Insects in the city: How urban trees could better support biodiversity

By Carolyn Ali

Why planting trees that support insects and microbes matters to people, too

You probably know why trees matter to people in cities. They beautify our neighbourhoods, offer community gathering spots and boost mental and physical health. They clean and cool the air, soak up rainwater and provide crucial shade for buildings and residents in a warming climate.

But have you ever thought about how trees benefit other living things in the city? This includes birds and squirrels, of course, but also other wildlife you may not see, such as insects and microbes. The latter are tiny living organisms such as fungi.

Insects and microbes matter to people because they support biodiversity in cities. And a diversity of plants and animals matters, because it supports things like pollination. Where wild bees are and aren’t, for example, impacts our food supply.

When city planners choose what kinds of trees to plant in Vancouver, they think about which varieties will thrive under local conditions. For example, European Hornbeam trees are often planted because they grow quickly, give good shade, can handle dry conditions and don’t get many diseases. However, this tree variety doesn’t offer good living conditions for native insects. It also doesn’t produce nectar, berries, or other things that nourish the city’s wildlife. We don’t yet fully understand how different tree varieties affect insects and microbes. To learn more, UBC researchers have launched a project that involves going out and literally shaking some trees.

What’s living in our trees?

The Campus Trees, Microbes and Insects (CTMAIN) project aims to find out how certain characteristics of trees can help us create more resilient ecosystems. This research can help city planners choose different trees to plant that not only thrive in the city but also help support other living things, and help to fight climate change.

Led by Dr. Michelle Tseng, assistant professor of Botony and Zoology in the Faculty of Science, and Dr. Tara Moreau, associate director of Sustainability and Community Programs at UBC Botanical Garden, the research is taking place on the UBC Vancouver campus. A city within a city, the campus acts as a living lab, where students and faculty can do crucial research that has impact for people off campus, in other cities and around the world.

UBC undergraduate students Julie Sieg and Oliver McDermott are part of the team that’s conducting the research. They spent the summer of 2023 collecting samples of insects and microbes from 20 species of trees on campus. The method was pretty low-tech: climbing a ladder and using a giant stick, they hit sample branches and collected the insects that fell into an inverted umbrella. Then they used a paintbrush to collect the insects and put them into vials containing ethanol, which kills and preserves them.

Later at the lab, the insects were pinned, categorized into large families, and then organized into species, providing data on how many of each type were on each tree. Microbes were also analyzed to help researchers better understand the ecosystem that different types of trees support. “The principles we’re studying here on what types of trees are good for insect biodiversity are going to be applicable anywhere that those trees or those families of trees exist,” explains McDermott. “Because urban areas tend to have the same species of tree, even in vastly different locations, there’s going to be a lot of applicable information for people who don’t even necessarily live in BC or Canada. It can still inform decisions elsewhere.”

Learn why a decline in insects matters to our food supply

Carolyn Ali is a writer for UBC Brand and Marketing. This article was published on March 12, 2025, and adapted from original material produced by the UBC Sustainability Hub. To republish the original material, contact UBC Sustainability Hub.