For more than 15 years, Georgia Tech has provided the City of Atlanta with the foundational data and insight that shape how the city tracks, understands, and plans for changes in its tree canopy. The latest cycle of this research — delivered through the Center for Urban Resilience and Analytics (CURA) — continues that legacy by offering a high-resolution, citywide canopy assessment using satellite imagery and field validation.

The assessment, funded by the city’s Tree Recompense Fund, uses advanced remote sensing tools such as WorldView-2 satellite data and a random forest classification model to categorize land into three land cover types. These include tree canopy, non-tree vegetation (grass, shrubs, and low lying vegetation) and non-vegetation (water, pervious surface). The methodology delivers a detailed spatial picture of land cover across the city.

“This is simply a tool in their planning arsenal,” said Anthony Giarrusso, who has led every canopy study since 2008. “Before they did any of this work in 2008, everything was anecdotal. It was reactionary.”

The new study is not advocacy — it’s information. Giarrusso emphasized that while researchers stay neutral in the politics of urban growth and conservation, their work equips city leaders with science-based knowledge to make more effective zoning and planning decisions.

In addition to mapping existing conditions, the Georgia Tech team developed the Potential Planting Index (PPI), a scalable tool that identifies where tree planting is physically possible based on current land cover. The tool quantifies the difference between tree canopy and non-tree vegetation, indicating zones with restoration potential.

Another key insight is the challenge of interpreting canopy change without understanding land use patterns. “It gives you a false sense of stability if you don’t understand the underlying land use,” said Giarrusso. “You might see canopy regrowth on paper, but that land could be cleared again tomorrow.” He explained that this false signal is particularly common in stalled development sites: “We saw a lot of properties where trees had regrown after initial clearing, but it was temporary and monoculture, low quality canopy. Several of those areas were cleared again for construction later.”

Giarrusso pointed to these “loss-gain-loss” cycles as one of the more misleading aspects of tree canopy analysis without strong land use context. “Some of them were pipe farms — land cleared for development with infrastructure like water and sewer lines installed, but then construction never happened. So trees grow back, and you get a canopy gain that doesn’t last and is nowhere near the quality of the trees originally cleared.”

He stressed that policymakers need to consider the permanence of canopy when using the data. “If it’s just going to be cleared again in two years, it’s not really a gain. That’s why long-term tracking and land use analysis together are so important.”

The city has incorporated these tools into broader planning efforts, including zoning reform and tree ordinance revisions. The research supports recommendations such as restricting full lot clearing in certain zoning categories and adjusting setback or lot coverage limits to better preserve existing canopy.

Giarrusso underscored the urgency of protecting larger, intact forested tracts. “If you can see it from space and it’s still forest — save it,” he said. “Once it’s cleared, you don’t get it back.”