The contingent valuation method has been applied to quantify
the economic benefits associated with a wide range of wildlife
species. See Richardson and Loomis (2009) for a summary of
studies applying this method to quantify the total economic value
of threatened, rare, and endangered species. Regarding wildlife
viewing opportunities specifically, this method has been applied to
value general wildlife viewing nationwide (Aiken and La Rouche,
2003), wildlife viewing in the state of Pennsylvania