Climate Change Mitigation, Air Pollution, and Environmental Justice in California.

Climate change mitigation policies can have significant co-benefits for air quality, including benefits to disadvantaged communities experiencing substantial air pollution. However, the effects of these mitigation policies have rarely been evaluated with respect to their influence on disadvantaged communities. Here we assess the air pollution and environmental justice implications of California's cap-and-trade mitigation program through analysis of (1) the sources of air pollution in disadvantaged communities, (2) emissions-reduction offset usage under the cap-and-trade program, and (3) the relationship between reductions in greenhouse gas emissions and reductions in co-pollutant emissions. Our analysis suggests that the cap-and-trade program has limited impacts, including limited disproportionate impacts, on air quality in disadvantaged communities. The sources of most air pollution in these communities have not been subject to the cap-and-trade program, and the use of emissions-reduction offsets is only marginally higher in disadvantaged communities than in other communities. Furthermore, reductions in greenhouse gas emissions imply smaller proportional reductions in co-pollutant emissions. While climate policies lead to important air quality co-benefits in some contexts, especially through reduced coal usage, targeted air quality policies and regulations may be more effective for reducing air pollution in disadvantaged communities in California and throughout the state.

Climate-driven risks to the climate mitigation potential of forests.

Forests have considerable potential to help mitigate human-caused climate change and provide society with many cobenefits. However, climate-driven risks may fundamentally compromise forest carbon sinks in the 21st century. Here, we synthesize the current understanding of climate-driven risks to forest stability from fire, drought, biotic agents, and other disturbances. We review how efforts to use forests as natural climate solutions presently consider and could more fully embrace current scientific knowledge to account for these climate-driven risks. Recent advances in vegetation physiology, disturbance ecology, mechanistic vegetation modeling, large-scale ecological observation networks, and remote sensing are improving current estimates and forecasts of the risks to forest stability. A more holistic understanding and quantification of such risks will help policy-makers and other stakeholders effectively use forests as natural climate solutions.