With astounding growth, Grand Canyon has the danger of becoming a vicitm of it's own popularity. Hosting about 4 million visitors a year, the risk to the natural beauty is high. As a result, Grand Canyon has worked hard to reduce air pollution from neighboring states in an attempt to reduce the haze and air pollutants that affect the canyon. They have also instituted a 'zero impact' philosophy.
Zero impact is a version of 'leave no trace'. This means enjoy the outdoors, but minimize your impact on the ecosystem in the process. Staying on trails to decrease damage to vital cryptobiotic soil crusts, properly disposing of trash (including packing it back out with you), not intentionally or unintentionally feeding the wildlife, take only photos (not rocks, twigs or other bits), and respecting the natural quiet of nature are all little ways we can preserve the park and all natural lands.
Keep in mind, some animals already have bad habits as a result of careless visitors. The crows seem to KNOW people and their bags have FOOD! So be cautious and courteous during your visit to not contribute to the problem, but be part of the solution ;)
Please don't litter. The National Parks are one of the last sacred areas for everyone to enjoy!
Find the correct area the deposit what you want to get rid of. Most visitors do a nice job of keeping the Parks free of trash.
Do not litter, or throw cigarettes any where in this area. It is a National Park, and violators will be fined heavily. Do not poach (kill) wildlife her either. It is Millions of years old, but humans have the ability to destroy things quickly.
One thing I remember distinctly about the Grand Canyon is not to litter! You won't be arrested or anything, but they do take that stuff seriously...so seriously that in fact when you travel there---you will feell like a park ranger looking out that others don't litter!