“And God blessed them, and God said unto them, be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth.”

— Genesis 1:28, KJV

This scripture was written around the sixth century BCE, when an estimated 150 million people inhabited Earth. The current global population is approaching 7.7 billion. It is imperative that we reconsider the human population burden and our role as stewards of the Earth.

Homo sapiens originated approximately 200,000 years ago, but it was not until 1800 CE that the population reached one billion. By contrast, in the last 200 years the human masses have exploded eight-fold. If the entire history of our planet was scaled to one 24-hour day, humans arrived only in the last 30 seconds, taking 29.95 seconds to reach one billion people, and just the final 0.05 seconds to reach 7.7 billion.

Sometime during the 1960s, the global population growth rate began to decline and continues to do so, particularly in developed nations. Despite slowing growth, the United Nations World Population Prospects estimates that by the year 2100 the population will be between 9 and 13 billion people. The critical question remains unanswered: What is the sustainable number of humans that our planet can support, not only now, but for millennia to come?

In 1992 the Union of Concerned Scientists penned the “World Scientists’ Warning to Humanity” (signed by 1,700 independent scientists including most living scientific Nobel laureates) stating that “a great change in our stewardship of the Earth and the life on it is required if vast human misery is to be avoided.” They outlined concern regarding present and impending global environmental crises including ozone depletion, freshwater availability, marine life depletion, forest loss, biodiversity destruction and climate change. Importantly, they implored that we stabilize the human population as our swelling numbers continue to overwhelm all other environmental efforts to realize a sustainable future. Yet, in the quarter century since that publication, the world population grew by another 2 billion, and with the exception of stabilizing the stratospheric ozone layer, other environmental crises have only intensified.

Consider also the tragic loss of global biodiversity estimated in a May 2014 review from the journal Science: Through our collective habits and growth, humans have unintentionally begun the sixth mass extinction of species in the last 540 million years, with extinction rates greater than 1,000 times the natural background. There is legitimate concern that, by the year 2100, up to half of all marine and terrestrial species alive today will be extinct. We will have more than 9 billion people, yet half of the world’s other species will be gone.

The present global human population is exceeding long-term global sustainability. Without significant restraint of our global habits of human growth, environmental destruction and resource depletion, our planet will become progressively more inhabitable to life as we know it. Importantly, the solution must include the ethical and attentive matching of human population numbers with longer term sustainability. This oft overlooked concept should be a developed global value at the center of all environmental discussions.

Women’s education and empowerment in family planning should be at the forefront as globally this is one of the most important methods of mitigating uncontrolled growth. Nationally, focus should be on reducing our collective environmental footprint and ardently valuing long term sustainability as we select governmental representation. For posterity, we must embrace our role as stewards of the global environment with a sustainable vision for succeeding millennia.


Andrew Freeman, M.D., is a pulmonary and critical care physician from Salt Lake City.