a wide variety of orchids, and adapt mowing practices to better provide food plants for the local marsh fritillary population.

All of the above suggests that we are making great strides around our transport corridors to make better green corridors and larger nature networks. ScotRail and Scottish Canals are skilfully showcasing the many things we can do to help wildlife. Good news all round for our pollinators.

Find out more:

ScotRail’s Adopt a Station

Scottish Canals Heritage and Environment

Mining their own business

By Athayde Tonhasca

With a girth (Equatorial circumference) of over 40,000 km and a land mass of more than 148 million square kilometres (29% of the total; the remainder is water) planet Earth may seem like a home roomy enough to accommodate its many land-based creatures. But these figures are misleading, because all forms of terrestrial life are confined to a slim layer between the top of trees’ canopies and the bottom of aquifers. Every physical, chemical and biological process necessary for life happens within this wafer-thin coating. Gail Ashley labelled this living skin ‘the Critical Zone’. 

Earth’s critical zone. Artwork by R. Kindlimann © Chorover et al., 2007, Wikimedia Commons.

The narrow Critical Zone has an even narrower core, which is responsible for the vital water, carbon, nutrient and decomposition cycles: the soil – which is also the growing medium for the majority of plants and countless other organisms. Soil sustains life on the planet, but is also shaped by living beings such as ants, termites, beetles, earthworms, millipedes, woodlice, mites and nematodes. They degrade organic matter and help create humus, and also shuffle soil around: the uprooting of trees displaces and turns lumps of earth, moles dig and burrow, ants and termites build earthen nests above ground. This form of ecosystem engineering is known as bioturbation, which is the subject of ichnology: from the ancient Greek íkhnos (footprint), it is the study of existing and fossilized tracks and excavations made by animals. Ichnology was an obscure and fringe scientific field until Charles Darwin had a go at it. Unsurprisingly, his endeavours had enormous repercussions.   

In 1837, Darwin visited his uncle and future father-in-law, Josiah Wedgwood, who suggested that earthworms were responsible for the slow burial of chunks of marble scattered around his property (Huxley & Kettlewell, 1965. Charles Darwin and his World. Viking Press, New York). That titbit of domestic chitchat stirred Darwin’s scientific imagination, so much so that he conducted observations and experiments with earthworms on-and-off for over 40 years. His efforts culminated in his last book, published about six months before his death: The Formation of Vegetable Mould Through the Action of Worms, with Observations on their Habits. Darwin didn’t think much of it: “I have now [1881] sent to the printers the manuscript of a little book on The Formation of Vegetable Mould through the Actions of Worms. This is a subject of but small importance; and I know not whether it will interest any readers, but it has interested me.” (Barlow, 1958). He was wrong: the book was a huge success, selling as many copies as On The Origin of Species (Feller et al., 2003).

Darwin was largely responsible for changing the perception of earthworms from garden pests to major contributors to the formation and ecology of soils. Since then, other ground-living organisms have been identified as contributors to soil morphology. Among them, ants and termites are considered particularly important simply because they are spectacularly abundant; both groups comprise a huge chunk of terrestrial animals’ biomass.  

Biomass estimates for groups of animals © Eggleton, 2020.

Ants, termites and a few other ground-dwelling insects such as dung beetles transport and rearrange soil particles, affecting soil structure and the cycling of water and nutrients. So they rightfully have received a great deal of attention as ecosystem engineers. But one group is absent from the select club of bioturbation agents: bees. 

Most of us are familiar with honey bees and bumble bees, and we may assume that other bees are like them – but they are not. Of the 20,000 or so known species of bee in the world, most (~80%) don’t live in colonies; they are solitary, that is, each female constructs and provisions a nest by herself. And around 60% to 80% of them are fossorial (from the Latin fossor for ‘digger’), meaning animals adapted to digging and living underground. These bees are known as mining bees or miners. Each female’s nest consists of a tunnel that may branch into cells. For some species, tunnels can be 10 mm wide and up to 0.5 m deep. The female will stock each cell with pollen and lay an egg on it; the larva will feed on the pollen until it is ready to emerge as an adult. Collectively, mining bees (mainly from the genera Andrena, Anthophora, Amegilla, Eucera, Halictus, Lasioglossum and Melitta) make up the most important group of crop pollinators (Kleijn et al., 2015), despite spending most of their lives underground.

