Ten years ago today, Disney (NYSE: DIS) opened its fourth Florida theme park. It was no coincidence that the family entertainment giant chose Earth Day to unveil its eco-friendly Disney's Animal Kingdom attraction.

Like most new Disney parks, Animal Kingdom went through its growing pains at first. A lack of rides and air-conditioned attractions had many guests bolting for the exits early in the afternoon. The park initially resorted to shortening its operating hours, rather than responding with the influx of family-friendly diversions that patrons expected at a full-day park.

Attendance fell during each of the first four years, bottoming out at 7.3 million guests in 2003. Recent upgrades, including a family-friendly roller coaster in 2006 and November's debut of the first table-service eatery within the park itself, have helped the park grow both its attendance and its operating hours.

2007 Attendance

Change
From 2006 

Magic Kingdom

17.1 million

2.5%

EPCOT

10.9 million

4.5%

Disney's Hollywood Studios

9.5 million

4.5%

Animal Kingdom

9.5 million

6.5%

Source: TEA and Economics Research Associates.

The park's turnaround leaves Disney's California Adventure theme park in Anaheim as the company's only domestic laggard. Attendance there fell by 4.5% to an abysmal 5.7 million last year, well behind the 14.9 million guests going to the adjacent Disneyland.

This doesn't mean that the coast is clear for Disney in Florida. Disney has historically opened new theme parks within eight to 10 years of each other. Today marks the end of that streak. It's not as if Disney is dry for concepts. And it's not as if Disney is running low on resort lodging, as it is perpetually adding inventory to its hotel and timeshare properties.

It's not even as if Disney is in a funk in Florida, since attendance at its parks grew at a healthier clip than nearby year-round theme parks run by Anheuser-Busch (NYSE: BUD) and General Electric (NYSE: GE).

It may just be that Disney has only begun to work on the canvas that is Animal Kingdom. As Disney's largest park in terms of acreage, it makes little sense for Animal Kingdom to be the least popular in terms of annual attendance.

This brings us to this week's announcement -- also no doubt tied to coincide with Earth Day -- of the launch of Disneynature, a studio project that will produce nature documentary films. The first film, Earth, will come out for Earth Day next year.

Now that big-screen maker IMAX (Nasdaq: IMAX) is inking multiplex deals hand over fist, and Planet Earth is a "must buy" for Blu-ray DVD owners, all of the ingredients are in place for Disney to reach back into a live-action niche that was a major part of its early history.

It will also be way too easy for Disneynature animal projects to tether themselves to the Animal Kingdom brand, creating even more cross-promotional opportunities, much like Pirates of the Caribbean helped Disney in both the celluloid and theme-park realms.

In short, Earth Day seems like yet another opportunity for Disney to add some green to its balance sheet.

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Longtime Fool contributor Rick Munarriz can usually be found at Walt Disney World. He's the one wearing the "Bob Iger Fan Club" T-shirt. He does own shares in Disney. He is part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.