The Quarry Connection: Linking Habitat Restoration and Bee Biodiversity (Ep. 56)

We’re exploring the hidden potential of quarries as unexpected havens for bee biodiversity and conservation. Dr. Felix Kirsch shares his research on how these sites, often seen as desolate, can support thriving wild bee communities. We discuss the importance of habitat connectivity, strategies for improving floral diversity, and recommendations for enhancing quarries to support native bees and other local flora and fauna. This is a fresh perspective on how abandoned landscapes can play a pivotal role in pollinator preservation.

Dr. Felix Kirsch is a researcher in the Institute for Biodiversity at the Thünen Institute, a scientifically independent research institution at the interface of science, politics and society. This is his research paper on limestone quarries and you can learn more about his work here.

Good to know

Felix talked about the importance of calcareous grasslands. These are unique ecosystems thriving on thin soils rich in chalk or limestone. The hardy plants found here—such as grasses, clover, and other herbs—are perfectly adapted to the challenging conditions. These grasslands play a crucial role in supporting biodiversity, serving as important habitats for insects like butterflies and bees. 

Interestingly, calcareous grasslands are man-made landscapes, shaped by traditional land use practices like grazing and hay seeding, mostly in Europe. As Felix mentioned, they now face significant threats, and dedicated conservation efforts are essential to preserving their rich variety of plant species and the life they sustain.

Transcript

Jacy: [00:00:00] Welcome to the Bees Knees. A podcast wild about native bees. Wild and native bees are under threat worldwide. In each episode, we look at actionable things we can do to support these adorable little guys whose pollination work is crucial for maintaining biodiversity. I’m Jacy Meyer and I thank you for being here.

What comes to mind when you hear the word quarry? Perhaps like me, you picture a scarred and desolate landscape abandoned once every ounce of material value has been stripped away. But what if I told you these sites often seen as symbols of destruction could be unexpected havens for biodiversity and crucial to habitat conservation.

Today I’m joined by Dr. Felix Kirsch, who explored nearly 20 quarries in southern Germany to uncover the fascinating interplay between wild bee [00:01:00] communities, landscapes, and quarry ecosystems. So what inspired you to study wild bees in limestone quarries and what makes these habitats unique for conservation efforts?

I

Felix: think that’s a relatively long story. At first, I was also just interested in wild bees like you maybe, and I wanted to learn about them. And then I was doing my master studies and there was a professor and she was an expert on agri-ecology. Yeah. And she gave a lot of lectures on wild bees and honeybees in agricultural landscapes.

So I participated in her classes. When it was about time to select a subject, I asked her what could I do? I really want to do something about bees. And she said, me, look, there is one old study from 1999 on bees and limestone quarries, and from this study they produced very impressive data set. And she really wanted to repeat that study to see whether the same [00:02:00] species are still around and whether the population changed.

So she asked me if I could do that, and I was very happy about that subject, so I accepted it, and so I ended up doing bees and quarry research and what makes them unique? That was second question. Yes. I think the most important aspect on the quarries is that they have a lot of open soil. So sparsely vegetated, open soil, and this is a very important nesting resource.

The majority of bees species is, I’m sure you already discussed that in the podcast, soil nesting. Um, so they really require that open soil patches, and we find them in quarries in large proportions. And also bees like slopey, uh, structures, for example, vertical cliffs and so on, and for sure you can find them.

Another nice aspect is that very often if this slopey, uh, vertical [00:03:00] structures are eastern or the southward facing, then they have a nice warm microclimate. And this is also an aspect which a lot of bee species really like. Then we have this early successional stages which are dominated by, uh, flower ridge pure vegetation.

There we have like, for example, agava blue weed or pork weeds, which the bees really like and that’s why I consider quarries to be very beneficial bee habitats.

Jacy: So your study highlighted the importance of the habitat. Mm-hmm. Connectivity to the neighboring dry mm-hmm. Grasslands. Why is this connection important?

And can you also just explain in general why connectivity matters for bee

Felix: populations? Um, so I would start with the second question. So why is connectivity important in the first place. I read a study some months ago and uh, the author used a nice term referring to connectivity as some form of spatial insurance. So if we, [00:04:00] for example, have an isolated bee population in a isolated.

Habitat patch completely surrounded by the hostile agricultural matrix, and this population goes extinct. It’s gone for good. Is that possible to say it like this? Gone for good. Okay. And so there’s no possibility for the bees to recolonize because there are no neighboring patches where subpopulation of the same species are around.

If we have nice or high value habitats, which are close to each other, then it’s possible that the bees are, or there’s a constant exchange of bee individuals and species between the patches and a constant genetic exchange. And even if one population goes extinct, it’s very likely that there, uh, some form of.

re-colonization gonna be happening. And so I think this is the most important aspect of why this connectivity is important. And also bees are central place foragers [00:05:00] so they require a lot of different resources. For example, the nesting resources, the flowering resources in the surrounding of their nesting sites.

This limes as our quarries and our dry grasslands that we selected in our studies, they have a lot in common. So they’re both on the same soil substrates. So both are like limestone or chalky substrates. And so similar plant communities can establish in the calcareous grassland, which is a very important habit type in Europe.

It’s a biodiversity hotspots of plant and animal biodiversity. I would say they had. Very important, but highly threatened because the traditional users, uh, like land use activities, uh, they stopped. So us uh, in the past we had, um, extensive grazing with sheep or goats there, or extensive, uh, mowing. But from a commercial point of view, it’s not so rewarding anymore, and that is why this [00:06:00] traditional forms of management stopped.

