Coverage of climate change in introductory biology textbooks, 1970–2019

physiology, and five (45%) studied cell or molecular biology. Only two other authors focused on science education or science writing. This increase in the percentage of authors who studied cell or molecular biology, or the decline in authors focused on science communication, sup- ports the idea that the author’s expertise and interest may play a role in the textbook’s coverage of environmental issues. Location of climate change passage in textbooks We predicted that the start location of the passage addressing climate change would move for- ward in the book, as an indication of its growing importance. However, the start location of the passage moved toward the rear of the book. Biology textbooks usually organize content from small-scale concepts (i.e., molecular biol- ogy and cell anatomy) to large-scale topics (i.e., evolution and ecology). However, this organi- zation dates from the 1930s when biology, rather than organismal topics of botany and zoology, took hold in the curriculum. The 1934 textbook Biology for Today by Curtis, Caldwell, and Sherman was the first to group conservation, reproduction, and evolution at the back of the book [16]. These topics are arguably most controversial and, given the documented omis- sions of end chapters and the timing of this arrangement (the 1930s marked a turning point in biology textbooks due to the anti-evolution movement, eugenics and other race-related top- ics), it is likely that the placement allowed these topics to be easily excluded. Over time, repro-

duction shifted forward in the book to be addressed with heredity or physiology, and evolution moved forward to be addressed following cellular topics. These shifts left conserva- tion issues as the last topic covered in the book. Climate change content analysis and figure analysis We found mixed outcomes in our analysis of content. Passages shifted from providing only a simple description of the greenhouse effect to including more coverage of the effects of a warming climate. Sentences incorporated a greater range of effects, mirroring the data pre- sented in the passage’s figures. The increased variety of effects of climate change, presented through examples and data figures, could improve students’ acceptance of climate change through inductive reasoning. However, content addressing actionable, productive solutions peaked in the 1990s and has decreased in the past two decades. This creates an uncomfortable message for students, that climate problems are large and without solutions, and reinforces helplessness, anxiety, and depression [31]. Additionally, the solutions to climate change addressed in textbooks focus on national or international actions, leading students to believe that their individual actions are inconsequen- tial. While a single person has a small impact on carbon emissions, textbooks and other instruc- tional materials contribute to the education of millions of young people. Awareness of industrial carbon contributions could change consumer practices and impact corporate deci-

sion-making. Concentrating on political solutions is disconnected from the textbook’s audience since fewer than half of 18-25-year-olds engage in political elections [32, 33]. However, family planning, transportation and housing options, and food choices are prominent issues for this age group and are among the most influential individual behaviors on carbon emissions. While we acknowledge that textbooks emphasize descriptions of concepts and processes rather than advice on personal behaviors, there are examples of such content dealing with other biological topics. Textbooks of the early 20th century frequently included advice about hygiene, agriculture, and nutrition. Modern textbooks often include sidebars or breakout boxes on topics such as sexually transmitted disease, skin cancer, endocrine disrupting PLOS ONE Climate change in biology textbooks, 1970–2019 PLOS ONE | https://doi.org/10.1371/journal.pone.0278532 December 21, 2022 12 / 16