Among the many tricks we will try to keep fitting ourselves onto this planet, there is one that we already know. The technology is cheaper than all the others by many orders of magnitude. It is reducing the numbers of bodies to feed by managing our reproduction, before nature steps in to do that for us.

The following is an excerpt from Countdown , a book by Alan Weisman that explores the different ways that humanity can stop population growth from getting out of control and threatening planetary survival even more than it already has. In this chapter, Weisman discusses the possibilities of male birth control.

It is not perfect technology: for a small percentage of women, the chemistry of contraception causes migraines or depression, although the copper‑T IUD is a benign alternative, easily reversible as long as a trained medical practitioner is handy. Those chemical effects are not confined solely to women’s bodies, because while nearly half of estrogen is metabolized, the rest is excreted. Flushed away, a portion is removed in sewage treatment, but the rest finds its way into the ecosystem.

Some of the gender-bending estrogens feminizing not just minnows but trout, bass, and perch in lakes and rivers worldwide are identical to the ones in oral contraceptives. In every big river of North America except the Yukon, female egg cells are now common in two-thirds or more of male largemouth and smallmouth bass. In several studies in the United States, Canada, and England, however, research indicates that, compared to industrial and agrochemical sources, female contraceptives are a minuscule part of the artificial hormonal assault on the environment.

Among the most promising options is to counter conception through a far simpler pathway: by short-circuiting male sperm delivery.

That doesn’t mean that current technology needn’t be improved; however we can minimize chemical exposure to women and to the ecosystem, the better. Among the most promising options is to counter conception through a far simpler pathway: by short-circuiting male sperm delivery.

Two possibilities are male versions of the Pill, which, unlike their female counterparts, don’t manipulate hormones. One, already tested at Kansas State University on rats, rabbits, and monkeys, uses a compound called H2‑gamendazole that stops sperm from forming in men’s semen without reducing their sex drive, and is reversible within weeks. The other oral treatment uses a compound developed in the Bradner Laboratory at Boston’s Dana-Farber Cancer Institute called JQ1, which targets a testis-specific protein to lower sperm numbers and retard their swimming capability. Again, test mice show no lowered libidos, and regain fertility when they stop taking it.

Two of the most imaginative approaches aren’t chemical, but mechanical interventions. Risug–reversible inhibition of sperm under guidance–is already offered in several cities in India, and as of 2012 was in FDA trials in the United States. It involves a 15-minute outpatient operation using local anesthetic via a tiny incision in the scrotum to reach the vas deferens tube, into which the doctor injects an inexpensive polymer gel. Within three days, the gel forms a lining that allows semen to pass normally, but electrolytically destroys sperm. The spermicidal effect lasts for ten years, but can be reversed by injecting a baking soda solution. The same Indian developer has been testing another method at the University of North Carolina that uses ultrasound to heat testes for 15 minutes, resulting in six months of sterility in test animals.

One method uses ultrasound to heat testes for 15 minutes, resulting in six months of sterility.

Each of these techniques portends to be cheaper and safer both for humans and the environment than female chemical contraception. For a woman in a steady relationship with a willing partner, it could shift the stress of birth control from her uterus, conserving that organ for the sole use that nature intended. Reliance on male contraception would also, however, mean relinquishing control over her own reproduction, inserting a new test of trust into intergender dynamics. For men, it could mean liberation from the interruptive frustration of using condoms–although, outside of monogamy, there would be a loss of protection from sexually transmitted disease. As long as one epidemic that threatens human existence, HIV, is spread through seminal fluids, protection and contraception must remain related but separate issues.