How Much Trash Gets Left on the PCT? Two Scientists Thru-Hiked It To Find Out

Ever come across a trashed campsite while out hiking and wonder exactly how much trash gets left behind in the backcountry? You’re not the only one. Last year, two scientists thru-hiked the entire Pacific Crest Trail to measure the total amount of litter along the 2,650-mile footpath.

Can you imagine combining thru-hiking with what might be the most ambitious backcountry trash survey ever conducted? They weren’t even just counting the trash, guys. They were also packing it out as often as they could.

As a certified Lazy Person, I couldn’t wrap my head around it, so I caught up with the scientists of No Trace Trails to find out how they did it.

No Trace Trails

Tori McGruer, 29, has her PhD in Environmental Toxicology. Macy Gustavus, 25, has a Master’s in Watershed Science. Their project, No Trace Trails, aims to answer a simple question: how much trash gets left behind on the PCT?

Macy Gustavus (left) and Tori McGruer.

To come up with a meaningful answer, the pair thru-hiked the PCT and stopped every 10 miles to document and pack out all the trash they found within a defined sampling area.

By the end of the hike, they had enough data to estimate the total amount of litter on the trail: roughly 200,000 pieces. Their data also shows what types of trash are most prevalent and where it’s most concentrated. (The pair stresses, for instance, that the majority of those 200,000 pieces of trash were concentrated in a few hotspots — the majority of the PCT is actually pretty clean.)

A Labor of Love

hiker crouches on trail in semi-darkness with a headlamp

“Microplastic sampling happened at any time of day!”

Thru-hiking is hard. Thru-hiking while conducting an empirical trash survey is even harder.

McGruer and Gustavus recall the end of one long day in the Sierra, when juggling the demands of the trail with their research duties felt Herculean. Haggard and hungry, all they wanted at the time was a hot meal and a shower. It wasn’t far to the town of Mammoth, CA: they knew that if they hurried, they could still catch a ride before sunset and sleep indoors for a change.

But they couldn’t. Their next survey site — or transect — happened to fall right before the road crossing, and being tired and hungry was not a good enough excuse to skip work.

By the time they finished surveying, the sun had gone down, so instead of a luxurious night in Mammoth, they wound up camping in the trailhead parking lot. “It was kind of a sad moment,” recalls McGruer, laughing. (This, by the way, is the definition of Type II Fun.)

This kind of thing happened more than once. “I very admittedly threw tantrums about it sometimes,” says Gustavus. “Like, ‘man, I just want to go eat dinner.’ ”

pct trash survey study lead tori mcgruer reclines on the trail with a hat over her face

The work didn’t end when the pair reached town, either. Besides surveying trash every 10 miles, they were also collecting soil samples every 50. These they would bring to town and ship to a lab to be analyzed for microplastic content. “We were busy in town, I think busier than some other people,” Gustavus admits.

But at the same time, the work kept the pair motivated. “We (were) doing something that’s really going to contribute to a knowledge gap, because there haven’t been surveys like this before,” Gustavus explains. “It was really nice, when things got hard, to have the survey” as a reason to keep going.

The pair’s trail family echoes this sentiment. Lauren “Scraps” Davis hiked almost the entire trail with the scientists. She noticed right away that the women seemed even more driven than the average thru-hiker; it was one of the reasons she loved hiking with them. “ ’I’ve gotta stick with these girls,’ ” she recalls telling herself. “ ’They’re a good influence on me.’ ”

Davis found the project fascinating and eventually began assisting with surveys whenever she could. “I really liked that they found a way to merge their hiking with their profession … They just always seemed like they had such resolve and dedication, I feel like in part because of that project.”

Indeed, Gustavus and McGruer’s findings could be invaluable to policymakers and land managers. How bad is the litter situation on the PCT? Where should cleanup and educational efforts be concentrated? Without empirical data, decision makers can only speculate. No Trace Trails could make a difference, and McGruer and Gustavus know it.

Packing It Out

McGruer and Gustavus only skipped transects on rare occasions, such as when the ground was snow-covered.

Each trash transect was one kilometer long and extended six feet on either side of the trail. It took the pair an estimated 13 to 17 minutes to complete each one. At every fifth site, they would spend additional time sampling soils.

While most sites had only a small amount of litter, a few were trashed. To save time, the scientists would stop counting when they hit 100 pieces of trash. From there they could extrapolate the total amount of litter in the transect.

And the pair went beyond mere counting: they actually packed the garbage out. Most of what they encountered was small: plastic bags, bits of old snack wrappers, baby wipes, and the like. There were heavier things too, like bags of dog poop and one mysterious butter knife. They left behind anything too large, like old car parts.

Even so, they often hauled an extra six to ten pounds of trash and soil samples along with their own gear and supplies.

MiniP and Puffy Take the Trail

In time, McGruer took the trail name Puffy in honor of her love of midlayers. She normally carried the trash, dog poop and all.

