Climate Change

Climate plays an important part in determining the average numbers of a species, and periodical seasons of extreme cold or drought seem to be the most effective of all checks. I estimated (chiefly from the greatly reduced numbers of nests in the spring) that the winter of 1854-55 destroyed ⅘ of the birds in my own grounds; and this is a tremendous destruction, when we remember that 10% is an extraordinarily severe mortality from epidemics with man. The action of climate seems at first sight to be quite independent of the struggle for existence; but in so far as climate chiefly acts in reducing food, it brings on the most severe struggle between the individuals, whether of the same or distinct species, which subsist on the same kind of food. Even when climate, for existence extreme cold, acts directly, it will be the least vigorous individuals, or those who have got the least food through the advancing winter, which will suffer most.

~ Charles Darwin (1809-02-12 1882-04-19 age:73) Origin Of Species