Farming carbon: an economic analysis of agroforestry for carbon sequestration and dryland salinity reduction in Western Australia

摘要

The widespread removal of native trees from the agricultural zone and replacement with annual crops and pastures is a major cause of dryland salinity in Australia. It has been recognised that a large proportion of the landscape needs to be replanted to trees to prevent further salinisation. However, for much of the agricultural zone, agroforestry is not an option due to lack of species that can viably generate the products currently demanded by the market. The emerging carbon market may provide a new agroforestry option for landholders, through carbon sequestration. This analysis assesses the viability of growing trees for the purpose of selling carbon credits, from a landholder’s perspective. Benefits of trees in preventing the onset of dryland salinity are accounted for. Two regions in Western Australia; a low rainfall (330 mm/year) region and a medium rainfall (550 mm/year) region, are analysed. At the expected carbon price of A$15/tCO2-e, growing trees for carbon is not a viable alternative for landholders in the low rainfall region, due to low sequestration rates. In the medium rainfall region, growing trees for carbon and timber is a viable alternative; however the opportunity costs of land mean the carbon price would still need to be higher than expected for growers to choose this alternative. Accounting for the salinity prevention benefits makes growing trees a more attractive investment for landholders in both regions. However in both regions, even after accounting for salinity benefits, the price of carbon would need to be A$25–A$46/tCO2-e higher than expected to make growing trees a worthwhile investment.