Weather and Populations

Weather has tremendous effect on the populations of earth. All species have been shaped by experiences related to weather conditions. From the last Ice Age to modern-day global warming, weather trends have had an impact on the world’s flora and fauna. Displacement, changes in physical and mental health, the spread of disease and even death can be attributed to weather. The effects of weather can spread through populations, changing them clearly or subtly. Those populations in turn can affect another, the ramifications rippling out across the globe. <?xml:namespace prefix = o ns = “urn:schemas-microsoft-com:office:office” />

Severe weather is a catalyst for displacement. This was seen recently after Hurricane Katrina nearly destroyed New Orleans. The storm was one of the deadliest in the recorded history of the United States. Of the survivors, nearly twenty percent have not returned to the city. Of those who chose to return, many now experience sub-standard living conditions, lack of available jobs and poor health conditions.

During the 1930’s, the American central and south central states experienced several years of extreme drought and heat. These conditions coupled with poor agricultural practices resulted in what was called The Dust Bowl.’ The effect of the heat and lack of rain had an obvious effect on the crops of the region; nothing grew in the arid soil. With no ground cover to keep the soil in place, great dust clouds and storms blew across the land. Hampered by the dust and with no crops to sell, the farmers had little choice but to leave in search of other employment. As the farmers left, the town stores they had solicited lost business, forcing many to close. These displaced people moved to various regions in the United States, but none so heavily as the west coast. People already living in the area found they were losing out on job opportunities to the refugees. Conflicts often arose between the two groups. Local governments and aid groups were also affected by the inundation of people unable to find jobs. The Dust bowl is attributed with lengthening the Great Depression. The extension of the Depression resulted in greater displacement when people moved to look for work and food.

Weather can have a strong effect on peoples’ health and quality of life. A sunny day may briefly help brighten someone’s day, yet could be detrimental to his or her overall health. Without proper protection, sunlight can damage eyes and skin. Taking into account proper sun-protection practices, a group of people living in New Mexico or Australia is at greater risk of developing skin cancer than a similar group living in Vancouver or London.

There are studies that examine the effects of extreme heat and cold on both mortality and morbidity (the number of diseases in a given population). In 2003 France experienced a severe heat wave. The French National Institute of Health and Medical Research attributes eighteen thousand deaths to the intense heat. The effect of extreme cold does not seem as drastic, but is enduring and just as consequential. There can be a significant number of deaths due to severe cold through exposure. After a cold wave has passed, people may still die from stress to their systems brought on by the cold. Intense cold weather affects incidences of cardiovascular and respiratory disease. In general the population groups most affected are the elderly and the very young.

Weather affects mental health in many ways. Certain behavioral and emotional disorders can be exacerbated by extreme heat. One of the most common effects of weather on mental health is Seasonal Affective Disorder, or SAD. Lack of sunlight can trigger strong psychological responses in people. They can develop symptoms such as fatigue, lethargy and depression. SAD is a form of depression, and as such is treatable. The prevalent treatment is light therapy. When people have survived a severe weather event such as a hurricane or a tornado, they may suffer emotional trauma. Survivors may develop depression or anxiety or experience such deep feelings of guilt for surviving that they contemplate suicide.

Populations can be affected by weather in more subtle ways as well. Vector-borne disease is one that is transmitted from the infected organism to another organism via an agent. Familiar agents include the mosquito, flea and tick. The human population in Medieval Europe lived in close proximity to rats and fleas. In the early fourteenth century rats carrying fleas from the east began to arrive in Europe. They were carrying the virus Yersinia pestis, the plague bacillus that caused bubonic plague or The Black Death. Severe weather across Europe had weakened people and left them more susceptible to disease. The already weakened humans suffered severely, losing close to one quarter of the total population. The consequences of the plague reached around the globe and are still with us today.

Humans have a better understanding today of what causes disease and how to control the spread of contagion. Even so, we are still susceptible to infection. In 2006 there were six reported cases of bubonic plague in New Mexico. The outbreak was blamed on an explosion in rodent population following unusually high amounts of rainfall. Rainfall can also affect mosquito populations. An increase in local mosquito population may directly affect a neighboring human population through the spread of diseases such as malaria or the West-Nile virus.

Weather is much more than a sunny Saturday forecast or a rained-out round of golf. Weather has drastic effects on all earthly populations. From crops to insects to humans, the impacts of weather can be sudden or subtle. Weather may determine demographic shifts, the spread of disease, or mortality rates in any given species. Recent changes in global temperatures open new avenues for exploration and study. Perhaps humanity can learn from collective past experiences to better serve earth’s populations in our uncertain future.

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Weather and Populations

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