Consequences of omitting non-lethal wildlife impacts from stated preference scenarios

Stated preference (SP) research on willingness to pay (WTP) for improvements to wildlife populations focuses almost universally on measures related to whether organisms live or die. Preferences for changes in non-lethal harm to wildlife are generally overlooked. To evaluate the consequences, this article develops a theoretical model and corresponding discrete choice experiment (DCE) to evaluate whether and how the omission of information on non-lethal wildlife harm influences WTP estimation, grounded in a case study of marine plastic reductions in the North Atlantic. The theoretical model suggests that when environmental programs have both lethal and non-lethal impacts on wild species, DCEs that omit information on the latter may not produce valid welfare measures. Empirical results show that the omission of this information has multiple impacts on welfare estimates, largely consistent with theoretical predictions. Results suggest that welfare estimates for wildlife improvements can be confounded by the omission of information on non-lethal harm from SP scenarios. Results also demonstrate the hazards of excluding potentially welfare-relevant information from SP scenarios when respondents might assume relationships between omitted information and other material included in the questionnaire.