How Forest Forensics Could Prevent the Theft of Ancient Trees

To track down timber thieves, researchers are turning to new tech and tried-and-true criminal justice techniques

For tree poachers, sometimes known as "midnight burlers," redwoods can present a lucrative opportunity for theft. New research recommends ways to deter this hard-to-trace wildlife crime. Chad Ehlers / Alamy

Northern California’s redwoods tower majestically above the forest floor, protected and cherished by all. All, that is, except tree poachers, who lurk in the shadows waiting to hack into some of the world's oldest organisms and extract valuable chunks of knotted burl. Theirs is an unlikely prize: a heavy, knotted chunk of rust-red wood, nestled near the base of older trees and reminiscent of a large hornet's nest. In the right hands, these chunks of ancient wood can prove infinitely valuable.

Burls grow like large, knotted tumors from the base and spine of a tree, but are filled with smooth flesh. That makes them perfect for use in manufacturing tables, mantels, picture frames and souvenirs like salt and pepper shakers. For poachers—often dubbed “midnight burlers”—they’re accessible and surprisingly valuable. Large slabs can fetch thousands of dollars; one furniture manufacturer estimated that a heavy stump with a burl could retail for upwards of $3,000.

Three years ago, California’s storied Redwood National and State Park groves suffered a spate of burl poaching. In the mornings, rangers and maintenance staff would patrol the park, sometimes stumbling into a crime scene in the vast wilderness. Overall, they documented a whopping 18 known cases over one year.“It’s a crime of opportunity,” says Leonel Arguello, Redwood National Park’s chief of resource management and science. 

Not unlike the poaching of ivory or live-wildlife poaching, burl theft straddles the line between traditional crime and conservation nightmare. Burls are essentially seeds, filled with the nutrients needed to sprout a new tree, and imperative in the regeneration of groves that were once logged to near extinction.

Yet for law enforcement, this particular type of crime has been a doozy. With few law enforcement rangers and, in this case, 133,000 acres of protected park to patrol, it’s an almost impossible task to look for trees gored of massive chunks of wood hacked inexpertly from their base. As a result, most research on wildlife crime up until this point has been conducted not from the vantage point of criminology, but of conservation biology. 

Now that may be about to change, says Stephen Pires, a criminal justice professor at Florida International University. In an unpublished study, Pires and criminal justice colleagues at the University of Waikato in New Zealand and California State University at San Bernardino seek to analyze patterns in timber poaching, and link those patterns to the broader world of local crime. These new techniques, the researchers argue, can help identify patterns in criminal behavior that might be integral in wildlife crime prevention.

Almost all timber theft stories take place at night, or in the shadows. The body of a tree can move almost entirely within those shadows, harvested and sold in darkness, an organized crime relying on the conscious-blindness of everyone involved—from logger to mill owner to consumer. Midnight burlers deliver those burls to mills and “burl shops” without paperwork, where the wood is quietly and quickly processed, and sent on its way. 

To poach a burl, thieves hack into live and dead trees, carving out gigantic chunks that can then be either transported on the backs of trucks whole, or chunked into small, more manageable pieces. (“If you can pick it up yourself,” explains one mill employee, of smaller pieces, “it’s probably going to be $25.”)  Sometimes, poachers fell living trees to access burls higher up than the ground floor, or cut into already-felled logs. These burls are then transported to “burl shops,” located in nearby towns especially in the Pacific Northwest, where the wood is treated and sold.

While well-publicized charges were pressed against burl thieves by the Forest Service in 2014, it is rare for burl poachers to be charged: Redwood National and State Parks, for instance, had only charged three people in a 12-year period before 2014. Since then, burl poaching has become the subject of combined study between conservationists, forest managers, and crime scene investigators. 

The challenges for catching burlers are high. For one, timber theft is so localized that, apart from the unlikely circumstance that a ranger stumbles upon the theft taking place, it is very difficult to catch those that hack the edges out from burls once the crime is complete. And even if evidence is found at the base of a tree, pairing that evidence to stolen timber is almost impossible when it has already been sold and processed by burl shops nearby.

While there are some forensic processes that researchers have developed to catch poacherssuch as studying chainsaw marks like you would a ballistic analysis on a gunthat still requires finding the matching chainsaw. Arguello says that in some cases, this has been possible only because the thieves were incarcerated for other crimes.

Still, new techniques are being developed to track poached wood, not only in North America but globally. Dendrology, the study of a tree’s scientific taxonomy, is used in the emerging field of “forest forensics” to match intercepted wood with the stumps left at the scene of the crime. The Wilson Wood Collection, housed at the Smithsonian’s National Museum of Natural History, for instance, is being used to create a global database of thousands of tree chemical “footprints” that can help customs agents and law enforcement track endangered and trafficked wood.

