Is Homo sapiens a boom-bust species?

Projections suggest the human population will fall 50% by the year 2300.

The boom: Life in the fast lane

The basic facts are clear. Homo sapiens cruised along for most of our 200,000 years with a small population, probably less than a hundred thousand. Then something happened. We expanded, emigrating out of Africa and across the globe. About 10,000 years ago, when our population was around four million, we developed agriculture. Cities and large organized societies – and money and writing – came along later. The human population really took off. This growth became exponential. Homo sapiens passed 1 billion around 1800, 2 billion in 1928, and 5 billion in 1987. Our impact on the earth has been so dramatic that geologists have coined a new geological epoch: the Anthropocene. When I was a child, I was told there were more humans alive on the earth than had ever existed in the history of the species. If that’s not the definition of a population boom, I don’t know what is.

Today we’re just over 8 billion, but we’ve passed an inflection point. The rate of increase is decreasing, from 2% per year in the 1960s to less than 1% now. The S-curve is forming. The top of the curve is bending, ultimately to be replaced by a decline. Demographers predict that human population will peak in 2064 at about 9.7 billion. After that, the decrease may be equally precipitous.  

In most “developed” nations, the fertility rate (the average number of children that a woman has in her lifetime) has fallen below 1.6. The fertility rate is 1.23 in Spain, 1.24 in Italy, 1.34 in Japan, 1.44 in Austria, 1.53 in Germany, 1.56 in the UK, and 1.64 in the United States. It takes a fertility rate of at least 2.0 to maintain a steady population (not counting immigration). The countries with the highest fertility rates, over 4.0, are in sub-Saharan Africa and Afghanistan, though even those are declining sharply. Every nation in the world may have a shrinking population by 2100.

Without immigration, high-income nations with low fertility rates will see much more rapid population declines. Regardless, all nations may have shrinking populations by 2100. Source.

The bust: It’s the end of the world as we know it

The worldwide average fertility rate is predicted to be 1.7 by 2100. That implies a population decline of about 9% each generation (about 25 years). This, in turn, implies a 50% decline in total population within 200 years, and a 90% decline, back below one billion, in 600 years. That’s basic math. That’s a freefall, a massive shrinking of human society.

The implications of a worldwide average fertility rate of 1.7.

This kind of population collapse is not unheard of in the natural world. Many species, from lemmings to locusts to crabs to passenger pigeons, are known as boom-bust species, with wild swings in their populations. Some research suggests that wild swings in animal populations may be the norm.

The bust – the fall, the decline, the collapse – is often driven by hitting the carrying capacity of the resources they depend on. Simply put, the species runs out of habitat or runs out of food. Life, literally, becomes too difficult. Animals may die or simply fail to reproduce.

When the world is running down, you make the best of what’s still around

What is it like to be an individual living during a bust cycle? Apart from a few perturbations in history (see Collapse by Jared Diamond), it’s a world that humans are unaccustomed to.

The economy will be shrinking, both supply and demand. The stock market will fall daily, for most businesses will be in decline. Stores will be closing, never to re-open.

The number of working age adults (assuming some migration between nations).

By definition, deaths will outnumber births, which means the demographic age mix will be decidedly older. By definition, many won’t have children to look after them. They will need to rely on paid caregivers, which will be in short supply.

We have a hint of that economic upheaval now, with supply shortages as we emerge from the Covid pandemic. Recent research suggests that half the lost workers in the US today are actually a result of Trump’s crackdowns on legal immigration. It is immigrants, after all, who make up the difference in the US’s low fertility rate. Those labor shortages, and the resulting supply chain problems and inflation, are caused by more people aging out of the labor force than aging in. This can only be mitigated by immigration.

When immigrants are no longer available, how does a nation manage a declining economy, a permanent recession? Public services – police, fire, water, electricity – will be difficult to provide everywhere. Service will be terminated in rural areas. Outlying areas and small towns will be abandoned as people seek services (primarily medical at first) in larger cities. Schools, healthcare clinics, stores, and homes will crumble as the population concentrates into remaining urban centers. All production, especially agriculture, will need to efficient, relying less and less on labor. With a lack of private investment, will government need to play a stronger role to guarantee the provision of goods and services?

What does this mean for culture? So many of the values, customs, and social rules of the past ordered growing societies, supporting the family, state, and nation. In a declining society, the center, the things we hold dear, does not hold. Things fall apart. Sure, one can strive for personal peace and meaning, but family lines will end. There are no “greatest” generations building infrastructure for the future.

