Growing more, emitting less
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As international negotiators participate in the Paris climate change talks this week, we might all wonder how world leaders plan to address another slow-onset, existential challenge of the 21st century: How is everyone going to eat?

Over the next 35 years, the global population will increase 30 percent, to 9.7 billion, while the share of global population classified as "middle class" will also leap dramatically.

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Together, these immense increases in population and wealth will fuel a 70 percent hike in consumer-driven demand for food, feed, fiber and fuel, the U.N.'s Food and Agriculture Organization (FAO) says. Some put the figure at as much as 100 percent.

At the same time, greenhouse gas (GHG) emissions must be reduced as quickly as possible to avert catastrophic climate change. The stakes at the Paris climate talks this December could hardly be higher.

To meet these two great challenges, governments, farmers, agribusiness and civil society must act now. They must collaborate to help farmers grow more and waste less while also emitting less.

The good news is we know this can be done. In fact, it's already being done. The trick is to do more of it.

Although it's not generally recognized, the agriculture and forestry sector is currently the source of almost a quarter of GHG emissions. The bulk of these agricultural emissions arise from inefficient livestock and crop production, deforestation and conversion of land to agriculture, and poor soil management practices.

Farmers, ranchers and forest managers in the United States and other developed countries have already shown, however, that a combination of conservation practices and innovation technologies can greatly reduce these emissions — even as they boost production.

Consider: According to a 2010 Stanford University study published in the Proceedings of the National Academy of Sciences, total global crop yield between 1961 and 2005 increased by 135 percent. At the same time, global cropland grew by only 27 percent. The net effect of these higher yields per acre, primarily from cereals and oilseed crops, prevented vastly greater levels of deforestation and land conversion to crop production. The net emissions averted represented the equivalent of preserving as much as 100 million acres of forest per year, or taking 2.7 million automobiles off the road annually. Absent these yield improvements, agriculture's contribution to global GHGs over the 44-year period would have more than doubled.

But the momentum that has produced these improvements in the developed world must be maintained and increased. And these practices and technologies must be adopted in the developing world as well.

In the United States, long the world leader in agricultural productivity, annual growth in agricultural output has slowed from its historical rate of 1.5 to 2 percent to less than 1 percent. More troubling, perhaps, is the decline in the growth rate in what we call Total Factor Productivity (TFP), which is the ratio of agricultural outputs — crop and livestock production — to inputs — land, labor, fertilizer, feed, machinery and livestock. Maximizing TFP is the key to reducing and mitigating the GHG impact of agriculture.

In the 1980s, TFP growth in the United States surpassed 2 percent a year; in recent years, the pace has declined to about 1.5 percent. For the world to feed itself sustainably in 2050, my organization has calculated, TFP growth worldwide needs to average 1.75 percent. To maintain its longstanding leadership in agriculture, therefore, the United States needs to return to the growth rates of a few decades ago.

This can be done. One important factor in TFP growth is public investment in agricultural research and development (R&D), which has fallen 6 percent in the United States since 2000. The historical rate of U.S. R&D inflation is 3.73 percent a year. If policymakers increase public spending and mobilize private-sector and foundation resources to keep pace with that rate, the United States would be on course to boost agricultural output by 73 percent by 2050. That would be with less land, livestock and capital — in other words, simply through greater productivity.

Meanwhile, worldwide adoption of many of the practices and technologies that have been pioneered in the developed countries would enable the agriculture and forestry sectors to reduce net GHG emissions to half of current levels by 2050, according to the 2014 International Panel on Climate Change (IPCC) report (see p. 24). That's while still providing the food, feed, fiber and biofuels required for the booming global needs.

Although the list of practices in need of wider adoption is a long one, improved management of cropland and of grazing lands stand out especially.

With respect to cropland, better crop genetics and conservation practices, both of which increase yield and reduce the amount of land required, are crucial. Certain high-yielding, genetically modified (GM) crops also contribute to reduced fuel because they require less frequent herbicide or insecticide applications, decreasing the need for machinery and the energy that fuels it. Crop management practices, particularly rotations with nitrogen-fixing legumes, enable soils to store carbon and soil organic matter and improve soil quality. Emerging precision agriculture technologies also offer great potential for helping farmers to both "farm smart" and "conserve smart."

At the same time, grazing lands must be managed so they are neither over- nor under-grazed: Both practices result in suboptimal storage of carbon in pastureland. Methane emissions from cattle and sheep can be cut significantly with techniques including better feeding, improved soil quality in pastures, dietary additives and improved breeding. Milk and meat production per animal can also be boosted — and emissions cut — with improved genetics and care practices.

All of these practices must be adapted to local needs and extended to farmers of all sizes, including smallholders, across the planet. Considerable evidence shows this is entirely practical, and is illustrated in our "2015 Global Agricultural Productivity (GAP) Report."

Taken in combination, these kinds of practices and technologies will mitigate agriculture's contribution to climate change and shrink the environmental footprint of food production. And they will give us the food, feed, fiber and fuel we need for a growing world.

Zeigler is executive director of the Global Harvest Initiative.