Between Asphalt and Agriculture: Where Bees Find a Home (Ep. 62)

As urbanization continues to impact ecosystems worldwide, there’s increasing interest in understanding how our ever-growing cities interact with native pollinators like bees. The assumption that urbanization spells disaster for biodiversity is often considered a given. But let’s think differently today.

We’re talking to Leonardo Lorenzato whose recent study found no significant link between urban sprawl and pollinator species richness. Instead, it revealed that landscape heterogeneity and the presence of urban green spaces—both hallmarks of urban sprawl—positively influenced pollinator visitation rates.

Leonardo is a researcher at Venice’s Ca’ Foscari University. He’s also leading the PollinAction project, which aims to mitigate the pollination crisis through strategic planning and implementation of green infrastructure. He came on The Bee’s Knees earlier this year to talk about it. Catch-up with that episode here. Learn more about pollinator abundance in urban areas in the paper Leonardo and I discussed.

Good to know

We talked about how smart urban green spaces can boost biodiversity and support native bees, but only touched on the other benefits of introducing more trees and flowers into our cities. Trees and vegetation provide shade and release moisture into the air, naturally cooling neighborhoods and reducing energy demand for air conditioning. Plants also filter pollutants from the air and help manage stormwater runoff, reducing the risk of flooding and improving water quality. Spending time in nature—even small doses—has been shown to reduce stress, anxiety, and depression, plus green spaces often become gathering places, fostering a sense of community and belonging. Create pollinator habitat in your urban area with these guidelines from Leonardo.

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

for us. bee Folk. Whether you live in a bustling city or out in the countryside, you probably think about how your local landscape is supporting or not supporting your native bees. General thinking goes that urbanization is bad news for biodiversity. So today we’re going to think differently about the relationship between urban sprawl and pollinators.

Leonardo Lorenzo looked at how urban sprawl interacts with pollinator populations in one of Italy’s most intensively farmed regions, the Eastern [00:01:00] Po Plain. What he found challenges some of our assumptions. Let’s talk to Leonardo. So your research found that having a mix of parks, gardens, and different types of land actually helped bees visit more flowers.

Why do you think these patchwork style landscapes attract so many native bees?

Lorenzo: Well, that’s, uh, an interesting question and it is all related to the needs of bees. Bees needs basically two things. The first thing is resources. They need to feed on flowers, and the second thing is areas where they can construct or find a nest and all of that landscapes that are.

Really modified by humans such as agricultural landscapes or urban sprawl, urban sprawl is a landscape with [00:02:00] 50 50 percentage coverage of agricultural landscape and artificial areas in all of these kind of landscapes, green areas. Of mandatory importance for wild bees because they are the only places where they can find resources and nesting opportunities.

And I’m not talking about semi-natural green areas, but I’m talking about urban green areas, manmade green areas, because if the landscape is heavily modified, also these areas. Can be of paramount importance for wild bees. And moreover, they are an opportunity because they are heterogeneous in a kind of way.

For example, if we imagine a park yes, maybe it has a lot of management. For example, the grass is [00:03:00] mowed very often, but you can find also some bushes, some hedges, and these little part of the green areas are what guarantee the survival of pollinators.

Jacy: So in this study you found that more bees were showing up to feed, but the number of different bee species didn’t go up.
Why might that be and should we be concerned about it?

Lorenzo: Yes, we should be concerned about it. And well, the reason why we saw more busy is, well, pretty obvious, and that’s because in these green areas, there were more flowers than, for example, uh, in agricultural fields where there were no flowers at all. So more flowers means more pollen, more nectars, and so more food for pollinators.

The problem is that, as you said. Yes, we [00:04:00] saw more individuals of pollinators, but we didn’t see an increase in pollinator species. And this is probably related to the context in which the study took place. We did the study in Northern Italy, specifically in the Po Valley, which is, uh, heavily modified areas and.

Since pollinators are not able, in the majority of the cases, flight for longer distances, well, if the landscape is too of style for them, you can have many. Green areas, urban green areas, but pollinators will be not able to move from like source areas, for example, semi-natural grasslands to these urban green spaces.

So the problem is that in an heavily modified landscape, you can help [00:05:00] local pollinators, but it’s extremely difficult. To give the opportunity to outside pollinators to come in and colonize these areas, and this is a big problem. Since pollinator pollinate, the majority of the species and this species exist also.

Inside urban areas and there are, uh, tons of publications that underline the importance of trees and plants within cities. For example, they mitigate the temperature. That’s widely known, but their plants have, uh, also give a psychological like boost to people. If people live in a greener area, they are usually more fine with themselves.

So yeah, bees are important because they guarantee the reproduction [00:06:00] of plants, but are important because also they guarantee the survival of humanity.

Jacy: So let’s talk a little bit more about the bees not moving in from the farmlands or the agricultural landscapes. So what could towns or cities do to make it easier for native bees to travel and settle in new areas, and how much is this something we want to encourage?

Lorenzo: Well, it is in a way simple to colonize these areas and the only thing, uh, you need is to have little green areas all around the landscapes. I’m talking about very small. Patches. But the important thing is that there must be many and close to each other because as I told before, pollinators are not able to fly for large distances.

And in addition to that, it is important also to guarantee. [00:07:00] A certain coverage of semi-natural areas because one results, or maybe I can say a known results of this paper is that semi-natural areas didn’t influence at all the presence of pollinators. And that is something very strange because we could expect that.

If we have more semi-natural areas, I should encounter more pollinators. But in this case, that wasn’t the case. And the reason is related to the extreme low coverage of these areas that in our case study, they were. An average of 2.5% of the landscape taken into consideration. So in order to have more pollinators in our cities, the two main important things are.

Giving them more green [00:08:00] areas, both urban and natural. And the other things is, of course, don’t use too much pesticides in the agricultural settings that we can encounter around urban settlements, for example. But the main problem, the main issue is the landscape composition.
Jacy: So we’ve got our bees into our urban areas.

What kind of green spaces are the biggest hit with them? Are there certain plants or designs that make a park or garden extra welcoming?

Lorenzo: Well, I think that there is a word that answer this question, and the word is heterogeneity, both in term of the composition of the green areas and also in terms of the plant species.
In the first case, pollinators needs. Resources and nesting sites close together. So the more heterogeneous is [00:09:00] a green area. The better it is for pollinators if you have bushes, uh, little pond areas with taller grasses and areas with shorter grasses, areas with bare soil. Because there are so many species that needs bare soils to construct their nest.

If the green areas has these characteristics, it is optimal for pollinators Regarding the second. Or rather the heterogeneity of the plant communities. In order to have a big pollinator population, you need to add many plant species, but these plants. Need to be different in terms of their traits. For example, you should have a lot of species with different colors, different shape of the flowers, and also different flowering times because you must give [00:10:00] pollinators an opportunity to feed all around the flowering seasons.

First of all, the, the management of these areas is important. If you do not like, respect the timing of the flowering, and for example, you cut all the grass at in the beginning of May, you don’t guarantee a proper plant community.

Jacy: While urban sprawl might not be boosting the number of pollinator species it is helping the ones that are already there thrive, especially when cities include many interconnected green spaces and diverse landscapes, even in human dominated environments, full design and planning can make a big difference for biodiversity.

And let’s not forget, green spaces help cool our concrete cities and are good for our mental health. Thanks to Leonardo for sharing his work with us and [00:11:00] to you for listening on our website, you’ll find a great resource from Leonardo sharing guidelines for creating and maintaining pollinator habitat in urban spaces.

Until next time, be green and stay cool.