Yields vs. Land Use: How the Green Revolution enabled us to feed a growing population

Over the last 50 years global population has more than doubled. This factor has inevitably reduced the land available per person to live and grow food. How have we managed to feed a rapidly growing population with ever-shrinking land resources?

There are two key variables we can change to produce more food crops. We can opt for:

• Expansion: increase the area of land we grow our food over
• Intensification: increase the yield output (i.e. kilograms of crop produced per unit area of land). This is typically achieved through a combination of chemical inputs (such as fertilizer, pesticides and herbicides); improved water use (e.g. irrigation); mechanization and improved farming practices; and the use of higher-yielding crop strains or seeds

At the global level, how has crop production changed over the last fifty years? Here, we focus on cereal production: cereals form the base component of energy intake in most diets, comprising more than half of total caloric intake in many countries, and also dominate global arable land use by area. In the chart below we have mapped four variables: total cereal production; average cereal yield; land area used for cereal production; and total population. These are measured as an index relative to their respective values in 1961 (i.e. 1961 is equal to 0).

From 1961 to 2014, global cereal production has increased by 280 percent. If we compare this increase to that of total population (which increased by only 136 percent over the same period), we see that global cereal production has grown at a much faster rate than the population. Cereal production per person has increased despite a growing population.

Have we achieved this through land expansion or improved yields? As we can see in the chart, expansion played a very small role: over the last few decades land use for cereal production has increased only marginally. In 2014, we used 16% more land for cereal production than we did in 1961 (approximately equivalent to double the area of Germany). Overall, this means we use less land per person than we did fifty years ago.

Most of our improvements in cereal production have arisen from improvements in yield. The average cereal yield has increased by 175 percent since 1961. Today, the world can produce almost three times as much cereal from a given area of land than it did in 1961. As we will explain below, this increase has been even more dramatic in particular regions.

Although food is globally traded, the relative distribution of food production is crucial to food security. The evolution of these trends at national and regional levels is therefore critical. Below we have explored a number of varied and interesting examples of these trends across the world. The change in cereal production, population growth, and the relative contribution of yield gains and land expansion are different in each.

One of the most critical turning points for global agriculture was the so-called ‘Green Revolution’, which began in the mid-20^th century. The Green Revolution is used to describe the large-scale transfer and adoption of new technologies in the agricultural sector, particularly in the developing world. These technologies included chemical inputs (such as fertilizers and pesticides), irrigation technologies, farm mechanization (such as tractors), and high-yielding rice, wheat and maize seed varieties. Overall, this led to a significant shift in agriculture from ‘traditional’ to ‘industrial’ practices across the developing world. However, progress and adoption has not been equal across countries.

In the chart below we see cereal production, land use and yield trends for Mexico over the period 1961 to 2014. Mexico was one of the first countries to be linked to the Green Revolution of the 20^th century.¹

As we can see, the increase in cereal production in Mexico has greatly exceeded population growth (meaning output per person has increased). And while agricultural expansion has played some role in this (land use for production increased by 32 percent), the adoption of advanced agricultural technologies and practices has led to impressive gains in yield of 224 percent. Because Mexico’s total output of cereals increased faster than its population, the availability of cereals per capita increased in this period.

In the chart below we see the evolution of India’s agricultural system since 1961. In the 1960s and the decades which followed, India also underwent a Green Revolution in agricultural production and reform. In order to address recurring cycles of severe famine under British rule in the 18th, 19th and first half of the 20th century, independent India made large economic, technological and social investments in improved agricultural practices—particularly in wheat and rice crops.²

The adoption of higher-yielding cereal varieties, subsidization of fertilizer and irrigation inputs, and investments in agricultural research and development all led to rapid gains in cereal yield.³

Shown below, we see that since around 1970, cereal output has grown at a faster rate than India’s population (increasing by 238, and 182 percent, respectively). In contrast to Mexico, this increase in production has been achieved almost completely through agricultural intensification and yield improvements. Throughout this period, the total area of land used for cereal production barely changed. This reduction in area needed per person is particularly important for countries like India, where the total population continues to increase. Over the next 50 years, it is projected that India will have around 400-450 million extra mouths to feed.

China’s transition—shown in the chart below—has several parallels to that of India. China has managed to achieve an impressive increase in cereal output (increasing 420 percent) with almost no expansion of area used for cereal production. As a result, the share of China’s population who are undernourished has fallen from 24 percent to less than 10 percent since 1990 alone.