Or were heavily reduced or they depend on subsidies. And that’s why this habitat types, they are transformed into time by time due to the succession they are, uh, turning into, uh, shrubland or even forests. And that’s not nice ’cause it results in a cooler microclimate. And the flower rich habitat, uh, there’s a flower.

Rich vegetation is lost. Yeah. And in the quarries, probably if we are lucky, similar plant communities can establish and therefore they yeah. Act as a form of refuge for the bee communities formally widespread in the calcareous grasslands and patches.

Jacy: Can you talk about how to improve or even provide floral diversity within these quarries?

I

Felix: think one important aspect is that if you have this quarry and the chalky limestone soils, something similar [00:07:00] to a calcareous grassland community can establish in the quarry, but not necessarily so without intervention, you have something which is maybe quite close, but not as. Valuable. So therefore you need some form of interventions.

And that could be, for example, that you transfer mowing material from close by calcareous grassland patches to the sites or even the seeds. Of this plant species, which you yeah, desire to be there, but it’s very important that you select native plant material from the surrounding habitat patches and not bring them from, I don’t know, 200 kilometers away to not, uh, support local animal farmers.

Uh, for example, like small holder shepherds and so on, which. Need to move their sheep between the limestone quarries and the close by calcareous , grassland patches. And by this also can transfer the seeds [00:08:00] directly with the, if that’s in their fur or on their hooves, is that correct? Yes. Um, so that they spread the seeds of the plants you really need, I mean, that’s a traditional form of land use we want.

So this migratory herding, which is not taking place so much anymore in nowadays.

Jacy: So you mentioned earlier about mm-hmm. Shrubs and they can be a problem. So you were found that it does have a negative effect on the bee communities. Do you have recommendations on how to manage this issue?

Felix: So maybe at first I should, I.

Or put some emphasis on the fact that for sure shrub is not always bad for bees. So especially in spring we have flowering shrub, which is a nice, uh, forging resource. And also some bee species are nesting in that wood or in, I don’t know, cavities in, in woody structure. So, so I don’t wanna say that shrubs are

always bad, but later [00:09:00] in the season when the flowering is over and the canopy of the trees or the shrub is closed, then we have this effect. And I think I mentioned that before, that we have a cooler microclimate due to that. And also the flowering resources, which are sometimes in the spring forest, uh, very abundant.

Like the spring gale fruits, they’re gone. And so the bees won’t find so much foraging resources anymore. And also due to the overgrowth with the woody vegetation, like the open soil is gone, which is required for nesting. So that’s why I would say it’s important to keep the shrub cover in the quarries at a moderate level, completely erase everything.

Just look that there are still a sufficient amount of open habited patches, which are then characterized as we wanted here. Like the open soil is the warm microclimate, the slopey structures there should not be, uh, overgrown by the shrub [00:10:00] and to ensure that they are really, yeah, that we have remaining like open this nice open flower ridge structures and this can be done again by grazing.

With sheep or goats. Goats are nice because they’re also eating all the woody structures, but I also saw some, uh, quarries where, which were managed by cattle or horses, and what else can be done. Extensive mowing is a good idea, so maybe mow the site once or twice a year to get rid of the emerging shrub.

Jacy: So you learned a lot doing this.

Let’s look at the bigger picture. How could your findings kind of maybe guide future conservation strategies for wild bees across Europe?

Felix: I hope that my research put some emphasize on the importance of the landscape context. I mean, I guess that policy makers in Europe are well aware that what really matters in biodiversity conservation is the landscape and how diverse it is.

I think [00:11:00] that the people are well aware of this, but I hope that my study puts more emphasis on that fact, and also highlights the importance of calcareous grasslands as very important, crucial habitats, which needs to be conserved and restored with this traditional management practices. And we know we have already the NA 5,000 network in Europe, which is also including calcareous grasslands as a habitat type of special interest.

So people are aware of that, but I think the quarries and that they really can function as some kind of keys or step stone habitat, which is. Connecting the remaining calcareous grassland patches. I think this is an aspect which is maybe not so well known, and I guess maybe some policy makers can also include or consider whether limestone quarries or quarries in general can serve as an important habitat to improve the connectivity at a landscape scale.

[00:12:00] I hope that policy makers think. Maybe we should not turn quarries which are not used anymore into forests or arable land or, uh, recreational areas for, I don’t know, swimming. So leave it as it is with minimal interventions and yeah, let nature go. And then maybe put some local plants, pieces you want to establish there.

I think that would be nice.

Jacy: So if you could encourage people to do just one thing to support native bees, what would it be? Um,

Felix: I think one aspect, which is very often forgotten is the open soil, which is so important for bees and for the majority of bee species. So I really would recommend people to take care in their gardens, to have small patches of open soil, a sparsely vegetated soil, which can be used by the bees for nesting.

I think that would be very helpful.

Jacy: I have to say, I’ve gained a newfound [00:13:00] appreciation for quarries. Many of them offer ideal nesting conditions for wild bees, and when paired with native florally diverse grasslands, they create superb connectivity that supports thriving abundant bee communities. A big thank you to Felix for shining a light on this often overlooked landscape and sharing his passion for wild bees with us.

His actionable advice is simple, yet impactful. Think about nesting sites. Bees need bare ground and loose soil to build their nests. And don’t forget those sunny spots they love. Thanks so much for tuning in, and until next time, let’s let nature go.