Agriculture and Climate Change

Agricultural GHG Emissions

While agricultural activities generate emissions from fossil fuel consumption these are reported under the Transportation sub-category in Canada's National Inventory Report. The main GHG emissions categories attributed to agriculture are agricultural soils, enteric fermentation, manure management and CO2 from carbon-containing fertilizers. From within these categories the net GHG emissions in 2015 were roughly 52% N2O (mainly from the use of N fertilizer on soils), 44% CH4 (mainly from livestock enteric fermentation and manure management) and 4% from CO2 released after application of carbon-containing fertilizers.

Nitrous oxide is the major GHG produced from agricultural soils and accounts for more than half of Manitoba agriculture's GHG emissions. These emissions can be further broken down into sub-categories:

Direct sources of N2O from soils include use of synthetic fertilizers (largest contributor), livestock manure applied as fertilizer, decomposing crop residue and soil organic matter decay that is stimulated by tillage, summerfallow, irrigation, and the cultivation of histosols (organic soils).

Indirect sources of N2O from soils are those that come from movement of nitrogen from agricultural soils to surrounding soil or water. When either synthetic fertilizer or manure is applied to agricultural soils, some of the nitrogen is transported off-site through volatilization and subsequent redeposition or through leaching, erosion, and runoff. This nitrogen can then go through subsequent nitrification and denitrification to produce N2O.

Manure is also a source of N2O from agricultural soils is. Nitrogen in the manure undergoes transformations, such as ammonification, nitrification, and denitrification that produce N2O.

N2O emissions from agricultural soils not only contribute to agricultural GHG emissions, but also represent a loss of costly nitrogen fertilizers. Therefore there are both environmental and economic benefits for producers to optimize their nitrogen use efficiency by implementing beneficial management practices.

Enteric fermentation makes up the second largest proportion of GHG emissions from agriculture in Manitoba. Methane is released from ruminant livestock as a by-product of digestive fermentation. Significant research has been and continues to be conducted on developing mitigation strategies for enteric CH4 production, however to date there is no long term solution to prevent ruminant methanogenesis. However mitigation options are available for enteric fermentation such as providing high quality forages to ruminant livestock to improve feed efficiency and managing herd health for maximum growth and reproductive efficiency.

Both N2O and CH4 are emitted as a result of manure management, which makes up the smallest portion of GHG contributions from agriculture in Manitoba. Depending on the manure storage system, the manure characteristics (animal source, solid versus liquid) and the quantity of manure, the amount and type of GHG produced will differ. Manure begins to decompose shortly after it is excreted. Should the conditions be anaerobic (without oxygen) then CH4 is predominately produced, however if the manure is well aerated then N2O will be produced. This also applies to manure storage facilities; those that are covered and are exposed to little oxygen will primarily produce CH4 and little N2O, while open air manure storage facilities will produce more N2O and little CH4.

A summary of GHG production and elimination for an agricultural setting in Figure 2 shows all of the sources and sinks. Identifying the major on farm GHG emissions is the first step to mitigation. 

Greenhouse gas sources and sinks within an agricultural system
Figure 2. Greenhouse gas sources and sinks within an agricultural system
Source: Farming Futures

Potential Climate Change Impacts for Agriculture

(Figure 3, Table 1). In North America, warmer conditions are projected to benefit food production, but strong regional differences are anticipated (Field et al, 2007).

Potential Climate Change Impacts for Agriculture
Click to enlarge

Figure 3. Potential impacts of climate change on agricultural crops in Canada
Source: Natural Resources Canada, Climate Change Impacts and Adaptation: A Canadian Perspective.

Table 1.  Potential impacts of climate change on livestock in Canada

Projected Changes Positive Impacts Negative Impacts
Warmer Temperatures Predominately in winter months:
  • Lower feed requirements
  • Increased survival of young
  • Reduction in energy costs
  • Expansion of pasture lands and grazing times
Predominately in summer months (heat waves):
  • Death of livestock
  • Reduced milk and meat production
  • Reduced reproduction in dairy
  • Suppression of appetite resulting in reduced weight gain
  • Migration of livestock pests and pathogens northward
Increased frequency of extreme climatic events
  • not applicable
  • Drought – resulting in reduction in cattle stock to preserve pasture land
  • Extreme rainfall/flooding
  • Possibility of power outages
  • Unpredictability
Enhanced atmospheric CO2
  • Increase growth rates in grasslands and pastures with potential for higher livestock productivity.
  • Promotion of foreign species into grasslands, resulting in possible reduction of nutrient quality
  • Possible decrease in nutrient concentration of desirable forage species

Source: Natural Resources Canada, Climate Change Impacts and Adaptation: A Canadian Perspective.

The agricultural sector’s vulnerability to climate change is dependent on the nature of climatic change, regional climatic sensitivity and the capacity to adapt to changes (Lemmen and Warren, 2004). Vulnerability to climatic change is multi-dimensional; it is determined by the sector’s response to interacting factors such as economic competition, farm management and cultivar selection, as well as indirect climatic stressors such as water availability and pest competition (Field et al., 2007).

Although the benefits associated with warmer temperatures, longer growing seasons and increased CO2 concentrations are anticipated to deliver benefits to agriculture, other factors may counteract them. The impacts from reduced soil moisture, soil degradation, extreme climatic events and heightened presence of pests could exceed the benefits experienced (Lemmen and Warren, 2004). For benefits to be observed, practices will need to be chosen that can accommodate the current and changing climatic conditions.

 

References:

Field, C.B., Mortsch, L.D., Brklacich, M., D.I. Kovacs, P., Patz, J.A., Running, S.W. and SCott, M.J. (2007) North America; in Climate Change 2007: Impacts, Adapatation and Vulnerability. (Contribution of Working Group II to th Fourth Assessment Report of the Intergovernmental Panel on Climate Change), (ed) M.L. Parry, O.F. canziani, J.P. Plautikof, P.J. van der Linden and C.E. Hanson;; Cambridge University Press, Cambridge, United Kingdom, p. 617-652.

Lemmen, D. S. and Warren, F. J. eds., Climate Change Impacts and Adaptation: A Canadian Perspective (Ottawa: Climate Change Impacts and Adaptation Directorate, 2004).

 

For further information, contact your local Manitoba Agriculture Office.