“For every action there’s a reaction,” says Mark Webber, a master arborist and horticultural investigator at Robson Forensic, which provides expert investigations, reports and testimonies for various criminal cases, including tree and timber theft.  “Let’s say, for example, that somebody took a burl off a redwood in California and we can prove that [a specific] person was there at the time. There would most likely be some type of wood response on the redwood that you could date to determine when the crime occurred.”

To the trained eye, this wood response, also dubbed “wound wood,” is evident in the tree’s growth rings. At the same stage, Webber notes advancements in tree DNA science that make it easier to determine the “fingerprints” of trees. By studying the fibers of seized wood under a microscope and determining genus and species, “you can in many cases trace back that genetic footprint from that plant to where it was harvested from,” explains Webber, who owns his own wood library from which he makes comparisons.

Applying traditional crime scene investigation and law enforcement techniques to this wildlife crime is both obvious and difficult, the kind of challenge that park rangers might enjoy if it wasn’t so impossible. In combining the two fields, interesting twists of language take place. For instance, terms distinct from ecology and nature are applied to wildlife crime. Burls and trees are “victims” in this regard, and their theft a form of “victimization,” at least in the new study.

That’s why researchers like Pires suggest that the preventative aspects of traditional crime investigations be prioritized over reactionary measures tied to the scene of the crime. In September 2016, Pires and the Redwood National Forest completed the first deep study of redwood burl poaching, and came up with a much-needed risk analysis. The team used mapping software and the digital tool LiDAR (light detection and ranging) to examine the surface of the earth over the park, plotting the location of hundreds of redwood trees.

“This kind of narrows the scope of where risk is more likely to occur,” says Pires.

From there, the researchers mapped sites of known burl thefts. What they found was surprising: “Poaching was more likely to occur in areas that had more accessible redwood targets, and were in close proximity to burl shops,” says Pires. The criminologists had expected an out-of-the-way, dead-of-night crime. Yet rather than occurring deep within the backwoods, poaching most often took place less than 400 feet from a road.

But for park officials, it echoed what they had already observed in their daily patrols—that vandalized trees were often clustered near each other, and close to access roads.

The results of the study suggest that, rather than concerning themselves with patrolling the backwoods, park officials should draw a buffer 1,000-feet on every side of all park roads. From there, “target” trees can be identified and monitored. “For instance, when we were mapping out these incidents, we noticed that there’s, at least in some areas, a number of redwood trees with burls that were low to the ground that were not targeted. So these seemed likely targets,” says Pires.

This, he says, is similar to the way that burglars will repeatedly visit homes and neighbourhoods that they have already targeted: they know the goods are worthwhile, and will be replaced once they’ve been stolen. This can, in turn, guide rangers to where a next poaching target might be. “You can’t repeatedly target the same burl, but you can repeatedly target burls that were near a burl you had previously poached,” Pires says. 

The study outlines a number of recommendations for park rangers, all grounded in “situational crime prevention”—that is, the idea that crimes that are easier to prevent than solve. Essentially, these precautionary measures seek to alter the “situation” rather than the criminal itself. For instance, Pires suggests CCTV and license plate imaging at park gates: “Someone goes in without a burl and comes out with a burl, we know someone did something funny,” he says. Studies have proven the effectiveness of this approach in cases of home vandalism prevention, for instance, which have seen a decrease in the past when fences and access gates were installed.

From the park’s perspective, Arguello says one option is to use this data to find valuable trees and applying some sort of marker (Though, he qualifies, “I would never advocate spiking”—a controversial method that involved shooting metal spikes into the trunk to break chainsaws) that the tree can be tracked with. “There’s no real ways to enforce it a vendor wants to use material to turn it into a table or clock, unless there’s an active investigation into a shop,” Arguello adds.

Pires suggest that the solution could be rooted in a more urban policing method. In the tradition of pawn shops, he argues that requiring burl shops copy the photo identification of all sellers, and allow the police to check those IDs when reports of burl poaching comes in, could do wonders in preventing burl poaching. But he doesn’t think that will happen anytime soon: “They know exactly what they’re doing, so this is the opportunity for the offender and the burl shop,” he says. “They’re both happy to continue this type of operation.”

Editor's note, September 27, 2017: This article has been updated to reflect the current affiliations of Stephen Pires' colleagues.

Get the latest Science stories in your inbox.