5.

3 The Green
nibbles a cassava leaf. Uncovering a cassava
root, Juma splits it open with one swing of
his hoe. He sighs—the creamy white flesh is
Revolution streaked with brown, rotting starch.

The following is an adapted excerpt from National Geographic To save enough of the crop to sell and to
Describe changes in agricultural practices. feed his family, Juma will have to harvest a
month early. I ask how important cassava is
Something is killing Ramadhani Juma’s to him.
cassava crop. “Maybe it’s too much water,”
he says, fingering clusters of withered “Mihogo ni kila kitu,”
yellow leaves on a six-foot-high plant. “Or he replies in Swahili.
too much sun.” Juma works a small plot, “Cassava is
barely more than an acre, near the town of everything.”
Bagamoyo, on the Indian Ocean about 40
miles north of Dar es Salaam, Tanzania. Most Tanzanians are subsistence farmers,
eating what they can grow. In Africa, small
On a rainy March morning, trailed by two of family farms grow more than 90 percent of
his four young sons, he’s talking with a all crops, and cassava is a staple for more
technician from the big city, 28-year-old than 250 million people. It grows even in
Deogratius Mark of the Mikocheni marginal soils, and it tolerates heat waves
Agricultural Research Institute. Mark tells and droughts. It would be the perfect crop
Juma his problem is neither sun nor rain. for 21st-century Africa—were it not for the
The real cassava killers, far too small to see, whitefly, whose range is expanding as the
are viruses. climate warms. The same viruses that have
invaded Juma’s field have already spread
Mark breaks off some wet leaves; a few throughout East Africa. “How can you help
whiteflies dart away. The pinhead-size flies, us?” he asks.
he explains, transmit two viruses. One
ravages cassava leaves, and a second, Answering that question will be one of the
called brown streak virus, destroys the greatest challenges of this century. Climate
starchy, edible root—a catastrophe that change and population growth will make
usually isn’t discovered until harvest time. life increasingly precarious for Juma,
Juma is typical of the farmers Mark Kagembe, and other small farmers in the
meets—most have never heard of the viral developing world—and for the people they
diseases. “Can you imagine how he’ll feel if feed. For most of the 20th century humanity
I tell him he has to uproot all these plants?” managed to stay ahead in the Malthusian
Mark says quietly. race between population growth and food
supply. Will we be able to maintain that
Juma listens carefully to Mark’s diagnosis. lead in the 21st century, or will a global
Then he unshoulders his heavy hoe and catastrophe beset us?
starts digging. His oldest son, who is ten,
The United Nations forecasts that by 2050 this process, Norman Borlaug, an American
the world’s population will grow by more biologist, created a dwarf variety of wheat
than two billion people. Half will be born in that put most of its energy into edible
sub-Saharan Africa, and another 30 percent kernels rather than long, inedible stems.
in South and Southeast Asia. Those regions The result: more grain per acre. Similar work
are also where the effects of climate at the International Rice Research Institute
change—drought, heat waves, extreme (IRRI) in the Philippines dramatically
weather generally—are expected to hit improved the productivity of the grain that
hardest. feeds nearly half the world.

Last March the Intergovernmental Panel on

Norman Borlaug holding the old wheat variety (left) and the new, improved
Half a century ago disaster loomed just as larger seed variety (right).
ominously. Speaking about global hunger at
a meeting of the Ford Foundation in 1959, From the 1960s through the 1990s, yields of
one economist said, “At best the world rice and wheat in Asia doubled. Even as the
outlook for the decades ahead is grave; at continent’s population increased by 60
worst it is frightening.” Nine years later Paul percent, grain prices fell, the average Asian
Ehrlich’s best seller, The Population Bomb, consumed nearly a third more calories, and
predicted that famines, especially in India, the poverty rate was cut in half. When
would kill hundreds of millions in the 1970s Borlaug won the Nobel Peace Prize in 1970,
and 1980s. the citation read, “More than any other
person of this age, he helped provide bread
Before those grim visions could come to for a hungry world.”
