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Marcin Kadej: Bumblebees Need Your Help

Marcin Kadej
Fot. Michał Raińczuk/UWr/CC BY 2.0

We talk with Dr Marcin Kadej from the Institute of Environmental Biology, one of the authors of a recently published book Pszczoły w mieście. Trzmiele Wrocławia, about how bumblebees could use some more buzz and how to effectively protect these useful relatives of the honey bee against their numerous threats.

For over a decade there has been a lot of talk about honey bees: how they need protection, how vital they are to our own existence, how their numbers are dwindling. We keep silent about bumblebees, though. Do honey bees have better PR? Or maybe they are more useful to humans and thus get more attention?

That’s a good question, straight to the point. The honey bee, Apis mellifera, is under special protection. Out of approximately 200 million bee colonies all around the world almost half, 100 million, is under human supervision. We want to keep them. For some people it’s a hobby, for others – passion combined with livelihood or business, which before 2004, in the so-called „old” European Union, generated income for at least 600 000 individuals. If we also count Poland and the entire Central Europe which became a part of the EU, the number will grow even higher. We talk here about billions in revenue. However, our average citizen doesn’t know anything about bumblebees and other solitary bees, which is alarming. We all can observe today the decline of bee colonies (CCD – colony collapse disorder) happening all around the world. We try to understand what is the cause of such a massive extinction of bees, which are indispensable to our orchards, gardens, and agrocenoses. But bumblebees and other solitary bees are just as important for the ecosystem and pollination. In some cases one could say they are even more vital than honey bees.

We scientists don’t deny that honey bees are hard-working insects. Worker bees can leave the hive up to 70 times to collect nectar or pollen. But if the temperature outside drops to 11-12 degrees Celsius, they won’t want to fly. They will stay in warmth. Bumblebees can work in worse weather: in drizzling rain, in fog. They take flight, forage, pollinate. Many plants are entomogamic, which means they need to be pollinated by insects, not birds, bats, or snails.

Moreover, honey bees exhibit the so-called floral fidelity – they visit only one kind of the currently most abundant flower on any given foraging trip. They are opportunistic, choosing what’s easy. Why bother? But this behaviour affects the diversity of other plants, commonly referred to as weeds. As a side note: I dislike this term, so practical and focused on agriculture. For us biologists, especially environmental biologists, every species is important and performs its ecosystemic function. We don’t use terms such as weed or pest.

Bumblebees don’t exhibit floral fidelity. They are perhaps less efficient than bees, cannot carry as much pollen, but they can visit much more flowers, which is vitally important as we’re facing a biodiversity crisis, which we’ve been signaling at least since 1992 Rio de Janeiro Earth Summit. We observe the biggest extinction event in history, caused by reasons other than the natural ones. Extinction of species, just as their emergence – as a result of evolution – is a natural process.

Trzmiel wrzosowiskowy Bombus jonellus to jeden z rzadszych gatunków trzmieli
Heath bumblebee Bombus jonellus is one of the rarest bumblebee species. | Fot. Marcin Sikora

Not on such a scale.

Extinctions we know from history were just as massive. But our anthropocentrism and our everyday decisions definitely affect the environment.

But back to bumblebees. Not all flowers are designed to be pollinated by bees, due to its structure, depth of the calyx, and the length of the bee’s tongue. This organ, proboscis, measures 6,3-6,5 mm. In short-tongued bumblebees – because we divide them into short-, medium-, and long-tongued – this length is 9 mm, while in long-tongued insects – even 15 mm. Another crucial characteristic of bumblebees is buzz pollination. The bumblebee hangs by a tomato or blueberry flower, grasps a fragment of the corolla’s petal by the mandibles, and with its own muscles – wings, because it’s still airborne, it provokes a shock wave of 400 Hz, which causes the anthers to open and release pollen, which settles on the insect’s body.

Even though bumblebees, just as honey bees, are social insects, we don’t keep them on a scale smilar to bees. Still, they function effectively in our environment. They can live in different habitats: wooded areas, allotment gardens, forest and agricultural areas, as well as mountain and sub-mountain ones. They nest in abandoned rodent holes, in heaps of stones left by the fields. They occupy old trees. They even colonise buildings, because why not? They can nest there, too. In short, they can live in places that even wild bees – unless certain specific conditions are met – won’t colonise.

To answer the question from the beginning of the interview: yes, bees have better PR. We’re definitely more focused on the care for their wellbeing. After all, bees give us honey we can sell, beeswax, propolis, royal jelly, and apitoxin which can be used in apitherapy and cosmetic and pharmaceutical industry.

So we care so much about bees, because we can „milk” them.

Surely. It has been estimated that only in Poland honey bees generate 350 million dollars. Solitary wild bees – 35 million. Somebody may say: The second number is only one-tenth of the first. But is 35 million such a small number after all?

Humans are always greedy.

Research has shown that in places where bumblebees or other solitary bees appear alongside honey bees, the latter becomes much more effective pollinator. It’s probably the result of competition for resources, pollen and nectar. This is an important discovery of this century.

