Sustainable agricultural systems are needed now more than ever, as food growers worldwide struggle to meet the needs of an ever-increasing global population.
That according to Dr. Jeffrey C. Silvertooth, associate dean of Education for Economic Development and Extension in the University of Arizona’s College of Ag and Life Science.
Because many people are concerned about GMOs (genetically modified organisms – crop seeds, in this case), Ag Day Chairman Claire Owen invited Silvertooth to discuss how our food is being modified.
Giving examples of questions people are asking, Owen said, “When you are modifying food, what will it do to us? What will it do to the animals you feed it to? Are there ramifications to eating modified beef?”
“On the other hand, yield is increased and it solves other problems,” Owen told the Range News.
“We have to feed the whole (increasing) population of the word.”
At the beginning of his Ag Day presentation, Silvertooth said that global population is expected to jump from a current 7.1 billion people to 9.2 billion people in 2050.
As if that weren’t enough of a challenge, only 11-percent of the earth’s surface is arable land, making agronomic factors, such as pest control (insects, weeds, and diseases); plant nutrition, and natural resource management imperative in maintaining sustainable agriculture for the future, he said.
Silvertooth presented a chart showing world population (in millions), spanning 100 years from 1950 to 2050. The graph began at 2,000 in 1950, steadily increasing to a projected 10,000 (million) in 2050.
The challenge of feeding this ever-increasing global population is compounded by the fact that “we are already using most of the potentially arable land on the planet for crop production,” he said.
Silvertooth presented a graph on land use, showing the world with 56-percent non-arable and 10-percent arable land potentially arable land, which “produces little or no food.”
The rest he categorized as 11-percent arable and 23-percent grazing land in the world.
“We have already extensively exploited these lands and have continued to move onto increasingly marginal lands for crop production over the past 50 years,” said Silvertooth, adding that the development of new arable lands is not really an option.
He explained that 44-percent of the world’s population lives below the $2 per day international poverty line, and consumes only 1.3 percent of the annual global product.
On the other hand, affluent countries consume 81-percent of the annual global product, said Silvertooth, explaining that accounts for only 16.7-percent – or one-sixth – of the world’s population.
Silvertooth talked about the “Millennium Project,” a 2008 “State of the Future Report,” which suggests that global food production will have to increase 50-percent by 2023, and then double by 2050 to meet the demands.
He also discussed “The Bottleneck,” by E.O. Wilson of Harvard University, which foresees maximum human population levels; as well as maximum demand on natural resources, and on human ingenuity to meet these challenges.
Silvertooth also talked about 18th century Malthusian theory.
It was Thomas R. Malthus who raised the problem in 1798 of sufficient food for a population that continues to increase in a world of limited land area, he told the audience.
Malthus argued, “Mankind could increase sustenance only in mathematic progression, i.e., compound interest law,” Silvertooth said.
“Yields might be doubled once or even twice, but there is a limit beyond which increases are impossible,” said Silvertooth, adding that the maximum limit set by the food supply “is a basic check on population increase.”
On the subject of increasing food production, Silvertooth talked about the need to improve:
• Genetics, including plant breeding/improvement through biotechnology -- GMOs;
• Pest management; and
• Agronomic practices, namely plant and soil management; insects, weeds, and diseases; as well as improved soil-plant relations.
Silvertooth also discussed the work of Dr. Norman Borlaug, with the “International Maize and Wheat Improvement Center.”
In 1943, Borlaug, along with George Harrar, worked on the development of semi-dwarf varieties, and improved disease resistance, primarily with the rust diseases.
The next year, Borlaug accepted an appointment as geneticist and plant pathologist, organizing and directing the “Cooperative Wheat Research and Production Program” in Mexico.
This joint program with the Mexican government and Rockefeller Foundation conducted scientific research in genetics, plant breeding, plant pathology, entomology, agronomy, soil science, and cereal technology.
Within 20 years, Borlaug was “spectacularly successful in finding a high-yielding short-strawed, disease-resistant wheat,” Silvertooth said.
Borlaug’s scientific and practical humanitarian goals were:
• To develop and place new cereal strains into extensive production in order to feed the hungry of the world.
• “A temporary success in man’s war against hunger and deprivation;”
• A breathing space in which to deal with the “population monster;” and
• The subsequent environmental ills that too often lead to conflict between men and between nations.
By 1963, Mexico became a major exporter of wheat; and between 1965-70, wheat yields nearly doubled in Pakistan and India, greatly improving food security, Silvertooth said.
