The Next Species: The Future of Evolution in the Aftermath of Man (11 page)

The Rothamsted sample archive is a unique collection, since it comprises some three hundred thousand samples of crops and soils taken from agricultural field experiments for which the history is fully documented. “The samples are used by scientists worldwide to understand how changes in agricultural practices affect crop production, soil fertility, and biodiversity,” says Coleman.

But what these vessels also contain is something researchers are not so proud of: a chronicle of human pollution. Over two centuries of industrial growth, soils have recorded what we’ve put into the atmosphere as well as what we’ve poured onto the ground. The Rothamsted sample archive holds evidence of nuclear atmospheric testing in Nevada and on the Bikini Atoll during the 1950s and 1960s. It also has a record of polychlorinated biphenyls (PCBs) from the manufacture of plastics and polycyclic aromatic hydrocarbons (PAHs) from power plants, fresh asphalt, and the fumes of automobiles. There are dioxins, the primary ingredient in Agent Orange, used to defoliate Vietnam. And plenty of heavy metals like zinc and copper from animal feed, cadmium from artificial fertilizers, chromium from tanning, and lead from pipes, vehicle fuel, industrial exhaust, and coal-fired power plants.

Many of these pollutants are deathly persistent. PCBs, the fluids that keep on lubricating and causing cancers, as well as DDT, the pesticide that keeps on killing, continue to appear in nature. Though amounts have gone down significantly since the 1970s, when both these chemicals were banned from most nations, PCB residuals continue to show up in the breast milk of Inuit mothers, and DDT continues to appear in freshwater fish and the raptors that eat them. DDT is still used in India to control malaria.

But the toxic residuals in our soils are something we may just have to live with. Right now, we have to get planting or starve.

That afternoon, out in the fields, Paul Poulton, a Rothamsted scientist, led me down rows of wheat stalks that displayed the results of a momentous moment in the evolution of agricultural products, the “green revolution.” The seed heads were so thick that the plants appeared to be mostly seed, with a short, thick stock and little else.
A light wind rippled through the rows in front of us, looking like ocean waves of wheat grain. The use of these new grains started shortly after World War II and spread like wildfire over much of the planet. Says Poulton, “Rothamsted switched over to these shorter, thick wheat plants about the same time the rest of the world did.”

Norman Borlaug, an American agronomist, won the Nobel Peace Prize in 1970 for creating the first green revolution. A forester and plant pathologist, he walked away from a job at DuPont, a chemical company, in 1944 to join the Rockefeller Foundation’s Mexican hunger project. His first post was as a genetics expert, but by the time he received his Nobel Prize in 1970, he was the director of the Wheat Improvement Program in Mexico.

Wheat was in poor shape in that country, the victim of a plague of maladies, including rust. Borlaug crossed Mexican wheat with rust-resistant varieties from elsewhere and obtained rust-resistance in wheat that grew well in the Mexican environment. Then he bred this wheat in the Sonoran Desert in winter and the Mexican central highlands in summer and developed breeds capable of growing in different climates.

Farmers in that country adopted the new varieties and wheat output began to climb. By the late 1940s, researchers knew they could induce higher grain yields with extra nitrogen, but the seed heads containing the wheat grains grew so heavy that the plants would topple, ruining the crop. So Borlaug worked at crossing wheat with strains that had shorter, thicker, more compact stocks. These plants could produce enormous heads of grain, yet their stiff, short bodies could support the weight without toppling. This transformation tripled and quadrupled production.

When researchers from India applied this idea to rice, the staple crop for nearly half the world, yields jumped several-fold compared with traditional varieties. Chinese agriculturalists started using semidwarf varieties to feed their people, a decision that aided China’s
rise to industrial power.

Now scientists tell us we need another green revolution if we are to meet the food demands of the next several decades. Our friends at Rothamsted are trying to participate in this, but it’s not easy. Their current professed goal is to get twenty metric tons of wheat per hectare in twenty years, the so-called
20:20 Wheat. But Poulton says, “The average wheat grain yield for the UK is currently about 8.0 metric tons per hectare, but on the best soils with good management and favorable weather a farmer could hope to get 12 metric tons per hectare.”