We should not forget about the presence of close relatives of the honey bee, about which we talk and write so much, and do so much for. I fully support all such projects as bee adoption, building hives in cities, green roofs – but on one condition: that alongside them we also provide food and water, quality habitat, not only for the honey bee, but bumblebees and other bees as well, such as mining bees, mason bees, halictus bees, plasterer bees, carpenter bees. Let’s appreciate all pollinating insects! We know that virtually the entire order of hymenoptera plays a vital role in pollinating, but let’s not forget that the same work, perhaps less efficient, but still, is done by flies, beetles, butterflies. What’s interesting, we often reverse this hierarchy and put butterflies in the first place.

Because they’re pretty.

Again – that’s aesthetics. But if we conduct proper research, it will turn out that beautiful butterflies come fourth if it comes to pollination.

Insects and invertebrate animals take a top place in terms of numbers and species diversity. According to many estimates, they constitute between 78 and 90 percent of species diversity in land ecosystems. Why there’s so many of them? The simplest, maybe even trivial, answer that comes right to my mind is that nature needs them. If so many insect species are around us, it means they’re important to the ecosystem. Up till now we have been discussing only one of their functions, pollination. However, we should not forget that insects take part in the process of decomposing dead organic matter, along with bacteria and fungi. They feed on other organisms, which we aren’t especially fond of. They control populations by their role as parasites, parasitoids, disease vectors.

We already know that we should take care of honey bees, bumblebees, and other pollinators. But how?

We cannot think about the issue only in terms of species protection, because it doesn’t work – I know it from practice. If we want to do something to protect species around us, whether they are plants, animals, or fungi, we have to remember to preserve their habitats and connections between them. But in today’s world we destroy the existing habitats, partially or completely, we divide them. Distance between appropriate, suboptimal and optimal, habitats for a given species becomes too great to cross.

When we understand why we need bumblebees, we start to appreciate them, recognise our coexistence, take care of their habitats by providing food available within flight range of given species, that is 300-500 metres on average. Research has shown that constructing artificial shelters only is futile. Bumblebees don’t live in bumblebee houses. We don’t know why. We build them or buy them, but then it turns out they are not used. The idea itself is right, but we don’t get expected results. It seems that better solution is not to destroy what is already around us. Or act in a way that allows natural emergence of things. So, let’s leave stones in heaps, let’s stop milling tree stumps and removing rootstocks. This preserves structure in the landscape. Let’s not destroy microhabitats. Let’s create conditions in which the mother, the future queen, after it has been impregnated, after it has survived the winter and hibernation – when it is exposed to predators, parasites, and mould fungi – next spring gets a place to establish first cells, lay and take care of her first eggs.

Trzmiela rudonogiego Bombus ruderarius rozróżniamy po czerwonawych włoskach na trzeciej parze odnóży. Na zdjęciu samiec na chabrze Centaurea sp.
We recognise the red-shanked bumblebee Bombus ruderarius thanks to reddish hairs on the third pair of legs. In the photo – a male on a cornflower Centaurea sp. | Fot. Marcin Sikora

I must use this argument when my mother-in-law asks me again why our plot looks so neglected. It’s partly my laziness, true, but not only that…

That’s an important point, be lazy! (laughs)

Now we face another issue. Let’s assume that the mother survived. She found place for a home – because there was any. This is her victory. But soon she will have to provide food in the form of nectar, pollen, for her offpsring. At the beginning she will have to take care of that herself, there won’t be anybody to help her. If she flies a long distance to find food, it will be very taxing. What if she gets attacked by predators? What if any other misfortunes prevent her from returning to the nest? Larvae won’t feed themselves on wax that the egg cell is made of. So if she has to take flight, it would be ideal to have food nearby. The same goes for her first daughters, which will take care of next generations of their sisters, daughters of this queen mother. Neglecting pollinators’ food base – and not just once, but in the entire period when the bumblebee family is outside, from early spring until autumn – or its extermination, is a death sentence to insects, which are – I cannot stress this enough – very important to the ecosystem and to us in terms of our finances and economy.

Species protection is a weak link in protection in general. The most crucial point we environmental biologists communicate is the need to preserve habitats, avoid further deterioration of the existing ones, and as an ideal scenario – to expand their area. That is why we encourage farmers to leave some land uncultivated, to preserve balks and shrubs, to stop using lines straight as a ruler and one pattern or design, because for natural environment plantation is a desert. Nothing can live there, especially if we use chemical agents which kill everything. And then this „everything” gets eaten by other organisms, which will also suffer from its effects or even die. We can take care of microhabitats virtually everywhere. We can cultivate various flowering plants around us, just like our grandmothers and great-grandmothers did. Somebody may say: Okay, but the world has changed, we used to have more time on our hands. This is a matter of choice.


