**6. Sustainable agriculture**

The vulnerability of the world food system and hence global food security to fossil fuel prices, as illustrated in Figure 11, renders critical the need for a transition to sustainable agricultural systems.

Fig. 11. Coupling of oil and food prices (Hughes, 2011b). The red line represents the FAO food price index; the black line represents the cost of West Texas Intermediate crude oil.

No one doubts the existence of a vast geological shale gas resource, but, as for coal, conversion to producible reserves depends as much on energetics and economics as on technology. Such considerations about shale gas production will determine the ultimate magnitude of global natural gas production. Given the importance of natural gas for synthesis of nitrogen fertilizer, the evolution of shale gas production in the coming decades

In this regard and as mentioned above, the dependence of global agriculture on mined phosphorus also is a relevant concern. To the extent that fossil fuel availability contributes to

On a marginally hopeful note, Rutledge (2010) concludes that actual fossil fuel consumption will be less than projected in *any* of the emissions scenarios considered by the IPCC (2000), yielding a peak atmospheric CO2 concentration of 455 parts per million. If he is correct, the world has already experienced roughly half of the maximum temperature rise that will occur from fossil fuel burning—although impacts such as rising sea levels and vanishing

It is unlikely that the possible stabilization of long-term climate will greatly relieve stress on agricultural systems by mid-century—especially compared to the associated direct challenge

The vulnerability of the world food system and hence global food security to fossil fuel prices, as illustrated in Figure 11, renders critical the need for a transition to sustainable

Fig. 11. Coupling of oil and food prices (Hughes, 2011b). The red line represents the FAO food price index; the black line represents the cost of West Texas Intermediate crude oil.

will have a direct impact on the cost of conventional efforts to maintain soil fertility.

the cost of mining, it will impact the price of this other critical soil nutrient.

**5.4 Fossil fuels and climate change** 

glaciers will continue to unfold beyond 2150.

of rising fossil fuel prices.

agricultural systems.

**6. Sustainable agriculture** 

The great success of the Green Revolution in expanding food production faster than population during the second half of the 20th century depended on multiple developments in plant genetics, expanded use of synthetic fertilizer, increased irrigation, mechanization, petroleum-based herbicides and pesticides, and policies at the national and international levels (Smedshaug, 2010, pp. 219-222). Many of the innovations depended on low energy costs, especially for oil, that are unrepeatable. Particularly in developed countries, cheap energy has led to widespread intensification, indeed, industrialization of agriculture, with capital and fossil fuel inputs producing very high yields (e.g., in kg/ha) with very low inputs of human labor (Pimentel & Pimentel, 2008, Chapter 10). A social consequence of this has been disruption of agricultural communities and migration to cities where unemployment has been a common outcome (Berry, 2010).

For all its success, industrial agriculture is unsustainable (Tilman, 1998; Kimbrell, 2002), owing to its diverse negative effects on the environment and on social systems, which include the following.


All of these impacts threaten the stability of global food production, and hence threaten food security. In addition, for all its productivity, industrial agriculture has failed to provide adequate food access to roughly 15% of the global population. Consequently, discussions of food security increasingly stress the need for agricultural systems to move to methods that can be sustained over generations (Pimentel & Pimentel, 2008, Chapter 23; Science, 2011; Smedshaug, 2010, pp. 222-225; Smil, 2010; Worldwatch, 2011). The coupling of food prices to rising prices of fossil fuels compounds this need.

The following subsections highlight proposed approaches to sustainable agriculture. Owing to the complexity of the global agricultural system, including huge differences between developed and developing countries, as well as linkages to economic and social policy, it can only provide a sampling of available information. Topics include agroecology; organic cultivation; crop breeding, including both genetically modified organisms (GMOs) and perennial crops; competition with biofuels; and proposed broad strategies.
