- Farmers, food and beverage manufacturers, grocery stores, and restaurants will need to review and evaluate their supply chains to ensure access to required inputs.
- Costs might increase for crops that are negatively impacted as local and global heat stress, drought, and increasing prevalence of diseases decrease crop yields and quality.
- Some crops might benefit from longer growing seasons and warming temperatures. For example, as Ontario’s wine regions continue to warm there will be opportunities to grow warm climate grape varieties (e.g., Syrah). However, this has negative implications for cool climate grape varieties (e.g., Riesling) unless adaptation measures are taken.
Changes in temperature and precipitation patterns will have significant implications for regional agricultural operations that may present a mix of positive and negative impacts depending on location and crop/livestock grown. Under the high emissions scenario, the average length of the growing season and climatic suitability for certain crops is expected to increase, while the level of crop heat stress and pests is also expected to increase. The combination of impacts will call for further analysis of climate change impacts on smaller spatial scales so agricultural businesses and those that relay on them can implement adaptation measures suitable to their particular situations. Innovative adaptation strategies will need to be found to mitigate the impacts of heat stress and pests without causing further environmental damage.
During the historical period of 1971-2000, the average annual growing season was 166 days in length, typically starting around May 12 and ending around October 23 . The high emissions scenario projects an expansion of the growing season into April and November by the 2080s, resulting in an approximate addition of 51 days or roughly two months of growing season by the end of the century . This presents a substantial expansion of the growing season with important implications for agriculture, wildlife, and ecosystems.
Some crop species may benefit from the longer growing period, resulting in higher yields and new planting opportunities. As the growing season lengthens with warming temperatures, crop growing degree days (GDD) increases as well.
GDD provides an index of the amount of heat available for the growth and maturation of plants and insects and typically considers a minimum temperature threshold important for physiological development . Under the high emissions scenario, many of the major crops in Ontario, such as corn, canola, and beans see an increase in growing degree days over the 21st century. However, GDD calculations provide only an approximate assessment of potential crop growth and do not always account for other climatic factors. Many GDD calculations do not account for maximum temperature thresholds over which crop growth is impaired, providing a caveat that must be considered when using this parameter for climate change impact assessments. In the case of corn for example, growth is impaired when temperatures reach 30°C or more (known as extreme heat days), suggesting that warming temperature trends may have adverse effects on crop yields if temperatures are too high for too long . Extreme heat days are expected to increase by 22 – 30.7 days by the 2050s and between 37 – 41 days by the 2080s, compared to the historic average of 11 days .
Increasing temperatures also make the climate more suitable for various crop pests. TRCA projections under the high emissions scenario show that the growing degree days for the risk of pests (base temperature of 15°C) rise from 518.6 GDD during the baseline period to 1072 GDD by the end of the century . A more suitable climate for certain crop pest species may lead to more infestations or the expansion of pest species ranges into new territories. Crop species that experience stress from potential drought or extreme weather events may also be more vulnerable to disease . For example, the brown marmorated stink bug (Halyomorpha halys) has received growing attention in Quebec for its expanding range with the changing climate. The insect is known to attack many plant species, including corn and soybean, and could see its range expand from the Montreal area to become established elsewhere across the province and into the Ottawa region with rising temperatures .
Warming temperatures and changing precipitation patterns over this century will have multiple impacts on agriculture in the GTA. Warming temperatures have led to increases in growing season length, a trend which is projected to continue. Longer growing seasons may allow for greater crop yields or the growth of other crop species that require warmer temperatures. Warmer temperatures also mean later frost days and fewer extreme cold events. However, extreme heat and increasing variability in precipitation can be damaging to both crops and livestock, resulting in lower yields and productivity. This means that in order to take advantage of the longer growing season, risk mitigation measures will need to be implemented to ensure high yields.
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- Impact: Human Health
- Impact: Buildings and Infrastructure
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- Impact: Financial and Regulatory
 Toronto and Region Conservation Authority (TRCA), 2021. TRCA Climate Change Projections under RCP8.5 and RCP4.5 (1971-2100) (Version 1). TRCA Open Data. https://data.trca.ca/dataset/trca-climate-change-projections
 Environmental Protection Agency (EPA). August 2, 2022. Climate Change Indicators: Growing Degree Days. Accessed August 19, 2022. URL: https://www.epa.gov/climate-indicators/climate-change-indicators-growing-degree-days.
 Sanchez, B., Rasmussen, A., and Porter, J.R. 2013. Temperatures and the Growth and Development of Maize and Rice: A Review. Global Change Biology. DOI: 10.111/gcb.12389
 Boland, G.J., Melzer, M.S., Hopkin, A., Higgins, V., and Nassuth, A. 2004. Climate change and plant diseases in Ontario. Canadian Journal of Plant Pathology. 26: 335-350.
 Plouffe, D. May 25, 2022. Crop Pests and Climate Change. Accessed August 22, 2022. URL: https://climatedata.ca/case-study/the-brown-marmorated-stink-bug-in-quebec/