X-ray imaging of mining bee burrows. a, b: relatively straight, unbranched and predominantly vertical burrows of the vernal colletes (Colletes cunicularius); c, d: highly branched and curved burrows of the sharp-collared furrow bee  (Lasioglossum malachurum) © Tschanz et al., 2023.

Most mining bees, like those in the genus Colletes, produce a resin that becomes a transparent, waterproof film when exposed to the air. Female bees brush this glandular secretion on the walls of the brood cells to protect them against excess moisture and possibly against pathogens. This feature explains why these bees are known as plasterer bees, cellophane bees, or polyester bees. Other species line their nests with petals, leaves, pebbles or other materials. Besides protecting the brood, these home improvements help to uphold the nest structure, so that air and water keep flowing along the tunnels long after the emerging bees are gone.

Brood cells of a cellophane bee © Delaplane, 2010.

A solitary mining bee is no match for the digging capacity of termite or ant colonies, but the term ‘solitary’ is deceiving. Each bee builds her own nest, but many species nest close to each other, perhaps to take advantage of relatively scarce good spots. These nest aggregations can be massive: the heather colletes (Colletes succinctus) can reach concentrations of 80,000 tightly packed nests along a 100-m stretch. These gatherings give the impression that bees are swarming: watch them going at full tilt.

A female heather colletes © gailhampshire, Wikimedia Commons.

Heather colletes aggregations may seem overcrowded, but they are sleepy villages when compared to those put together by Calliopsis pugionis: they can reach over 1,600 nests/m² (Visscher & Danforth, 1993). Mining bees’ relentless burrowing and tunnelling produce one important by-product: enormous volumes of spoil. 

In temperate areas, earthworms can deposit 10- 50 t/ha of castings (soil-enriched poo) on the soil surface annually, while ants and termites move 1- 5 t/ha of soil, reaching 10 to 50 t/ha in some instances (Wilkinson et al., 2009). These figures do not impress the alkali bee (Nomia melanderi), a prodigious soil engineer in its native deserts and semi-arid areas of the western United States. One gigantic colony, estimated to house around nine million bees, dug out 96 t of soil to the surface in one year. Much of this earth is taken away by wind and rain, which would result in a loss of 4 cm of soil surface in 50 years (Cane, 2003). In Japan, Andrena prostimias deposited 27 t/ha of soil in a temple’s garden. The volume does not seem that impressive until we learn that the excavation was completed in one week (Watanabe, 1998).

A female alkali bee by her nest and a concentration of nests © James Cane, United States Forest Service.

Bees are hardly ever considered soil organisms, but that’s a gross oversight. Thanks to their burrowing activity, mining bees are likely to contribute to nutrient cycling, water storage, soil structure and atmospheric composition: their inclusion in the roll of bioturbation agents is much justified. And you thought they only contributed to ecosystem functioning by being great pollinators. 

A wee earth-digger machine: an ashy mining bee (Andrena cineraria) arriving home with a load of pollen © Orangeaurochs, Wikimedia Commons.

Both sides of the coin

It was Joni Mitchell who sang the sensible words ‘I’ve looked at life from both sides now’. It was a wise thing to contemplate. The Netherlands-based European Invertebrate Survey (EIS Foundation) would surely agree.  This highly respected centre for insects and other invertebrates recently revealed bumblebee results for 2023 which indeed show two sides of the same coin.

Operating out of Leiden, the agency shares knowledge on insects and other invertebrates and conducts and promotes research to aid policy and management to help insects in The Netherlands. Mention the EIS in pollinator circles across Europe, and you can be pretty confident that you will receive a glowing appraisal.  

I was intrigued recently to hear of their preliminary overview of the 2023 season ‘A bumblebee year with two faces’. For a group which supports more than 60 working groups and works with somewhere in the region of 3,000 volunteers I’m always interested to hear that they have to say.

2023 marked the sixth consecutive year in which EIS had been collating and monitoring bumblebee numbers. As the 2023 season for activity drew to a close, they were quickly able to establish a few interesting headline facts to share. As is often the case when studying nature, the picture was not always straightforward.  Indeed, first up was the need to concede that counting numbers in the first half of the season had been low, only to surge upwards as the year progressed. It was what football commentators would call ‘a game of two halves’.

