The latest scientific studies prove that the climate is changing significantly compared with recent eras. These studies confirmed that this change is developing much faster than was expected some years ago. From the Fourth Assessment Report “Climate Change 2007” presented by the IPCC (Intergovernmental Panel on Climate Change) we can deduce that, from a scientific approach, there is no doubt that humans are the main cause of global warming.
But climate change also has other effects as a consequence of increase in temperature: changes in rainfall patterns, melting of polar ice caps, alteration of salinity and acidification of the oceans, ocean circulation change, extreme meteorological events...
Climate change in the Mediterranean
Although there is still much uncertainty about the particular effects that climate change will cause in different areas, most mathematical models show that the Mediterranean basin will be one of the most strongly affected areas by climate change. Models expect annual average temperature in southern Europe to increase by about 0.2-0.6ºC every ten years.
Models forecast a substantial increase in water shortage, due in larger part to the increase of temperatures than to the decrease in rainfall; therefore, the risk of drought in summer will increase around southern Europe.
A study, coordinated by the MEDCIE Southeast (Studies and Development of Interregional and European Cooperations) in 2008, on climatic simulations, showed that mean temperatures could increase of 2.1°C by 2030 and 5.2°C by 2080 at the regional scale (Provence-Alpes-Côte-d’Azur). Some areas in Southern Europe are subjected to high ozone levels caused by the road traffic and industrial emissions, combined with the strong hot season of the Mediterranean climate and megalopolis contribution (Marseille, French Riviera, Genova, Po River plain in Italy). Visible leaf injury on particularly sensitive species is one symptom of this pollution.
What are the impacts on forests?
As trees are long-lived organisms they are likely to be particularly vulnerable to the rapid change in climate predicted for the 21st century. Mediterranean forests will be especially vulnerable to negative impacts in a context of global warming.
Climate change affects some species phenology (advance in flowering or rising of pollinators) and the geographical distribution of plants. Some species will follow altitudinal or latitudinal migrations with changes in structure and composition of communities.
While deforestation is responsible for approximately one quarter of global greenhouse gas emissions, healthy forests have the capacity to remove CO2 from the atmosphere, thus mitigating climate change, as well as influencing water cycles and reflectivity of the earth’s surface. These changes may alter the capacity of plants to fix CO2 and could diminish the current capacity of forests to mitigate climate change effects.
Due to the alteration in temperature conditions, humidity and concentration of CO2 in the atmosphere, trees and other plants living in forests may undergo metabolic and physiologic changes: short-term changes (productivity, evaporation and transpiration) or long-term changes (modification of nutrient reserve and new plant communities).
In addition, climate change will increase frequency and intensity of forest plagues, fires and other perturbations such as a decrease of annual production and growth of trees.
The climate change highlights the ozone problem = Environmental issues targeted
Indeed, global warming will also have effects on background ozone levels. A significant correlation is observed between ozone concentrations, global radiation, relative humidity and temperatures (Sicard et al., 2009).
Furthermore, O3 acts as a strong greenhouse gas in the free troposphere, the third most important greenhouse gas, and as such is a significant contributor to climate change. The warming effects of tropospheric ozone are about 25% of that contributed by CO2.
Ozone is an important air quality issue and causes serious health problems and damage to materials and ecosystems (De Leeuw et al., 2000). At the moment, the greenhouse gas tropospheric ozone is the most worrying atmospheric pollutant for ecosystems and forests.
The project FO3REST will allow the refinement of criteria and thresholds for Mediterranean forest protection against ozone and climate change.