Why not release balloons?

This is why... The animals can eat them, and it kills them. Many like to promote a cause, but please think about the world around you.

These landed in our meadow, and got tangled in the trees. It took me forever to get them down. I was afraid our deer or turkeys would get them.

They get caught up on personal property, and they are garbage.
I would ask that you refrain from releasing balloons. It's just plain wrong to do this to the environment. These were attached to our trees and I tried to get them and deflate them, but they drifted off.
This is not right.
Do not release them. Do not release mylar balloons. Do not group them in clusters.

Time for a complete ban on mass balloon releases? - Wildlife Extra

Apr 3, 2009 – All balloons sold near to a balloon release should be weighted so that they fall to the ground near-by.

Balloons take 4 years to decompose. 

They contain chemicals that can poison.

Turtles eat them and the latex will block their digestive tract.

Ribbons become tangled around beaks and legs.

Balloon HQ Presents: Balloon Releases and the Environment

REFERENCES

1. Discussion with David Tucek, Meteorologist, National Weather Service, Louisville, Ky. July, 1989.
2. Standard Atmosphere Table, Mechanics of Fluids, Irving Shames, McGraw-Hill, 1962.
3. General Meteorology, Horace Robert Byers, Sc. D., McGraw-Hill, 1959.
4. Rubber Technology and Manufacture, C. M. Blow, Institution of the Rubber Industry, London, England, 1971.
5. The Language of Rubber, E. L DuPont de Nemours & Co. Elastomers Chemicals Dept., Wilmington, Delaware, 1957.
6. Pilot Experiments Concerning Balloon Ingestion by Sea Turtles; Peter Lutz; University of Miami; Miami, Florida.
7. Physical Climatology - Second Edition; by Helmut Landsberg; Grey Publishing Co., Inc; Penn 1962 (Table 40, p. 127)