São Paulo deploys lidar to assess trees to reduce fall risk

In December 2025, winds exceeding 90 km/h swept through São Paulo, Brazil, and its surrounding areas, resulting in 1,327 reported incidents of fallen trees in the São Paulo Metropolitan Area alone, leading to several injuries. More than two million inhabitants were left without power. 

Now a group of biologists and engineers from the University of São Paulo (USP) have applied lidar technology to investigate the health of trees and optimize pruning with the aim of reducing the risk of them falling.

The laser-based sensing technology creates a 3D point cloud, which reproduces the tree’s architecture. The replica is then used to apply a pruning algorithm based on “topological optimization”.

The technique simulates in a tree model the strength of the wind to identify the regions in the plant presenting the biggest mechanical vulnerability. In this manner, the system calculates exactly which branches must be cut off so that the tree can redistribute stress and become stronger and more balanced.

The group’s ultimate goal is to use lidar to help create a pruning app that will make trees less susceptible to wind, thus avoiding the risk of falling.

“Improper pruning leaves trees vulnerable to wind, which can uproot or break trunks and branches, especially in isolated trees, at high speeds. The problem is exacerbated by wind tunnels, known as urban canyons. Gusts of wind, rain, and temperature fluctuations during the rainy season increase the risk of trees falling,” said Marcos Silveira Buckeridge, from the Department of Botany at USP, who is co-author of a paper published in May in the journal Trees: Structure and Function.

Methodology

The researchers scanned a rosewood tree located on USP’s campus. This tree is commonly used in urban landscaping. A point cloud of 30 million points was formed to capture the tree’s shape. “Using this, [fellow researcher] Luís Otávio developed relevant equations. The leaves were removed from the 3D images, leaving only the trunk. Then, we applied wind from various directions and observed the tree’s sensitivity,” said Buckeridge. 

The results show that pruning a branch creates topological asymmetry and makes the tree more vulnerable to wind. “This article is important because it’s a proof of concept, using mathematical equations to demonstrate that it’s possible to use lidar for this purpose.” The biologist states that mathematical modeling is well-suited to predicting whether a tree might fall.

The pruning algorithm based on topological optimization recommends removing material based on the stress distribution obtained through FEM. The team aims to minimize structural weaknesses by ensuring that no more than 20% of the tree’s total mass is removed during pruning. According to researcher Nelli Silva, topological optimization prioritizes regions with greater mechanical flexibility, resulting in a balanced, resistant structure. In other words, pruning calculated by the algorithm improves the tree’s response to wind, especially in cases where the tree is unbalanced due to fallen branches or disease.

Buckeridge states that the methodology can also be applied to eudicotyledonous angiosperms – the largest group of flowering plants in the planet, encompassing beans, soybeans, oranges, strawberries, roses, and sunflowers – which have a “classic structure of branches and twigs”.

However, the author emphasizes that human labor in pruning remains essential. “We aren’t talking about replacing humans in pruning work, but rather providing a tool to facilitate it and, at the same time, make the tree more resilient.”