Crop intensification, land use, and on-farm energy-use efficiency during the worldwide spread of the green revolution

Abstract

We analyzed crop production, physical inputs, and land use at the country level to assess technological changes behind the threefold increase in global crop production from 1961 to 2014. We translated machinery, fuel, and fertilizer to embedded energy units that, when summed up, provided a measure of agricultural intensification (human subsidy per hectare) for crops in the 58 countries responsible for 95% of global production. Worldwide, there was a 137% increase in input use per hectare, reaching 13 EJ, or 2.6% of the world's primary energy supply, versus only a 10% increase in land use. Intensification was marked in Asia and Latin America, where input-use levels reached those that North America and Europe had in the earlier years of the period; the increase was more accentuated, irrespective of continent, for the 12 countries with mostly irrigated production. Half of the countries (28/58), mainly developed ones, had an average subsidy >5 GJ/ha/y (with fertilizers accounting for 27% in 1961 and 45% in 2014), with most of them (23/28) using about the same area or less than in 1961 (net land sparing of 31 Mha). Most of the remaining countries (24/30 with inputs <5 GJ/ha/y), mainly developing ones, increased their cropped area (net land extensification of 135 Mha). Overall, energy-use efficiency (crop output/inputs) followed a U-shaped trajectory starting at about 3 and finishing close to 4. The prospects of a more sustainable intensification are discussed, and the inadequacy of the land-sparing model expectation of protecting wilderness via intensified agriculture is highlighted.

Keywords: EROI; Jevons paradox; land sharing; land sparing; water–energy–food security nexus.

Fig. 1.

(A) Annual energy input (GJ⋅ha⁻¹⋅y⁻¹) as the sum of fertilizers (N, P, and K), machinery (construction and maintenance), and fuel. (B) Total annual energy production from all crops (output; GJ⋅ha⁻¹⋅y⁻¹). (C) Annual EUE for each continent estimated as the ratio of crop production (GJ) to energy input (GJ) (note log scale). Solid and dashed lines in A and C are for 10- and 30-y machinery lifespans, respectively (Supporting Information). Data are shown for six geographical continents, excluding countries with 30% or more agricultural land under irrigation in 2005 (these are presented separately as MICs and are listed in Materials and Methods). Data for input, production, and land are from FAOSTAT (20); input ECs are from Table S1; crop ECs are from the FAO (Supporting Information).

Fig. 2.

Total annual energy input (in EJ), crop production (in EJ), and EUE of the 58 main crop-producing countries. “Outdated” and “Updated” N-fertilizer technology refer to industrial energy efficiency in synthesizing ammonia (Supporting Information). Energy input and EUE are presented for two machinery lifespan scenarios: 10 y (solid line) and 30 y (broken line).

Fig. 3.

Crop production as a function of energy input for the 58 main crop-producing countries (average of 10- and 30-y machinery lifespan assumption). The black dashed line represents the world excluding MICs and excluding improvements in N-fertilizer manufacturing (using outdated technology). The arrows start at the averages for 1961–1965, 1975–1980, 1985–1990, 1995–2000, and 2003–2008, and the last ends in 2010–2014. Three fixed EUE lines (3:1, 2:1, and 1:1) are presented as reference.

Fig. 4.

Most important agricultural countries (responsible for 95% of global crop production) classified by average energy input (GJ/ha/y) and net percentage of land cleared or incorporated for agriculture. Energy input (GJ/ha/y) is the sum of fertilizers (N, P, K), machinery (construction and maintenance), and fuel from 1961–2014 (Supporting Information). The percentage of net land cleared or released for agriculture between 1961–1965 and 2010–2014 is the FAO’s Agricultural Land and Permanent Crops average. Pink panels conform to the land-sharing hypothesis, and blue panels conform to the land-sparing one. Italics indicate generalized irrigation (MICs).