Agriculture and Climate Change

Agricultural GHG Emissions

In 2011, agriculture accounted for about 8% and 30% of total GHG emissions in Canada and Manitoba, respectively. Manitoba's agricultural GHG emissions increased 41%, from 5100 to 7200 kt CO2 equivalent between 1990 and 2008 and then declined to 5900 kt CO2 equivalent in 2011 (Figure 1). This can be explained by the rising and falling trends of livestock populations (beef cattle and pigs) and synthetic nitrogen (N) fertilizer use throughout this time frame.

Agricultural GHG emissions in Manitoba from 1990 to 2011
Figure 1.  Agricultural GHG emissions in Manitoba from 1990 to 2011.


The major sources of agricultural GHG in Manitoba are:

    1.     Carbon dioxide (CO2)from
    o    The burning of fossil fuels by equipment and facilities
    o    Losses in soil organic matter
    2.     Methane (CH4)from
    o    Livestock manure
    o    Enteric fermentation of ruminant animals
    3.     Nitrous oxide (N2O) from
    o    Fertilizer use, predominately synthetic N fertilizer
    o    Decomposing crop residues
    o    Manure on pasture and in storage
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 and manure management. From within these categories the net GHG emissions are roughly 60% N2O (mainly from the use of N fertilizers on soils) and 40% CH4 (mainly from livestock enteric fermentation and manure management).

Nitrous oxide is the major GHG produced from agricultural soils which 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 disrupted by tillage, summerfallow, irrigation, and the cultivation of histosols (organic soils) (Environment Canada, 2010).

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.

The smallest contributor of N2O from agricultural soils is from manure excreted on pasture, range, and paddock from grazing animals. Nitrogen in the manure undergoes transformations, such as ammonification, nitrification, and denitrification that produce N2O.

Nitrogen is a necessary component of soil and crop productivity; however, in some forms it also has negative effects to the atmosphere. Any nitrogen added to or existing in the soil is able to undergo denitrification via the nitrogen cycle (Figure 2).  N2O emissions from agricultural soils are primarily due to synthetic and organic nitrogen fertilizers which 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.

Figure 2.  The Nitrogen Cycle

The Nitrogen Cycle

Source: John Arthur Harrison, Ph.D. "The Nitrogen Cycle: Of Microbes and Men", Vision learning Vol. EAS-2 (4), 2003.

Enteric fermentation makes up the second largest proportion of GHG emissions in Manitoba agriculture (Figure 3). Methane is released from ruminant livestock as a by-product of digestive fermentation. Manitoba is home to approximately 1.2 million cattle and on average one cow produces 65 kilograms of CH4 per day (Statistics Canada, 2009; Science & Technology Canada 2007). 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 ruminant methanogenesis. However mitigation options are available for enteric fermentation such as providing high quality forages to ruminent livestock as it improves their feed efficiency and reduces CH4 production.

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 (Environment Canada, 2010).

A summary of GHG production and elimination for an agricultural setting (Figure 3) brings together all of the sources and sinks and allows for development of the best possible solutions for individual operations. Identifying the major on farm GHG emissions is the first step to mitigation. Manitoba Agriculture offers numerous resources to help achieve individual reduction goals.

Figure 3.  Greenhouse gas sources and sinks within an agricultural system

Greenhouse gas sources and sinks within an agricultural system

Source: Farming Futures

Potential Climate Change Impacts for Agriculture

Agriculture is significant to Manitoba’s economy and is intrinsically sensitive to climate. There are advantages and disadvantages that may be experienced by agricultural crops and livestock as a result of climate change (Figure 4, Table 1). In North America, warmer conditions are projected to benefit food production, but strong regional differences are anticipated (Fields et al, 2007).

Figure 4.  Potential impacts of climate change on agricultural crops in Canada

Potential Climate Change Impacts for Agriculture

Click to enlarge

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

Table 1.  Potential impacts of climate change on agriculture's 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
  • 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 (Warren et al., 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 (Fields et al., 2007).

Although the benefits associated with warmer temperatures, longer growing seasons and increased CO2 concentrations are anticipated to improve agricultural activities, there are other factors that may serve to counteract them. Reduced soil moisture, soil degradation, extreme climatic events and heightened presence of pests could exceed the benefits experienced (Warren et al., 2004). For benefits to be observed, practices will need to be chosen that can accommodate the current and changing climatic conditions.

For further information, contact your local Manitoba Agriculture Office.