Making a film about wild animals has challenges that filmmakers using human actors never have to cope with.

Wild animals just don't stick to the original script. They tend to improvise. And they chew more than the scenery. Even more than Al Pacino does.

Wild beasts can attack the film crew, on purpose or by accident. And they also are busy living their own lives, protecting their young, finding food and struggling for survival in the eat-or-be-eaten animal kingdom.

Directors Alastair Fothergill and Mark Linfield, the creative team behind "Earth," the first film from Disneynature, talked at a recent press conference about the No. 1 rule of filming wild animals: Never interfere with nature.

And both men admit that this rule often brings them to tears. (Caution, the audio on the clip is quite low)

One prime example: watching a mother polar bear try to feed her young while the ice melted beneath their feet. Then there is the stunning aerial shot of the exhausted, starving male polar bear, swimming by himself in the ocean, searching for ice and food and trying in vain to make a meal out of a baby walrus.

That said, "Earth" is a heartwarming and breathtaking combination of action, scale and location capturing the most intimate moments of our planet's wild creatures.

And for every "Earth" ticket purchased from Earth Day, April 22, through April 28, Disney will donate a tree.

So far, over half a million tickets have been sold.

That's a lot of trees.

Posted by:Lora Victorio