Happy 100th to America's great outdoors.

• Author: Jewell, Sally
• Position: Ecology

THIS YEAR we acknowledge the 100th birthday of the National Park Service--a time when we celebrate the more than 400 natural, historical, and cultural sites that make up the most incredible parks system on Earth, places that attract visitors from around the world and inspire other nations to follow our lead.

However, being the "best" was not always a forgone conclusion. During World War II, national parks fell into a state of disrepair. Congress, needing to fund the war effort, directed much-needed resources elsewhere. After the war, veterans packed up their families and drove to the national parks, looking to heal and reconnect in the way that we know getting outside uniquely can do. Instead, the war heroes and their families were greeted by crumbling buildings, roads full of potholes, and huge crowds.

The state of the parks got so bad that Harper's Magazine ran an essay in 1953 entitled, "Let's Close the National Parks." The author, Bernard DeVoto, hoped the shock of suggesting that Yellowstone, Yosemite, and the Grand Canyon should be shut down until they were worthy of visitors would push Congress to funding the nation's crown jewels properly. So, that could have been the end of the story, the tombstone reading: "Here lies the national parks. Loved to death." Thankfully, DeVoto's essay, plus a few visionary leaders--like Conrad Wirth, who was Park Service director in the Eisenhower Administration--spurred a historic investment in our national parks.

Starting in 1956, and over the course of the next 10 years, more than $1,000,000,000 of capital improvements were completed. Roads were fixed, sewer systems upgraded, and visitor centers added--just in time for the Park Service's 50th anniversary in 1966. Mission 66, as it was called, was rooted in the simple idea that investing in our national parks was an investment in the heart of our nation--not only our economy, but our very identity.

Corporations also stepped up to help, like the memorable ad campaign of the day: "See the USA in your Chevrolet," a jingle that my generation still can hear in our minds. What happened to all of those kids who were loaded into the backs of station wagons and taken to Rocky Mountain National Park for their summer vacation? They grew up and became today's champions for the national parks. The real legacy of Mission 66 is that it inspired an entire generation--Baby Boomers, my generation--to love and visit and support the great outdoors.

You do not need to look too hard to see the parallels to today. Our national parks are being visited in record numbers--307,000,000 visits in 2015 alone, but our maintenance backlog (nearing $12,000,000,000) also is at record levels, while budget crunches have left our national parks and public lands understaffed and struggling to keep up with day-to-day operations.

Who are the people visiting the parks? It still is the Baby Boomers. The majority of visitors to National Parks today look like me: older and whiter, which means we have not found a way to connect with contemporary young people, who are more diverse, tech-savvy, and disconnected from nature than ever before.

Those trends coincide with the emergence of an extreme movement to seize public lands-from Oregon to Puerto Rico--putting lands that belong to all Americans at risk of being sold off for a short-term gain to the highest bidder. This movement has propped up dangerous voices that reject the rule of law, put communities and hard-working public servants at risk, and fail to appreciate how deeply democratic and American our national parks and public lands are.

What is more, climate change--the most pressing issue of our time--threatens our land and water in existential ways, with longer, hotter fire seasons, record-breaking droughts, and more frequent and severe superstorms. Some scientists believe that we are on the brink of the planet's sixth mass extinction, with humans playing a major role in wiping out species at a rate 53 times greater than normal. In fact, an analysis by Conservation Science Partners finds that natural areas out West are disappearing at the rate of a football field every two-and-one-half minutes.

If you add that all up, you are looking at a pretty bleak picture. If we stay on this trajectory, 100 years from now national parks and wildlife refuges will be like postage stamps of nature on a map--isolated islands of conservation with run-down facilities that crowds of Americans visit like zoos to catch a glimpse of our nation's remaining wildlife and undeveloped patches of land.

Now, that cannot--and will not--happen, but we as a country need to make a major course correction in how we approach conservation to ensure a bright future for our public lands and waters. Here is what I believe that course correction looks like:

First and foremost, we need to kick off the new century of conservation by issuing a giant, open invitation to all...