It seems the next jumps in crop production will come not from big discoveries like compact wheat but from a series of smaller changes that agronomists hope will add up to larger production. Rothamsted is currently looking at genetic improvements to increase the amount of grain; advanced pest and disease controls to protect plant yields; improved understanding of soil and root interactions to improve water and nutrient uptake; and a number of plant and environmental interactions to mitigate climate change.

Agricultural scientists at the institute are keeping an eye on what others across the Atlantic are doing as well.
Jonathan Lynch, professor of plant nutrition at Penn State University, thinks that developing more aggressive root systems might be the answer to increased fertilizer efficiency and water usage. Crossing US beans with several varieties of ancestral stocks found in the high Andes Mountains, he’s working to obtain belowground plant systems with lateral root reach sufficient to search for phosphorus in the topsoil and deeper taproots to go after receding groundwater and rapidly draining nitrogen.

Susan McCouch, professor of plant breeding and genetics at Cornell University, focuses on acid soils, a problem on 30 percent of the earth’s surface. Acid releases aluminum into the ground, which inhibits root growth in plants, so the plants stop taking up water and nutrients, and they die. But McCouch is creating hybrid species of grains from ancestral lines, some in the wild, to achieve aluminum
tolerance.

Researchers at Rothamsted are also working with the problem of acid soils by the use of biochar, what Brazilians refer to as
terra preta
, or black earth. Ancient Indian societies along the Amazon thrived using
terra preta
—charcoal from slow, smoldering fires—to enrich the relatively sterile tropical rain forest soils. Researchers are hoping that modern-day societies can do the same.

To get a picture of the
potential of
terra preta
, one must visit the central Amazon near Manaus. I flew into Venezuela in early August and took a two-day ride aboard a bus, which climbed up and over the Sierra de Pacaraima down into the Amazon Basin. The road wound through the forested mountains in the dark night, and the way looked clear until around the bend ahead came another bus. At the last second, both buses veered toward the outer shoulders, and as we whisked by each other dangerously, a hanging limb from the jungle struck our right front window and turned it into a giant spiderweb of glass, which the driver chose to ignore. His side of the double window was still clear.

We traveled all day, first through savanna, then dense tropical forest, and arrived by evening in the city of Manaus perched at the junction of the Rio Negro and the Amazon River. The city was alive with vendors, farmers, and tourists in the afternoon sun. Manaus is the largest city in the central Amazon. A group of archaeologists greeted me at the station, and soon I was headed by ferry across the Rio Negro to their field site on the Amazon.

By morning we rolled out of hammocks, ate a hearty breakfast of eggs, fruit, bread, and coffee, then headed out to the field. University of São Paulo archaeologist Eduardo Góes Neves and some fifty volunteer archaeologists from Latin America, the US, and the UK were excavating an archeological site on a papaya farm that overlooked the Amazon River. This location harbored community graves and other ancient relics going back more than two thousand years. The
lush orange color of the fruit and the robust green leaves on the trees were due to the soils left by ancient Indians who once occupied these lands.

The banks of the river were plentiful with
terra preta
, a gift of civilizations past. While most
Amazonian soils were notoriously nutrient-poor, yellowish, and sterile,
terra preta
was dark, fragrant, and rich—a farmer’s delight. Neves and others believe that by devising a way to enrich the soil, early inhabitants created a foundation for agriculture-based communities that harbored far greater populations than was previously imagined.

Amazonian soils have very little rock in them, which means that early civilizations made their homes and worship sites from wood. These structures, no matter how elaborate, degraded over time, leaving little evidence of past human glory. The principle evidence of ancient civilizations was in the ceramics they formed and fired, pieces of which have survived in the soil.

Early Amazonian life wasn’t easy. Indians used stone axes to fell trees along the banks of the rivers. The task was long and tedious, taking days to weeks to cut down large trees. The process created small openings in the forests, letting in some light, but not enough to thoroughly dry out the vegetation. Farmers started fires to clear the forest for crops, and the fires would smolder for days, creating charcoal that was the basis of
terra preta
.