This growth is almost entirely attributable to improvements in productivity and yield. It has, however, achieved a much greater gap than India in cereal output relative to population (the increase in per capita cereal production, and caloric supply has been much more dramatic). What is this additional cereal crop used for? Per capita caloric supply in China has more than doubled over the last 50 years, however, only 44 percent of cereal production is used domestically for food. Nearly the same amount—40 percent of cereal—was used for animal feed in 2013, with smaller quantities diverted to industrial uses such as biofuel production.

Brazil’s cereal production has increased by a remarkable 574 percent since 1961—well above its population increase of 175 percent.

Unlike India and China, Brazil has achieved this through a combination of both yield improvements and land use expansion. It thus provides a perfect example of the trade-off between extensification and intensification. Over the 1960s and 1970s, Brazil’s land area under cereal production almost doubled—this correlates with a 20-year period of almost stagnant cereal yields. This expansion has been of particular concern from an environmental perspective, with the expansion of agriculture often happening at the expense of forested areas and ecologically important regions such as the Amazon.⁴

From 1980 onwards, however, we see the inverse of this relationship. Since 1980, cereal yields have increased almost three-fold, allowing the land under cereal production to remain almost unchanged. This development aptly highlights the transition from extensification (low yields, large area expansion) in the 1960s and 1970s to intensification (increasing yields, constant land use) from 1980 onwards.

The adoption and success of the Green Revolution has not been consistent across the developing world. Africa – particularly Sub-Saharan Africa – has been a region of particular concern in terms of food security. Despite making significant progress in reducing hunger in recent decades, undernourishment in Sub-Saharan Africa remains the highest in the world (with almost one-in-five people living there defined as undernourished).

Africa’s cereal production has struggled to keep pace with population growth. Despite an increase in cereal output of around 300 percent, per capita output has been declining. Overall, we see much greater emphasis on agricultural expansion in SSA. Relative to Asia and Latin America, SSA’s improvements in yield have been much more modest.

If we look at trends on an individual country basis (by selecting ‘Zimbabwe’, for example, using the “change country” wheel on the chart below) we see that the agricultural systems of many countries across SSA suffer from large volatility in production, yield and land allocation. In the years to come, it will be crucial for SSA to effectively adopt new technologies and practices to ensure steady and consistent improvements in yield at a faster rate than it has achieved to date.

Since 1961, the US’s population has been growing modestly. Simultaneously, cereal production has achieved well in excess of this rate of increase. Overall, we see that land allocated to cereal production in the United States has actually declined by around ten percent. As a result, gains in yield have grown at a faster rate than total cereal output—however, since yields were already high in 1961 relative to countries such as Mexico, India, and China, overall improvements have been slightly more modest.

Like China, while some of this additional per capita output is consumed by humans (per capita consumption increased over this period),⁵ much—indeed, in this case the overwhelming majority—of cereals produced in the United States are diverted to other uses. Based on data from the UN FAOstat database, in 2013 only 8 percent of cereal crop grown in the USA was eaten by US citizens; 32 percent was fed to animals; and 32 percent was allocated for industrial uses, such as biofuel production.

Here we use Germany as a representative of a high income country with a stable population size—in this regard, its trends are approximate to many countries across Europe. Below we see that despite a roughly constant population size, Germany’s cereal output has continued to increase. Like the United States, the total land used for cereal production has marginally declined over this period. Increases in cereal output have therefore been achieved through yield improvements alone.

Again, some of this increase in per capita cereal output is reflected in higher consumption levels of the population.⁶

However, like the US and China, the majority of domestic cereal production is allocated to uses other than domestic food consumption. In 2013, only 19 percent of Germany’s cereal production was eaten by German citizens, in contrast to the 56 percent which was fed to animals. Cereal exports from Germany are also high, reaching around 35 percent in 2013.

Although there are a few exceptions—notably across Sub-Saharan Africa—the continued increase in cereal yields across the world has been the major driver of total cereal production. This has inevitably allowed us to ‘spare’ land we would have otherwise had to convert for cereal production.

In the chart below we see that the global area under cereal production (in blue) has increased from 625 to 721 million hectares from 1961-2014. For context, this difference is approximately equal to one-tenth of the area of the United States. If global average cereal yields were to have remained at their 1961 levels, we can see (in red) the amount of additional land we would have had to convert to arable land to achieve the same levels of cereal production. This ‘spared’ land amounts to 1.26 billion hectares in 2014—close to the area of the United States and India combined.

We currently use approximately 50 percent of global habitable land for agriculture. Without yield increases, this may have risen to 62 percent. Such agricultural expansion would have likely crept into fertile forested land. The UN FAO estimates that since around 1960, we have lost just over 400 million hectares of forest. If land for cereals had therefore replaced forested land, we would have lost four times more forestry than we have in reality.