Images of wildfires engulfing trees, often with fleeing residents cast in silhouette, have become one the most ubiquitous illustrations of how global warming is affecting the West, especially California. But in a recent analysis, fire ecologist Jon Keeley saw a remarkable pattern that he feels has been overlooked by media, activists, and politicians.
Climate change isn't causing most fires. People are.
Keeley, a UCLA professor and senior research scientist with the U. S. Geological Survey's Western Ecological Research Center, studied records of tens of thousands of wildfires that occurred in California from 1919 to 2016. Although lightning strikes were responsible for as many as a quarter of all fires in several inland mountain regions, in two thirds of California counties, human activity sparked 95 percent of all wildfires. In Alameda County, 98 percent were attributed to human origins, in Contra Costa 93 percent, in Marin 99 percent.
Keeley believes that population growth is equally or even more responsible than global warming as the proximate ignition source of California's wildfire plague. "Politicians just want to say that global warming is the big problem," he said. "To me, climate change is a distraction from the population problem. ... They're comfortable with global warming because they can't be held accountable, whereas population growth is something that much more directly affects their constituents, right now."
Although U.S. birth rates fell to a 32-year low in 2018, neither California nor the Bay Area is immune to global population trends. Our regional population has grown profoundly — primarily caused by people moving to the Bay Area, mostly other Americans. And they don't just bring wildfires.
The Bay Area's 7.8 million people — 600,000 more numerous than in 2010 — are the source of urban sprawl and housing shortages, congested highways and crowded trails, air pollution and species extinction. By the 2040s, the Bay Area could be home to another 1.7 million people on top of that, and no matter how much new housing is constructed, some observers believe it won't ever be enough to outpace the demand for it. "It's an unsolvable problem," said Randy Rentschler of the Metropolitan Transportation Commission. "The Bay Area is choking on its own success."
Human population growth is the root cause of just about every resource-related problem afflicting both the Bay Area and global society. By 2100 — the year now so often treated as the forecast horizon for humanity — nearly all of the 7.3 billion humans currently alive will be gone. But in their place could be 11 to 12 billion others, dominating a planet overrun with noise, litter, livestock, and pollution, and stricken by resource depletion, ocean acidification, farmland degradation, water-supply overextension, and the cascading effects of climate change.
"We think about population growth in the most incredibly selfish way," said sustainable seafood activist Casson Trenor, who once worked for Greenpeace and recently authored a children's book about humans' relationship with the ocean. "There will be a whole lot of new people who didn't ask for this planet, who didn't ask for this situation, but will be brought into this world by our choice, and it's our responsibility to provide for them the best world that we can."
Although seldom invoked by name, population growth gnaws at the fabric of our lives and politics. The populist wave that has transformed politics across the developed world in recent years is largely a backlash to rising immigration from countries with higher birth rates and less economic opportunity. Economist David Zetland, who studied at U.C. Davis but now lives and teaches in the Netherlands, summarizes that political worldview as "white people who are afraid of darker-skinned people having more children." Consider for instance the infamous words of Donald Trump, who last year objected to migrants entering the United States from "shithole countries" (with Black populations) such as Haiti or in Africa, but specifically welcomed the (primarily white) residents of Norway.
Yet even though population trends lie at the very heart of our national politics, the topic is oddly absent from contemporary conversations.
"It dwarfs everything going on now, but people don't acknowledge it or if they do, it's sort of a sky-is-falling-let's-talk-about-something-else approach," said Trenor, who also cofounded San Francisco's Tataki Sushi and Sake Bar, widely applauded for focusing on the sustainability of its seafood. He calls the planet's growing population "the 800-pound invisible gorilla in the room."
So why don't we talk about it?
'Is It OK to Still Have Children?'
People have worried about overpopulation for at least 300 years. Late in the 18th century, Thomas Malthus theorized that the rapid growth of the human population would be checked by a limited capacity to grow enough food.
But Malthus was wrong; his forecast did not come true. Population growth was real enough, but it was accompanied by advances in farming, sanitation, manufacturing, medicine, and other realms that enabled more and more humans to live in closer and closer proximity, even while extending their average ages and qualify of life.
Following the 1968 publication of a low-budget paperback called The Population Bomb, many people again believed civilization was on a crash course with doom. The book, which sold millions of copies and made a celebrity of its author, Stanford professor Paul Ehrlich, warned that the human population had exceeded the Earth's carrying capacity and would experience catastrophic famines.
