We address the need for a more systematic and comprehensive investigation of affect and emotion in the environmental domain and introduce the Environmental Trait Affect Questionnaire (ETA-Q), an instrument assessing an individual's disposition to experience affect in several types of environmentally relevant situations. Across five studies (N_total = 9064), we confirm that individual differences in Environmental Trait Affect can reliably be described using five factors. We map the nomological network of these factors and demonstrate that they contribute substantially to the prediction of environmental judgment and decision-making in several decision situations, including consumption, investment, donation, and political decisions, over and above previously identified predictors of environmental decision-making. By investigating the interactions of ETA-Q factors with specific decision situations, both in experimental tasks and in real-life situations, we point out new strategies to leverage the adaptive function of affect and emotions to tackle a fundamental challenge of our time.