Estimated carbon sequestration benefit under climate change: a case study of the Mediterranean shrublands maquis

Climate projections in the Mediterranean region point to a potential acceleration of climatic trend, with rising air temperatures (1-6 °C) in the 21st century and a precipitation amount decrease by 22% from April to September. Climate change could significantly affect carbon (C) acquisition in Mediterranean areas considering that spring rainfall is more important than total annual rainfall. Climate change could make these ecosystems more vulnerable because in contrast to forests growing on comparable soils, shrubs are less capable of exploring deeper soil layers for water. The contribution of Mediterranean ecosystems to the global carbon cycle has received low attention in the past and few estimates have been carried out to date. Species, composition and structure of the Mediterranean shrublands developing along the Latium coast (Italy) were analyzed in order to evaluate their contribution to C sequestration, also taking into consideration the economic benefits at a national level. The total yearly CO2 sequestration was calculated multiplying the total photosynthetic leaf surface area of each species by the mean yearly photosynthetic rate and the total yearly photosynthetic activity time (in hours). Taking into account the frequency of species, the total CO2 sequestration of the Mediterranean maquis was quantified by 80 Mg CO2 ha-1year-1, corresponding to 22 Mg C ha-1year-1. From a monetary point of view, this quantity could be valued to more than 500 US$ ha-1 year1. Extending this benefit to the Mediterranean shrublands throughout the whole country, we obtained a nationwide estimated annual benefit in the order of $500 million