Will there be a collective future to aspire to? Perhaps divisions of the past – gender, race, nationality – will lose meaning in the face of a shared human condition. On the other hand, we already see those tensions exacerbated as people glimpse the future, desperate to cling to the past.

Perhaps a shrinking economy can be managed. Perhaps there is a soft landing to societal collapse, to shrinking our footprint to a new steady-state in a sustainable harmony with nature.

We don’t know yet. We’re still on the crest of the wave, the top of the curve, enjoying the best of times. It’s our kids and grandkids and great grandkids who will come up against that carrying capacity. And that’s exactly why many are choosing not to have kids. Others don’t have kids because they have other economic or personal opportunities, thanks to our societal successes. But even in this decision, they feel no imperative to have kids. Indeed, the imperative is to reduce our impact on the earth. It looks as if that will happen. For the earth, a short-lived Anthropocene will no doubt be a good thing. For the people living during the collapse, perhaps not.

How do economies and societies function when it gets to the point that they are obviously shrinking?

A marsh in Richmond: what a restoration project taught me about racial bias, white privilege, and environmental justice

IMG_8286The people of Richmond did not like our choice for a restoration project; they wanted a different one. They called us racist. At first, we were perplexed. Eventually, I realized they were right.

As a natural resource economist for the California Department of Fish and Wildlife, it was my job to assess injuries to wildlife and habitat due to pollution events, and to seek compensation, thru restoration, to “make the public whole.” Working with partners from the US Fish and Wildlife Service, NOAA, and other state and federal agencies, we enjoyed our work— suing oil companies and using the recovered funds to do habitat restoration. We were “the trustees”; we represented the people and the natural resources and acted on their behalf. We were the Lorax; we spoke for the trees. We had been as innovative as we were successful, pioneering seabird restoration on breeding colonies in Canada, Alaska, Mexico, and even New Zealand to benefit bird species killed by oil spills in California. Those were the only places they nested, so we did what made the most biological sense.

In 2012 we began assessing damages to Castro Cove in San Pablo Bay near Richmond. It had been contaminated by oil, mercury, and lead associated with the adjacent Chevron refinery. To compensate for the injuries (in addition to cleaning up Castro Cove), we proposed to restore saltmarsh wetlands at Cullinan Ranch, part of San Pablo Bay National Wildlife Refuge, about ten miles to the north. We immediately met opposition from locals. They wanted the settlement funds to stay in Richmond; Cullinan Ranch was too far away.

We have project selection criteria set in federal regulations. Top of our list is always nexus— we aim to restore the same type of habitat and species that were injured. But there are also other things to consider: feasibility, partnering funds to make the project bigger, cost (bang for the buck), etc. When it came to evaluating restoration options, Richmond had little to offer. The refinery was merely one of several industrial or former industrial sites along their bay front. Contamination issues were everywhere. A poster child for environmental injustice, Richmond is also poor and predominantly non-white. We thought Cullinan Ranch was a good solution.

The people of Richmond wanted us to spend the funds restoring Breuner Marsh. This was a 238-acre parcel just north of Castro Cove wedged between the bay and the railroad tracks. Across the tracks was Parchester Village, a housing tract built after World War II to house African Americans enticed to move there and work in the nearby factories. It was one of the few places offering FHA home loans to non-whites. They came primarily from Louisiana, a land of marshes. They would cross the tracks and enjoy the wetlands as a place to hunt and fish. To this day, Parchester Village remains predominantly black. Whitney Dotson, and his father Reverend Dotson, have been fighting development proposals there, by a man named Breuner, for decades.

Initially, we, the natural resource trustees, fought the people of Parchester. The Cullinan project exceeded the Breuner project by most criteria. It was already part of a protected refuge. It had ten feet of elevation gain to buffer sea level rise. And the project, modifying the levee system, promised to restore 1500 acres; it had serious bang for the buck. And we asserted that ten miles away was no big deal.

But the distance was a big deal, and we didn’t understand why. I did not understand that other subcultures in the US don’t hop in their Prius and drive an hour to see a rare bird like me. They don’t throw their kayak on their Suburu and head for the boat launch. Nor were the people of Richmond, working two jobs and long shifts, going to drive to Cullinan, which had little parking and no bus service. They wanted to protect and restore their own marsh across the tracks from their neighborhood. They knew, better than we, that using our criteria, places like Marin County across the bay, one of the wealthiest counties in the nation, would win every time. No prior contamination? Check. Partnering funds? Lots. Contiguous with other protected areas? Of course.

