New Collection Wall Spotlights Cool Urban Ecology Research

By Olivia Barney 

Noortje Grijseels weighing the amount of PM2.5 collected on a leaf sample.

Recent visitors to NHMU may have noticed one big change: the massive, 35-foot-tall collections wall has had a makeover. This is the third time that objects within the collections wall have been switched out, and it’s not done for aesthetics only. Even artifacts need time to rest. Constant display can cause wear and tear to objects, with sunlight fading some of the once brilliant colors. To counter this, museum objects are regularly rotated and assessed for signs of wear.

But updating the Museum’s iconic collections wall has other benefits too. Within the last few years, the Natural History Museum of Utah has added several new people to their collections and research team, bringing new scientific disciplines to the Museum. 

The Urban Ecology division, for example, was created in January of 2023, when Alexandra Ponette-González, Ph.D., joined the NHMU team. Urban ecology focuses on studying our cities as complex ecosystems that affect and are affected by humans and the natural world. Scientists in this field may study biodiversity within urban areas, community green spaces, or climate conditions, like air pollution. 

A New Window into Urban Ecology 

Since the previous edition of the collections wall was created before Ponette-González came to NHMU, this update gave her team the opportunity to have some of their important work highlighted in the latest edition. 

“NHMU’s mission is to illuminate the natural world and the place of humans within it," said Ponette-González. "The representation of urban ecology in the collections wall does precisely this — it reminds us of the intricate relationship between modern societies and the environment.”

When it came to selecting something to place in the artistic display, they had to strike the right balance of including something scientifically interesting and visually appealing. After a bit of brainstorming with the exhibits team, Ponette-González and her colleague Noortje Grijseels opted to include a selection of leaves and filters used in their ongoing study of dust and other particulate matter accumulation on tree leaves. The research poses interesting questions: How much dust is collecting on our trees, and what can that dust tell us about our environment? 

Tracking Pollution Through Tree Dust 

Urban areas are (unsurprisingly) prone to air pollution. From construction work to manufacturing plants, car exhaust and campfire smoke, there’s plenty of dust and debris floating through the air. But did you know that in certain places trees can help clean our air by collecting pollutants?

Ripley Dossett using a pruner to clip a leaf sample from a Norway maple tree on the corner of 700 E and 1300 S.

The Urban Ecology team at NHMU is interested in studying this process to determine how much dust collects on leaves, which tree species are more efficient in dust collection, and whether or not the same species produce the same results in other cities. The answers to these questions could help city planners and developers as concerns about air pollution continue to rise. 

Our research has the potential to indicate where and when air pollution is highest in urban communities as well as where trees are most needed for human benefit. 

The research project spans three cities: Salt Lake City, Utah; Cleveland, Ohio; and Eugene, Oregon. In each of these cities, an army of undergraduate and graduate students alongside Ponette-González and Grijseels collected leaves (or needles) from six species of trees that were abundant across all three cities. These species include Norway maple, green ash, Bradford pear, Austrian pine, London plane, and cherry plum. 

Alexandra Ponette-González separating leaves from branchlets in the lab at NHMU.

As samples from each tree were gathered, the team made sure to gather branchlets from each side of the tree (north, south, east, and west), and throughout each of the four seasons (though only the evergreen trees were sampled during the winter). Each season, the team returned to the same trees — totaling 80 trees per city and 240 trees in all. 

Once back at the Natural History Museum of Utah, the team got to work washing, drying, scanning, measuring, and freezing each leaf. As the leaves were agitated and rinsed with water, the water was collected and filtered. When you visit the collections wall, you can see some of these leaves and filters. The largest filter says PM100, meaning it’s filtering out particulate matter that’s 100 micrometers in size or smaller. The smaller filter says PM2.5, which means it’s filtering out tiny particulate matter that’s 2.5 micrometers or smaller. (For scale, the end of one strand of your hair is about 70 micrometers across.) The smaller the particle, the more harmful it is to human health. For this reason, it’s important to sift through and measure the size of particles landing on these leaves. 

Bringing Urban Ecology to Museum Visitors 

This project is far from over, though initial research findings will be published in the coming months. You can check back later for updates on what the Urban Ecology team have discovered or subscribe to our Research & Science News email list to get alerted when new research is posted. 

In the meantime, check out the newest rendition of the NHMU collections wall (no ticket required), to see the samples and filters that represent this tremendous project. While you’re there, you’ll discover a greater sense of awe for the wonder of the natural world and an appreciation for the intelligent women and men who research it.  

“Urban ecology matters because our cities represent critical spaces for human-nature connections," said Ponette-González. "They are also opportunity spaces for new ways of managing the land that can increase urban sustainability, urban livability, and access to nature for all communities, including those historically deprived of/or excluded from nature.”