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

Climate change impacts on society and the environment Climate change impacts human health, agriculture, weather patterns, infrastructure, and extinction rates. The World Health Organization states, “Climate change is expected to cause approximately 250,000 additional deaths per year, from malnutrition, malaria, diarrhea and heat stress” [1]. Since the 1980s, each decade has been warmer than the previous one, with 2021 recorded as the sixth hottest year since planetary temperatures have been recorded [2]. Extreme temperatures account for more than five million deaths each year globally, making up 9.4% of all deaths between 2000 and 2019 [3]. According to the UN Office for Disaster Risk Reduction, economic losses have increased by 151% due to climate-related disasters. The total economic loss from extreme heat in the United States is over $100 billion annually due to productivity losses; this number is predicted to rise to $500 billion annually by 2050 [4]. Sea level has risen 21–24 cm since 1880 [5]. Kulp and Strauss estimate that 630 million peo- ple live on land projected to sit below annual flood levels by 2100 [6]. Flooding due to climate change also impacts food and water supplies as saltwater intrusion endangers access to freshwa- ter. The global urban population facing water scarcity is projected to increase from 933 million people in 2016 to 2.4 billion people in 2050 [7]. Climate change is expected to reduce maize crop yields by 24% as early as 2030 [8]. Roma´n-Palacios and Wiens warn that if climate change

continues to increase at the current rate, up to 30% of their study’s 538 animal and plant species may face extinction within 50 years, even with an expected shift in the species’ niches [9]. Americans are among the top emitters of carbon dioxide per capita. Because of the severe climatological, ecological, and societal effects of greenhouse emissions, understanding the pro- cess of climate change and options to limit or resolve it should be a priority for the United States. Climate change in educational settings Educational topics, and the time devoted to them, often change depending on the knowledge and needs of society. For example, Gangwani and Landin found that insect-based lessons declined in U.S. textbooks after the 1950s, when pesticide use eased the agricultural and health effects of insects on American society [10]. Textbooks shifted to expand molecular biology top- ics after 1960 following seminal DNA and genetics research publications [11]. Textbook fig- ures of cell anatomy changed following the publication of a revised illustration in Scientific American in 1961 [10]. Given the serious effects of climate change, its growing influence over human society, the high impact of U.S. carbon emissions, and the massive increase in research and publications related to the topic, we would expect comparable coverage of the topic in American educational settings. Science teachers exhibit denial of, or confusion about, climate change. Plutzer et al. exten- sively studied teachers’ classroom methods and educational backgrounds pertaining to climate

change [12]. They found that, while most teachers cover the topic, 31% report sending explic- itly contradictory messages in effort of teaching “both sides.” Almost one-third of the teachers emphasized that recent global warming is “likely due to natural causes,” and 12% do not emphasize human causes at all. Fewer than half of teachers reported formal education in cli- mate change in college. Only 29 U.S. states and the District of Columbia have educational standards that address anthropogenic climate change. The National Council for Science and the Environment evalu- ated state science standards in 2020; while Wyoming was the only state to receive an A for how it addressed climate change, 10 states received a D or worse, including populous states such as Florida and Texas [13]. PLOS ONE Climate change in biology textbooks, 1970–2019 PLOS ONE | https://doi.org/10.1371/journal.pone.0278532 December 21, 2022 2 / 16 Competing interests: The authors have declared that no competing interests exist.