pass, the green revolution transformed
✎Summarize Borlaug’s contribution:
global agriculture, especially wheat and
rice. Selective breeding involves choosing
parents with particular characteristics to
breed together and produce offspring with
more desirable characteristics. Through
The Green Revolution manufactured using fossil fuels, and they
The Green Revolution started a shift to new themselves emit potent greenhouse gases
agricultural strategies and practices in when they’re applied to fields.
order to increase food production, with both
positive and negative results. Pesticides
Pesticides can be applied to crops and they
Some of these strategies and methods are: can eliminate pests. Herbicides kill weeds
● Selective breeding (discussed on previous page) which compete for sunlight, soil nutrients,
● Mechanization and space with the crop. Insecticides can
● Fertilization kill insects such as caterpillars or flies that
● the use of pesticides, feed on crops.
● irrigation, and
Pesticides use leads to the pesticide
● genetically modified organisms
treadmill… where pests evolve resistance to
(GMOs).
the chemicals used, meaning they have
genes which allow them to survive. This
Mechanization
leads farmers to use new, stronger
Farmers were encouraged to use machines
pesticides. This pattern continues, and
to make a farm more efficient, instead of
“super-pests” can evolve.
relying on human labor. This increased
productivity and yields, however heavy
Pesticides also can be persistent, meaning
machinery can squoosh soil down and
they do not break down naturally and can
cause soil compaction. This decreases the
remain in soil and water for decades after
amount of space between soil particles,
use. They can enter the food chain and
and therefore soil can have less room for
accumulate in living organisms: this is
air and water and plant roots.
called bioaccumulation. When organisms
higher in the food chain eat many
Machines also rely on fossil fuels to
organisms that have bioaccumulated
operate, which can be costly and releases
pesticides, they are receiving large
carbon dioxide into the atmosphere, which
amounts. This is called biomagnification,
is a greenhouse gas.
and explains how organisms at the top of
the food chain have much greater levels of
Fertilization
chemicals in their tissues.
Farmers can use fertilizers to improve soil
nutrient levels, especially for Nitrogen and
Irrigation
Phosphorus, which are limiting nutrients.
Irrigation means bringing water to your
crops instead of waiting for the rain. This
We know that fertilizers can run-off into
can mean diverting water from a river or
surface water and lead to eutrophication.
stream to temporarily flood your fields, or
pumping up groundwater to spray on fields
Fertilizers are often unaffordable for small
with sprinkler systems. There are many
farmers like Juma, and they pollute land,
water, and air. Synthetic fertilizers are
different methods of irrigation that we will crops. First released in the 1990s, they’ve
learn another day. been adopted by 28 countries and planted
One potential downside or irrigation is on 11 percent of the world’s arable land,
overuse of water and depleting land that can support plant growth,
groundwater, which is unsustainable since including half the cropland in the U.S.
aquifers take many years to replenish. About 90 percent of the corn, cotton, and
soybeans grown in the U.S. are genetically
Another downside happens in arid regions, modified. Americans have been eating GM
which are dry and hot. When fields are products for nearly two decades. But in
irrigated, the water can quickly evaporate, Europe and much of Africa, debates over
leaving small amounts of salt behind. the safety and environmental effects of GM
Repeating this process can create high crops have largely blocked their use.
levels of salt in the soil, which is called soil
salinization, and is toxic to plants since the Proponents like Fraley say such crops have
soil salinity is outside of their ecological prevented billions of dollars in losses in the
tolerance. U.S. alone and have actually benefited the
environment. A recent study by the U.S.
