What do you do, where do you go, when you pull into your favorite national park and can't find a place to park or a trail without crowds?

Those are good questions probably going through many people's minds as the national parks become more and more popular with more and more people.

Mike Oswald might have the answers you're looking for, at least for the Western half of the country. Oswald is the writer and publisher behind Your Guide to the National Parks, a thick, fact-filled guidebook to the 63 national parks in the country. This year he's veering outside of the parks with a new book titled, simply, Public Land, 1,000 Western Wonders.

Congaree National Park is an often-overlooked unit of the National Park System. Indeed, only about 250,000 visitors set foot in Congaree each year. Those who do are awestruck by the size of the trees there, as the park contains the highest concentration of champion-sized trees anywhere in North America.

Our guest today is Professor Kimberly Meitzen from Texas State University. Before arriving at Texas State, she studied at the University of South Carolina, where she fell in love with Congaree, its floodplain, and its big trees.

A growing majority of bat species are in serious trouble, largely because of white nose syndrome, a deadly fungal disease that resembles a white fuzz on infected bats.

As the disease has spread across the country, it's decimated bat populations – killing upwards of 99 percent of some populations – and turned up in many national parks.

As part of the National Parks Traveler's Threatened and Endangered Species Project, contributing writer Kim O'Connell has been looking into the situation with bat species.

Big Bend National Park lately has drawn a lot of national attention, and not in a good way. Recently the U.S. Customs and Border Patrol announced that it wanted to build some sort of border wall along all or part of the 118 miles of border the national park shares with Mexico. Is that a good idea? Will it adversely impact the park? Can it even be done?

To discuss those and other questions, our guest today is Bob Krumenaker, whose long Park Service career included a stint as Big Bend's superintendent. Bob also is chair of the Keep Big Bend Wild organization that is pushing to see a large portion of the park designated as official wilderness.

To put some perspective on the National Parks Travelers' monthslong coverage of threatened and endangered species, we're going to go back in time a bit today to replay a podcast in which we discussed the ESA — and possible changes to it — with Jake Li, a vice president with Defenders of Wildlife, and Stephanie Adams, director of wildlife at the National Parks Conservation Association.

At Cumberland Island the National Park Service currently is crafting a visitor use management plan that critics say poses a great threat to the national seashore's official and potential wilderness.

To get an understanding of what's at risk, we've invited Jessica Howell-Edwards, the executive director of Wild Cumberland, which advocates for the seashore's wilderness area and ecosystems, to join us.

The Florida Reef stretches from Biscayne National Park south past Everglades National Park and down to Dry Tortugas National Park in Florida. It's roughly 350 miles long, and is the only coral reef in the continental United States.

When it comes to reefs around the world, the Florida Reef is the third largest. But, unfortunately, it's under a lot of pressure. It's dealing with pollution, ocean warming, damage inflicted by anchors, and disease. Perhaps the most serious disease infecting the reef is Stony Coral Tissue Loss Disease, which can be fatal to corals.

Our guest today is Beth Firchau, who works for the Association of Zoos and Aquariums. Part of her role is to manage the association's safe coral program, and part of her role is AZA's coordinator for the Florida Reef Tract Rescue Program. And part of her work involves a network of aquariums across the United States that are holding samples of corals from the Florida Reef.

Whitebark pines are a Western icon that the National Park Service has designated as a "vital sign" species because they are critical to ecosystem functions. But they are at risk of extinction due to climate change, beetles, and a fatal fungus from Eurasia.

Our guest today is Dr. Elizabeth Pansing, the director of forest and restoration science for American Forests, a nonprofit organization that strives to create healthy and resilient forests.

This program was made possible in part by the Park Foundation.