Meanwhile, Gustavus shouldered the soil samples. This is part of how Gustavus got her own trail name, Mini Pony, or MiniP for short. “Because I’m small, but I’m strong,” she quips.

a hiker holds a ziplock bag of soil and a metal trowel

MiniP with a soil sample.

I ask the pair over the phone whether they saw themselves more as hikers or as scientists on the trail. They’re thoughtful. “I don’t know if one was first and one was second,” answers McGruer at length.

“I think that was a question we had for ourselves before the hike,” adds Gustavus. “We didn’t know yet how the survey was going to impact our time and our pace. We thought that we might not be a part of the hiker community in a traditional way.”

But they needn’t have worried. They ended up hiking with a large group in southern California. Later, they joined another trail family in Washington.

Gustavus (far left) and McGruer (far right) with friends.

“We got really lucky with the people we were around. I think the hiking community was really excited about what we were doing,” says Gustavus. Lauren “Scraps” Davis wasn’t the only one of their companions who got in on the trash-surveying action either.

“We’d be hiking with people, and then it’s like, ‘This is our spot. Anybody wanna help us count trash?’ ” says McGruer, chuckling. Their friends were usually excited to take part. The researchers noted how many people helped each time, accounting for the possibility that more participants would detect more trash.

A Leap of Faith

McGruer and Gustavus only met in person once before starting their ambitious thru-hike. The pair connected when Gustavus came across a post on X by McGruer about her plans for a PCT trash survey. Intrigued, she contacted McGruer about getting involved.

At first she only planned to help with data processing. But soon she began considering joining McGruer for a section hike. Before she knew it, she was committing to the whole enchilada.

In October of 2022, the pair met up in Red Rocks, NV for a climbing trip. “That would be the first and last time we met each other in person before stepping foot on the trail together,” Gustavus writes of the experience in her blog on The Trek.

According to Halfway Anywhere’s PCT surveys, most thru-hikers start the trail solo. Doing so has some logistical advantages. Starting with a friend can cause angst if you end up being incompatible in hiking pace, style, or goals.

“Even though we only met once in person, we were always talking, so we got to know each other that way,” says McGruer. “But that’s very different than figuring out, can you hike well together? The first few weeks we were like, ‘This could have gone so poorly!’ ”

They did end up hiking at different paces, but would reunite at breaks and at camp, as many thru-hikers do.

As they got more comfortable, sometimes they would even conduct surveys solo. McGruer began handling odd-numbered transects, while Gustavus surveyed the even ones.

“I think our personalities just match really well,” says Gustavus of their partnership. “It was a really fun six months.”


gustavus and mcgruer high-five at the northern terminus at the end of their pct trash survey

At the northern terminus.

The PCT wasn’t exactly McGruer’s first trail trash survey. In 2018, she and some friends did a 70-mile hike in the Sierra. They noticed a tally at the ranger station tracking how much litter rangers had packed out.

Intrigued, McGruer decided to do an impromptu trash survey as she hiked. At the time, it was the longest backpacking trip she had ever attempted.

The dataset was small and didn’t end up yielding publishable results, but it planted a seed.

When she began dreaming of the PCT, she recognized the opportunity to try the survey again. But this time, she’d go in with standardized methods and a much larger dataset.

“Once I knew I was going to do the PCT it was like, ‘OK, this is a really good opportunity to like take what we learned on that smaller trail and try to do something much bigger.”

She was in the early stages of planning when Gustavus messaged her and joined the team. No Trace Trails secured $16,000 in funding, hammered out their methodology, and settled on 28 March 2023 as a start date.


two hikers traverse a narrow, barren ridgeline with snow patches

This time, McGruer and Gustavus do intend to publish their findings. It’s a work in progress, as they’re still awaiting results from the microplastics side of the study. Those results will help them understand the relationship between litter and microplastic contamination.

On the trash side, the survey has already revealed interesting trends.

Before the hike, McGruer and Gustavus had posted about No Trace Trails on Reddit. Several users were quick to point out that most trail trash is not left by thru-hikers.

Having now completed the trail, McGruer agrees. “Most of the trash is not intentionally left there. Maybe close to trailheads where you see larger pieces of things tossed … That’s one thing. But it’s not like people are like, ‘I don’t want to carry this wrapper. I’m just gonna leave it on trail.”

Instead, trash concentrations were highest near vehicle access points and more populous areas, and the garbage was mostly stuff that thru-hikers would never carry in the first place.

The most trashed part of the PCT was a roughly 100-mile section from Big Bear to just past Wrightwood in California’s San Gabriel Mountains, one of the closest sections of trail to Los Angeles. McGruer and Gustavus say a third of the trash they documented came from this one section of the trail.

Balloons, Butter Knives, and Cold Hard Cash

Coyote scat with a plastic bag or wrapper embedded in it.

The pair also saw many PCT transects with little or no trash, especially in more remote areas. It’s worth noting that they weighted all trash equally. A fragment of a bar wrapper counted the same as a rusted car door, for instance. So even in sections of the trail where the surveys yielded trash, often the litter itself was tiny.

