One bag of Cheetos can be "world-changing" — and a teachable moment.

• That’s what Carlsbad Caverns National Park in New Mexico said in a recent Facebook post, describing the consequences of one visitor littering an open bag of Cheetos inside a cave.

Why it matters: "To the owner of the snack bag, the impact is likely incidental. But to the ecosystem of the cave it had a huge impact," the post says.

Zoom in: "The processed corn, softened by the humidity of the cave, formed the perfect environment to host microbial life and fungi."

• "Cave crickets, mites, spiders and flies soon organize into a temporary food web, dispersing the nutrients to the surrounding cave and formations. Molds spread higher up the nearby surfaces, fruit, die and stink."
• "And the cycle continues."

Littering the bag was likely 10 seconds of thoughtlessness. But rangers spent 20 minutes carefully ridding the cove of foreign mold and detritus invited in by the bag, the post adds.

Zoom out: 70 million pounds of waste is collected from America’s national parks each year. That includes what’s thrown out in bins and litter collected from trails and elsewhere.

• Some 80% of that waste is made up of plastic items, which can be especially harmful to wildlife and ecosystems.
• Look for the trash problem to get worse as the number of visitors to national parks keeps increasing.

What we can do: If dropping just one piece of litter can have such a serious impact, then picking up one piece of litter can make a difference.

1. Pick up trash in your local parks or on beaches when you see it.
2. Avoid single-use plastics when spending time in nature. Bring a reusable water bottle, and be prepared to carry your trash with you.
3. Connect with your community. There are local, statewide, national and even global efforts to get together and clean up the green spaces around us — and have fun doing it!

"We're in the process of dropping off our son for his first year at St. Andrews University in Scotland," Finish Line reader John Mulligan of Bethesda, Md., tells us.

• "During his orientation week, we took a trip to Oban to do some touring and reminiscing. Here's the picture from our hotel room!"