Ecosystem Service Arguments Enhance Public Support for Environmental Protection - But Beware of the Numbers!

- A survey-based experiment tests the effects of pro-environmental arguments on public support for environmental protection.
- Arguments based on the loss of ecosystem services significantly reduce approval of an environmentally harmful hydropower dam.
- Moral-ecological arguments for environmental protection are even more effective in reducing dam approval.
- Combining the two types of arguments reduces dam approval the most.
- Including monetary values of ecosystem services can either decrease or increase dam approval

The trend in the discourse around environmental protection towards arguments based on ecosystem services and monetary valuation has prompted considerable controversy among academics and practitioners concerned with conservation. This paper informs the debate by exploring which arguments are most effective in garnering support for environmental protection. In a survey-based online experiment, participants stated their level of (dis)approval of a large-scale hydropower dam project after being presented with various kinds of arguments and information about the environmental impacts. The results show that ecosystem service arguments reduced levels of approval of the dam significantly (i.e. they increased support for environmental protection). However, moral-ecological arguments for protecting the environment proved even more effective, while a combination of both types of arguments reduced the dam approval ratings the most. Including a cost-benefit analysis (CBA) with monetary valuation of the costs of losing ecosystem services altered dam approval upwards or downwards, depending on the outcome of the CBA. The approval rates of males, of older participants and of politically right-wing participants were particularly sensitive to the outcomes of monetary valuation. More research is needed to understand the short and long term influence of different environmental discourses on peoples' judgments and levels of environmental concern.