Saturday, March 23, 2013

Peak Farmland?

Peak Farmland?:
“Humanity now stands at Peak Farmland, and the 21st century will
see release of vast areas of land, hundreds of millions of
hectares, more than twice the area of France for nature,”
Jesse Ausubel, the director of the Program for the
Human Environment at Rockefeller University, in a December lecture.
Ausubel was outlining the findings in a new study
he and his collaborators had done in the Population and
Development Review
. Unlike other alleged resource “peaks,”
peak farmland reflects not the exhaustion of resources but the
fruits of human intelligence and growing affluence.
The trend toward reducing farming’s impact on nature took off
with the Green Revolution of the 1960s. That leap in agricultural
productivity was sparked by plant breeder Norman
and his colleagues, who created new high-yield
varieties of wheat and rice, an effort so successful that Borlaug
received the Nobel Peace Prize in 1970.
While Borlaug was working to avert famines, others were
declaring them inevitable. “The battle to feed all of humanity is
over. In the 1970s the world will undergo famines—hundreds of
millions of people are going to starve to death in spite of any
crash programs embarked upon now,” the Stanford biologist Paul
Ehrlich declared in his 1968 dystopian screed,
The Population Bomb
. The epicenter of Ehrlich’s alarm
was impoverished India.
In 1960 India’s population was 450 million, and the average
Indian subsisted on a near-starvation diet of just more than 2,000
calories per day. Indian farmers wrested those meager calories from
161 million hectares (400 million acres) of farmland, an area a bit
more than twice the size of Texas. By 2010, Indian population rose
by more than two and half times, national income rose 15-fold, and
the average Indian ate a sixth more calories. The amount of land
devoted to crops rose about 5 percent to 170 million hectares. Had
wheat productivity remained the same that it was in 1960, Ausubel
and his colleagues calculate that Indian farmers would have had to
plow up an additional 65 million hectares of land. Instead, as
people left the land for cities, Indian forests expanded by 15
million hectares—bigger than the area of Iowa.
The trajectory of rising agricultural productivity was similar
in post-Mao China. China’s population doubled, and its GDP rose
45-fold. While the amount of land harvested for corn in China also
doubled, each acre produced 4.5 times more than it did in 1960.
Ausubel and his colleagues calculate that rising Chinese corn
productivity spared 120 million hectares (an area more than twice
the size of Texas) that would otherwise have been plowed up. The
United Nations’ Food and Agriculture Organization reports that
Chinese forests expanded 30 percent between 1990 and
In the United States, corn production grew 17-fold between 1860
and 2010, yet more land was planted in corn in 1925 than in 2010.
(The area planted in corn has started increasing again, thanks to
the federal government’s biofuels mandates and subsidies.) Today
U.S. forests cover about 72 percent of the
area that was forested in 1630
. Forest area stabilized in the
early 20th century, and the extent of U.S. forests began increasing
in the second half of the 20th century.Land spared for nature
If global crop yields had remained stuck at 1960 levels, Ausubel
noted in his lecture, farmers around the world “would have needed
about 3 billion more hectares, about the sum of the USA, Canada,
and China or almost twice South America.” Plowing down this amount
of the world’s remaining forests and grasslands would have produced
what Ausubel calls “Skinhead Earth.”
What about the future? The researchers offer a 50-year forecast
via their ImPACT equation, which calculates how much land will be
used for crops (Im) by multiplying population trends (P), affluence
(A) as GDP per capita, consumption (C) as calories per GDP, and
technology (T). The United Nations expects population growth to
continue to slow, global affluence to increase at around 1.5
percent per year, people to spend relatively less on food as their
incomes rise (Engel’s
), and the amount of crop per each hectare to rise by 2
percent annually. (In aggregate, farmers today can produce nearly
three times the food they did in 1960 on the same amount of land.)
The authors also take into account the growing global desire for
meat, which means growing more grains to feed animals, and the
diversion of crops into other non-food products such as
Currently, American corn farmers average about 180 bushels per
acre, and the world average is around 82 bushels per acre. The
authors assume a modest 1.7 percent per year increase in corn
yields between 2010 and 2060, which implies that “the average
global yield in 2060 would resemble the average U.S. yield in
One concern is that farmers may be approaching the biological
limits of photosynthesis, which would constrain crop yields. But
the authors note that the winners of the annual National Corn Yield
Contest currently produce non-irrigated yields of
around 300 bushels per acre
, nearly double average U.S. yields.
Ausubel suggests that the difference between the global average of
82 bushels and contest-winning 300 bushels per acre yields means
that “much headroom remains for farmers to lift yields.”
Cranking various population, economic growth, and yield trends
through the ImPACT equation, the authors conservatively conclude
that in 2060 “some 146 million hectares could be restored to
Nature, an area equal to one and half times the size of Egypt, two
and half times France, or ten times Iowa.” Under a slightly more
optimistic scenario—one where population growth slows a bit more,
people choose to eat somewhat less meat, agricultural productivity
is modestly higher, and there’s less demand for biofuels—would
spare an additional 256 million hectares from the plow. That would
mean nearly 400 million hectares restored to nature but 2060, an
area nearly double the size of the United States east of the
Mississippi River.
As Ausubel notes, sparing land usually also means sparing water,
which would lessen pressure on the world’s fresh water supplies.
Crops need nitrogen to grow, but excess nitrogen fertilizer running
off fields pollutes streams and is responsible for algal blooms
that produce low-oxygen
dead zones
in many coastal regions. Researchers are hard at
work on producing
biotech varieties that need far less nitrogen
Efforts to dramatically
boost the photosynthetic efficiency
staple grain crops
are moving forward, prompting optimistic
conjectures that “farmers could grow wheat and rice in hotter,
dryer environments with less fertilizer, while possibly increasing
yields by half.” Currently about 40 percent of the world’s grain is
fed to livestock to produce meat. In the ultimate move toward what
Ausubel calls “landless agriculture,” the biotech company Modern Meadows hopes to use tissue
engineering and 3D printers to make meat. Obviously, such
breakthroughs would free up even more land.
“Now we are confident,” the authors conclude, “that we stand on
the peak of cropland use, gazing at a wide expanse of land that
will be spared for nature.” Now that’s a real Green Revolution!