Mediterranean shrublands carbon sequestration: environmental and economic benefits

To date, only a few attempts have been done to estimate the contribution of Mediterranean ecosystems to the global carbon cycle. Within this context, shrub species, composition and structure of the Mediterranean shrublands developing along the Latium coast (Italy) were analyzed in order to evaluate their contribution to carbon (C) sequestration, also taking into consideration the economic benefits at a national level. The considered shrublands had a shrub density of 1,200 +/- 500 shrubs ha(-1). Shrubs were classified into small (S), medium (M) and large (L), according to their volume (V) and leaf area index (LAI). The total yearly carbon dioxide (CO2) sequestration per species (SCy) was calculated multiplying the total photosynthetic leaf surface area (spt) of each species by the mean yearly photosynthetic rate and the total yearly photosynthetic activity time (in hours). Q. ilex and A. unedo had the highest SCy (46.2 +/- 15.8 kg CO2 year(-1), mean value), followed by P. latifolia (17.5 +/- 6.2 kg CO2 year(-1)), E. arborea, E. multiflora, C. incanus, P. lentiscus, R. officinalis, and S. aspera (6.8 +/- 4.2 kg CO2 year(-1), mean value). The total yearly CO2 sequestration per shrub (SCshy) was 149 +/- 5 kg CO2 year(-1) in L, decreasing 30 % in M and 80 % in S shrubs. Taking into account the frequency of S, M and L and their SCshy, the total CO2 sequestration of the Mediterranean maquis was quantified in 80 Mg CO2 ha(-1) year(-1), corresponding to 22 Mg C ha(-1) year(-1). From a monetary viewpoint, this quantity could be valued to more than 500 US$ ha(-1) year(-1). Extending this benefit to the Mediterranean shrublands throughout the whole country, we obtained a nationwide estimated annual benefit in the order of $500 million.