Thou shalt not sell nature: How taboo trade-offs can make us act pro-environmentally, to clear our conscience

•Money-nature trade-offs are morally offensive and thus considered 'taboo', unthinkable.•Taboo trade-offs induce compensation 'moral cleansing' behaviour.•We study if money-nature trade-offs induce 'cleansing' pro-environmental behaviour.•Money-nature trade-offs increased participants' decision to act pro-environmentally.

Many nature/natural areas are threatened by economic development and urban expansion. Oftentimes nature is not considered part of the cost/benefit analyses preceding such economic development, and most people find it offensive to price-tag nature. To pit (sacred) nature-values against other monetized values (these are so-called taboo trade-offs) is seen as morally offensive. Non-nature related taboo trade-offs (e.g. between life-saving and money-saving) were found elsewhere to induce moral cleansing - attempts to reaffirm one's own moral position by performing overly moral 'cleansing' behaviour. This study investigated whether trade-offs between nature as sacred value and money as secular induces such moral cleansing in shape of pro-environmental behaviour (PEB).A laboratory experiment measured self-reported (hypothetical) and real donations to an environmental cause, after participants were presented with a taboo or non-taboo trade-off. Taboo trade-offs affected participants' real, but not hypothetical behaviour. Findings support prior evidence that confrontation with certain trade-offs affects people's behaviour, and expand the scope of sacred values to include nature, and moral cleansing-behaviour to PEB.