7.01.00 - Impacts of air pollution and climate change on forest ecosystems
Mission: to promote international cooperation, to encourage an interactive process between scientists, policy makers and representatives of local to regional governments and institutions, in order to share scientific knowledge and harmonize effective strategies aimed to reduce the risk for forests related to air pollution and climate change.
Rationale: There is an increasing awareness in both the science and policy communities of the importance of addressing the linkages between the traditional air pollutants and greenhouse gases. Many air pollutants and greenhouse gases have not only common sources, but also their emissions interact in the atmosphere, and may join to cause a variety of environmental impacts on the local, regional and global scales. Many air pollutants contribute to the Earth’s radiative forcing. Examples are nitrogen oxides, carbon monoxide and non-methane volatile organic compounds which are precursors to tropospheric ozone. Tropospheric ozone is particularly relevant for the linkages between climate change and air pollution. Climate change, on the one hand, influences ozone concentrations through dynamical and chemical changes in the atmosphere. On the other hand, increasing background ozone concentrations affect climate change because ozone is a potent greenhouse gas itself and indirectly influences the lifetime of other greenhouse gases such as methane. Other examples of linkages between air pollution and climate change are: i) SO2 contributes to acidification and also plays a role in climate change, partly off-setting the greenhouse effect due to increased amounts of sulphate aerosols in the atmosphere; ii) acidification and nitrogen deposition affect emissions of CH4 and N2O in some ecosystems; iii) increased temperatures affects nitrate leaching; iv) climate change may alter atmospheric transport patterns of air pollutants and the sensitivity of ecosystems for acidifying deposition; v) CO2 emissions are almost entirely produced by burning fossil fuels, which is also an important source of several air pollutants; vi) emission of volatile organic compounds may be affected by both climate and pollution, and in turn affects air quality by stimulating the formation of O3 and secondary organic aerosol (SOA); vii) anthropogenic airborne particulate matter may interact with forests (deposition, biomass burning); viii) climate change induced stratospheric cooling is likely to delay the recovery of the stratospheric O3 layer by approximately 20 years. In turn stratospheric O3 determines tropospheric OH levels, important for air pollution, and the amount of detrimental UV radiation arriving at the earth’s surface.
Aim: to address complex effects of air pollution and climate change on forest ecosystems through an active interaction between specialists in several areas of forest sciences. Monitoring of forest responses, climate and pollution as well as biogeochemical, hydrological, physiological, biochemical and genetic effects are addressed, with a main aim of providing prospects for adaptation and mitigation.
State of Knowledge
The impacts of air pollution and climate change on ecosystems have been investigated in many studies in the last decades. These studies showed, for example, that climate change has already affected plant distribution, or that nitrogen deposition has large impacts on ecosystem species composition. Impacts of climate change and air pollution on ecosystems interact in two basic ways: (a) climate change can modify the effects of exposure of ecosystems to air pollution, and vice versa; (b) air pollution can change sensitivity of ecosystems to specific impacts of climate change. The exposure of ecosystems to air pollution can change as a result of phenological changes induced by climate change (e.g., changes in the length of the growing season) as well as by altered spatial and temporal distribution of air pollutants through new weather patterns. Their sensitivity may change as a result of, inter alia, climate-induced changes in ecosystem vitality, soil processes and biodiversity. More recent results are synthesized in our summary reports from the RG7.01 biennial conferences (see Publications).