Izaak Walton League Publications

The World at 7 Billion

By Laurie Mazur

When I was a kid in the late 1960s, my favorite spot on Earth was a patch of woods not far from my home in suburban Baltimore, Maryland. I would ride my bike through the development where we lived, past farms and fields and finally into the woods — a remnant of the great temperate forest that once blanketed the eastern seaboard. “My” woods had a rocky little stream that ran through it, where I caught tadpoles in the spring and slid on the ice in winter.

I went looking for that spot a few years ago, but it was gone — its tangle of brush and towering trees replaced by a grid of townhomes, driveways, lawns, and roads. No rocky stream, but a foul-smelling drainage, corralled in concrete, ran behind the houses.

It’s a familiar story to anyone who loves the outdoors: A favorite spot — a fishing hole or inspiring view — transformed or destroyed to make room for the ever-growing human enterprise. Since the middle of the 20th century, the population of the Chesapeake Bay watershed, where I grew up, has more than doubled from 8 million to 17 million people. Same with the world population, which grew from 3 billion in 1960 to 7 billion today. At the same time, our collective impact on the natural world has increased as never before.

In late October, the world population officially reached the 7 billion mark. So it seems an appropriate time to consider the relationship between human numbers and the natural world — both the wild places we love and the resources that sustain us.

Population by the Numbers
In the 1960s, while I was catching tadpoles in the creek, something truly extraordinary was happening: The world population was growing as never before (or since). Thanks to improved sanitation and vaccines, more children survived to have children of their own. That happy development launched an unprecedented expansion of human numbers. While it took about 200,000 years — from the dawn of human history until 1800 — for our numbers to reach one billion, in the next two centuries our numbers grew sevenfold.

Growth has slowed in recent years, but we are still adding about 78 million people to the human family each year — roughly the population of Germany. Growth is likely to continue in the short term, but the future is far from clear. Demographers envision a range of possibilities: Population could peak at 8 billion by midcentury and then decline, it could grow steadily to 16 billion by 2100, or anything in between.

Can we provide food and water — not to mention jobs — for billions more? Is it possible to protect the natural systems that sustain us, and the wild places we love, in an ever-growing world?

The answer is…well, it’s complicated. In the last half century, we have learned that population growth has a significant impact on the natural environment. But that impact is neither linear nor uniform, and it is shaped by many factors including technology, consumption patterns, economic policies, and political choices.

Put simply, some of us have a much greater impact than others. For example, the average citizen of Tanzania emits about a tenth of a ton of the greenhouse gas carbon dioxide each year. The average American emits that much every 28 hours. But population is growing most rapidly in places like Tanzania, where per-capita environmental impact is low. So our impact on the environment is determined not just by our numbers but by how we live. How many people can the Earth support? Here, too, the answer is complicated by great disparities in consumption. Consider food. If everyone on the planet ate like the citizens of India (mostly vegetarian), world agricultural output could feed a population of 10 billion. On the other hand, if everyone ate a typically meat-intensive American diet, we could feed only 2.5 billion.

Where We’re Headed
Of course, the current disparities in consumption are not fixed for all time. And when we consider the aspirations of the world’s 7 billion people — as well as the state of the natural world — a sobering picture emerges.

It is true that some people consume a far greater share of the world’s resources than others. But collectively, human beings are already using natural resources more quickly than they can regenerate. Today, fully two-thirds of the planet’s ecosystems — including fisheries and fresh water — are being used in ways that simply cannot be sustained. And when resources are used unsustainably, they eventually collapse.

That’s what happened to the cod fishery off the coast of Newfoundland in the 1990s. Growing demand from world markets led to decades of overfishing, after which the fishery collapsed, leaving cod stocks at just one percent of their previous numbers. The loss of the fishery devastated coastal communities, leaving 35,000 fishers and plant workers unemployed in Newfoundland alone — and reflects the pressure that growing human appetites have placed on natural resources.

The Newfoundland cod fishery is not an isolated case. In the last 50 years, human beings have cut down four-fifths of the planet’s forests and destroyed two-thirds of its coral reefs and mangroves. We have brought about the greatest mass extinction of plant and animal life in our history. Every year, some 30,000 species become extinct — about three per hour.

In the span of just five decades, we’ve altered the planet’s ecosystems more than in all of human history combined. In previous millennia, the Earth was transformed by massive forces of nature — the advance of glaciers, volcanic eruptions, the clash of continents. But in the late 20th century, human beings became the most powerful force of environmental change. Humanity has developed the capacity to transform — and destroy — the fundamental processes of nature that sustain us.

