Food and Greenhouse Gases: Climate change, agricultural production and food demand.

Post written by C.Will

Our recent blogs have been discussing food security, and the role agricultural production has to play in ensuring a sustainable future. Below are two recently published papers that incorporate the effects of climate change into this discussion.

“Climate change effects on agriculture: Economic responses to biophysical shocks”. By Nelson et al. 2013. Published in Proceedings of the National Academy of Sciences (PNAS).

Abstract:

“Agricultural production is sensitive to weather and thus directly affected by climate change. Plausible estimates of these climate change impacts require combined use of climate, crop, and economic models. Results from previous studies vary substantially due to differences in models, scenarios, and data. This paper is part of a collective effort to systematically integrate these three types of models. We focus on the economic component of the assessment, investigating how nine global economic models of agriculture represent endogenous responses to seven standardized climate change scenarios produced by two climate and five crop models. These responses include adjustments in yields, area, consumption, and international trade. We apply biophysical shocks derived from the Intergovernmental Panel on Climate Change’s representative concentration pathway with end-of-century radiative forcing of 8.5 W/m2. The mean biophysical yield effect with no incremental CO2 fertilization is a 17% reduction globally by 2050 relative to a scenario with unchanging climate. Endogenous economic responses reduce yield loss to 11%, increase area of major crops by 11%, and reduce consumption by 3%. Agricultural production, cropland area, trade, and prices show the greatest degree of variability in response to climate change, and consumption the lowest. The sources of these differences include model structure and specification; in particular, model assumptions about ease of land use conversion, intensification, and trade. This study identifies where models disagree on the relative responses to climate shocks and highlights research activities needed to improve the representation of agricultural adaptation responses to climate change.”

“The future of food demand: understanding differences in global economic models”. By Valin et al. 2013. Published in Agricultural Economics.

Abstract:

“Understanding the capacity of agricultural systems to feed the world population under climate change requires projecting future food demand. This article reviews demand modeling approaches from 10 global economic models participating in the Agricultural Model Intercomparison and Improvement Project (AgMIP). We compare food demand projections in 2050 for various regions and agricultural products under harmonized scenarios of socioeconomic development, climate change, and bioenergy expansion. In the reference scenario (SSP2), food demand increases by 59–98% between 2005 and 2050, slightly higher than the most recent FAO projection of 54% from 2005/2007. The range of results is large, in particular for animal calories (between 61% and 144%), caused by differences in demand systems specifications, and in income and price elasticities. The results are more sensitive to socioeconomic assumptions than to climate change or bio-energy scenarios. When considering a world with higher population and lower economic growth (SSP3), consumption per capita drops on average by 9% for crops and 18% for livestock. The maximum effect of climate change on calorie availability is −6% at the global level, and the effect of bio-fuel production on calorie availability is even smaller.”

Food and Greenhouse Gases: Emissions Intensity of Nutrition Sources

Post written by C.Will

New research published in Nature Climate Change argues that reducing the number of ruminant livestock, especially cattle, could significantly reduce greenhouse gas (GHG) emissions.  They find the GHG emissions from ruminants are 19-48 times higher than emissions from high protein foods obtained from plants. This comparison is based on full life cycle analysis including both direct and indirect environmental effects from ‘farm to fork’ (enteric fermentation, manure, feed, fertilizer, processing, transportation and land-use change are considered).

This offers a compelling argument for significantly reducing our consumption of animal protein to reduce our GHG emissions. However, it is important to consider the nutritional differences between animal protein and high protein foods obtained from plants.

A previous blog of ours discussed studies that look into the debate about GHG emissions from animal protein products and the nutritional difference between animal protein and other high protein sources. To get a comparable amount of energy from fruit and vegetables, larger portions are needed because animal protein products are a rich source of energy. Therefore, when comparing animal protein products and fruit and vegetables on a measure of GHG emissions per unit of energy (in kilocalories), the difference is much smaller.

The problem is complicated and the solution is not clear, but it is important to understand that the food choices we make as individuals do have an impact on the environment. Together we can improve the food security problem by making better informed decisions about our consumption.

Food and Greenhouse Gases: An Ominous Future?

Post written by C. Will

In a world increasing in population and wealth, food production needs to be steadily increasing to meet the growing demand. However, a recent study in Nature Communications (discussed here) argues the rate of yield gains in wheat and rice production have plateaued, despite increased investment in R&D and education. Other studies (for example Ray et al. (2013)) have also found evidence that the current yield gain in major crops is insufficient to reach the estimated 60% increase in production required by 2050. If wheat and rice production have approached a yield ceiling it provides an ominous future for food security.

Previous increases in yield gain have been driven by investment in technologies that were largely one-time innovations and cannot be repeated. For example, innovations in genetically modified grains, major investment in irrigation infrastructure and increased use of fertilisers and pesticides saw steady increases in grain production.

Is livestock agriculture also at risk of approaching a yield ceiling?

New Zealand has experienced significant annual increases in livestock productivity for more than 20 years.  As we discussed in a previous post even with existing technology there is room for significant ongoing improvement as less efficient farmers catch up with those who are more efficient. In the short term, constraints on yield per hectare (intensity) are likely to be environmental (water quantity and quality) rather than technological (as noted by the Parliamentary Commissioner for the Environment’s report on water quality). Internationally, the enormous differences in livestock productivity suggested by differences in emissions per unit of output suggest space for considerable yield gains.  

Globally we need to be making all the efficiency gains that we can to resolve the food security problem and New Zealand has an important role to play in this through the livestock sector.