The collective increases in yield of these programs has been called the “Green Revolution,” which is often credited with saving more than a billion people from starvation.
In 1970, Borlaug received a Nobel Peace Prize for his work in “recognition of his contributions to world peace by increasing food supply,” he said.
Silvertooth began a more technical part of his presentation entitled, “Transgenic and Molecular Breeding.”
As to plant breeding, Silvertooth called selection in its most fundamental form, “an elementary process initiated by early humans,” that is still practiced today.
Silvertooth used the example of the Orzya, which has “enormous phenotypic diversity.”
“The wild Orzya species are agronomically inferior grasses, but contain a virtually untapped reservoir of genetic variation that can be used for crop improvement,” he said.
Silvertooth explained that, as it is practiced, transgenic breeding is a conservative breeding methodology.
“The recipient cultivar (variety) is only improved for the one or two traits being transferred,” Silvertooth said.
“There is no forward progress for any other traits,” because “transgenic breeding is usually practiced using ‘backcross’ methods,” he said.
In transformation methodology, a gene construct carries the gene of interest, which is “inserted into a plasmid, which in turn is introduced into a bacterium (Agrobacterium tumefaciens),” Silvertooth said.
He defined a plasmid as “an independent, circular, double-stranded, self-replicating DNA molecule, found in bacterial species.”
“In numerous species, including cotton, only a few genotypes have the capacity for producing embryos from callus tissue (embryogenesis),” which are referred to as
embryogenic or regenerative genotypes, Silvertooth said.
“In some species, regenerative genotypes have not been identified,” he added.
Post- transformation activities include:
• Selection among somaclonal and insertional variants for the best agronomic phenotype expressing the transgene at optimal levels.
• Initiation of a backcross program to move the transgene from embryogenic genotype to an agronomically elite genotype.
In a discussion on backcrossing and transgenic varieties, Silvertooth called backcrossing the most common technique used to “incorporate transgenic properties into a desirable, commercial variety.”
It “usually requires about six generations of backcrossing and continual selection to bring the transgenic line to a common level of the recurrent parent line,” he said.
“Transgenic breeding adds generations and years to the cultivar (variety) development process,” Silvertooth explained.
“Only high value traits are considered as candidates for transgenic transfer.”
Silvertooth also talked about the importance of the cotton-growing industry in Arizona.
It has a $7 million economic impact on the state, with some 150,000 to 250,000 acres grown annually, he explained.
Arizona can boast some of the “highest yields in the world; more than 1,500 pounds annually, said Silvertooth, adding that Pinal County has the most production by county in the United States.
Production constraints include “an extremely long season (February-December); high input costs (water, pest control, etc.), and market variability,” he said.
Silvertooth said that when he came to Arizona in 1987, it wasn’t uncommon for the cotton industry to be averaging 11 to 12 sprays per year.
That has changed over the years to the “deployment of selective tactics for key pests,” he said.
“The big thing that changed was Bt cotton,” Silvertooth said.
He explained that for cotton growers, 1990 “was a devastating year with pink bollworm.”
In 1995, the Environmental Protection Agency determined potato plants producing the Bt (Bacillus thuringiensis) toxin to be safe, making it the first pesticide-producing crop to be approved in the U.S.
After that, pink bollworm eradication began, and a Lygus bug feeding inhibitor and new Arizona IPM plan were introduced, Silvertooth explained.
“These are very clean materials -- very specific to the pest,” he said.
This resulted in a 92-percent reduction overall broad-spectrum insecticides (number of sprays), as well as an 82-percent reduction in all insecticides.
“As agronomists walking the field that’s positive,” said Silvertooth, adding, “We see it. We live it. We know it. It’s real to us.”
In the final part of his presentation, Silvertooth explained that GMOs are a tool “for consideration and appropriate use” in feeding the world’s ever-growing population, but that both benefits and dangers associated with their use must be understood.
Sonya Gasho, with the Cochise-Graham Cattlegrowers Association, asked Silvertooth how best to get the truth out about the use of GMOs.
“You can tell people the scientific evidence all day long,” but in the end, their opinion “is an emotional one,” she said.
Silvertooth agreed, saying that fundamentally “what we need to do is to increase the education in the general public.”
He reminded the audience that as citizens of one of the world’s most affluent nations, those concerned about GMO foods “have the luxury of not eating it.”
“We can afford to do what we want,” said Silvertooth, adding, “Folks in other parts of the world are starving.”