Which property of $\mathrm{CO}_2$ makes it biologically and geo-chemically important ?

The property of low solubility of carbon dioxide in water makes it biologically and geo-chemically important. Carbon dioxide on reaction with water form carbonic acid, which dissociates to give $\mathrm{HCO}_3^{-}$ions. $\mathrm{H}_2 \mathrm{CO}_3 / \mathrm{HCO}_3^{-}$ buffer system helps to maintain pH of blood between $7.26-7.42$.