Ehrlich issued his warning precisely at the modern peak of the population growth rate; globally, our numbers were rising more than 2 percent per year at the time, double today's rate. The author viewed those trends as unsustainable. In an interview in 1970 with CBS, two years after publication of The Population Bomb, he declared, "Sometime in the next 15 years, the end will come, and by 'the end' I mean an utter breakdown of the capacity of the planet to support humanity."
In fact, Earth's human population has doubled since 1968, and projections suggest it will reach 11 billion by 2100. Yet even as population has surged, human life expectancy has only increased, and discussion of the issue itself has gradually receded from popular dialogues — replaced by such planet-wide concerns as pollution, deforestation, overfishing, and global warming.
Although projections such as Ehrlich's did not come true, they arguably were quite influential in helping to slow down birth rates in the developed world. All across the Northern Hemisphere and the southernmost parts of the Southern Hemisphere, birth rates have plunged in the years since The Population Bomb was published. The United States' birth rate has gone negative — to 1.8 children per woman. Across the globe, advances in education and the empowerment of women have radically reduced fertility rates and family sizes in the nations farthest from the Equator — including Europe, industrialized Asia, Australia and New Zealand, the southern half of South America, Canada, and the United States — home to roughly two fifths of the planet's population. The home of the other three fifths — including Africa; the Mideast; Central, South, and Southeast Asia; the Caribbean; Central America; and the northern half of South America — have much higher fertility rates.
These realities arm contemporary discussions of population with racial and ethnic tripwires.
"Population growth in Africa — yes, it's a problem," said consulting ecologist Josiah Clark, a San Francisco native. "But by focusing on that, we're making it into a Third-World issue, like we can blame them for the problems we're causing."
When some people ask other people to refrain from reproducing, Zetland noted that it sounds like "a big fuck you" to anyone who has chosen to have children. Even though bringing humans into the world has negative impacts on shared public resources, the acts of procreation and parenting are treated as inalienable rights.
"What do politicians do?" Zetland quipped. "They kiss babies, so they're not going to go around telling people to have less of them."
In a rare exception to this dynamic, several months ago Rep. Alexandria Ocasio-Cortez suggested in a video that it's appropriate for young people to ask, "Is it okay to still have children?" Not surprisingly, she was immediately disparaged by conservative talking heads like Sean Hannity, Pete Hegseth, and Tucker Carlson, all of whom basically accused her of trying to sabotage civilization.
Because population growth is closely linked to economic growth, it can be dangerous for elected officials to scorn reproduction. In fact, Republican lawmakers often encourage population growth, ostensibly for the benefit of society.
In March, Republican senator Mike Lee, of Utah, gave a speech in which he called for Americans to "fall in love, get married, and have some kids." He claimed that having more people on the planet, not fewer, is the best way to provide the needed brainpower to think our way out of the climate crisis. Back in 2017, Representative Paul Ryan told reporters, "We need to have higher birth rates in this country," explaining that the social assistance programs that he has tried to weaken through funding cuts are at risk of sinking if birth rates decline.
However, the same politicians who call for higher birth rates also tend to oppose liberal immigration policies, even though replacement migration — how some European countries now maintain their populations — is a viable and humane mechanism for populating economic sectors like agriculture and construction.
"They're certainly looking to grow only certain populations in the United States," said Stephanie Feldstein, the population and sustainability director with the Center for Biological Diversity.
This dynamic is seen in other countries, too. Israel's high birth rate of 3.1 children per woman has been applauded by pro-Israel analysts as a boost to its political and economic standing — and preferable to the alternative of simply accommodating would-be immigrants.
"In 2018, Israel is the only advanced economy and Western-style democracy endowed with a relatively high fertility rate (number of births per woman), which facilitates further economic growth with minimal dependency on migrant labor," wrote Yoram Ettinger in a 2018 article at JewishPolicyCenter.org.
Japan, on the other hand, is where to best study the economic ramifications of population decline. Its population keeps steadily shrinking as the lowest birth rate found among any modern nation continues to decline — now just 1.42 births per woman. In 2018, the nation's total population dropped by 445,085, to 124 million people. In 2009, about 128.5 million people inhabited Japan.