This was largely due to a wet and cold spring that supressed insect numbers. An army of volunteers were noting that bumblebee numbers appeared much lower than on average for the time of year. 400 dedicated volunteers across the Netherlands were unanimous in this finding, based on their meticulous monthly observations along agreed fixed routes.

Using flight graphs, the EIS volunteers gather information which quickly suggested that the six most common bumblebees were seen less than on average as the 2023 bumblebee season got underway. To quote the report ‘numbers lagged behind the average of previous years’.  The usual spurt in numbers seen in May, as colonies gather momentum, simply wasn’t there. Fortunately, it was pushed back to later in the year, indeed June saw good numbers.

Summer brought even better news. The peak numbers of all bumblebees seen in the summer proved higher the average if previous years. And quite remarkably the actual peak fell once more slap in mid-July, despite that slow start to the season.  That said there will likely be concern about increasingly wet springs and hotter summers.

There was a welcome return for some consistency in numbers and species seen. The three most common species: Common Carder Bee (Bombus pascuorum), Red-tailed bumblebee (Bombus lapidarius) and Buff-tailed bumblebee-group (Bombus terrestris-group) (Note that for the purposes of this study this is an aggregate of terrestris, lucorum, magnus and cryptarum).  were once again over ten times more likely to be recorded then the other relatively common Netherlands species the Early Bumblebee (Bombus pratorum), the Garden Bumblebee (Bombus hortorum) and the Tree Bumblebee (Bombus hypnorum).

The volunteer network observed that the most commonly-sighted bumblebee was the Common Carder Bee. The average sightings in the past five years was ten bumbles per kilometre of counting. In 2023 it was twenty. The tree bumblebee on the other hand enjoyed what could best be termed an average season. Spring saw numbers and flying time as comparatively normal based on recent years for that species. 

EIS researchers noted that the four other common bumblebee species: Red-tailed bumblebee (Bombus lapidarius), Garden Bumblebee (Bombus hortorum), Early Bumblebee (Bombus pratorum) and Buff-tailed Bumblebee-group (Bombus terrestris-group), all exhibited a late increase in numbers. The Buff-tailed grouping and the Red-tailed bumblebees were roughly one or two weeks behind their previous years in terms of numbers. The terrestrial bumblebee unfortunately had one of its poorer years since monitoring began. 

Just as Queen bumblebees are tucked up for winter so the Leiden folks begin to hunker down for winter – although in their instance it is time to calculate trends rather than peacefully slumber.  This is done with help from Central Bureau of Statistics, which will help coordinate and analyse figures from the busy Bumblebee Monitoring Network.  Winter may be drab and dreary but the number crunching is anything but.

Five years into the bumblebee monitoring programme the good news is that the surveying work is paying off. 

Indeed, looking ahead, the bumblebee monitoring network was delighted to form part of the Netherlands standard Ecological Monitoring Network (NEM) for the first time in 2023. This network endeavours to help scientists and environmentalists in the Netherlands analyse the trends of all kinds of groups of animals and plants. The bumblebee monitoring network is delighted to be part of this wider work and recognises that it has learned much from earlier butterfly monitoring networks run out of Leiden. There is a strong appreciation of shared methodology and personnel in Netherlands bumblebee circles. 

Work of this nature is essential in the Netherlands. Bumblebees, it is widely acknowledged, require special attention. Two-thirds of the Netherlands bumblebees are on the Red List and in the past century around 25% of their bumblebee species have disappeared.

That is why it is vitally important to properly map the numbers and range of the remaining species. The information gleaned from a dedicated and well-trained network of monitoring volunteers will surely form the basis for future bumblebee protection in the Netherlands. And that’s good news no matter which side of life you look at it from.

Find out more:

EIS Insect Knowledge Center

De Vlinderstichting

With sincere thanks to Johan van ‘t Bosch, EIS Kenniscentrum Insecten en andere ongewervelden, p/a Naturalis Biodiversity Center, for both his help with the text and the images.

