Climate change effects onDurum wheat(Triticum durumL.) in Mediterranean area

This study work is carried out within the Agroscenari Project - Scenarios of adaptation to climate change in Italian agriculture, funded by the Ministry of Agriculture and Forestry with DM 8608/7303/08 of 7 August 2008. Within the different agricultural systems, this is the only work that considered rainfed agricultural systems with cereals as main crop, and specifically durum wheat. In the EU, too, cereals are the most widely produced crop. Cereals in fact account for over 50 % of some regions' UAA (Utilized Agricultural Area). Agricultural systems worldwide over the last 40-50 years have responded to the effects of the interacting driving forces of population, income growth, urbanization and globalization on food production, markets and consumption (Von Braun, 2007). To these forces can be added the twin elements of climate variability and climate change which have direct effects and serious consequences for food production and food security (Parry et al., 2004). Climate change is considered as one of the main environmental problems of the 21st century (Reidsma et al., 2010). It is definitively accepted that our climate is changing due to increased “greenhouse gases” atmospheric concentrations and this change is expected to have important impact on different economic sectors (eg. Agriculture, forestry, energy consumptions, tourism, etc) (Hanson et al., 2006). In particular, for agriculture, such a change in climate may have significant impacts on crop growth and yield, since these are largely determined by the weather conditions during the growing season. Even in temperate regions, there are some early warning signs of climate change impacts on the yields of some major crops like wheat. A slower increase in grain yields compared to past decades has been reported in a range of countries, including Europe. Specifically climate change is projected to have a significant impact on temperature and precipitation profiles in the Mediterranean basin. The incidence and severity of drought will become commonplace and this will reduce the productivity of rain-fed crops such as durum wheat. The semi-arid regions, like Mediterranean area, are particularly sensitive to climate change for their characteristic climate conditions and increases in temperatures and in rainfall variability could generate negative impacts because high summer temperatures and water stresses already now limit crop production, according to the latest Assessment Report of the IPCC, Climate-Change 2007 (IPCC, 2007). Durum wheat is a rain-fed crop that is widely cultivated over the Mediterranean Basin. The major climatic constraints to durum wheat yield in Mediterranean environments are high temperatures and drought, frequently occurring during the crop’s growth cycle (Porter and Semenov, 2005; Garcìa del Moral et al., 2003). As a consequence, projected climate changes in this region, in particular rising temperatures and decreasing rainfall (Gibelin and D´equ´e, 2003), may seriously compromise durum wheat yields, representing a serious threat to the cultivation of this typical Mediterranean crop. Different aspects of climate change, such as higher atmospheric CO2 concentration [CO2], increased temperature and changed rainfall all have different effects on plant production and crop yields. In combination, these effects can either increase or decrease plant production and the net effect of climate change on crop yield depends on the interactions between these different factors (F. Ludwig, S. Asseng,2006). Higher CO2 almost always increases plant production (Amthor, 2001; Poorter and Perez-Soba, 2001), but higher temperatures can, potentially, both increase or decrease grain yields (Van Ittersum et al., 2003; Peng et al., 2004). Assessments of climate change impacts on European agriculture (potential crop yield and biomass production) are examined using the Crop Growth Monitoring System (Supit et al., 2010) and suggest that in northern Europe, crop yields increase and possibilities for new crops and varieties emerge (Ewert et al., 2005; IPCC, 2007a; Olesen and Bindi, 2002). This study was carried out to assess the effects of climate change on Durum wheat yields at field scale using a crop growth simulation model, EPIC and a climatic scenarios in order to simulate the crop response in future weather conditions. The climate scenarios were generated by General Circulation Models (GCM) and adapted to the field scale through downscaling processes. Specifically ECHAM 5.4 and RAMS were used. Understanding the consequences of long-term climate change is important for the agricultural policies and the choice of mitigation strategies. If consider wheat yields as main parameter influenced by climate change, drought conditions were the main factors limiting grain yields on clay soil in a Mediterranean-type environment, in particular this condition was observed for the Oristano site. The simulation experiments with long - term historical weather records suggest that environments characterized by low rainfall have negative impacts on crop growth: future climate change including higher temperatures and less rainfall will reduce grain yields despite elevated atmospheric CO2. In fact the CO2 positive effects fail when we consider temperature and precipitations patterns in association with increased CO2 concentrations. Probably yields reduction, for Oristano site in the first set of results, was connected both to the falling of rain. The same simulation experiments carried out in the other two sites, Benevento and Ancona, showed a different situation: higher yields were observed in the future, maybe caused by higher future rainfall respect to the future condition. The results suggest priorization of adaptation strategies in the regions condisidered, including development of local cultivars of drought – and het resistant crop varieties, earlier planting to avoid heat stress, development and adoption of slower-maturing varieties to increase the grain filling period.