As for birth control, there is no real environmentally friendly pill. These pills use a variety of hormones that find their way into our water supplies. There are some cases where hormones from the pill are so heavily concentrated in water supplies that it effects the sexual development of fish (http://blogs.westword.com/latestword/2010/07/transgender_fish_cus_david_nor.php). Condoms on the other hand do have some greener alternatives but they come at a price. Natural Lamb or sheepskin Condoms are a slightly better alternative for the environment (All natural membrane), but they are not nearly as effective against STD's. A french company also claims to have created an eco-friendly condom called the "Original Condom". They buy Carbon Credits to offset their production of condoms (http://www.theoriginalcondom.com/en/environment-carbon-offsetting/) Be Safe!

New intrauterine devices are promoted as being the greenest contraceptive available. They produce the least waste and are 99% effective. They can also last up to 10 years.

Another option is vegan condoms made by Glyde condoms.

fischer16 gave a very good answer. Unfortunately, hormonal birth control can make its way into waterways and affect the sexual development of fish.

cox01 was also very accurate in his description. Intrauterine devices (IUDs) are very effective and last a long time. However, they mostly work after fertilization of the egg has occurred. Thus, there are some ethical issues surrounding the use of IUDs. Since nobody knows when a fetus is endowed with a soul, I would caution against the use of an IUD until more research has been conducted.