When the people we are supposed to be compensating are complaining about our proposal, that’s a red flag that perhaps our criteria are biased, our evaluation is wrong, and that their values are not the same as our values. And they are the ones who matter. As trustees, we were supposed to ensure the compensation of the impacted people. We are obligated to see the world through their lens.


The $14 million dollar project has re-contoured the wetlands and planted native grasses, as well as extended the Bay Trail with a paved bike path, parking lot, and restrooms. When I visited recently, two Golden Eagles, normally rare next to the Bay, skirmished over a kill in the grasses. 

A similar conflict arose in Mississippi after the Deepwater Horizon oil spill. At a contentious public meeting between the predominantly African American public wanting one type of restoration and white agency scientists proposing another, one exasperated woman stood up and asked, “Why are you all white?” When the government officials told me about this, they were scoffing. But it’s a great question. We all know the answer. They got their positions in government because they had college degrees. This in turn was highly correlated with a good high school and a good neighborhood. The money that financed all that started with their parents or grandparents, who probably began accumulating their family’s wealth after a subsidized college degree and home loan thru the GI Bill, or an FHA home loan, or maybe even a free plot of Native land via the Homestead Act, all programs that built the white middle class—and largely excluded people of color. The odds of a black person qualifying for one of these government positions were slim. That’s why that panel of restoration experts was all white. And they brought their cultural values with them.

In the end, we caved in and split the funds between Cullinan and Breuner (begrudgingly). I went to the Breuner Marsh project dedication ceremony, which featured speeches by both Whitney Dotson and Representative George Miller. There I learned everything I should have known earlier. That the people of Parchester Village had been fighting to save that marsh for decades.

They have since renamed the marsh; it is now the Dotson Family Marsh.

Oceanography, plastic pollution, and Big Ag in the Amazon: What you can learn from the beach in the Yucatán


Plastics and rotting sargassum, Sian Ka’an Biosphere Reserve, Quintana Roo, Mexico

The beaches south of Cancun, Mexico were once famed for their talcum powder white sand and leaning coconut palms. Now they tell you a lot about the world.

Waves pile sargassum seaweed up to ten feet high along the waters edge while the sun cooks the rotting vegetation higher on the beach. I saw it about two feet high. It smells and traps baby sea turtles, preventing them from reaching the sea. And it’s not from Mexico. Sargassum is a floating algae, different from the seagrass that is anchored to the sea bottom offshore. Fed by warming seas and nutrients from agricultural runoff from the Amazon and other rivers to the south, sargassum has bloomed in recent years. Wind and currents bring it to the Yucatán Peninsula, where it has affected tourists’ enjoyment of the beaches.


But that’s not all. The beaches are littered with plastic garbage— mostly bottles and containers associated with beverages, personal care products, or automotive fluids. I couldn’t read the labels on most of them— they had clearly been at sea too long, drifting from too far away– but it appears most of them are not from Mexico either. Of the 47 labels I could read, here are the results.



I searched about 400 meters of beach at the Sian Ka’an Biosphere Reserve, south of Tulum, Mexico on the Yucatán Peninsula. There were about a thousand plastic containers. I could only read the labels on 47 of them. They came from all over the Caribbean, as well as Central and South America, and even West Africa and Asia.

The countries of origin based on the labels on the plastic containers are correlated with distance and currents. Cruise ships are an unlikely source– dumping plastics at sea has been banned for over a decade in the Caribbean.


Skin cream from Togo.

The disproportionate percentage of plastics from Haiti (mostly energy drinks) suggest this trash comes primarily from land-based sources, not cruise ships, and is correlated with poverty and the ability to address garbage. The high percentage from the US may be from local tourists or even Puerto Rico. Mexico is undoubtedly over-represented in my sample– those plastics come from the nearest and are likely less degraded and easier to read. Given that over 95% of the containers were so worn they were unreadable, it is likely they drifted from far away.


This beach, the lee of a point, was the cleanest one I encountered.


The Coming Green Wave

This op-ed in the New York Times boldly declares:

“if just one unorganized voting segment, the 60 million bird-watchers of America, sent a unified political message this fall, you’d have a political block with more than 10 times the membership of the National Rifle Association.”

There are other fun stats, like there are more yoga instructors in the US than there are coal miners. Enjoy. And vote.