Attention voyagers and excursionists: There's an increasing effort to preserve the beauty and historic value of natural attractions and ancient ruins by capping visitor numbers and upping entry fees, while others are on the brink of disappearing altogether. Our advice? Visit these five bucket-list places while you still can.
Glacier National Park, Montana
This huge park sits in the Rocky Mountains of northern Montana. As the name implies, the landscape was carved by glaciers, which left behind rugged peaks, more than 700 lakes, more than 500 streams, and a one-of-a-kind experience for visitors. Today, the park is a favorite destination for hikers (you can see the glaciers up close), fishermen, photographers, cyclists, and outdoor enthusiasts of all stripes.
Why visit now: The glaciers are disappearing. One hundred years ago, there were 150 glaciers in the park. Today, there are 25. According to scientists at the United States Geological Survey, the park's most visited glacier, Grinnell, has lost almost 50 percent of its footprint in the last 50 years.
Learn more: Glacier National Park (U.S. Park Service)
The breathtaking experience of Machu Picchu can include fun surprises.
Machu Picchu, Peru
These majestic Incan ruins stand on an Andean mountaintop ridge. The steep drops and surrounding forest make it a breathtaking experience. The mystery surrounding the vast ruins adds to the experience: This ancient city was built in the 15th century and later abandoned for no known reason. Visitors can get to the site a number of ways: via a four-day/three-night hike along the Inca Trail (you must travel with a sanctioned group or tour agency); via train from nearby Cusco, Ollantaytambo, or Aguas Calientes; or via bus from Aguas Calientes.
Why visit now: Access is getting more limited. Peru recently instituted new rules: Visitors need to purchase either morning or afternoon tickets and leave within the allotted timeframe. All visitors must be accompanied by an official guide and stay to three defined circuits rather than wandering around the site at will. These restrictions will be revisited in 2019 — it's possible they'll get even tighter.
Learn more: Peru Travel
A diver gets up close to reef-dwellers at the Great Barrier Reef.
Great Barrier Reef, Australia
The biggest coral reef in the world covers more than 1,400 miles off the coast of northeastern Australia; it's home to myriad species of fish, turtles, dolphins, and other aquatic life. Visitors can experience the reef multiple ways: by boat tours, snorkeling or SCUBA diving, helicopter tours, and more.
Why visit now: Overheated seawater in 2016 and 2017 has led to bleaching events that stop the coral from reproducing. Some scientists say that the reef may disappear altogether by 2030; others think the situation is less dire. Time will tell who is right.
Learn more: Tourism Australia
A walk along the Great Wall of China can be like walking back in time.
The Great Wall of China
The largest military structure ever built and one of the Seven Wonders of the World, the Great Wall of China stretches for more than 5,500 miles and took more than 2,000 years to build. Today, visitors enjoy guided hikes, camping, hotels, and even a marathon along the wall.
Why visit now: One-third of the wall has crumbled thanks to time, the elements, and locals and tourists pilfering material for souvenirs or building purposes. While renovations are being made to some parts of the wall, they are often of poor quality and incongruous, or even worsen the problem — when five miles of the 700-year-old Xiaohekou section of the wall were renovated, workers flattened historic guard towers.
Learn more: UNESCO World Heritage Centre
Penguins are a popular attraction at the bottom of the world.
The world's southernmost landmass is a unique, icy, barren landscape that's home to skuas, seals, and millions of penguins — a popular attraction. Antarctica also offers the best stargazing location in the world. Most visitors travel by cruise ship, though airplane tours are available as well.
Why visit now: Trips to Antarctica, the world's least visited tourist destination, are already carefully controlled, but many scientists see tourism as a boon — it brings much-needed attention to the environmental difficulties caused by climate change. Visitors to Antarctica often become ambassadors for raising awareness about climate change. Go with a clear conscience.