“I’m sure we left things behind,” McGruer acknowledges, indicating herself and Gustavus. It happens. You pull out a snack and miss the empty wrapper that falls out at the same time. Your trekking pole tip snaps off mid-hike and you don’t even notice it’s missing until later. Over 2,650 miles, accidentally leaving some trash behind is pretty much inevitable.

Bar wrappers and other soft plastics accounted for much of the trash found in the study. The researchers also found their share of mylar balloons, cigarettes, and plastic bottles. There were also stranger things, such as a $1 bill, the aforementioned butter knife, and a plastic film embedded in a pile of coyote scat. The animal must have ingested and later pooped out the trash.

On Trail Magic and Trash Magnets

trash overflows a plastic bin left near a pct trailhead

What counts as trash? “We had a lot of existential conversations (about that) ahead of time,” says McGruer. They were anticipating edge cases like unattended trail magic that might be difficult to categorize.

In the end, they decided to exclude anything from the survey that still had a current use. “If someone left a cooler of beverages out, even if that maybe isn’t the recommended way of doing trail magic, we would say that has a current use … We’re assuming that person is going to come back and get their cooler.”

Regardless, one issue with unmanned hiker feeds is that they can become trash magnets. People start leaving trash, assuming the trail angel will come collect it. The mess can snowball. McGruer and Gustavus encountered this a few times.

McGruer recalls finding a bin overflowing with thru-hiker trash near a trailhead. “An animal got into it. I don’t know what that bin was originally, but this isn’t currently being used. It’s just a pile of trash.”

a hiker holds a piece of trash in a pair of clear salad tongs along the pct with snowy mountain in background

Gustavus stresses that incidents like this were rare. She suspects that only a slim minority of thru-hikers were dumping trash in this way.

Still, she says there’s widespread confusion about certain elements of Leave No Trace. “You need to pack out your toilet paper! Especially if you’re using wipes … if you don’t pack it out, I will find you,” she jokes.

Same goes for orange peels and pistachio shells. Just because they’re biodegradable doesn’t mean you should leave them on the trail. “It will break down, but this isn’t the environment it’s made for so it shouldn’t be there. That is still garbage,” Gustavus says.

What’s Next?

pct trash survey experts maci gustavus and tori mcgruer pose atop a snowy peak, mcgruer holding up an ice axe

Would McGruer and Gustavus bring No Trace Trails to another long-distance hike? They demur.

Gustavus would like to hike the CDT someday but isn’t sure if another trash survey would be in the picture. “The survey did impact our hikes … There’s responsibilities that come with what we were doing. So in some ways, I am interested in doing a long trail without that — to see what the experience is like when you’re you’re giving up all of your worldly responsibilities.”

On the other hand, she feels a sense of duty to carry their work further. “Who else is going to do it?”

McGruer doesn’t currently have future long-trail plans. Still, she admits it would be fascinating to compare the Triple Crown trails. Whether she and Gustavus, or another research team, continue the research is up for debate.

“If people are interested in carrying the torch to other trails, maybe there’s a way we can set it up so (the work) can continue.” Someone has already told the pair they’re considering doing a similar study on the PCT next year.

What Can You Do?

three people crouch in the sand wearing black t-shirts that say rubbish in pink letters

Per Gustavus: “Tori and I with Win, our project manager at the Moore Institute of Plastic Research, testing out the Rubbish App before using it on trail for the survey.”

Despite all the trash McGruer and Gustavus packed out from the PCT last year, more will accumulate. And the PCT is one trail out of thousands.

The hike is complete, the samples gathered, and the trash surveyed. But McGruer says you can still help. The project is currently seeking funding to support their microplastic analyses. You can donate through Moore Plastic Institute to support the team’s fundraising goals.

You can also download and use the Rubbish app to track litter you clean up — whether on the PCT or elsewhere. In doing so, you’ll contribute to a crowdsourced dataset on trash trends.

McGruer and Gustavus believe this work matters. “Hopefully we can do something that contributes to a very small body of knowledge and grow it so it’s useful in the future,” Gustavus says. “We can make an impact on the trails that we’re so lucky to enjoy.”

No Trace Trails blurs the lines between hikers and researchers in the best way possible. Gustavus — Mini Pony — puts it best. “We were scientists, but we were also trash-food–eating, no-showering, dirty, having-a-great-time hikers.”

That door swings both ways. No Trace Trails invites the trash-food–eating hikers of the world to be scientists too.

All photography, including featured image, courtesy of Tori McGruer and Macy Gustavus. Featured image graphic design by Chris Helm.

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Comments 1

  • Greg : May 4th

    I don’t know what kind of “science” was done but I can tell you one thing. I’ve hiked the PCT through the sierras for a dozen years and only one single time did I find a piece of bar wrapper that got away from someone. I’ve seen relatively zero trash. I’d bet the majority was by wanna be hikers who don’t do the sierra…I don’t see long trail hikers disrespecting the trail like that. Its day hikers and bums that live off trail near towns.
    Have a blessed day folks


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