11.8.1.3 Co-benefits for agricultural production

While a strong body of literature demonstrates that there are important co-benefits from GHG mitigation and health benefits from improved air quality, there has been less research addressing co-benefits from improved agricultural production. The potential positive, long-term, effect of higher CO₂ concentrations on plants can be counteracted by short-term damage from increased air pollution. The effects of tropospheric ozone exposure on plant tissues and crop yields are well established, and the scientific literature has already been reviewed in US EPA (1996) and EC (1999). Chameides et al. (1994) estimate that 10–35% of the world’s grain production is in locations where ozone exposure may reduce crop yields. Surface ozone levels are sensitive to, inter alia, NO_x and VOC emissions from fossil-fuel-burning power plants, industrial boilers, motor vehicle exhaust, gasoline retail outlets, and N-fertilizer-induced soil emissions of NO_x.

Using an atmospheric ozone formation model and an economic general-equilibrium model, O’Connor et al. (2003) find, for a CO₂ mitigation strategy in China, that the monetary benefits from increased agricultural productivity due to lower ground-level ozone are comparable to the health benefits. Together, these benefits would allow China a 15–20% CO₂ reduction without suffering a welfare loss. Agricultural benefits have important distributional implications. When agricultural effects are not taken into consideration, poor rural households experience welfare losses from carbon mitigation even at low levels of abatement. Once agricultural effects are considered, rural households in this study enjoy welfare gains up to a ten percent abatement rate. So while a purely health-based measure of ancillary benefits tends to show benefits from a climate commitment to be urban-biased, a broader definition of benefits alters the picture considerably.

11.8.1.4 Co-benefits for natural ecosystems

A few studies have pointed out co-benefits of decarbonization strategies from reduced air pollution on natural ecosystems. VanVuuren et al. (2006) estimate that, in Europe, compared to an energy policy without climate targets, the implementation of the Kyoto protocol would bring acid deposition below the critical loads in an additional 0.6 to 1.4 million hectares of forest ecosystems, and that an additional 2.2 to 4.1 million hectares would be protected from excess nitrogen deposition. The exact area will depend on the actual use of flexible instruments, which allow for spatial flexibility in the implementation of mitigation measures but do not take into consideration the environmental sensitivities of ecosystems that are affected by the associated air pollution emissions. Syri et al. obtained similar results (2001).

While sustainability and the protection of natural ecosystem have turned out to be important policy drivers in the past (for example in the case of the emission reduction protocols of the Convention on Long-range Transboundary Air Pollution for Europe), there is no generally accepted method for quantifying the monetary value of the existence and function of natural ecosystems. It therefore continues to be difficult to include co-benefits on natural ecosystems in a comprehensive monetary cost-benefit calculation of mitigation measures.