Productivity co-benefits for crops and trees from US power plant carbon standards
Power plants are the nation’s largest source of carbon dioxide emissions that contribute to climate change. They also release other pollutants like sulfur dioxide, nitrogen oxides and particulate matter, precursors to smog and soot that are harmful to humans, plants, and animals. Power plant carbon standards are aimed at curbing carbon dioxide emissions from the power sector to help address climate change. Depending on how the standards are designed, the policies may also decrease emissions of the smog and soot-causing pollutants, which can reduce harm to economically important trees and crops, helping them improve productivity.
This study analyzed the anticipated environmental co-benefits of three different power plant power plant carbon standard that would reduce carbon dioxide emissions by 2020. In a previous study, the researchers calculated and mapped the effects of the same three power plant carbon standards on surface-layer ozone concentrations across the country through 2020. In this new study, the researchers calculated how much tree and crop productivity benefit would be achieved via the projected ozone reductions under each policy scenario.
One policy option combines power plant upgrades with new end-user energy efficiency measures. This option is most similar to the EPA's proposed Clean Power Plan, and results in the largest air quality and health benefits. Another policy option only implements power plant upgrades. This option results in slightly lower air quality and adverse health effects. The third policy option mimics a national carbon tax. In this scenario, the tax combined with market forces drive the power sector to reduce carbon dioxide emissions. This policy option achieves the deepest cuts in carbon emissions, but does not produce the largest health benefits because this option lacks new end-user energy efficiency.
The team looked at the consequences of lower ozone for five crops whose primary growing season, June through August, corresponds with the peak season for ground-level ozone concentrations. They also evaluated the consequences for 11 tree species, including eastern cottonwood, black cherry, quaking aspen and several species of pine. These crops and trees have been used as standard indicators in environmental research. Based on previous research by crop and tree scientists, the team could relate their models’ ozone-exposure findings to the productivity of crop and tree species.
Under the highest performing scenario that most closely resembles EPA's Clean Power Plan, damage to corn production is reduced by 15.7 percent, damage to soybean production is reduced by 8.4 percent and damage to cotton cotton production is reduced by 6.7 percent.
Under the policy option focussed on power plant upgrades alone, the productivity of soybean, potatoes, and cotton is reduced about 1.5 percent, with only slight impacts on corn. These levels of production only slightly improve under a policy scenario that includes only “inside the fenceline measures” such as improving the efficiency of coal-fired power plants.
Under the policy option that resembles a carbon tax, the researchers project improvements for corn, soybeans, and cotton that are not as large as under the scenario that most closely resembles EPA's Clean Power Plan. Damage to corn productivity is reduced by 12.1 percent, damage to soybean productivity is reduced by 6.6 percent, and damage to cotton productivity is reduced by 3.8 percent.
Productivity among tree species, as measured in biomass yield compared to the reference scenario, also suggests that the plants will benefit from ozone-reducing policies. The tree species that are most susceptible to ozone damage, black cherry and eastern cottonwood, show damage to productivity is reduced by 7.6 and 8.4 percent respectively, under the scenario most like the Clean Power Plan.
These benefits to corn, soybean, cherry and cottonwood are nearly immediate and occur in urban and rural communities across the US.