Agriculture and livestock
The ingredients for plant life to grow and thrive seem deceptively simple: start with a seed and add sunlight, water and nutrients.
Anyone who has struggled to keep a houseplant alive knows that it’s not always so easy. Plants need just the right balance of light, water and nutrients: too much or too little of anything can cause them to wilt and die.
Farmers know that growing plants on a large scale is even more complex. It’s an incredibly important part of life in Ontario, which is home to more than a quarter of total farms in Canada. [1] The province is a leader in farming commodities such as soybeans, corn for grain, and greenhouse products.
Roughly half the total land area in Grey and Bruce counties is dedicated to farmland. Huron County is the most agriculturally productive county in Ontario, with more than 2,500 farms and capital assets of more than $12.2 billion.[2]
Crops (and livestock) can thrive or wither depending on a multitude of interrelated factors. Temperature, climate and weather affect the growth of plants, the quality of the soil, whether certain pests or diseases can proliferate, and much more.
Growing season
Rising temperatures could mean longer growing seasons, as winters are expected to become shorter and milder.
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An important measure of this is the “frost-free season,” which is the number of days between the last spring frost and the first fall frost. Longer days between these frosts means crops have a longer window of time to grow and mature. [3]
From 1950 to 2020, the frost-free season lengthened by approximately 19 days in Grey, Bruce, and Huron counties, from around 151-153 days to 170-172 days. This could extend between 31-51 days longer by 2080, with some predictions expecting a frost-free season of more than 213 days. [3]
Number of days between the last spring frost and the first fall frost. Hover or click on the graph to see individual values. Tap the legend to highlight or toggle scenarios. Find out more about what each scenario means here.
A longer growing season has the potential to increase agricultural productivity. What’s more, some plants such as small grains and oilseeds can benefit from the increase in atmospheric carbon dioxide concentrations that are expected, since increased CO2 increases photosynthesis and crop water use efficiency. [5]
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However, with the longer season comes an increase in extreme temperature events and more variable precipitation, which can pose challenges for crops. Since different plants have different temperature tolerances, farmers will likely also need to adapt to new plant varieties that are suitable for the changing climate.
How does your
garden grow?
Temperature is critical to plant growth and development. Each plant species has a preferred temperature range. Temperatures that are too high or too low can stress the plant, inhibit growth, or cause damage to foliage.
Processes such as photosynthesis (the process by which plants convert light into chemical energy), respiration (a process that releases energy from stored sugars for cellular activities), and transpiration (the rate at which plants lose water through their leaves) all tend to increase with increased temperatures. [6]
Researchers have come up with ways to describe the way air temperature is relevant to plant growth.
Growing Degree
Days (GDDs)
These provide an index of the amount of heat available for the growth and maturation of plants. Different types of plants require different base temperatures to thrive.
Growing degree days can help horticulturalists, gardeners, and farmers predict when their plants will reach maturity.
Corn Heat Units (CHUs)
These are a temperature-based index used to estimate if the weather is warm enough (and not too warm) to grow corn.
Corn doesn't grow when the temperature is below 10 °C, and temperatures above 30 °C do not increase the plant’s growth rate. Generally, at least 2,200 CHUs are needed to mature most varieties of corn.
In Grey, Bruce, and Huron counties, growing degree days and corn heat units are all projected to increase significantly in the coming century, depending on the amount of warming. CHUs, for example, are expected to increase to 3,800-4,300 by 2080, up from around 3,300 currently.
Livestock
It’s a sweltering day. You’ve been outside for most of the day, working or playing in the sun, with little relief from the heat.
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You notice you’re sweating profusely. Then you start to feel weak, fatigued, dizzy, and nauseous. These are symptoms of heat stress or heat exhaustion, illnesses that happen when our bodies have trouble cooling off.
Stay out in the heat long enough and the body’s core temperature can rise to dangerously high levels, leading to heat stroke. Heat stroke is a medical emergency, with symptoms including seizures, rapid pulse, and loss of consciousness. If left untreated, it can cause permanent disability or even death.
We’re not the only creatures who can struggle in the heat. Increased temperatures can affect the health of livestock, too. This can reduce meat, egg, and milk production, and even lead to livestock fatalities.
Dairy cattle are particularly susceptible to heat stress, which can lead to reproductive complications, reduced milk production, and an increased risk for disease and mortality. The dairy sector has been estimated to bear more than half the costs of heat stress to the livestock industry in the United States. [7]
A 2015 study examined heat waves in Southern Ontario from 2010 to 2012 and their effects on dairy cows. They found that the heat waves (defined as three consecutive days of 32 °C or above) were associated with increased on-farm cow mortality. [8]
The heat waves were measured in heat stress indices (HSIs), a relative measure of discomfort based on temperature and humidity. The typical rise of HSI associated with a heat wave increased the mortality rate by 27% compared to a control period without a heat wave.
Heat waves promise to become increasingly common, and farmers will need to take measures to mitigate their risks and protect their livestock. This could include adapting infrastructure to provide increased cooling or adopting more heat-tolerant breeds.
This figure indicates Ontario dairy farm cow density in 2013.
Direct physical effects from the heat are just one way that livestock are affected by climate change. Changes to the growing season and soil will also have ripple effects on the availability and quality of livestock feed. Drought and water quality issues can impact drinking water. And finally, new diseases and pests may pose a threat. [10]
This figure indicates heat wave maps from 2010-2012 of farms reporting cattle deaths.
Diseases and pests
It’s a struggle as old as agriculture itself:
the battle of farmers versus pests. Climate change will have a direct impact on many of the insects, fungi, diseases, rodents and other organisms that can threaten both crops and livestock.
Our winters are getting milder, making it easier for insects to survive the season
(a process known as “overwintering”).
Pest species such as:
epicgardening.com
bean leaf
beetle
Tamal Das
cereal leaf
beetle
cereal pest AID
cabbage seedpod weevil
thepetenthusiast.com
flea
beetles
can overwinter in the top layer of crop residue, and are likely to thrive.
Pests that normally migrate in from warmer areas, like corn earworm and stalk borer, are already starting to overwinter farther north and are likely to expand into the Great Lakes region. [11]
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Like fish, insects are exothermic (“cold blooded”). Their development and growth are affected by the temperature of their environment. Shorter, milder winters and a longer growing season will give pests more time to develop and grow. Some insects, like the potato leafhopper, could go through an extra generation per season. [12]
The increase in pest pressure could result in an increase in the number of pesticide applications per season, which can lead to pesticide resistance. Some resistant pest populations have already expanded their ranges from the southern United States into Ontario. [13]
Climate change will also affect plant diseases, although predicting exact impacts is difficult thanks to the complex interactions between plants, pathogens, and the environment. Some factors are better understood than others. For example, an increase in relative humidity tends to be favorable for many fungal-caused diseases. [14]
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Our approach to agriculture can amplify these effects. For example, the monoculture practice of growing large fields of the same, densely planted crop has accelerated the spread of virulent diseases.
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Much more research is needed to understand the complexities of pests and pathogens, but land management practices will certainly play a large role in mitigating the effects of climate-accelerated diseases. [15]