Come in – if you insist

By Athayde Tonhasca

Philip Miller (1691-1771), author of the renowned The Gardeners Dictionary and Fellow of the Royal Society, was a keen experimenter in plant propagation. In a 1715 letter to a friend, Miller described his observations of bees visiting tulip flowers, “which persuades him that the Farina may be carried from Place to Place by Insects” – Farina is the Farina Fecundens (fertilizing flour), or pollen, which fellow naturalists suspected played an important part in plant reproduction. Meanwhile in America, Arthur Dobbs (1689-1765), Governor of North Carolina, promoter of expeditions in search of the Northwest Passage and amateur scientist, came to a similar conclusion: “I think that Providence has appointed the Bee to be very instrumental in promoting the Increase of Vegetables”.

His excellency Arthur Dobbs esq., captain general, governor in chief and vice admiral of the Province of North Carolina in America, circa 1753 © The New York Public Library Digital Collections.

Philip Miller and Arthur Dobbs were two of the pioneer naturalists who recognised and assessed the role of insects in plant reproduction. We learned a great deal since then, so that today plant-pollinator associations are considered some of the best examples of mutualisms, that is, relationships between two species that benefit both. ‘Mutualism’ invokes noble concepts such as cooperation, teamwork, union, and common good; so, analogies with human behaviour were just too tempting. The anarchist Peter Kropotkin (1842-1921) cited examples of mutualism in the natural world as arguments against ruthless competition in human societies, while ecologist Warder Clyde Allee (1885-1955) and colleagues, in their influential Principles of Animal Ecology, made numerous references to human cooperation in discussions about mutualism (Boucher et al., 1982). These comparisons with human values risk distorting the true character of mutualism in the natural world, as is the case with pollination. There’s little collaboration here: plants give away as little pollen and nectar as possible because these products are metabolically expensive; sometimes they cheat, giving no reward at all to flower visitors. Pollinators on the other hand would take as much resource as possible, with no altruistic regard for plants’ needs. Instead of cooperation, this type of relationship is best described as mutual exploitation (Westerkamp, 1996). Or, as Danforth et al. (2019) put it, ‘pollinators are like an overly demanding lover – they are great to have around at times, but if left without boundaries, they can take over your life and ruin it.’

Plants are in a delicate position: they need to attract insects to transfer their pollen but must be parsimonious in their rewards, otherwise these will be quickly depleted. To sort out this dilemma, many species evolved a range of adaptations to regulate access to pollen and nectar, and to discourage floral robbers (consumers that do not pollinate). Some plants exclude unsuitable visitors by restricting their pollen to specialised buzz pollinators; others rely on explosive pollen release, while some take the route of morphological tinkering such as keel flowers.

Keel flowers have five petals: a large one on top called the banner (also known as the vexillum or standard petal), two concave ones on the sides (the lateral wings or alae), and two at the base: these are stuck together to form the keel, which encloses the reproductive organs.

Parts of a keel flower: 1. Banner; 2. Wings; 3. Keel © Kembangraps, Wikimedia Commons.

Keel flowers are common in the subfamily Papilionoideae (or Faboideae) of the legume family (Fabaceae). They are also known as papilionate flowers, from their resemblance to butterflies – papilio in Latin. Papilionoideae comprises an estimated 14,000 species, or over 70% of all legumes. They are found in a range of habitats, and many of them are important sources of human and animal food, such as soybean (Glycine max), beans (Phaseolus spp.), clovers (Trifoliumspp.) alfalfa (Medicago sativa) and peanut (Arachis hypogaea).

The ungainly shapes of keel flowers seem to have been designed to make life a bit difficult for pollinators. Not to put them off completely – that would be suicidal – but to make them work hard for their reward. To access the nectar, a visitor must grab the flower, push the keel down, while simultaneously prising apart the lateral wings, engaging their legs and mouth in elaborate contortions. These manoeuvres expose the stigma (female parts) and the anthers (male parts), which touch the visitor and ensure pollen transfer. 

Brown hemp (Crotalaria juncea) pollination. a: Megachile bicolor grabbing the base of the banner with its mandibles; b, c: M. bicolor and M. lanata pushing against the lateral wings with their legs and abdomen, so that style and anthers touch the bees’ scopa (pollen gathering bristles); d: the carpenter bee Xylocopa fenestrata repeating the process © Kumar et al., 2019.

