Humans Boom while Birds Crash

Starling murmuration
European Starling murmuration (James Wainscoat: Unsplash)

The United Nations estimates that our population reached 8 billion this week. In 1900, it was 1.6 billion but by the turn of the 21st century, we had grown to over 6 billion. That is nearly 2 billion more mouths than only 22 years ago and the graph is still rising. Meanwhile, most wildlife populations across the globe are plunging. There’s a connection and it’s called the Sixth Great Extinction.

It is harder to estimate populations of birds than terrestrial animals, but North America alone is reckoned to have 3 billion fewer birds than 50 years ago. Seventy species out of a total of over 500 are thought to be close to a tipping point, meaning the threshold for sustaining their presence.

The Cornell Lab for Ornithology released a tool this month that maps trends in the abundance of birds from 2007 to the present. The data were provided by citizen scientists through eBird and mapped in 27×27 km squares (roughly the area of a small county). Birders and gardeners have noticed fewer birds in their localities, especially “common” birds, and this impression now has numbers. Typing the name of any species prompts the map of North America to show the trend in blue boxes for an increase, red for a decrease, and white where it can’t yet be determined with confidence.

I tested the tool for the mid-Atlantic region where I live. The good news is that geese and swans have increased spectacularly, and waterbirds and ducks are doing well too. The protected status of wetlands where there is less pollution and human disturbance is probably responsible.

There are reassuring trends for some raptors (eagles, owls, and the Red-shouldered Hawk) as well as for vultures and ravens. The Pileated Woodpecker, Carolina Wren, Wild Turkey, and Ruby-throated Hummingbird hold up well too.

But the news overall is bleak. Insectivorous species are down from a loss of habitat and prey, a large group that includes warblers and swallows. American Robins and Gray Catbirds are declining, but whatever is responsible hasn’t affected Northern Cardinals that have overlapping habitats. Hearing American Crows every day, I am surprised they are in decline, and will likely appreciate them more if they become rare!  

We can do little about the rising human population, but every landowner can help to mitigate the decline in birds by making their property a friendly habitat. This should be easier because few birds are regarded as pests. Many are beautiful and some provide services we appreciate. Farmers can leave field margins fallow for foodplants and insects to thrive. Roadside verges and hedges should be mowed and pruned after the breeding season and boring roundabouts planted with wildflower seeds. Gardeners can set aside corners of their yard for nature to creatively flourish, often as beautiful as a tidy flower bed. Our individual efforts seem paltry against the scale of the problem, but taken together they amount to an area much larger than nature preserves.

If I am around in another 15 years, I am confident of seeing more blue boxes than red on the eBird map if we manage the land differently.

Demography of IVF and World Population

Predicting the future is fickle, as Stephen Hawking once observed: “it exists only as a spectrum of possibilities.” And, yet, divining the future is irresistible and physicists strive to forecast the future of stars, black holes and climate. Biologists are more chary, although even they venture to predict extinctions. I recently indulged my curiosity, not by straining at tea-leaves or astrological charts but using math with the help of my son and a statistically-sophisticated friend. We are interested in an aspect of world population that hasn’t stirred much attention. Yet.

The United Nations projects world population growth to the year 2100, but no one has previously estimated the contribution of infertile people. “Eh?” I hear you say. That sounds absurd.

Infertility is an original scourge. Didn’t Jacob’s wife cry, “Give me children or I die!” It was always a private grief with few options, and even fewer effective remedies. I remember a generation or two ago hearing whispers, like, “Why didn’t Uncle Joe and Auntie Jane have children?” No one dared ask them. It was less embarrassing to ask some poor soul if they had cancer. Thankfully, infertility has ‘come out,’ mainly due to attention on revolutionary in vitro fertilization or IVF.  The revolution started a few minutes to midnight on July 25, 1978, when Louise Brown was born as the world’s first test-tube baby.

Male infertility, premature menopause and some other relatively common problems were resistant to standard treatment with pills and surgery, but starting with the hub of basic IVF for bypassing blocked Fallopian tubes, a bevy of new technologies has sprouted. Almost no one is now denied a chance to become a parent if they want, provided they can afford to pay in countries where no subsidy is offered. There is now egg, sperm and embryo donation with freezing for longer-term preservation, sperm microinjection, IVF surrogacy for women without wombs, and genetic testing to avoid a blighted conception (PGD).

Since Louise Brown, about seven million babies have been conceived who would not otherwise exist. The children grow up to be as healthy as the rest of the population, and they become fertile adults. The first ones are now having babies of their own.

How will this industry making babies grow in future? We wanted to know how many will be added by technology to the world in decades to come up to 2100. We were even more interested in the broader question of how many people will owe their existence to IVF either directly as test-tube babies OR as their children and grandchildren as IVF services rapidly expand across the globe. We chose conservative data for our calculations, and expect our predictions will underestimate growth, unless there is a global catastrophe. But our estimates still surprised us.

The paper came out today. It is short, readable and currently offered free until May 15 by the publishers. Click Science Direct. I will send a pdf if you have problems connecting.

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