How ground penetrating radar is changing urban forestry

By Dr. Nadina Galle

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Jim Hosick never planned on becoming an expert in what lies beneath our feet. But as the founder of Landmark Environmental Group, a company specializing in consulting arboriculture, urban forestry and landscape architecture, he quickly realized that what you can't see might be just as important as what you can see.


"I grew up in rural Ontario," Hosick recalled. "My first job was cutting someone’s lawn when I was 10. That led to work at a local cemetery, then with a landscape firm, and before I knew it, I was deep into turf grass management and arboriculture. I’ve always been drawn to learning about how trees and landscapes fit into our urban environments. That curiosity eventually led me to question how we could protect them while accommodating the rapid pace of urban development."


This question became even more pressing as Hosick witnessed firsthand how urban development has long conflicted with tree preservation. The classic battle between gray and green — progress versus preservation — plays out daily in cities worldwide. But what if there were a way to bridge the gap between developers and conservationists? Enter ground-penetrating radar (GPR), a technology that’s quietly revolutionizing urban tree protection.


Hosick has been at the forefront of advocating for and using GPR in Ontario. "When we first introduced GPR, people were skeptical," Hosick said. "They couldn’t believe we could map roots without digging up the soil." His firm introduced the technology two years ago, not just to expedite development but to provide a defensible scientific foundation for tree preservation.


Traditionally, determining a tree’s root structure required air spading — a labour-intensive, noisy and costly method that exposes roots by blasting air into the soil. GPR, on the other hand, offers a non-invasive alternative, mapping underground structures using radio waves. The results? A detailed, three-dimensional image of root systems that allows arborists to pinpoint where and how development can proceed without harming trees.


The technology has already proven its worth. In one case, the Town of New Tecumseth faced a dilemma: a 200-year-old red oak sat at the intersection of a planned sidewalk repair. By mapping the tree’s roots, GPR revealed that the work could proceed without compromising its stability, preserving a living piece of history while accommodating infrastructure needs.


Yet, GPR isn’t just about saving trees — it’s also about resolving disputes. Ontario’s 2013 Superior Court ruling on boundary trees means developers now require neighbouring property owners' written consent before removing any shared tree. This has led to a rise in legal battles, with some homeowners using tree protection as a tool to block developments. GPR provides an impartial solution: clear, visual evidence of whether a tree’s roots truly extend into a disputed zone, cutting through the emotion-driven debates that so often stall projects.


The implications for urban forestry are vast. Beyond legal disputes, GPR can help municipalities plan tree-planting initiatives, monitor the health of heritage trees and assess risks in storm-prone areas. As climate change intensifies and cities strive to maintain green canopies, technologies like GPR offer a way to balance progress with ecological responsibility.


Looking ahead, the use of GPR is expected to play a crucial role in addressing the affordable housing crisis. "Housing is a priority, but so is preserving our urban canopy," Hosick states. "GPR helps us find solutions that work for both — without having to sacrifice one for the other." With increasing pressure to build more housing in urban areas, many development projects face delays due to tree protection disputes. GPR could help resolve these conflicts efficiently, allowing construction to move forward while preserving as many mature trees as possible. This approach would enable cities to meet housing demands without sacrificing urban forest cover, ensuring that communities remain both livable and sustainable. As more disputes arise between developers and conservationists, GPR offers a solution that aligns urban growth with ecological preservation, providing a much-needed compromise in an era of heightened environmental awareness.


Still, skepticism remains. Some homeowners are hesitant to trust a digital map over physical evidence, and while GPR has been accepted in U.S. courts, its role in Canadian legal proceedings is still evolving. But with urban expansion showing no signs of slowing, the demand for innovative, science-backed solutions is greater than ever.


Hosick believes that, in time, GPR will become an indispensable tool in urban forestry. “It’s not about choosing between trees and development,” he says. “It’s about using the right technology to make sure we can have both.”
As cities grow and the stakes of climate resilience rise, that balance may be exactly what we need.