Population and the Environment — Time for Another Contraception Revolution

During the second half of the 20th century, many political and academic thought leaders were concerned about the rapid growth of the human population, which had increased exponentially from less than 1 billion in 1800 to 5.5 billion by 1980. Thomas Malthus, an 18th-century English cleric and scholar, had famously predicted that with geometric population growth, human need could eventually outstrip Earth’s resources. Several popular books were published in the 1970s and 1980s forecasting dire consequences of human overpopulation. During this time, research on contraception was relatively well funded by private foundations and government agencies, and research on human reproduction was mainstream and highly regarded in respected academic institutions such as the Harvard Medical School Laboratory for Human Reproduction and Reproductive Biology (LHRRB), where I worked. At least half a dozen large U.S. drug companies were spending heavily on contraception research and development.

By the end of the 20th century, however, the mood had changed. The fertility rate had peaked in 1962 and was declining, although projections showed that population growth would not level out until at least the middle of the 21st century. Apocalyptic consequences of overpopulation had not materialized, and the agricultural Green Revolution promised engineered crops and other resources to keep pace with population growth.¹ Activists voiced concern about coercive and antifeminist aspects of contraception. Funding for contraception research from government and private institutions plummeted, and pharmaceutical companies and international agencies with innovative contraceptive methods in clinical trials stopped their programs.²

Yet the Green Revolution and continued population growth have created serious problems that were not clearly foreseen in the 1980s. Scientists warn that dangerous atmospheric levels of greenhouse gases produced by human activity are causing global warming and climate disruption. Waste from megacities and widespread agriculture and livestock industries pollute the land, air, and water. Rapid depletion of resources from forests and oceans is destroying natural habitats and further contributing to climate change. Many animal species are experiencing catastrophic decline, and naturalists warn that as many as 50% of species living today may be extinct by 2100 owing to human activities.³

As the global population con tinues to grow, these pressures will increase and become more critical. Currently there are 7.7 billion people on earth. The United Nations (U.N.) predicts that the human population will reach 9 billion by 2050, and probably 11.2 billion by the end of the century. Estimates of the number of human beings the Earth can support range from fewer than 2 billion to more than 100 billion (median, 8 billion). The actual number depends on variables such as acres of arable land, amount of fresh water, and human dietary habits. If the sustainability of ecosystem health and biodiversity are factored into the equation, modern estimates of the planet’s carrying capacity become much lower — 1.5 billion to 5 billion people¹ — and have already been exceeded.

The U.N., the World Health Organization (WHO), and others are increasingly sounding the alarm, and action is being taken on multiple fronts. The Paris Agreement within the U.N. Framework Convention on Climate Change has provided an ambitious global road map for the reduction of greenhouse gases. Organic farming and calls for less animal-intensive diets are gaining traction. Conservationists are working hard to protect the environment and animal species. In the United States, energy-efficiency policies and programs initiated at the state level and the Green New Deal promise to jump-start sustainable-energy projects and introduce new environment-friendly regulations.

The population-growth side of the equation is also receiving attention. London Family Planning Summits in 2012 and 2017 set an ambitious goal of expanding access to voluntary family planning services in the lowest-income countries, where 222 million women have an unmet need for family planning. The Gates Foundation recently prioritized the empowerment of girls and women, with an initiative expected to have a major moderating effect on human population growth.¹

The contraception revolution of the 20th century produced several effective birth-control methods that reshaped society. The leading methods used today are male and female sterilization, hormonal methods, long-acting methods such as intrauterine devices and implants, and male and female barrier methods. However, many men and women still cannot find a method to meet their needs. Sterilization is not suitable for people who desire to have children in the future; hormonal methods have side effects that many women find unacceptable; and barrier methods have a high failure rate when used inconsistently. Furthermore, all methods except for male condoms normally require medical prescriptions or interventions that put them out of reach of many people because of cost and lack of access.

Population watchers report that of the approximately 210 million human pregnancies that occur each year worldwide, at least 40% (more than 80 million) are unintended; of these, about 30 million end in abortion or miscarriage and 50 million result in unplanned live births.² Notably, the rates of unintended pregnancies are high in both high-income countries (47%) and low-income countries (39%). A disproportionate number of unintended pregnancies occur in young, unmarried women, who often lack access to comprehensive sexuality education and modern contraception; the WHO has pointed out that unplanned pregnancies in this group are a major contributor to maternal and child mortality and to intergenerational cycles of poverty and poor health. More accessible, effective contraception choices are needed to ensure that all children are planned and wanted. Such an advance could significantly reduce population growth to meet realistic goals for sustainable development.¹

The time seems ripe for another contraception revolution to provide options for the diverse populations that are not currently being served by modern contraception. Appropriate leadership and an infusion of funding could reignite contraception research, education, and services. This investment would be quickly offset by savings in health care and other costs attributable to pollution and global warming, whose U.S. costs currently total $240 billion per year and are expected to increase to $350 billion per year in the next decade if drastic mitigation steps are not taken. Globally, the health costs of climate change are projected to exceed $1 trillion per year.⁴

New products are in the pipeline that could help fill the remaining contraception gap. Vaginal gels and films with powerful spermicidal activity could prove to be popular as over-the-counter, on-demand methods for women. Male hormonal birth-control pills, gels, and patches that act on the hypothalamus–pituitary–testis axis to suppress spermatogenesis, and other drugs that temporarily inhibit sperm production or sperm function, are being developed for male contraception. The concept of a new approach called multi-purpose prevention technology (MPT) that offers dual protection against unintended pregnancy and highly prevalent sexually transmitted infections (STIs), such as human immunodeficiency virus type 1 (HIV-1) and herpes simplex virus type 2, has been enthusiastically endorsed by women and could boost the popularity of contraceptive methods.⁵ MPT products under development include a combination of antiretroviral therapy and hormonal contraception, as well as topically delivered nonhormonal agents such as monoclonal antibodies that specifically target sperm, HIV-1, and other STIs.

A new contraception initiative could promote innovative strategies by leveraging recent advances in well-funded scientific fields such as HIV prevention, molecular biology, nanotechnology, and bioinformatics, among others. New contraceptive discoveries could improve the health and well-being of women and their families and could help to further reduce and stabilize human population numbers globally, offering an additional step toward rebalancing the planet and preserving its natural treasures for future generations.