These operations require strength and technique; visitors that do not have the physical apparatus or sufficient power such as butterflies and flies are mostly excluded from keel flowers. Hummingbirds and other birds are also barred, as they can’t open the petals with their beaks and the keels are not big enough for landing (Westerkamp, 1997). Only bees, and only the larger ones at that, can deal with the challenge. Watch bumble bees expertly working their way around lupin (Lupinus sp.) flowers, and note the spike-like structure – the keel – poking out between the lateral wings as bees push them apart. On touching the keel, bees are dusted with pollen. And here, a leafcutter bee (family Megachilidae) illustrates the labour required to get the nectar in a brown hemp flower.

Keel flowers block the less desirable visitors, saving pollen and nectar for the reliable larger bees. It’s not surprising then that so many plant species have adopted this aesthetically peculiar but highly effective flower shape.

On the bee trail in Caithness

Sibster is a relatively new broadleaf woodland on the site of an old Caithness farm – you might not immediately associate it with bees and helping our pollinators.  But that is exactly what it does. Join the 3km bee trail here and you are invited to ‘Bumble along through the wildflower meadows by the Sibster Burn that are protected as a bumblebee conservation area.’

Forestry and Land Scotland (FLS) are the people behind the inspirational project, although they are quick to acknowledge the help of a band of dedicated volunteers.

They have been planting brightly-coloured wildflowers amongst the young growing trees here. Not just for their aesthetic appeal, but to help boost numbers of a rare species of bumblebee and boost the fortunes of other pollinating insects.  

It’s been a labour of love. The wildflowers in question have been lovingly tended by dedicated North Region FLS staff in polytunnels in nearby Lairg. Once ready they were then planted out in the autumn by eager volunteers from the Caithness Environment Volunteer Group in two meadows at Sibster. And this is welcome news in the battle to conserve the Great Yellow Bumblebee. 

The Great Yellow Bumblebee was at one time widespread across the UK. But changes in land use and a fragmentation of their preferred habitat saw their range dramatically reduced, to the point where now in the UK this a bee alarmingly only found in the western and northern fringes of the Scotland.

It’s one of the key species for the Species on the Edge project, and the work being carried out in Caithness is a fantastic boost. 

Neil McInnes, was a key player in getting the project at Sibster up and running, and knows that this is no short-term fix. It takes planning and considerable determination to get an ambitious project such as this off the ground.

“It really takes a while for a healthy meadow to get going’” he explained, “it’s the same for it to become well established so we’ve been working on this project for several years now. 

“Adjusting the mix of plants is a slow, steady process. Working with Bumblebee Conservation Trust and local ecology volunteers and tapping into the expertise of new FLS staff with horticultural industry experience has given us a great mix of skills and knowledge – from basic botany to plant propagation and species conservation – that are helping to shape and transform the two meadows.  

“It goes to show the range of our conservation work, and highlights that sometimes it’s the things that you can do at the very local level that can make all the difference in helping endangered species. 

“Our partners will regularly monitor the meadows in the years to come and help keep a close eye on the fortunes of these particularly rare bees.”  

At NatureScot we can’t thank Neil and his colleagues enough. Theirs’s is a marvellous example of partnership working and going beyond the norm to make a big difference.

The new meadows are located in two of several large, open areas within a forest that was originally planted in 2011 on a former agricultural site.  The work to introduce the meadow took careful planning. Starting in 2014, initial steps involved controlling and reducing the fast-growing rye grass and creating the spaces that would allow the less vigorous, pollinator-attracting flowering plants to take root and establish. 

These early works were enhanced in 2017 thanks to the planting of a Hawthorn and Blackthorn hedge alongside one of the meadows both to provide more blossom and to create a ‘bank’ and tussocky grasses, where Great Yellow Bumblebees mght nest.  

Mary Legg, Secretary of the Caithness Environment Volunteers, is rightly proud of their input. “The volunteers are happy to spend a few hours a month helping a variety of projects that allow the biodiversity of Caithness to flourish. In this case it was planting out wildflower plugs and, as Sibster woodland is already popular with local people, this should increase the opportunity for them to see and hear a variety of pollinating insects including the great yellow bumble bee.”

