Ever compare Acadia National Park to a piece of Swiss cheese? You should.

Acadia is a majestic place — from the breathtaking views of Frenchman Bay from atop Cadillac Mountain to top-notch hiking trails like the Beehive and the Precipice to the storied carriage roads — it is one of Maine’s and America’s greatest treasures.

But the park is scattered with “holes.” More than 130 parcels of land within Acadia’s boundary are privately owned, and the park doesn’t have adequate resources to purchase the land as the tracts come up for sale, making the lands vulnerable to inappropriate development within our prized national park.

We should, and do, expect more. Every acre of land within Acadia’s boundary should be permanently protected.

On Thursday, Mainers have a special opportunity to help protect Acadia. Officials from the Department of the Interior, the agency that manages our national parks, and several other federal agencies will be in Bangor for a public listening session — part of America’s Great Outdoors Initiative. They want to hear from citizens directly as they develop a “21st century conservation plan” to protect America’s great landscapes, rivers and wildlife habitat. Acadia National Park should be a top priority.

On a per-acre basis, Acadia is the most visited national park in the country, even before President Barack Obama and the first family spent part of their summer vacation in the park. And the number of visitors is up 20 percent over last year, with people from all over the country coming to enjoy Acadia’s natural splendor. Together, they contribute more than $145 million a year to Maine’s economy, supporting jobs for more than 2,580 people.

Most visitors to Acadia do not know that seven tracts of land within the park’s boundaries are up for sale right now. Nor do they likely know that iconic places such as Burnt Porcupine Island and Rum Key are not permanently protected.

Development inside Acadia’s boundary could fundamentally change the character of the park for the worse.

Imagine if houses were built on Burnt Porcupine Island and Rum Key, which are highly visible from the summit of Cadillac Mountain, sections of the Park Loop Road and several of Acadia’s hiking trails. These undeveloped islands are part of the larger Acadian Archipelago, which combine a rugged topography of rocky headlands, cliffs, cobble and shingle beaches, and coniferous and mixed deciduous forests. They support a diverse array of coastal species, including nesting shorebirds and roosting and foraging habitat for bald eagles and osprey.

Or consider the potential development of Northeast Creek. This is a unique and fragile area of wetland habitats, including estuarine salt marsh, freshwater forested and shrub wetlands, and freshwater marsh and bog. The ecosystem provides valuable habitat for a variety of fish, water birds, raptors, songbirds and mammals, including a number of state-listed and federally rare species. It is bounded by two major public roadways, offering the public unparalleled opportunities to paddle, view wildlife, hike and even pick cranberries from your canoe in the fall.

Frankly, it wouldn’t take a lot to protect all of the land within Acadia’s boundaries. The park simply needs the resources to purchase the remaining tracts of land as they come up for sale.

Congress established the Land and Water Conservation Fund 40 years ago to accomplish projects like the completion of our national parks, but year after year Congress has diverted much of the funding to other purposes, leaving relatively little for conserving America’s great lands.

The good news is that earlier this summer the House of Representatives passed a bill that includes full and dedicated funding for the program, directing $900 million annually from the proceeds of offshore oil drilling to benefit all Americans by preserving treasured places.

With greater conservation needs than ever before across the country, as well as here at Acadia, it is now time for the Senate to act on its version of this legislation — and for Sens. Olympia Snowe and Susan Collins to vote for it.

Acadia National Park is a spectacular place — one that deserves to be protected. Filling in the holes in the park is the single most important step that can be taken to protect Acadia now and for future generations.

Thursday’s event is from 3 to 6 p.m. at the Bangor Civic Center. For more information, visit http://www.doi.gov/americasgreatoutdoors/Information-for-Maine-Listening-Sessions.cfm.

Emily Figdor is director of Environment Maine. Marla S. O’Byrne is president and CEO of Friends of Acadia.