Climate change offers a dramatic example. Our emissions of heat-trapping gases — from burning fossil fuels, agriculture, deforestation, and other activities — have already warmed the planet’s land areas by about one and a half degrees Fahrenheit. As a result, scientists predict the 21st century will bring widespread famine in Africa and elsewhere, more violent storms, and the extinction of nearly a third of the Earth’s species.

Nature is inherently resilient; ecosystems regenerate after disturbances like hurricanes and wildfires. But we have weakened nature’s ability to bounce back by removing key species, by harvesting resources more rapidly than they can renew themselves, and by loading ecosystems with more wastes than they can absorb.

In so doing, we have weakened our own resilience. Healthy ecosystems are the foundation of human well-being; they provide a range of essential goods and services to humankind, such as food and fresh water, pollination, and protection from storms. But we are chipping away at that foundation. As a result, a recent global survey found that “the ability of the planet’s ecosystems to sustain future generations can no longer be taken for granted.”

Take water, for example, the substance on which all life depends. We live on a planet covered by water, but very little of it is fresh. In fact, if all the world’s water could fit into a gallon jug, the fresh water available for us to use would equal only about one tablespoon. And that little bit of water is distributed very inequitably: Just six countries hold over half of the world’s fresh water.

So, while there is no global shortage of fresh water, a growing number of regions are chronically parched. And many of those regions are also where population is growing most rapidly. The World Bank has identified 45 “water poor” countries where shortages are especially acute. Those countries’ populations are expected to double by 2050.

In 1995, about half a billion people lived in areas of water stress or water scarcity. By 2025, largely due to population growth, 1.8 billion people will be living in countries with water scarcity, and fully two-thirds of humanity will be living in conditions of water stress.

Slower population growth is not a panacea for the world’s water problems. Much can be done to develop better technology and better policy on water use. But slower growth and smaller population numbers could help ease pressure on scarce resources. That’s true not only for countries dealing with the deadly combination of poverty and water scarcity but for the world as a whole.

Women’s Empowerment
When population growth spiked in the 1960s, fears of depleted resources and civil unrest gave rise to “population control” programs, some of which flagrantly abused human rights. Much has been learned since then. Today, we know that the best and most effective way to slow growth is by making sure that all people have the means and the power to make their own decisions about childbearing. That means access to education, opportunity, and health care services — especially for girls and women.

Take education, for example. Where girls receive just seven years of education, they tend to delay marriage by an average of four years and have two fewer children than their uneducated peers. But in the developing countries, nearly a third of girls ages 10–14 are not in school.

Less than a fifth of the world’s countries will account for nearly all of the world’s population growth this century. Not coincidentally, those countries — the least developed nations in sub- Saharan Africa, south Asia, and elsewhere — are also where girls and women have the lowest status. Too often, girls in those countries receive less food, medical care, and education than their brothers. They are often married as children or young teens, before their bodies have finished developing, which greatly increases their risks during childbirth.

But cultures change, and the low status of women is not a given. Nations can raise women’s status by enforcing laws against child marriage, educating girls, and improving women’s access to credit, land, jobs, and health care. Where women enjoy these fundamental rights, smaller (and healthier) families become the norm.

The well-being of girls and women in developing countries may seem a remote concern, beyond the reach of American citizens. But, in fact, we have considerable power and influence. U.S. foreign assistance, though it comprises less than one percent of the federal budget, helps set the agenda for development in poor countries. By prioritizing aid that improves the lives of girls and women, we can have far-reaching effects on the well-being of families, nations, and the world as a whole.

The Future
As the world population reaches 7 billion, I find myself thinking about the long-gone patch of woods in which I played as a kid. I also think about my own children and the world they will inherit. I hope that world will offer the abundance of resources and opportunities that I grew up with. And I hope it will offer quiet, green spaces where they — and their children — can catch tadpoles and play in sparkling, clear water.

Those of us who came of age in the second half of the 20th century witnessed the most rapid population growth in history. With that growth, much was gained and, inevitably, much was lost. That great wave of population growth has slowed, but it has not stopped. Choices made today will determine whether human numbers peak at 8 billion or continue to grow to 16 billion and beyond.

For the sake of our children — and their peers all over the world — we should aim for the lower number. Especially since the means to slow population growth — educating girls, improving women’s lives, broadening access to health care services — are worthy goals in their own right.

Laurie Mazur is the editor of A Pivotal Moment: Population, Justice and the Environmental Challenge (Island Press, 2009) and Beyond the Numbers: A Reader on Population, Consumption and the Environment (Island Press, 1994).

More articles from the Fall 2011 edition of Outdoor America....

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