A map tracking the distribution of chemical isotopes in tree wood acoss the Amazon could become a powerful new weapon against illegal logging.

The illegal timber trade remains one of the primary drivers of deforestation across the region.

By analyzing the ratios of different isotopes in elements like oxygen, carbon, nitrogen, and strontium, researchers can identify where a piece of timber came from with much greater precision.

This gives investigators a far more accurate way to trace the wood’s geographic origin.

The tool is being developed by a research group led by Luiz Antonio Martinelli, a professor at the Center for Nuclear Energy in Agriculture at the University of São Paulo.

It’s designed to address a persistent gap in how Brazilian authorities currently verify timber origin.

Illegal logging slips through
Environmental agencies and law enforcement in Brazil already rely on a range of tools to trace where timber comes from.

These tools include analyzing plant anatomy, cross-referencing species distribution, and consulting official paperwork like the Forest Origin Document.

However, these methods aren’t always sufficient to reliably confirm that a shipment of timber was actually harvested legally, leaving real gaps that illegal loggers can exploit.

Martinelli’s team is working to close that gap using isotopes, forms of a chemical element that share the same atomic number but differ in mass.

The approach involves building a detailed map of how these isotopic signatures naturally vary in wood from different parts of the Amazon.

Police could then compare seized wood samples against that reference map to help determine where the timber originated.

Isotopes are nearly impossible to fake
“Our goal is to provide the Federal Police with a tamper-proof method. You can’t falsify stable isotopes,” Martinelli said.

That tamper-resistance is central to the tool’s appeal, since it removes the possibility of loggers fooling the system by forging documents or otherwise manipulating more conventional tracking methods.

Once the isotope distribution map, known as an isoscape, is finalized, experts outside specialized research laboratories should be able to apply the methodology fairly easily.

A clear pattern written in wood
The core methodology involves calculating the ratio between two different isotopes of the same element, such as oxygen-18 and oxygen-16, found within the cellulose that makes up wood.

The analysis revealed a clear geographic gradient running from southwest to northwest across the Amazon. The lighter oxygen isotope was most abundant in the western part of the Amazon forest.

Wood from the western Amazon contains proportionally more oxygen-16 and less oxygen-18 compared to wood harvested from the eastern part of the forest.

That pattern traces back to basic atmospheric physics. As moisture originating from the Atlantic Ocean moves inland across the continent, it gradually loses the heavier form of oxygen along the way.

By the time that moisture reaches the western Amazon, it has already shed some of its oxygen-18.

As a result, plants in that region incorporate smaller amounts of the heavier isotope into their wood as they grow.

One isotope isn’t enough
Oxygen alone can’t carry the full weight of this identification task, though.

“Since the Amazon is so complex – a very large area – it isn’t possible to use just one isotope,” Martinelli explained.

To build a more complete picture, an ongoing doctoral project led by PhD student Isabela Maria Souza Silva is currently mapping the isotopic signatures of two additional elements, carbon and nitrogen.

The team also plans to eventually incorporate strontium into the model, adding yet another layer of geographic specificity.

Amazon helps Improve the isotope model
As it stands today, the tool still has real limitations worth acknowledging.

“Our best model can exclude 92 percent of the Amazon‘s forest area, which amounts to three million square kilometers,” Martinelli said.

“The problem is that 8 percent is still too much. To give you an idea, that’s roughly 240,000 square kilometers.”

In other words, while the current model can rule out the vast majority of the forest as a wood sample’s point of origin, the remaining zone of uncertainty still covers an area larger than many countries.

The tool also struggles with greater result variability specifically for trees sourced from the deforestation arc, the geographic band marking the active frontier of destruction within the biome.

That inconsistency makes the method harder to apply with confidence in precisely the regions where illegal logging tends to be most intense.

Expanding the sample size and toolkit
Martinelli and his team are working to narrow these limitations by expanding both the number of isotopes tracked and the number of physical samples collected.

“We’ve collected samples from 800 trees at 63 sites across the Amazon and found that if we want a more accurate model, we’ll need to collect from more trees in more locations,” he said.

Beyond simply adding more isotopes and samples, the team is also exploring entirely new chemical approaches that go beyond isotope measurement alone.

One promising direction involves building what researchers call an “elementalscape.” This is a map that tracks differences in the concentration of specific chemical elements found in wood across different regions.

By combining multiple approaches like these, the researchers hope to develop a much more precise tool.

It could give Brazilian authorities a reliable way to distinguish legally harvested Amazon timber from illegally harvested wood.

The study is published in the journal Molecules.
  
Source: earth.com