As Marco Garcia enters the third year of his PhD at UGA, he’s investigating how red mangrove trees protect coastal communities from hurricanes by putting their strength to the test.
Mangrove trees are found along coastlines and wetlands in tropical and subtropical regions around the world. They grow in both fresh and saltwater, allowing them to grow in places other trees can’t.
These trees with spider-like roots extending from their trunks are part of nature’s critical infrastructure, adapting to sea level rise and providing stability to shorelines in the face of more intense storm surge. The drag of stormwater through their complex root systems reduces the wave height and dissipates the energy of storm surges when hurricanes make landfall.
To test the stability and strength of mangroves, Garcia spent three weeks in his home country of Guatemala attempting to knock them down.
Putting trees to the test
A common way to test the mechanical stability of a tree is the tree-pull experiment: using one tree as an anchor, a test tree is pulled to an angle, allowing researchers to measure how much force it takes to bend the tree. This technique is rarely applied to mangrove species. The amount of force and the angle measured indicate how strong a tree is, and in this case, how likely it is to bend to hurricane-force winds and waves.
“We’re trying to find the mechanical properties and stability of mangrove trees through different ages, using both field and laboratory standardized tests” Garcia said. In his study of existing research on the topic, he found a problem with the literature on tree-pulling experiments: these tests often used pricey equipment–items that are difficult to purchase and even harder to take abroad.
“I realized that I could perform exactly the same test with low cost equipment,” Garcia said. “It was trial and error: testing in my backyard, so I could perform in the field.” He promised no trees were harmed in his backyard tests.
With his methods determined and a plan set for an exciting field season, Garcia left for Guatemala in November of 2025.
In a remote mangrove farm near the city of Retalhuelu, Garcia and collaborators tested the force required to make trees fall across differently aged stands, testing multiple young (5-year old), mature (10-year old) and adult (30-year old) trees.
“Failure occurs when the mangrove tree loses its strength and comes down, including its root system,” explained the UGA Compound Inundation Team for Resilient Applications (CITRA) in an Instagram post on Garcia’s experiments. These are tests that have not yet been done across different mangrove ages, a gap in the literature Garcia hopes to soon fill.
During this process, it became clear to the crew that those spindly roots aren’t just for show.
“I remember when we were pulling a tree, and when the roots failed, it lost all balance. It can extend more force because of the root,” Garcia recounted. “Their stability isn’t in the trunk, it’s in the roots.”
Not all of these tests involve trees falling, as the team’s approach included both destructive and non-destructive tests. After testing the trees’ strength on the ground, Garcia and collaborators also took samples of wood from several trees that were prepared by a carpenter and heat-treated to bring to the US. These samples will undergo additional tests in the lab at UGA.
As rising sea levels and increasingly intense storms slam coastlines around the world, researchers like Garcia are working hard to evaluate how mangrove forests can provide a protective and resilient nature-based layer against coastal threats.
From career success to coastal innovation
After graduating with a degree in civil engineering from the Universidad de San Carlos de Guatemala, Garcia had a full plate: teaching engineering courses at his university, starting and running a construction business and earning master’s degrees in business administration and structural engineering.
“I had been doing well in my country, I had what I needed, but I felt it was time to boost my career and take on new challenges,” he said. “I saw this Fulbright scholarship and asked my family, ‘Do you think we can start this life adventure?’ They said, ‘yes, definitely. We support you.’”
Garcia applied to five universities in the U.S., ultimately choosing the University of Georgia after a meeting with CITRA’s principal investigator, Felix Santiago-Collazo and IRIS Director Brian Bledsoe, who made him feel especially welcomed. Garcia began a PhD that builds on his structural expertise while opening new doors into natural infrastructure, with the ultimate goal of creating hybrid solutions that harness the strength of both.
Despite this dramatic shift in his career, Garcia has found ways to draw on his past experience. To get the tree samples to the U.S. efficiently, he registered his former construction company as a lumber exporter.
“It’s only 0.2 cubic meters of wood,” he said. “Anyone we talked to that already had that registration wasn’t interested, because it’s too small for them to bother with. So, I had to figure it out on my own.”
As the samples arrive at UGA this month, Garcia is getting the in-lab experiments and writing underway to explain the tree-pull experiments and his lower-cost method for them, which could open the door for replication by other researchers. The samples, spanning different ages, will help fill a critical gap in understanding how structural properties vary with tree maturity.
“Everything is changing,” he said. “We can’t stick with doing the same things to protect our communities–we need innovation, and one innovation is using these trees as living shorelines, which not only increase resilience but also provide multiple benefits for ecosystems and people.”
Learn more about the work UGA CITRA is doing across the world’s coasts here.