You can't not notice the trees that line the paths on Austin's many hike and bike trails. But have you ever noticed a fair amount of them are numbered? They're on small metal tags nailed to the trunks.

Writer Will Neely noticed them while he was running along the Butler Hike and Bike Trail, so he asked about it for our ATXplained project, a series where KUT answers questions about life in Austin.

“I use the Lady Bird Lake trails frequently and have noticed there are different tags on the many different species of trees. Do you know what these tags are for?” he asked.

Neely said he runs along the trails four to five times a week, and he’s always noticed tags.

“They kind of look a little bit like dogs' rabies tags,” he said. “I remember seeing gold ones, and also some red ones … silver and blue.”

He said he was eager to learn more about the tags after a friend asked about them. He reached out to the city’s Parks and Recreation Department, but wasn’t satisfied with its answer.

KUT's Nadia Hamdan reports

“They just kind of said, ‘Oh, well that’s just part of inventory,’ and I’m like – that doesn’t really answer the question,” he says. “I kind of get the sense there was probably like an intern or something that answered the question.”





Neely said he thinks the tags have something to do with the health of the trees, but he’s not sure because they can be pretty random. On the Butler trail, he pointed out a bunch of different tags, and he was right: It’s hard to find the rationale behind them.

One tree had two silver tags on it – one said 74, the other said 1347. It didn’t make sense.

Keeping Track Of The Trees

Kirsten Schneider is a supervisor in the forestry unit of Austin’s Parks and Recreation Department. She said the response Neely got from the department wasn’t necessarily wrong; it does use the tags for inventory.

“From a land management standpoint, we really want to be able to know what we’ve got in the parks,” she said, “because then we can sort of look at that on a large scale and make decisions about how we’re going to manage that park.”

The tag helps the department know the attributes of a tree, such as its size, species and age. A tree can be tagged for a variety of reasons, but it’s mainly to keep up with health and wellness – things like pruning of the trees, removing dead wood, raising canopies and providing clearance for playgrounds, trails and other pedestrian areas.

It’s estimated that there are about 34 million trees in Austin, but not all of them are tagged. Schneider said trees are usually only surveyed in landscaped areas.

“We don’t inventory, for the most part, trees that are in more natural areas like the Greenbelt, or any of the preserves,” she said.

A Virtual Filing System

When it comes to the trees on the Butler Hike and Bike Trail, the city partners with the Trail Foundation, which works to protect and improve those ecosystems.

The tags act as a virtual filing system that includes the geo-location of the trees and all the data associated with them. Both the city and the foundation can then monitor the health of a tree, remove invasive species and help inform what’s called “managed succession,” where they think about the next generation of trees.

But the tags are rarely used if a tree is slated for removal.

“If you’re going to remove the tree anyway, there is not really much point in tagging it,” Schneider said. “You’re not going to need to reference that tree again most likely.”

Anyone Can Tag A Tree

That made sense, but why do some trees have two tags and why are there so many different types? The tags can be aluminum or steel. They can be round or rectangular. Red, blue, gold and silver.

“Trees can be surveyed for any number of reasons so when you come across a tree that has a tag on it, there is really no telling what an individual tree survey meant,” said Emily King, the city’s urban forestry program manager. “There is not a master database of all the tree tags in Austin.”

That’s because it’s not just the city that survey’s trees.

Property managers all across Austin can order their own tags and survey trees. That’s why tags can look so different. But no matter what they look like, King said, once you start noticing them, you’ll probably start seeing them everywhere.

Environmental And Economic Value

And that was true for me.

Outside KUT on the UT campus, a number of trees have silver tags on them. It turns out, the university re-inventoried nearly 5,000 trees on campus last year.

“This one is just fairly awe inspiring and we just did a lot work around this site here too,” UT’s urban forestry supervisor, Jennifer Hrobar said, referring to a deodar cedar at the corner of Whitis and 24th. “You know, standing under this, you have no doubt that there is something special about it.”

The tree is the second largest of its kind in Texas. A native to the western Himalayas, the tree has been on the campus since 1893. It’s massive – with long, low-slung branches that droop gracefully around its trunk. It’s beautiful.

And it has a tree tag.

UT uses tags largely for inventory and maintenance, much like the city's parks department. But the school also uses them for something else, and it’s pretty cool.

The university sent information from the trees it surveyed to the U.S. Forest Service, which then sent back the "environmental value" of each one.

UT then put all that information in an app called MyTreeKeeper.

“If you go to that cedar elm over there and pull a tag on it, it’ll tell you pounds of carbon it's sequestered,” Hrobar says. “[It will also show the] water that’s diverted from storm runoff, the amount of energy that is saved, [and] the cooling benefits of the canopy of that tree.”

After adding all that up, UT found the value of the campus trees to be more than $25 millions. Hrobar said being able to quantify trees with a dollar amount reaffirms their value.

“[It’s] not just what would cost to replace this tree – and you couldn't replace this tree ­– but you can assign a dollar value to the property value of this site," she said, “and then the dollar value of those ecosystem benefits.”

According to the app, the deodar cedar sucks up almost 300 pounds of carbon dioxide and saves more than 10,000 gallons of water a year.

And all the information can be learned simply because of a tiny little tag.