And Mary is spot on in highlighting a crucial target when she rightly suggests that the work at Sibster “… might also encourage visitors to allow a little space in their own gardens for wildflowers.” 

The meadow here is a rich mix of plants such as red clover, vetches and knapweed that are amongst the preferred food plants of the Great Yellow Bumblebee.

What a fantastic project and what a great demonstration of the versatility of our colleagues at Forest and Land Scotland.  The Great Yellow Bumblebee will benefit, but we can be equally confident that a range of other pollinators will hone in on this site too.

Thank You: With sincere thanks to Reginald Stratton and Neil McInnes for their help in compiling this blog and for permission to use their images.

Find out more about Forestry and Land Scotland:

Find out more about the Great Yellow Bumblebee:

Find out more about Species on the Edge:

More than a car park

Car parks used to be car parks and nothing more, end of story.  Today, however, you are much more likely to find them fringed with trees and flowers. We’ve woken up to the potential to make much better use of these spaces in our villages, towns and cities.

I was reminded of this recently when I received an update about the excellent raingarden work in Kinross, which continues with boundless enthusiasm.

You may recall that the first phase of the Kinross Park & Ride Raingarden project was given the prestigious Susdrain UK Community Award in 2022. This was in recognition of a trial of perennial and annual native wildflower plantings as part of a new raingarden in the middle of the Park & Ride car park. It’s been good for nature and a rather pleasant consequence is that the council only needs to cut this area annually instead of 16 times a year. And it looks good visually for those who are passing through, although perennials don’t meet the expectations of the colour blastthat the new annuals created in the first year.

Now, Perth and Kinross Council have approved a further allocation of Nature Restoration Fund money to continue raingardens work in Kinross. Much of the new work will focus on further improving the area around the Park and Ride site, “building on success” you might say.

The green spaces around the Park and Ride are already popular and much appreciated for their nature benefits. The group behind the work are keen to stress that these are biodiversity improvement measures rather than cost-cutting practices. And the work isn’t finished. Moves are afoot to stop herbicide applications and bring an end to the bare soil strips of the car park edges, including the small ‘islands’ in the centre. Instead, the vision is to have pollen and nectar rich vegetation which would be maintained by the Council with an annual cut-and-remove regime where needed. Some occasional weeding of edges may be needed, and advice is being sought for suitable plants to establish there instead of the weeds.

There are two heavily shaded areas on the fringes of the car park, where it looks possible to introduce woodland floor flora more appropriate to the locality and soil. For those who know the area this is in effect the long edge of the car park beneath existing well-established tall trees.

Thought has been given to not only pollinator provision but the aesthetic value of the area for residents whose houses overlook the front of the car park. For that less shaded front edge of the car park therefore, swathes of colour from spring flowering bulbs are also proposed. This will complement the existing Kinross in Bloom containers on the hard surface near the bus stop.

The Park and Ride is the start of the Kinross Raingardens Trail. In parallel with the improvements for pollinators at the Park and Ride, work has been scheduled to enhance the wetlands along the Raingardens Trail on Junction Road. Two constructed wetlands there take overflow drainage from a wildflower-rich set of swales which serve the central length of Junction road, as well as a cluster of commercial properties. Over the years since the wetlands were created, extensive growth of reedmace (Typha latifolia) had suppressed other plants and wildlife. The benefits of last year’s work there should become apparent in spring this year; there will be a buzz of excitement there, hopefully! Early growth looks promising in particular for yellow flag, purple loosestrife, and lesser reedmace amongst others.

A third constructed wetland was created in spring 2023, in an area designated as a flood water space for extremely high flows in the local South Queich river tributary of Loch Leven. Additional work is scheduled there for February 2024, creating another new pond, and seeding with native water margin species. Again, it is anticipated that spring 2024 will be an exciting time to see the emergence of a variety of wild flowers and other native plants, as well as the associated insects and other animals. Already in January ladies smock is growing well, from plugs planted in new scrapes last year, as plugs of purple loosestrife and marsh marigold. This previously neglected area will become a biodiverse treasure on the edge of town, surrounded by a mix of housing, commercial and industrial development and road infrastructure.

