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Heat Advisory: Protecting Health on a Warming Planet
by Dr. Alan Lockwood

Drawing on peer-reviewed scientific and medical research, Dr. Lockwood meticulously details the symptoms of climate change and their medical side effects.

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Climate Impacts on Water and Agriculture

Climate change affects the frequency and intensity of rainfall. In some places, rainfall becomes less frequent, but when it comes, it is intense, leading to runoff and flooding.  Flooding can be especially dangerous in river and coastal areas. 

In rural areas, runoff picks up animal wastes, pesticides, and fertilizers.  

In cities, floodwaters not only carry toxins and other contaminants but can also overwhelm sewage systems, causing untreated sewage to flow directly into waterways.

Additionally, as temperatures rise, more moisture evaporates from land and water, leaving less water behind. This is creating a water displacement across the globe, leaving some areas with more rain or snow and some with less. As a result, severe droughts are becoming more extreme, and it is having negative effects on our water supply and agriculture.

Water Contamination

Contamination of drinking water by bacteria, viruses, and protozoa can trigger outbreaks of waterborne disease like the diarrheal diseases legionella, campylobacteriosis, and cholera.  Warmer water temperatures also promote the growth and reproduction of these diseases.

Heavy Rainfall and Flooding Can Affect Drinking Water Quality

Climate change increases the frequency and intensity of heavy rainfall, which leads to runoff and flooding, especially in river and coastal areas.  This can lead to the contamination of drinking water with chemicals, gasoline, coal ash, sewage and more.

Extreme precipitation events have been linked to increased levels of pathogens in treated drinking water and cases of gastrointestinal illness in children. 

For example, in 2000, a heavy rainfall event in Walkerton, Ontario, Canada, carried agricultural runoff containing E.coli into the town's primary water source, a shallow well. This extreme weather-related event caused 2,300 illnesses and seven deaths.

Groundwater wells receive limited water treatment. This makes them more susceptible to water contamination from extreme precipitation events and increases the risk of waterborne illnesses in those who consume it.

Agricultural Effects

Increases in global average temperatures, the frequency of extreme storms, and the duration of droughts can all endanger agricultural production and food security.

Higher global temperatures and drought induce crop heat stress, dry out the soil, and promote weeds.

  • Heat stress limits the growth, metabolism, and productivity of plants. High nighttime temperatures can reduce grain yields.
  • Heat stress makes plants more susceptible to mold. Corn, peanuts, cereal grains, and fruit are especially susceptible to mold growth and mycotoxin production (any substance produced by a fungus). Mycotoxin can result in illness and death.
  • Although the U.S. has regulations in place to prevent mycotoxins from entering the food supply, it may become more difficult to manage as climate change continues.
  • Rising temperatures and CO2 concentration favor the growth of weeds and can increase their range. If farmers respond by increasing their use of herbicides, that can lead to some weeds becoming herbicide-resistant.

Animals are also affected by high temperatures.

  • High nighttime temperatures increase stress on animals. This can result in reduced rates of meat, milk, and egg production.
  • Pollinators, like bees, are also affected by higher temperatures, as they can suffer from heat exhaustion and decreased immune response.

Climate change can cause dramatic reductions in water availability, such as droughts, depletion of groundwater aquifers, and uneven distribution of rainfall.

  • Droughts reduce crop production.  In the U.S. during 2012, severe drought impacted 67% of cattle production and about 70-75% of corn and soybean production. Soybean yields that year were the lowest in almost a decade.
  • An intense downpour falling on dehydrated soil can cause topsoil runoff and can damage growing plants.

As levels of CO2 increase, plant growth will spike -- but nutritional value may fall.  

  • Studies show that protein concentrations in barley, wheat, rice, and potato will decline by 6% to 15% when grown in the CO2 levels projected for the year 2100.
  • Protein concentration may be replaced with elevated levels of carbohydrates (starch and sugars).
  • In response to high levels of atmospheric CO2, cereal and staple crops will likely have lower concentrations of many nutrients important to human health, including iron, zinc, calcium, magnesium, copper, sulfur, and phosphorous.

Livestock production affects climate change

  • 18% of global greenhouse gases are attributed to livestock production. If we take a closer look, 39% of agriculture's greenhouse gas total is attributed to methane, a powerful atmospheric warming compound. Methane is a greenhouse gas 86 times more potent than CO2 over its first 20 years in the atmosphere.  
  • Beef and milk contribute 41% and 20% of the livestock sector’s Greenhouse Gas (GHG) emissions.
  • In contrast, some meat sources produce much less methane.  Pork contributes 9% of the livestock sector’s GHG emissions.  Poultry and eggs contribute only 8%.

Certain populations are particularly vulnerable to agricultural effects from climate change.

  • Reductions in food yield and food quality, as well as climate-related disturbances to transportation and distribution, can severely affect vulnerable populations’ access to sufficient quantities of nutritious, affordable food.
  • Growing urban populations that rely heavily on the global food market will be vulnerable to supply issues.
  • Losses of nutritional value and access to food will be felt disproportionately by infants, children, pregnant women, the elderly, low-income populations, agricultural workers, and those with weakened immune systems.


Page Updated October 6, 2016