7.01.01 - Detection and monitoring
Within the Divison’s mission we aim to exchange and share the evolving knowledge about detecting, monitoring and evaluating effects from air pollution and climate change on forests to contribute towards a solid risk assessment for forest ecosystems. While the effects of air pollution and climate change on forest ecosystems are complex and interactive the harmonization and quality assurance of applied methods for detection, monitoring and evaluation becomes even more important.
To gain a more profound knowledge of 'hot spots' in terms of air pollution and climate change effects on forests we consider our main objective to provide an international network for scientists, policy makers and representatives of local and regional governments and institutions for i) data and knowledge exchange, and ii) quality assurance and harmonization of the ongoing monitoring initiatives.
In the past, the main emphasize was on tropospheric ozone pollution as tropospheric ozone is considered to be particularly relevant for the linkages between climate change and air pollution. However, considering the expected increase of the global average surface temperature and the simultaneous alteration in precipitation patterns (IPCC, 2007) air pollution effects, in particular of tropospheric ozone, may change as well. The respective future findings based on detection, monitoring and evaluation will allow us a more profound understanding of the mechanisms to estimate a solid risk assessment for forest ecosystems.
State of Knowledge
Public concerns, evidence from research and increasing scientific knowledge are all driving widespread discussions on air pollution, climate change, and forest health problems. The issue is characterised by multi-causality with different strengths of association. This means that the links between exposures and their consequences depend on the environmental pollutants and conditions being considered, and are also influenced by factors such as genetic constitution, age, nutrition and adaptation. Many air pollutants and greenhouse gases have common sources, contribute to radiative balance, interact in the atmosphere, and jointly affect ecosystems. Tropospheric ozone (O3) is particularly relevant for the linkages between climate change and air pollution. Climate change, on the one hand, influences O3 concentrations through dynamical and chemical changes in the atmosphere. On the other hand, increasing background O3 concentrations affect climate change because O3 is a potent greenhouse gas itself and indirectly influences the lifetime of other greenhouse gases such as methane. In addition, surface O3 causes the most concern because of its phytotoxic potential. (From Schaub and Paoletti, 2007, Environmental Pollution, in press).
A key and as yet only partly answered question is what threat does ground level O3 pose to forest ecosystems? In order to address this, the United Nations Economic Commission for Europe (UN-ECE) has adopted an effectsbased approach, using the critical loads/levels concept in 1996. However, there is a general agreement that cumulative O3 uptake, the instantaneous rate at which O3 is absorbed via the stomatal opening, would lead to a biologically relevant estimate of O3 risk as compared to external exposure indices such as AOT40, SUM0, and mean ambient O3 concentrations. As such, there was the objective to develop a modeling approach, which could be applied to estimate and map stomatal O3 flux to major vegetation types across Europe. This move resulted in the establishment of a provisional flux and flux response model in order to estimate the ozone risk assessment for forest ecosystems (UN-ECE, 2004). (From Schaub et al., 2007, Environmental Pollution 145:636-643).
It is estimated that 49% of forests (17 million km2) will be exposed to damaging concentrations of tropospheric O3 by 2100. Global forest area at risk from S deposition may reach 5.9 million km2 by 2050, despite SO2 emission reductions of 48% in North America and 25% in Europe. Although SO2 levels have decreased, emissions of NOx are little changed, or have increased slightly. In some regions, the molar SO4/NO3 ratio in precipitation has switched from 2/1 to near 1/1 during the past two decades. Coincidentally, pattern shifts in precipitation and temperature are evident. A number of reports suggest that forests are being affected by air pollution. Yet, the extent to which such effects occur is uncertain, despite the efforts dedicated to monitoring forests. Routine monitoring programmes provide a huge amount of data. Yet in many cases, these data do not fit the conceptual and statistical requirements for detecting status and trends of forest health, nor for cause–effect research. There is a clear need for a re-thinking of monitoring strategies. (From Percy and Ferretti, 2004, Environmental Pollution 130:113-126).
For further state of knowledge summaries please refer to the 'Publications and references' section.