Fig. 1. Comparison of the recreational vs. climate implications of eutrophication.

A The welfare gain, 2015–2050, from a 40% reduction in phosphorus (P) loading to western Lake Erie reducing the frequency and extent of harmful algal blooms (HABs). The range of economic impact on recreational angling was estimated from the annual welfare gain¹⁷ assuming constant annual benefits and a 3% yr⁻¹ discount rate. The welfare gain from this same total P loading to Lake Erie was estimated from the corresponding reduction in CH₄ emissions (and CO₂-equivalent emissions) through 2050, using estimates and methods reported in Table 2. B The welfare cost of seasonal Lake Erie HABs sufficient to close beaches, 2015–2050. Benefit transfer work²⁰ estimates the 95% confidence interval of daily recreational losses from the closure of all 67 Lake Erie beaches in Ohio and Michigan. We aggregate to seasonal (115 day)³⁹ HABs occurring annually, 2015–2050, using a 3% yr⁻¹ discount rate. Methane cost estimates are derived from methane emissions under nutrient concentrations that would lead to closure of all of these beaches due to high chlorophyll from HABs as well as from chlorophyll levels that would lead to moderate risk of adverse health effects from beach use.