Most Amazonians today use “slash-and-burn” methods to create space for their crops. Natives use chain saws to clear much larger spaces than the ancient Indians did. This creates large spaces with lots of light, plentiful kindling, and huge, hot fires that produce quantities of ash but little charcoal. Ash has sufficient nutrients to last a few seasons, after which the land goes fallow, whereas
terra preta
, or biochar, can last far longer. One farmer near Neves’s study site cultivated crops on
terra preta
soil for forty years without ever adding fertilizer. William Woods, a soil scientist and professor of geography at the University of Kansas, claimed this was amazing and told me: “We don’t even get that in Kansas,” a US state famous for its soil.

Rothamsted Research has tested soils at several sites in the Amazon and found that
terra preta
took up, integrated, and retained carbon from organic matter much more freely than typical native soils, and this was one of the reasons for increased yields.

Perhaps this would stave off starvation.

On another trip much farther north, but still looking at dirt, I traveled with Dan Richter, professor of soils and forest ecology at Duke University, and several of his faithful graduate students in a caravan of cars heading south from Durham, North Carolina, and the Duke campus
to the Calhoun Experimental Forest, one of Richter’s favorite field sites. Located in Sumter National Forest near Union, South Carolina, the Calhoun was established in the 1940s to study the serious problems the region had with its soils.

Richter worked in the Piedmont area of the southeastern United States. Here, years of Southern cotton production on farms and plantations in the 1800s had eroded earth, extracted vital nutrients, and greatly diminished the productivity of the region’s soils and ecosystems.

The Calhoun’s initial location was picked to represent the “poorest Piedmont conditions” of agricultural soil erosion and cropland abandonment. Early studies on the Calhoun were aimed at soil improvement and watershed restoration in order to find the cheapest, quickest, most effective ways to improve tree growth and soil structure and to increase soil fertility for plants. Duke University’s long-running collaborative study with the US Forest Service has aimed at monitoring, sampling, and archiving information.

The Piedmont is a plateau region of the Eastern United States between the Blue Ridge Mountains, the eastern range of the Appalachian Mountains, and the Atlantic Coastal Plain. It stretches from the state of New Jersey in the north to Alabama in the south. It is an area of about 80,000 square miles (210,000 square kilometers), and the
soils in this region are predominantly clay and moderately fertile. In the central area of North Carolina and Virginia, tobacco is the main crop, while in the north, the focus is on orchards and dairy farming. In the south, where cotton was the chief crop in the 1800s and early 1900s, all that is left, said Richter, “is one of the nation’s most degraded landscapes.”

He took us to a place in the forest
where the soil had been excavated, exposing its profile. In the caravan there were a number of Asian students, including several from China who were eager to absorb the lessons and apply them to similar problems in their own country. China has long-term soil plots that are twenty and thirty years old “and they test soil and crop changes in a wide variety of soils to the major agricultural inputs, organic and inorganic,” said Richter.

He noted that only 150 years of Southern cotton production had caused the erosion of as many as eight inches of topsoil across the southern Piedmont. Native forest was coming back here as it has in the northeastern part of the US, and this was currently restoring some of the organic matter, but the region was still deficient in many vital nutrients, including nitrogen and phosphorus.

These are still agriculture’s two most important fertilizers. Though most crops need a lot less phosphorus than they do nitrogen, the smaller amount of phosphorus is critical to the mixture if you want to get robust growth. Nitrogen can be produced artificially, but phosphorus has to be mined, and the process is ugly.

West-central Florida produces much of the US phosphorus and most of that is taken along the Bone Valley Member of the Peace River Formation, one of the richest sources of the mineral in the world. Miners create what looks like iridescent volcanoes from above as they pull phosphorus ore out of the ground, crush it, and process it into acid lakes. There, the ore is separated into gypsum, which forms the volcano-like cone and the fluorescent green acidic liquid. Farmers use that liquid in a dry mineral form to feed their crops.