County Sustainability Group  

Table 1. Climate Change Impacts on Human Health*

Heatwaves are not only increasing in frequency, intensity and duration, but their nature is changing. Warmer nighttime temps [double the increase of average temperature since 1970 (Karl et al.)] and higher humidity (7% more for each 1ºC warming) that raises heat indices and makes heat-waves all the more lethal.
Asthma and allergies. Asthma prevalence has more than doubled in the U.S. since 1980 and several exacerbating factors stem from burning fossil fuels. Increased CO2 and warming boost pollen production from fast growing trees in the spring and ragweed in the fall (the allergenic proteins also increase). Particulates help deliver pollen and mold spores deep into the lung sacs. Ground-level ozone primes the allergic response (and O3 increases in heat waves). Climate change has extended the allergy and asthma season two-four weeks in the Northern Hemisphere (depending on latitude) since 1970. Increased CO2 stimulates growth of poison ivy and a chemical in it (uruschiol) that causes contact dermatitis
Infectious disease
The spread of infectious diseases is influenced by climate change in two ways: warming expands the geographic and temporal conditions conducive to transmission of vector-borne diseases (VBDs), while floods can leave “clusters” of mosquito-, water – and rodent-borne diseases (and spread toxins). With the ocean the repository for global warming and the atmosphere holding more water vapor, rain is increasing in intensity -- 7% overall in the U.S. since 1970, 2”/day rains 14%, 4”/day rains 20%, and 6”/day rains 27% since 1970 (Groisman et al., 2005), with multiple implications for health, crops and nutrition. Tick-borne Lyme disease (LD) is the most important VBD in the U.S. LD case reports rose 8-fold in New Hampshire in the past decade and 10-fold (and now include all of its 16 counties). Warmer winters and disproportionate warming toward the poles mean that the changes in range are occurring faster than models based on changes in average temperatures project. Biological responses of vectors (and plants) to warming are, in general, underestimated and may be seen as leading indicators of warming due to the disproportionate winter (Tminimum or Tmin) and high latitude warming.
Pests and disease spread across taxa: forests, crops and marine life. Pests and diseases of forests, crops and marine life are favored in a warming world. Bark beetles are overwintering (absent sustained killing frosts) and expanding their range, and getting in more ] generations, while droughts in the West dry the resin that drowns the beetles as they try to drive through the bark. (Warming emboldens the pests while extremes weaken the hosts.) Forest health is also threatened in the Northeast U.S. (Asian Long-horned beetle and wooly adelgid of hemlock trees), setting the stage for increased wildfires with injury, death and air pollution, loss of carbon stores, and damage to oxygen and water supplies. In sum, forest pests threaten basic life support systems that underlie human health.
Crop pests and diseases are also encouraged by warming and extremes. Warming increases their potential range, while floods foster fungal growth and droughts favor whiteflies, aphid and locust. Higher CO2 also stimulates growth of agricultural weeds. More pesticides, herbicides and fungicides (where available) pose other threats to human health. Crop pests take up to 40% of yield annually, totaling ~$300 billion in losses (Pimentel) Marine diseases (e.g., coral, sea urchin die-offs, and others), harmful algal blooms (from excess nutrients, loss
of filtering wetlands, warmer seas and extreme weather events that trigger HABs by flushing nutrients into estuaries and coastal waters), plus the over 350 “dead zones” globally affect fisheries, thus nutrition and health.

Winter weather
Increasing winter weather anomalies is a trend to be monitored. More winter precipitation is falling as rain rather than snow in the Northern Hemisphere, increasing the chances for ice storms, while greater atmospheric moisture increases the chances of heavy snowfalls. Both affect ambulatory health (orthopedics), motor vehicle accidents, cardiac disease and power outages with accompanying health effects.
Drought. Droughts are increasing in frequency, intensity, duration, and geographic extent. Drought and water stress are major killers in developing nations, are associated with disease outbreaks (water borne cholera, mosquito-borne dengue fever (mosquitoes breed in stored water containers)), and drought and higher CO2 increase the cyanide content of cassava, a staple food in Africa, leading to neurological disabilities and death.

Food insecurity.
Food insecurity is a major problem worldwide. Demand for meat, fuel prices, displacement of food crops with those grown for biofuels all contribute. But extreme weather events today are the acute driver. Russia’s extensive 2010 summer heat-wave (over six standard deviations from the norm, killing over 50,000) reduced wheat production ~40%; Pakistan and Australian floods in 2010 also affected wheat and other grains; and drought in China and the U.S. Southwest are boosting grain prices and causing shortages in many nations. Food riots are occurring in Uganda and Burkino Faso, and the food and fuel hikes may be contributing to the uprisings in North Africa and the Middle East. Food shortages and price hikes contribute to malnutrition that underlies much of poorhealth and vulnerability to infectious diseases. Food insecurity also leads to political instability, conflict and war.

*The Case for Young People and Nature: A Path to a Healthy, Natural, Prosperous Future. Hansen, James et al, p 20.

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