It’s this healthy desire to work to enhance the habitats and waters of Kinross-shire and Loch Leven, but simultaneously also strive for further improvement, which has made such a difference. And the improvements are stretching beyond the park and ride and the Raingardens Trail. At the Kinross rugby club, work has begun to create a biodiverse hedgerow swale along the car park edge in spring, tapping into the knowledge gained from earlier swale projects in Kinross. The car park extension and the club-house work have taken rainfall runoff away from the local combined sewer, into the swale system. The project is looking for more green infrastructure projects to help further with removing rainfall input to old sewers which overflow into Loch Leven from Kinross, a National Nature Reserve and Ramsar Wetland.

The group would love to have information signs on site to explain the changes and the benefits. These are likely to stress that the works here help deliver the national pollinator strategy. A sign of the times you might say.

Further reading:

Kinross Raingarden’s Trail

Making wildlife connections at Dance Connect

All images above Copyright (c) C A G Lloyd

(Left)Park & ride in summer, and right – Dance connect pollinators patch

Lesser celandines

Red campion

Bluebells grown from Scotia Seeds and
transplanted in the Dance Connect wooded mound. 

Vast armies with many skills

By Athayde Tonhasca

As natural history narratives go, the 1954 ant-inspired sci-fi motion picture Them! was not up to David Attenborough’s standards because giant, deranged, radioactive ants don’t exist. Despite the factual liberties, the film was a commercial success and had the novelty of depicting two myrmecologists (ant specialists) as heroes who helped to save the planet from a myrmecological doomsday. Malevolent ants have a long history in Western popular culture. In The Empire of the Ants (1905), H.G. Wells tells us the story of a gunboat forced to turn around and abandon an Amazonian village overwhelmed by intelligent killer ants.

A bad ant infestation in the New Mexico desert © San Bernardino Sun, 1954. Wikimedia Commons.

Those who have witnessed an army ant raid or had the unfortunate experience of stepping (or even worse, sitting) on a fire ant mound, understand why ants elicit fear or a grudging respect; many of the 14,147 – and counting – species of ants (family Formicidae) are territorial and highly aggressive to perceived intruders, man or beast.

Lieutenant da Cunha being overwhelmed and killed by evil Amazonian ants in H. G. Wells’ The Empire of the Ants © Amazing Stories, 1926.Wikimedia Commons.

But aggression is only one aspect of ants. They can be predators or feed on seeds, nectar, honeydew, or fungi they cultivate. They are found everywhere except Antarctica and a few remote islands, and are incredibly important in decomposing organic matter, recycling nutrients, and controlling plant-eating insects (many of them agricultural pests). Ants are essential ecosystem engineers: many species build nests and dig tunnels in the ground, increasing aeration and drainage, and improving soil fertility with their waste and food stores. Some seed-eaters are important for plant reproduction: they stock their nests with seeds that are not all eaten. The spared lucky ones germinate in a nutrient-rich, herbivore-free environment. More than 3,000 plant species depend on myrmecochory, which is seed dispersal by ants. Plant-eating by ants is not always benign; leafcutter ants (genera Atta and Acromyrmex) are incredibly destructive; in Brazil, saúvas (their local name) have been the scourge of agriculture since the beginning of European colonisation. French naturalist Augustin Saint-Hilaire (1779-1853) supposedly said that ‘Brazil must kill the saúva or the saúva will kill Brazil’, which was a slogan adopted in successive – and unsuccessful – eradication campaigns. 

Digging a leafcutter ant nest in Brazil. Concrete was poured into the nest to create a cast of the inside. The nest covers more than 67 m² and contains 1920 chambers © O’Brien & Bentley, 2015.

All these ecological services and impacts are intensified by ants’ mindboggling numbers. The distinguished myrmecologist E. O. Wilson estimated that 10¹⁵ to 10¹⁶ ants crawl on Earth’s surface at any given time (that’s quadrillions, figures usually discussed in astronomy). A later appraisal fine-tuned the number to 20 × 10¹⁵ individuals, which corresponds to ∼12 megatons of carbon. This is more than the combined biomass of all wild birds and mammals, and is equivalent to ∼20% of human biomass (Schultheiss et al., 2022). Another study following a different methodology suggested a population size of 5 × 10¹⁶, excluding arboreal ants (Rosenberg et al., 2023). So Wilson wasn’t far off, as a billion here or a billion there is not that important when we are talking quadrillions. For comparison, there are some 7.9 × 10⁹ human beings on the planet. 