Time is a certain value. Values can be categorised. If we value our surroundings, we will do everything to maintain status quo. We can also do it in cities by planting flowers on our balconies,  thus attracting pollinators. We can do it in our home and allotment gardens, which make excellent habitats to bumblebees. Let’s try to maintain food flow by cultivating varied plant species, blossoming at different times throughout the entire vegetation season. It will guarantee that the species living around us will have a chance for survival. But taking away this chance by reducing the landscape to a mere golf course planted with thujas…

Those wretched thujas…

… spruce, pines – I don’t have anything against conifers, though – is a complete lunacy. Somebody may now again say: It’s all about time, it’s easier to maintain. But what do you maintain? You also have to take care of a flower meadow or lawn, but ironically, they cost less, because we spend less time and energy on mowing, raking, composting, not to mention electricity and petrol. Why do we give up domestic decorative shrubs which blossom, providing sustenance first to pollinators, and then, in the form of fruit, to birds and small mammals? I often hear: Because of raking. So let’s rake leaves for hedgehogs! Their populations are also dwindling. It concerns both our domestic western hedgehog and eastern hedgehog. Why? Because we take away areas where they feed and overwinter. I haven’t been raking grape, willow and other leaves in my house garden for several years. I used to, though – I raked and composted leaves. Now I leave them in heaps, hoping that hedgehogs – which I observed on my plot – will use them to overwinter. The same goes for insects, invertebrates, performing a variety of functions.

Samiec rzadkiego trzmiela zmiennego Bombus humilis.
A male of a rare brown-banded carder bee Bombus humilis. | Fot. Marcin Sikora

So: simply, let’s create appropriate conditions.

First: let’s not destroy if we don’t have to. The keyword here is „have to”. I understand the weight of this phrase. Sometimes it’s really necessary, but the question is: is it always?

Surely not as often as we think.

Yes, it’s a matter of frequency in decision-making. Do we always have to – something you mentioned regarding your plot – keep everything so neat. And again a keyword appears. Neatness in nature doesn’t mean that we cleaned up leaves or turned a meadow into lawn where we can play golf, because it’s so green, so level. It’s a change in mentality which happened very quickly – from the old way of using space around us to seemingly easier way to manage it. I always admire plots with flowers, domestic shrubs, trees, including fruit trees, which add value because we can use them to make jams, juices etc. – something natural which we don’t have to buy. I really like to talk to the owners of such gardens. In spring, I want to plant flowers along the fence in my small, 70 square metres garden, so it becomes not only child- but also pollinator-friendly, to bumblebees, bees, flies, beetles – all living things that want to use this space.

In truth, it doesn’t take much to consider improving the situaton of species. It’s a matter of good will. Also awareness, of course, because one derives from the other. You can ask hundreds of thousands of people to donate 1 zloty for bee adoption. You can ask hundreds of thousands of people to set up gardens. You can ask hundreds of thousands of people to stop destroying balks, give nature some – a little – space. Or to go vegan. But how can they get involved without awareness? People take actions on the basis of conscious decisions. This is the way we work. Sure, there will be individuals who on impulse, without any support, get involved in some idea – but these are just individuals. What’s more important is that we, as groups, should make decisions on the basis of cause-and-effect relationship with nature – and in the end, with ourselves. Cutting down rainforests is not unrelated to us, even if we live thousands of kilometres from them.]

We often hear this argument: I’m not interested, it happens somewhere else.

Exactly! We have to understand the connections. The fact that some country signs an agreement to limit carbon emissions, but other does not, is demoralising. The impact of that other country, even located hundreds of thousands of kilometres from us, in Poland or in Europe, will be huge precisely because of wind circulation, climatic connections, ocean currents.

We’re experiencing a great crisis. 2010 was declared by the UN the year of biodiversity, and I very much regret that is was only one year, not a decade or two. I have the impression that people stopped listening to scientists, environmental and conservation biologists. We publish a lot and conduct a great deal of research. And what comes of it? Environmental biology isn’t trendy now. That’s a shame. The knowledge of species, their biology, ecology, allows to study their characteristics, which later become useful to us. This is something we forget. Maybe we need a strong impulse, such as Oh man! We’ve just lost a very interesting plant or animal species with unique properties which – if studied – could have been used to treat severe illnesses or chronic conditions. We have to show humility. The cardinal sin is always pride. Pride comes before a fall.

Interview by Michał Raińczuk

A monograph “Pszczoły w mieście. Trzmiele Wrocławia” by Aneta Sikora, Paweł Michołap, Marcin Kadej, Marcin Sikora, and Dariusz Tarnawski was created on the initiative of the members of „Natura i Człowiek” Society and the academic staff of the UWr Faculty of Biological Sciences.  The publication was co-financed from the funds of the Provincial Environmental Protection and Water Management Fund in Wrocław. This richly illustrated book aims to introduce biology and ecology of over 30 bumblebee species, both those present in Wrocław area, as well as in Poland as a whole. While presenting the properties of individual species, the authors also describe threats they face and problems in their protection. One of the goals of this publication is an attempt to raise people’s awareness of the need to protect the ecologically important insects, so that they become the ambassadors of the conservation of the biodiversity of species and their habitats in our collective consciousness.

Entomologists and doctors research death

Published by: Aleksandra Draus

18 Mar 2019

last modification: 6 Aug 2019