Peculiarities of the Mediterranean area

Since the formation of ozone (O3) requires sunlight, O3 concentrations show a clear increase from the northern parts to the southern parts in Europe, with the highest concentrations around the Mediterranean basin where ozone precursor emission, temperature and solar radiation are usually high, especially during summertime. In the South-western European Mediterranean Basin, high annual mean ozone concentrations, exceeding 40 ppb, were recorded and are higher than for the rest of Europe (Sicard et al., 2013). Despite a significant decrease of O3 precursor’s emissions over the Western part of the European Mediterranean basin, between 2000 and 2010, we showed that the O3 background level increased at urban and suburban stations, and slightly decreased at rural stations. The O3 control measures are effective at rural sites, while O3 concentrations are increasing in the cities (Sicard et al., 2013). The Mediterranean area can be considered a test area for studying global change and is the highest O3 risk in Europe, relative to human well-being and vegetation impacts (Sicard and Dalstein-Richier, 2015).

Environmental problem targeted - Climate change, air pollution and sanitary impacts

According to the Intergovernmental Panel on Climate Change (IPCC), there is a robust scientific consensus that human-induced climate change is occurring. The Earth surface is projected to warm by 1.40 to 5.80°C over the next 100 years, with land areas warming more than oceans and high latitudes more than the tropics (IPCC, 2007). The difference should be 3°C in the Mediterranean Basin that will be one of the areas subject to the most drastic reductions in precipitation. Even if atmospheric concentration of CO2 were stabilized at today’s concentrations, global average surface temperatures would likely continue to increase by 0.3-0.9ºC by 2100. As an example, in South-eastern France, the air temperature increased by 0.46 to 1.08°C in the last 20 years (Sicard and Dalstein-Richier, 2015). Tropospheric ozone is an important atmospheric pollutant and a significant contributor to climate warming (greenhouse gas). Current levels are high enough to negatively affect trees by inducing visible leaf symptoms (Paoletti, 2006), decreasing foliar chlorophyll content, accelerating leaf senescence, decreasing photosynthesis, growth and carbon sequestration, predisposing to pest attack and a variety of other physiological effects in plants.

Forests have significant functions for economic and recreational purposes (Kohut, 2005), environmental protection and nature conservation. Climate change and air pollution are two significant interacting stressors affecting the sustainable management of EU forests. Climate change and air pollution interact in affecting forests by changes in soil processes, tree growth, species composition and distribution, plant susceptibility to stressors, fuel built-up and fire danger, water resources, pest outbreaks. These disturbances can reduce forest productivity and change the distribution of tree species and individuals.

Towards a new legislative European standard to protect vegetation

Critical levels are defined as the “concentration, cumulative exposure or cumulative stomatal flux of atmospheric pollutants above which direct adverse effects on sensitive vegetation may occur according to present knowledge”. To protect vegetation, current European standards use the O3 exposure index AOT40, i.e. the cumulative exposure to O3 hourly concentrations exceeding 40 ppb over the daylight hours of the growing season (Directive 2008/50/EC). Ozone effects on vegetation depend not only on the atmospheric concentrations but also result from an imbalance between the internal O3 dose, i.e. the O3 uptake through the stomata into leaves or needles.
The stomatal flux-based approach estimates the amount of O3 that is absorbed into the leaves or needles through stomata and integrates the effects of multiple climatic factors, vegetation characteristics and local and phenological inputs on O3 uptake or flux. Phytotoxic Ozone Dose above a threshold Y of uptake (PODY) is the accumulated stomatal O3 flux over the growing season and can be modelled using the Deposition of Ozone and Stomatal Exchange model (DO3SE). Currently, PODY is under discussion as new European legislative standard. However, there is no scientific consensus regarding the time-window for POD accumulation and a validation of the threshold Y under field conditions is still missing. To date, most experiments to establish biologically relevant plant responses to O3, such as visible foliar injury, have been performed on seedlings under controlled conditions that are not representative of actual field conditions, so that the results may not help developing realistic standards. Epidemiological studies, where large-scale biological responses are compared with field data, may provide useful information for establishing the best standards and thresholds for forest protection from O3 and deriving new stomatal flux-based critical levels (CLef) for forest protection.

The main objectives of FO3REST were (i) to evaluate the performance of O3 risk metrics, i.e. POD0, POD1 and AOT40, by a large-scale field investigation in Southern Europe, (ii) to define which threshold Y is the most biologically-based; (iii) to determine the best time-window of PODY accumulation; (iv) to assess the most important environmental variables that affect crown defoliation, discoloration and visible foliar O3 injury of adult trees under field conditions; (v) to suggest new epidemiologically-based O3 critical levels for forest protection and (vi) to rank forest species on the basis of their sensitivity to ambient O3 in mature trees.

Why is it important to develop standards based on ozone absorbed by plants?