Department of Agriculture found that
The Next Green Revolution? pesticide use on corn crops has dropped 90
To keep doing that between now and 2050, percent since the introduction of Bt corn,
we’ll need another green revolution. There which contains genes from the bacterium
are two competing visions of how it will Bacillus thuringiensis that help it ward off
happen. One is high-tech, with a heavy corn borers and other pests. Reports from
emphasis on continuing Borlaug’s work of China indicate that harmful aphids have
breeding better crops, but with modern decreased—and ladybugs and other
genetic techniques. “The next green beneficial insects have increased—in
revolution will supercharge the tools of the provinces where GM cotton has been
old one,” says Robert Fraley, chief planted.
technology officer at Monsanto and a
winner of the prestigious World Food Prize The particular GM crops Fraley pioneered at
in 2013. Scientists, he argues, can now Monsanto have been profitable for the
identify and manipulate a huge variety of company and many farmers, but have not
plant genes, for traits like disease helped sell the cause of high-tech
resistance and drought tolerance. That’s agriculture to the public. Monsanto’s
going to make farming more productive and Roundup Ready crops are genetically
resilient. modified to be immune to the herbicide
Roundup, which Monsanto also
Genetically Modified Organisms manufactures. That means farmers can
The signature technology of this spray the herbicide freely to eliminate
approach—and the one that has brought weeds without damaging their GM corn,
both success and controversy to cotton, or soybeans. Their contract with
Monsanto—is genetically modified, or GM, Monsanto does not allow them to save
seeds for planting; they must purchase its cassava-growing areas of West Africa,
patented seeds each year. you’ve got a major food-security issue.”
Though there’s no clear evidence that
Roundup or Roundup Ready crops are Taylor and other researchers are in the
unsafe, proponents of an alternative vision early stages of developing genetically
of agriculture see those expensive GM modified cassava varieties that are immune
seeds as a costly input to a broken system. to the brown streak virus. Taylor is
Modern agriculture, they say, already relies collaborating with Ugandan researchers on
too heavily on synthetic fertilizers and a field trial, and another is under way in
pesticides. Not only are they unaffordable Kenya. But only four African
for a small farmer like Juma; they pollute countries—Egypt, Sudan, South Africa, and
land, water, and air. Synthetic fertilizers are Burkina Faso—currently allow the
manufactured using fossil fuels, and they commercial planting of GM crops.
themselves emit potent greenhouse gases
when they’re applied to fields. In Africa, as elsewhere, people fear GM
crops, even though there’s little scientific
“The choice is clear,” says Hans Herren, evidence to justify the fear. There’s a
another World Food Prize laureate and the stronger argument that high-tech plant
director of Biovision, a Swiss nonprofit. “We breeds are not a panacea and maybe not
need a farming system that is much more even what African farmers need most. Even
mindful of the landscape and ecological in the United States some farmers are
resources. We need to change the paradigm having problems with them.
of the green revolution. Heavy-input
agriculture has no future—we need Corn rootworms are evolving resistance to
something different.” There are ways to the bacterial toxins in Bt corn. “I was
deter pests and increase yields, he thinks, surprised when I saw the data, because I
that are more suitable for the Jumas of this knew what it meant—that this technology
world. was starting to fail,” says Aaron Gassmann,
an entomologist at Iowa State University
Which vision of agriculture is right for the and co-author of the report. One problem,
farmers of sub-Saharan Africa? Today, says he says, is that some farmers don’t follow
Nigel Taylor, a geneticist at the Donald the legal requirement to plant “refuge
Danforth Plant Science Center in St. Louis, fields” with non-Bt corn, which slow the
Missouri, the brown streak virus has the spread of resistant genes by supporting
potential to cause another cassava famine. rootworms that are vulnerable to Bt toxins.
“It has become an epidemic in the last five
to ten years, and it’s getting worse,” he says. In Tanzania there are no GM crops yet. But
“With higher temperatures, the whitefly’s some farmers are learning that a simple,
range is expanding. The great concern is low-tech solution—planting a diversity of
that brown streak is starting to move into crops—is one of the best ways to deter
central Africa, and if it hits the massive pests