Talking Trees — Part 3: How can we listen to trees?

Image by © Stephen Chambers
Published by RA Editions
Photography: FS@SCS

In my new series, Talking Trees, I’m translating findings from my PhD dissertation, called the "Internet of Nature", into seedling-sized blogs. My research advances ecological engineering by exploring the potential of novel technologies to monitor urban ecology, particularly urban soils and forests. I believe technology can be a powerful tool—and in this series, I hope to illustrate how digitising our urban ecosystems into useful data can help us build healthier, happier, and more resilient places to live.

In Part 2 of Talking Trees (read here if you missed it), we learned about the underground world of mycorrhizal fungal fibres that allows trees to ‘talk’ to each other. If they could talk, we wanted to know what they might be trying to say. We uncovered that they might share that they’d rather be in the woods. But as much as trees may be better off growing in forests, cities are undoubtedly better off with trees growing in them.

To combat urban deforestation caused by tree cover being swapped out for impervious cover, we need to better maintain existing trees and plant more, but that’s not all. We need also to address a fundamental premise: the city is to a tree what the desert can be to a human, harsh and volatile.

What if we could take a leaf from Nature's book and copy a mycorrhizal fungal network to an urban context? Allowing trees to communicate their needs not just to each other, but also to people?

Urban nature is a blossoming field. Concepts and tools for quantifying, standardizing, and classifying urban ecologies and biodiversity have only recently been emerging in the literature. As a result, it is difficult for local governments to:

1) acquire reliable biodiversity data across the city;

2) identify urban elements that have positive or negative effects on ecosystems;

3) design and evaluate effective interventions.

In short, we need real-time information to help urban nature survive and thrive.

What if ‘smart city’ technologies, usually reserved for traffic monitoring, waste management and smart grids, could record that information and, in return, strengthen our stewardship of the natural world around us?

Sensors providing data on moisture, temperature, electrical conductivity, pH, and oxygen, like those developed by Soilmania, may hold the answer. By placing a sensor in the soil during the planting or maintenance of a tree, we can constantly monitor the health of the soil. The data collected from the sensor is translated into a dashboard, showing exactly where and when a tree needs what. It’s almost as if the tree can talk to its manager, and in return, tree managers can listen to the tree’s needs.

Case in point: in the Dutch city of Maastricht, since planting in 2017, not one of the thousand linden trees planted on the top of a new tunnel has died. That's because three Soilmania soil moisture sensors constantly monitor the growing conditions of the trees. The tree care manager is notified when the trees need water. This way, not a single tree’s soil dries out.

If, after a number of years, the monitored tree is thriving and no longer requires special care, the sensor can easily be transferred to a new location. Water and other missing nutrients are not only critical to helping the tree survive, but watering and aiding the soil as needed means trees can grow in optimal soil conditions, so they grow three times faster. In an age of urban biodiversity and sustainable city agendas, the faster we can exploit a tree’s ecosystem services, the better. Rich ecosystems and biodiversity can exist in cities, and increase citizens’ health, well-being and productiveness.

Citizens, too, can listen to trees using sensors. In fact, in the Dutch village of Geijsteren, Soilmania's sensors were installed for trees located in the town square. Instead of tree managers, neighbouring residents receive watering updates, promoting citizen engagement and participation in tree maintenance.

Sensors measure data used to assess in real time whether the environment is suitable for beneficial microorganisms. In addition, the activity of soil life is mapped, for example, by following the respiration and mineralization processes.

Urban tree planting investments depend on trees establishing and surviving to maximize ecosystem services.

If we are going to plant and grow trees in cities, we owe it to them to listen.

Sensors may be the most direct line of communication we’ve got. Understanding exactly which tree we should water when and uncovering the soil’s needs (which coincide with the tree’s needs) is the first step we should take towards proactive tree care.

In the future, sensing technologies may help us to uncover where tree roots are lacking mycorrhizal fungi, so that we may inoculate the soil to support the re-establishment of the trees’ biological communication network, even in cities.
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Acknowledgements

Thank you to Stephen Chambers for the beautiful illustrations. My research is made possible by the generous support of the Connecting Nature H2020 project, University College Dublin, Trinity College Dublin, Stichting Fulbright Commission the Netherlands, and MIT Senseable City Lab.