As the median age of Japanese citizens increases, the matter is being treated as a national crisis. That age is now 46.3 years, with more than half the population 46 or older — statistics only slightly amplified above those seen in much of Europe. The problem with an aging population is that the number of retired individuals increases, and the workforce contracts, placing the burden of supporting them onto the shoulders of fewer and fewer people.
It also means fewer consumers, which upsets standard notions of economic growth.
"Politicians are obsessed with GDP and growth as metrics for their own success and a healthy economy no matter how unhealthy it is for the environment," Feldstein said. "There's this disconnect in our economy and in politics where they insist on this belief that infinite growth is possible even though we live on a finite planet."
Japan illustrates why. Although the causes of its woes are manifold, its economy has been in recession for more than 20 years, since around the time the country's birth rate first plummeted. The Japanese government has promoted campaigns to boost childbirths, but there seems to be no turnaround in sight. Projections show there could be as few as 100 million Japanese citizens by 2050.
If the entire planet were to follow this trajectory, there would be about 6 billion people in 30 years, rather than the expected 9.8 billion.
"If the population declines, it will take some rethinking of economic structures," Feldstein said. "Right now, that structure is based on growth. ... It seems impossible because we've only ever seen our population grow."
Mathis Wackernagel, founder of the Global Footprint Network, in Oakland, said the problem with perpetual economic growth is that it physically can't continue forever.
"It is a Ponzi Scheme," he said. "We are overusing resources of the future to pay for the present." Such schemes, he said, must be "maintained or they collapse. That's why we are so tied to this rat race. We cannot jump off so easily."
Zetland believes economies can prosper even if their populations stabilize or begin to drop.
"It's a total fallacy that the economy needs constant growth and a growing population," he said, noting that individual retirement accounts can potentially lift the burden of supporting the retired generation off the shoulders of the younger workforce.
Feldstein believes that leaders and policy makers should consider alternative metrics for measuring the success of societies.
"A few countries are measuring things like happiness indexes, and how we are providing for people, because it's not just about whether the economy or capitalism suffers, it's about whether people are suffering," Feldstein said. "If we shift our focus to that, then there doesn't need to be a decline."
It would alleviate pressure on the environment allow for smaller-sized families to better support each other.
'It's Kind of a Taboo to Talk About Population'
On a warm June afternoon in North Oakland, Nik Bertulis sat on the roof of his home, wondering if he would ever bring a new human into the world.
The 44-year-old would like to be a father. But he is among many people in their early middle age questioning the ethics and wisdom of having children. His concerns include subjecting children to an uncertain future as well as contributing to that uncertainty by adding another mouth or two to feed.
Bertulis and his partner live in a small community of tiny homes, with a dozen other residents, on a leased property converted from a vacant lot eight years ago into an urban garden space and artists' community. He views his living situation as 'regenerative,' which he defines as living "in a deeply reciprocal relationship with nature." They call it PLACE, for People Linking Art, Community, and Ecology. It's within the most coveted urban area in the West, with culture, music, and people as nearby as green space, trees, and gardens. In many ways, there could be no better place to raise a child.
"But because of the ecological destruction all around us, I've really leaned away from it," he said. "I don't know that my child would take up regenerative habits, and it could have negative impacts on the planet. Each new human added to the planet usually is going to have degenerative effects — there's no way around it."
Discussing such matters openly can be a delicate task.
"Reproduction is such a strong drive, biologically but also socially and culturally," Bertulis said. And older relatives often pressure their children and grandchildren to settle and have families, he noted. "Any time you start talking about the environment and population, it's like an immediate threat to that entire part of life," he said. "It's kind of a taboo to talk about population and its impacts on our environment."
The debate over how population trends affect economic vigor indicates our society's misplaced values, he said.
"Gross domestic happiness is a much more relevant indicator of how we measure wealth," he said. "If physical and emotional well-being is wealth, then let's measure true wealth rather than obscure, abstract concepts that destroy our environment."
Taken one person at a time, such personal decision-making is more symbolic than Earth-changing, and may not significantly alter the fate of our world. Because while Americans may not be reproducing as prolifically as they once did, they are still voracious resource hogs. Environmental constraints are not slowing us down.
Americans' per capita carbon footprint remains dozens of times greater than that of many other nations. That begs the question whether Earth is suffering more from overpopulation, or human consumption patterns. Ecologist Peter Raven, a San Francisco native and president emeritus of the Missouri Botanical Garden, believes it is both.
