The content of historical books as an indicator of past interest in environmental issues

In order to better understand public interest in environmental issues it is necessary to not only consider present and recent levels of environmental awareness, but to set a longer term historical baseline. Large databases derived from scanned historical books, such as Google Ngram, provide a resource which can be used to assess historical levels of interest in environmental issues. Historical trends in the occurrence of nine environmental indicator terms were analysed between 1800 and 2009, and it was found that usage of all terms was highest during the last 50 years of this period. However, the usage of seven of the indicator terms investigated has now peaked and is in decline, and in some cases this decline began around 20 years ago. The observed patterns may indicate reduced interest in the environment, acceptance of environmental issues, or shifting trends in the terminology used by the environmental movement.