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Figures for the death toll vary widely by area and from source to source, and estimates are frequently revised as historical research brings new discoveries to light. Most scholars estimate that the Black Death killed up to 75 million people [5] in the 14th century, at a time when the entire world population was still less than 500 million.
Black Death. The Black Death was a bubonic plague pandemic that occurred in Europe from 1346 to 1353. It was one of the most fatal pandemics in human history; as many as 50 million people [2] perished, perhaps 50% of Europe's 14th century population. [3] The disease is caused by the bacterium Yersinia pestis and spread by fleas and through the ...
Appearance. Theories of the Black Death are a variety of explanations that have been advanced to explain the nature and transmission of the Black Death (1347–51). A number of epidemiologists from the 1980s to the 2000s challenged the traditional view that the Black Death was caused by plague based on the type and spread of the disease.
The environment can directly affect the survival of a small population. Some detrimental effects include stochastic variation in the environment (year to year variation in rainfall, temperature), which can produce temporally correlated birth and death rates (i.e. 'good' years when birth rates are high and death rates are low and 'bad' years when birth rates are low and death rates are high ...
Epidemiological transition. Diagram showing sharp birth rate and death rate decreases between Time 1 and Time 4, the congruent increase in population caused by delayed birth rate decreases, and the subsequent re-leveling of population growth by Time 5. In demography and medical geography, epidemiological transition is a theory which "describes ...
A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, widespread violence or intentional culling. Such events can reduce the variation in the gene pool of a ...
The effects of climate change on human health are increasingly well studied and quantified. [1] [2] Rising temperatures and changes in weather patterns are increasing the severity of heat waves, extreme weather and other causes of illness, injury or death. Heat waves and extreme weather events have a big impact on health both directly and ...
Decline in amphibian populations. The Golden toad of Monteverde, Costa Rica, was among the first casualties of amphibian declines. Formerly abundant, it was last seen in 1989. Since the 1980s, decreases in amphibian populations, including population decline and localized mass extinctions, have been observed in locations all over the world.