"People sometimes try to say it's consumption that's the problem, not population, but those two things are like two sides to a rectangle," said Raven, who has studied the impacts of the growing human population on wild plant communities. "The more people you have, the more consumption, and the more consumption you have, the more impact. They're directly related. We need a level population."
There is certainly no doubt the planet's nonhuman residents are paying the price of overpopulation and unsustainable lifestyles. The mere presence of humans will drive many other animals away, disrupting their feeding and breeding behavior.
That's why many naturalists now advocate for half the Earth being allocated to other species. It's an idea popularized by author and Harvard biologist E.O. Wilson, who proposed in his 2017 book Half-Earth that allocating half the planet's surface to the natural world would relieve 85 percent of species of the threat of extinction.
Bertulis, referring to this philosophy, calls himself "a half-Earther." He believes that with proper landscape management — including densification of cities — that California could revive its waning resources.
He believes, for example, that Californians have the know-how and technology to restore the massive salmon runs that shaped much of California's natural and cultural histories. The fish teemed in coastal waters, and scientists think at least 2 or 3 million adults — mainly Coho and Chinook — spawned every year in coastal creeks, streams and rivers. Salmon supported much of the marine and inland food web, and thousands of people relied on the nutritious fish as a staple food source and a trade item. In Oregon and Washington, the bounty was just as plentiful, if not more so.
But just about everywhere in the northern hemisphere where salmon range naturally, human population growth and economic development have correlated with a decline and disappearance of local runs — a pattern documented by biologist Robert Lackey, of Oregon State University, who has predicted near-extinction of salmon south of Canada.
"We squandered our true wealth," Bertulis said. And while we're not going to have grizzlies again, he believes salmon runs could be restored. "We have the tools to restore 100 percent of ecosystem function and historic abundance, even in the Bay Area."
But that's an optimist's viewpoint. Wackernagel believes humans are sucking the life out of the planet faster than the sun's incoming energy can replenish it. His Global Footprint Network concerns itself largely with measuring the rate at which that is occurring.
Right now, he said, humanity is consuming resources at a rate that it would take 1.75 Earth equivalents to sustain.
"This means we're drawing down our assets," he said.
The network's annual Earth Overshoot Day illustrates this concept, marking the day of the year by which the planet's humans have consumed all the resources that the planet is able to produce in a full year. This year, we will have consumed a full year's worth of food and energy by July 29 — the 2019 date of Earth Overshoot Day. Last year, it was on August 1. In fact, it has been arriving sooner and sooner almost every year. In the 1990s, it arrived in September.
If all the world's residents lived like Californians, Earth Overshoot Day would fall in late March. That's because Californians are using between five and eight times the biological resources that are available with the state, Wackernagel said. In his native Switzerland, the populace consumes 4.5 times the resources that could be produced inside the nation.
"A lot of these people say, 'We have money, we'll just buy what we need,'" Wackernagel said. "But in the end, not every nation can be a net importer, not every nation cannot be using more than what they have."
Currently, on average, they are, and it's a problem many people argue outweighs the problem of population. But on average, Wackernagel said, per capita global consumption rates haven't changed much since the 1970s. That means the increased consumption rate of the planet is largely being driven by population growth.
'At Some Point There Are Limits'
The Population Bomb is widely viewed today as little more than a curiosity, reflective of a brief moment of social panic. Forecasts warning that 4 billion people on the planet would cause calamitous environmental collapse were obviously way off the mark. Still, Ehrlich's warnings shouldn't be shelved forever.
"When a stand of trees is planted too densely for its environment, at some point there's going to be a massive die-off," said David Keller, a former Petaluma city councilman who has advocated for various environmental causes. He said an even worse event resembling the flu pandemic that infected a third of the planet's population in 1918 and killed 50 million could strike again.
"There are carrying capacities," Keller said. "We see it in animal populations over and over and over again — you exceed the carrying capacity, and populations collapse." With humans, he said, the effects may be "increases in diseases, accidents, anxiety or migration away — at some point there are limits to what a habitat can support."
In the past 12,000 years of agriculturally based society, the human population has grown about 2,000-fold, from an estimated 4 million to 7.3 billion today.
