How many people could live on Earth? Many scientists have tried to calculate that number, with widely divergent results. Seventeenth-century biologist Antonie van Leeuwenhoek put the upper limit at 13.4 billion; in 1967, biochemist C.T. De Wit said one trillion. Population modelers now say there is no single answer. The population that Earth can ultimately carry, and the quality of life that those people will have, depends on political and environmental choices. sustainability-research organization in Boston, has made some of the most sophisticated predictions yet of how those decisions will play out. PoleStar, the computer simulation that Tellus developed, starts with projections of population and economic growth from consumption, land use and pollution. The simulation’s outcomes show that how we shape policy now will determine whether the next century’s population lives in a pleasant world or one of degradation and scarcity. It’s not too late to choose one of the brighter paths, says Richard Rosen, the executive vice president of Tellus, “but you’d have to get going immediately. There’s no leisurely way.
Four Futures
Market
Forces
Business as usual—the economy grows, technology advances. Poorer regions build up industries, and environmental problems become more serious.
Policy
Reform
Governments take rapid action to meet U.N. climate targets and other sustainability goals, but economic growth remains the strongest factor in developing new policies.
Fortress
World
Environmental, economic and social problems overwhelm current systems, and governments become authoritarian. The wealthy retreat to protected enclaves, leaving poor masses in a degraded wasteland.
Great
Transition
Society’s values change radically to prioritize environmental preservation, social equality and cooperation.
Population
Policies that make family planning available to all social strata will help control population growth. Without such measures, the global population could top 10 billion by the end of this century.
282 billion
The maximum number of people that could ultimately be packed onto the planet, with all other land used solely to grow food, according to geophysicists at the Potsdam Institute for Climate Impact Research in Germany.
In 2011, the global population reached
7 billion.
Hunger Incidence
In 2005, 14 percent of the population went hungry. Depending on how resources are allocated, this number could shrink to zero by 2100.
|15| |—| |12| |—| |9| |—| |6| |—| |3| |—| |0| |—| 2025 2050 2100
Environmental Impact
Energy Consumption
Exajoules
|1200| |—| |900| |—| |600| |—| |300| |—| 2025 2050 2100
CO2 Emissions
Gigatons of Carbon
| 20 |
|---|
| 15 |
| — |
| 10 |
| — |
| 5 |
| — |
| 0 |
| — |
| -5 |
| — |
| | 2025| 2050| 2100 |
| —|—|—|— |
Toxic Waste
Megatons
| 150 |
|---|
| 100 |
| — |
| 50 |
| — |
| 2025 | 2050 | 2100 | |
|---|---|---|---|
| 2025 | 2050 | 2100 |
|---|---|---|
| 9.2 | 9.0 | 7.9 |
| 8.4 | 8.6 | 7.7 |
| 10.2 | 9.5 | 8.0 |
| 7.2 | 8.0 | 7.5 |
Income Disparity
In 2005, the poorest 20 percent of society made 12 cents for every dollar the richest 20 percent made. How will policy decisions affect wages?
| 2025 | 2050 | 2100 | |
|---|---|---|---|
| Market Forces | 9% | 7% | 5% |
| — | — | — | — |
| Policy Reform | 12% | 12% | 11% |
| — | — | — | — |
| Fortress World | 8% | 4% | 2% |
| — | — | — | — |
| Great Transition | 14% | 21% | 36% |
| — | — | — | — |
| — | |||
| — |
Purchasing Power
Market Forces
Policy Reform
Fortress World
Great Transition
| $60,0000 |
|---|
| $50,000 |
| — |
| $40,000 |
| — |
| $30,000 |
| — |
| $20,000 |
| — |
| $10,000 |
| — |
| | | 2025| 2050| 2100 |
| —|—|—|—|— |
Water Shortage
2005
27%
| 2025 | 2050 | 2100 |
|---|---|---|
| 37% | 47% | 50% |
| — | — | — |
| 25% | 24% | 23% |
| — | — | — |
| 38% | 47% | 46% |
| — | — | — |
| 24% | 23% | 21% |
| — | — | — |
Land Use
In 2005:
Cropland
12%
Grazing
26%
Forest
30%
Built-up
2%
In four possible futures:
| Built-up | Cropland | Grazing | Forest |
|---|---|---|---|
Great
Transition
Policy
Reform
Market
Forces
Fortress
World
| 2025 |
|---|
| 2050 |
| — |
| 2100 |
| — |
| 2025 |
|---|
| 2050 |
| — |
| 2100 |
| — |
| 2025 |
|---|
| 2050 |
| — |
| 2100 |
| — |
| 2025 |
|---|
| 2050 |
| — |
| 2100 |
| — |
Natural Gas
Crude Oil
2034
2047
2049
2071
2088
2105
2123