How much nuisance should urban nature be allowed to cause? |
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Yellow adhesive tape around trees in Alkmaar highlights tension between biodiversity and human discomfort
Anyone walking along the Laat in Alkmaar may notice a striking yellow band around several trees. The adhesive tape is intended to prevent ants from climbing the trees and protecting aphids. This gives the aphids' natural predators more opportunity to control them and should reduce the nuisance caused by sticky honeydew. It is a simple intervention, but one that raises an interesting question: how much room should we give natural processes in cities when they cause inconvenience to people?
| Image for illustration, generated with AI |
The reason for the intervention is a fairly common problem. Aphids in the trees secrete honeydew, a sticky, sugar-rich liquid that eventually ends up on streets, cars and outdoor terraces. It does not directly harm the trees, but it can cause inconvenience for businesses and visitors.
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How much room should we give natural processes in cities when they cause inconvenience to people?
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Ants as bodyguards
The trees are also home to natural predators of aphids, including ladybirds and lacewings. However, these predators do not always have free rein. Ants are attracted to honeydew and benefit from keeping the aphids in place. They therefore protect the aphids from their natural predators.
According to Yvette Pronk of restaurant Thup's, this interaction is clearly visible along the Laat. 'Ants love that sweet substance. They milk the aphids. Those ants have an entire intensive farming operation going on in these trees,' she told Streekstad Centraal.
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The adhesive tape does not target the aphids directly, but disrupts the cooperation between ants and aphids
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Adhesive tape disrupts cooperation
Pronk decided to apply yellow adhesive tape around several tree trunks herself. The sticky band forms a barrier for the ants, making it more difficult for them to reach the aphids in the canopy. This gives ladybirds, lacewings and other natural predators more opportunity to prey on the aphids.
Rather than targeting the aphids directly, the measure deliberately intervenes in the interaction between different insects in and around the tree. That is precisely what makes this seemingly simple solution interesting for green space and tree managers.
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More urban nature also means accepting that nature can sometimes cause inconvenience
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When does nature become a nuisance?
Municipalities are increasingly focusing on biodiversity and allowing natural processes to take place in cities. At the same time, green space managers are expected to keep public spaces pleasant and usable. These two interests can conflict. In Alkmaar, the nuisance is relatively limited: sticky tables, cars and paving.
On a small scale, the yellow adhesive tape therefore illustrates a broader issue. Giving nature more space also means that insects and the processes associated with them become more visible. The question for urban green space management is where to draw the line: when is inconvenience simply part of urban nature, and when is intervention desirable?
This article was previously published on 10 August 2026 on the website of Stad + Groen.
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