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7.5 Billion and Counting: How Many Humans Can the Earth Support?
By Andrew D. Hwang
Can the Earth support this many people indefinitely? What will happen if we do nothing to manage future population growth and total resource use? These complex questions are ecological, political, ethical—and urgent. Simple mathematics shows why, shedding light on our species' ecological footprint.
The Mathematics of Population Growth
In an environment with unlimited natural resources, population size grows exponentially. One characteristic feature of exponential growth is the time a population takes to double in size.
Exponential growth tends to start slowly, sneaking up before ballooning in just a few doublings.
To illustrate, suppose Jeff Bezos agreed to give you one penny on Jan. 1, 2019, two pennies on Feb. 1, four on March 1, and so forth, with the payment doubling each month. How long would his $100 billion fortune uphold the contract? Take a moment to ponder and guess.
After one year, or 12 payments, your total contract receipts come to US$40.95, equivalent to a night at the movies. After two years, $167,772.15—substantial, but paltry to a billionaire. After three years, $687,194,767.35, or about one week of Bezos' 2017 income.
The 43rd payment, on July 1, 2022, just short of $88 billion and equal to all the preceding payments together (plus one penny), breaks the bank.
Real Population Growth
For real populations, doubling time is not constant. Humans reached 1 billion around 1800, a doubling time of about 300 years; 2 billion in 1927, a doubling time of 127 years; and 4 billion in 1974, a doubling time of 47 years.
On the other hand, world numbers are projected to reach 8 billion around 2023, a doubling time of 49 years, and barring the unforeseen, expected to level off around 10 to 12 billion by 2100.
This anticipated leveling off signals a harsh biological reality: Human population is being curtailed by the Earth's carrying capacity, the population at which premature death by starvation and disease balances the birth rate.
Humans are consuming and polluting resources—aquifers and ice caps, fertile soil, forests, fisheries and oceans—accumulated over geological time, tens of thousands of years or longer.
Wealthy countries consume out of proportion to their populations. As a fiscal analogy, we live as if our savings account balance were steady income.
According to the Worldwatch Institute, an environmental think tank, the Earth has 1.9 hectares of land per person for growing food and textiles for clothing, supplying wood and absorbing waste. The average American uses about 9.7 hectares.
These data alone suggest the Earth can support at most one-fifth of the present population, 1.5 billion people, at an American standard of living.
Water is vital. Biologically, an adult human needs less than 1 gallon of water daily. In 2010, the U.S. used 355 billion gallons of freshwater, over 1,000 gallons (4,000 liters) per person per day. Half was used to generate electricity, one-third for irrigation, and roughly one-tenth for household use: flushing toilets, washing clothes and dishes, and watering lawns.
If 7.5 billion people consumed water at American levels, world usage would top 10,000 cubic kilometers per year. Total world supply—freshwater lakes and rivers—is about 91,000 cubic kilometers.
World Health Organization figures show 2.1 billion people lack ready access to safe drinking water, and 4.5 billion lack managed sanitation. Even in industrialized countries, water sources can be contaminated with pathogens, fertilizer and insecticide runoff, heavy metals and fracking effluent.
Freedom to Choose
Though the detailed future of the human species is impossible to predict, basic facts are certain. Water and food are immediate human necessities. Doubling food production would defer the problems of present-day birth rates by at most a few decades. The Earth supports industrialized standards of living only because we are drawing down the "savings account" of non-renewable resources, including fertile topsoil, drinkable water, forests, fisheries and petroleum.
The drive to reproduce is among the strongest desires, both for couples and for societies. How will humans reshape one of our most cherished expectations—"Be fruitful and multiply"—in the span of one generation? What will happen if present-day birth rates continue?
We cannot wish natural resources into existence. Couples, however, have the freedom to choose how many children to have. Improvements in women's rights, education and self-determination generally lead to lower birth rates.
As a mathematician, I believe reducing birth rates substantially is our best prospect for raising global standards of living. As a citizen, I believe nudging human behavior, by encouraging smaller families, is our most humane hope.
Reposted with permission from our media associate The Conversation.
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By Johnny Wood
The Ganges is a lifeline for the people of India, spiritually and economically. On its journey from the Himalayas to the Bay of Bengal, it supports fishermen, farmers and an abundance of wildlife.
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By Jake Johnson
As a growing number of states move to pass laws that would criminalize pipeline protests and hit demonstrators with years in prison, an audio recording obtained by The Intercept showed a representative of a powerful oil and gas lobbying group bragging about the industry's success in crafting anti-protest legislation behind closed doors.
Speaking during a conference in Washington, DC in June, Derrick Morgan, senior vice president for federal and regulatory affairs at the American Fuel & Petrochemical Manufacturers (AFPM), touted "model legislation" that states across the nation have passed in recent months.
AFPM represents a number of major fossil fuel giants, including Chevron, Koch Industries and ExxonMobil.
"We've seen a lot of success at the state level, particularly starting with Oklahoma in 2017," said Morgan, citing Dakota Access Pipeline protests as the motivation behind the aggressive lobbying effort. "We're up to nine states that have passed laws that are substantially close to the model policy that you have in your packet."
Big Oil is now using its political power to try and criminalize protests of oil & gas infrastructure.— Friends of the Earth (@foe_us) August 19, 2019
"This legislation has potential to punish public participation and mischaracterize advocacy protected by the First Amendment."https://t.co/bmiHjONEhy
The audio recording comes just months after Texas Gov. Greg Abbott signed into law legislation that would punish anti-pipeline demonstrators with up to 10 years in prison, a move environmentalists condemned as a flagrant attack on free expression.
"Big Oil is hijacking our legislative system," Dallas Goldtooth of the Indigenous Environmental Network said after the Texas Senate passed the bill in May.
As The Intercept's Lee Fang reported Monday, the model legislation Morgan cited in his remarks "has been introduced in various forms in 22 states and passed in ... Texas, Louisiana, Oklahoma, Tennessee, Missouri, Indiana, Iowa, South Dakota, and North Dakota."
"The AFPM lobbyist also boasted that the template legislation has enjoyed bipartisan support," according to Fang. "In Louisiana, Democratic Gov. John Bel Edwards signed the version of the bill there, which is being challenged by the Center for Constitutional Rights. Even in Illinois, Morgan noted, 'We almost got that across the finish line in a very Democratic-dominated legislature.' The bill did not pass as it got pushed aside over time constraints at the end of the legislative session."
Many of the state bills restricting the right to protest have been "drafted by companies and passed through groups like ALEC, the secretive group of corporate lobbyists trying to rewrite state laws to benefit corporations over people." @greenpeaceusa https://t.co/ZxpTjWdrwT— Stand Up To ALEC (@StandUpToALEC) May 6, 2019
Reposted with permission from our media associate Common Dreams.