A representation of powers of 10 to help us grasp the magnitude of ants’ abundance: each block is ten times the size of the previous block, up to a billion (10⁹). One quadrillion would be 1.000.000 bigger than the billion block © Cmglee, Wikimedia Commons.

Ants are everywhere and interact with a vast number of animal and plant species, but they seem to be largely absent from one ecological process: pollination. Which is a bit puzzling, considering that bees, their close relatives, are the main pollinators of a large number of plants. Many reasons have been proposed for the dearth of ant pollination, from their grooming (self-cleaning) behaviour to scant ‘hairiness’ (body bristles), resulting in few pollen grains being transported. But bees groom themselves, and some ants are as hairy as bees. The ‘antibiotic hypothesis’ is the most accepted explanation for ants’ unsuitability for pollination. Most ant species feature a specialised gland located in the metapleuron (a thoracic plate; pl. metapleura). The metapleural gland – and to a lesser extent some other parts of the body – secrete chemicals that serve as signals for nest-mate recognition and territory marking, and especially as antiseptics that prevent the proliferation of bacteria and fungi. But these substances have a disagreeable side effect: they also inhibit pollen germination and the growth of pollen tubes.

Parts of a typical ant, highlighting the all-important metapleural gland © Mariana Ruiz, Wikimedia Commons.

Ants’ chemical defences seem to make them incompatible with the job of pollination. Which is a pity for the plants’ point of view, as ants often crawl all over them in search of nectar from their flowers and, in some cases, from specialised nectar-secreting glands. But inevitably and predictably, natural selection intervenes to fill the voids of missed opportunities.

Honewort (Trinia glauca) is an unassuming herb found on dry, rocky sites with sparse vegetation in southern England. Elsewhere, it ranges from continental Europe to southwest Asia. On some of the English sites, flowers of this rare plant are visited mostly by ants, especially Lasius alienus, which are also their main pollinators (Carvalheiro et al., 2008). 

Honewort on limestone, a habitat shared with its main pollinator, L. alienus © BerndH, Wikimedia Commons.

Honewort is an addition to the ever increasing number of reported cases of myrmecophily, or pollination by ants. These ant-friendly plants may have developed tolerance to the ill effects of metapleural gland compounds. This seems to be the case for the waxy-leaved smokebush (Conospermum undulatum) in Australia: in an experimental setting, pollen from some plant species suffered substantial decreases in germination after contacting the integument (‘skin’) of Camponotus molossus and other ants. Pollen of waxy-leaved smokebush however was not affected. Not surprisingly, ants contributed significantly to the plant’s pollination (Delnevo et al., 2020).

A, B: waxy-leaved smokebush flowers. Bee visitors: Leioproctus conospermi (C) and Apis mellifera (H), which only steals nectar. Ant visitors: C. molossus (D), C. terebrans (E), Iridomyrmex purpureus (F) and Myrmecia infima (G) © Delnevo et al., 2020.

Brute force is another possible explanation for myrmecophily. A single ant may be a poor pollinator, but a mass of them visiting flowers repeatedly may end up doing the job properly. Apparently this is the scenario in high mountains and arid zones, where ants make up a significant proportion of flower visitors (Gómez et al., 1996).

In their monumental 1991 Pulitzer Prize-winning book The Ants, Bert Hölldobler and Edward O. Wilson skimmed over myrmecophily, as it was taken as a minor feature. Bees, flies and moths are by far the champion pollinators, but more and more studies suggest ants are important for some plants in some habitats. So we can add pollination to ants’ long list of ecological services – unhinged, angry and radioactive ants notwithstanding.

Edward Osborne Wilson (1929-2021), myrmecologist, environmentalist, secular-humanist, and pioneer in the fields of ecology, evolution and sociobiology. Despite underhand attacks from some of his peers while he was alive and attempts at character assassination after his death, Wilson remains one of the greatest and most inspiring scientists of our times © Jim Harrison, Wikimedia Commons.