Ozone is the pollutant of most concern to vegetation health, because it is a strong phytotoxic oxidant gas. Concentrations in the air, however, are not representative of actual impacts on vegetation, as injury occurs only when O3 is absorbed into the plant. In contrast, the present European standard for vegetation protection, AOT40, is based on O3 concentrations in the air. AOT40 is inadequate to assess O3 damage to vegetation, and to derive scientifically-sound thresholds. AOT40 does not account for the different effects of tree species, genotype, forest type and site conditions on the plant capacity to absorb O3. To date, most experiments to establish biologically relevant plant responses to O3 are performed under controlled conditions, which are not representative of actual field conditions and may not provide realistic results for developing standards for protecting vegetation. Epidemiological evidence from the FO3REST project suggests that the responses of vegetation to O3 are related to the absorbed flux through stomata, i.e. the specialized apertures that allow plants to exchange gases with the atmosphere. The FO3REST project allowed suggesting new O3 flux-based critical levels for Mediterranean forest protection against O3 pollution.

Although the project focuses on Mediterranean forests, does it contribute to the development of a harmonised forest monitoring scheme for Europe?

The Mediterranean region is the most exposed to O3 pollution in Europe, and climate change is expected to be more pronounced in the Mediterranean Basin. Mediterranean environments, however, can be considered as a key study. Most European countries carry out forest monitoring, but the different approaches used by the countries make comparisons at the European level problematic. This creates difficulties in e.g. the EU actions for halting the loss of forest biodiversity and actions related to climate change. We need a harmonized European forest monitoring scheme.
The FO3REST results will serve as a harmonized forest monitoring technique concerning O3 monitoring and as a decision-support tool for national and European authorities. European standards may use this refinement of criteria and thresholds, more appropriated, to protect vegetation. The application of the FO3REST method to other European regions contributes to the convergence and policy leading up to the harmonization and effectiveness of forest monitoring by providing a framework for research and analysis.

Project significantly biodiversity-related

Forests are a major host of EU biodiversity and help to regulate the climate by taking up CO2 from the air and storing carbon. Climate change is a significant and increasing pressure on forests. Climate change and air pollution interact in affecting forest biodiversity by changes in soil processes, tree growth, species composition and distribution, plant susceptibility to stressors, fuel built-up and fire danger, water resources, pest outbreaks. These disturbances can reduce forest productivity and change the distribution of tree species and individuals. Global warming and loss of biodiversity are among the most prominent environmental issues of our time. FO3REST aims at developing more appropriated indicators for a more coherent policy on EU forest adaptation in response to the challenges of climate change. FO3REST contributed and will contribute to the achievement of EU Biodiversity targets, by developing a better understanding of climate change effects on biodiversity, resilience and associated services, and identifying ways to improve the legal and policy frameworks. FO3REST addressed EU-Target 3 by improving the targeting of policy instruments required for development and application of effective biodiversity conservation. FO3REST improved EU policy making and evaluation, particularly information for the implementation of EU forest protection and biodiversity policy area and increased awareness to promote biodiversity conservation. More information and awareness-raising is needed to reduce biodiversity loss and stimulate long lasting changes in EU and the world.

Expected results and environmental benefits

This project enabled the validation of the stomatal flux model, the refinement of criteria and the suggestion of validated thresholds for the protection of forests against ozone and climate change. These results will serve as a decision-support tool for European authorities in favour of the implementation of a climate change effects observatory, forest management and implementation of a follow-up system of biodiversity. With information in hand, policymakers can make informed decisions about proposed changes to legislation and associated activities. The indicators are needed to improve understanding and monitoring of the effects of air pollutants on ecosystems and to scientifically assess the effectiveness of air pollution control strategies (assessment of the effects-based ozone precursor emission reduction strategies) in Europe. The European standards will use these proper criteria and thresholds to protect vegetation. The establishment of a list of sensitive tree species interests the forest managers for the conservation of forest by an adapted global management. Adaptation measures are needed to ensure that the ecosystem services provided by forests will be maintained under future climates. Sustainable forest management is essential for reducing the vulnerability of forests to climate change.

Expected longer term results - Science-policy integration and policy input

FO3REST will (i) bridge gaps between science-policy-practice, (ii) link European policy goals of preserving biodiversity/forests and promoting sustainable ecosystem management, (iii) integrate scientific and traditional and local knowledge and (iv) develop a new long-term and short-term problem-solving by developing and employing reflective, trans-disciplinary and participatory research, knowledge exchange and learning. FO3REST directly addresses issues in the EU 2020 Biodiversity Strategy, the Seventh Environment Action Programme of the EU and the EU Forest Strategy (2013). It relates to aims of the UN Convention on Biological Diversity, the Framework Convention on Climate Change, the Millennium Ecosystem Assessment and the Common Agricultural Policy. Climate change is a significant and increasing pressure on forests that will alter habitats and ecosystems. In March 2010 a Green Paper on “Forest Protection and Information in the EU: preparing forests for climate change” (COM(2010)66) was released, as a follow-up to the White Paper on “Adapting to Climate Change: towards a European Framework for action” (COM(2009)147). The Spring European Council endorsed vision and targets on 26 March 2010, noting that "there is an urgent need to reverse continuing trends of biodiversity loss and ecosystem degradation". The Council recognized the importance of halting the loss of biodiversity and the degradation of ecosystem services in the EU by 2020: “Our life insurance, our natural capital: an EU biodiversity strategy to 2020” (COM(2011)244). More information and awareness-raising is needed to reduce the indirect drivers of biodiversity loss and stimulate the lasting changes in Europe and the world.