Mid-range forecasts from the United Nations show the population stabilizing at 11 or 12 billion in about 100 years. Higher-end estimates suggest a peak at 16 billion. Another U.N. projection, though, suggests a peak at 8.8 billion by 2050 and then a steady decline, dipping back to the present level by 2100.
Wackernagel noted that if every country's citizens reproduced and consumed resources as people do in Portugal, Spain and Italy, the planet would see a mighty reprieve, with a population decline to about 4.5 billion people by 2100.
"And the consumption level would drop from 1.6 planets today to 0.9 planets," he said.
Perhaps most notably, a truly global human population decline would require the social and political empowerment of women everywhere, through education and family planning.
So if populations do begin declining, recent Republican presidential administrations will deserve none of the credit. They have repeatedly cut funding or otherwise impeded international family planning programs. Ronald Reagan, George W. Bush, and Donald Trump have all disrupted efforts to provide women in developing nations with birth control and access to safe abortions. Barack Obama restored funding to the United Nations Population Fund after his predecessor held back $244 million in aid to the program over seven years.
But upon Trump's entrance into the White House, the current president signed an executive order prohibiting any organization that receives United States funding from even so much as recommending abortions — even if the organizations use their own money for any such efforts. The president's action has been widely rebuked as an assault on women in countries where getting pregnant at a young age means an end to education and all the quality-of-life perks that may come with it.
Of course, in pushing their conservative stance on family planning, Republicans are inadvertently encouraging third-world population growth. But when people born into poverty seek brighter opportunities in the United States, the same political party tries to lock them out.
Feldstein expects no better of an administration that has stripped immigrant children from their parents and locked them in cages. But notwithstanding such policies, she is optimistic about the future trajectory of the human population. In spite of Republican efforts to inhibit the aid programs that help boost women's social standing in developing nations, she said "we are seeing a drop in fertility rates."
'If You Don't Have Kids, Good on You'
On a blistering hot afternoon in San Francisco, thousands of people recently swarmed to Baker Beach, a five-minute bike ride from the home of Clark, the consulting ecologist.
"Most of these people are coming from Martinez, Antioch, Milpitas — they're desperate for relief from the heat," Clark said. "These people are climate refugees."
A San Francisco native who devotes much of his life to cultivating native plants, listening for rare birds, and kayak fishing for salmon, Clark would be thrilled if the crowds that now swarm the areas he once enjoyed in relative solitude somehow dissipated.
"But we have to let them in," he said.
Housing more people in denser urban centers is an idea that bristles the hairs of many NIMBYs. Clark, however, views the densification of San Francisco and its surrounding cities as less a threat to the Bay Area's biodiversity and open space than an opportunity to save it.
"Let's densify San Francisco so we don't have to build on Mount San Bruno," he said. "Let's densify Merced so we don't have to build all over in the Sierras." Local parks and trails may be trampled to dust in the process, but Clark sees no other way to accommodate the masses that are coming. "Let's let these isolated places and parks be our sacrificial areas, and save everything else," he said.
Dialogues about increased density often warn of huge buildings throwing their permanent shadows over neighborhoods, noted Urban Planner Ben Kaufman.
"But density doesn't have to happen as high-rises," he said. "The population of the Sunset District in San Francisco could be doubled by adding one story to every residential building." Such amendments, he said, could ease suburban sprawl and chronic traffic congestion in spite of population growth.
One path forward, said Kaufman, a member of the board of Transport Oakland, is the unappetizing option "to continue on the path we're on now toward more sprawl, which eats up farmland and open space. Or we can build denser and more transit-oriented, and protect our farmland and our wilderness areas, and generally adjust in a carefully thought out way to a reality of more humans living in the Bay Area."
Bertulis agrees, noting that many rural areas around the world are depopulating as people move to the cities. Densification could facilitate this shift.
"I think this is going to be good for rewilding our rural areas and restoring them to some of their previous glory and abundance," he said.
But even while people clamor for the privilege of living in the Bay Area's urban core, Bertulis said he's thinking of making the opposite migration.
"When we're younger, we tend to appreciate the culture and energy of more populated areas, but as we get older, we often seek more peace and solitude," he said. "I'm sort of at that point where I may be looking for that quieter place."
As for procreation, he might be leaving the task to others. He said he doesn't want humanity to dwindle away.
"Some people should be having children, absolutely, to perpetuate humanity," he said. "But if you don't have kids, good on you — well-played."