The potential of greenhouse sinks to underwrite improved land management: A case study from Western Australia

The current agricultural systems of broad areas of Australia are unsustainable, with large projected increases in salinisation, decreases in water quality and losses of biodiversity. Increased concentrations of greenhouse gases have been linked to global warming. The international response to this warming, the United Nations Framework Convention on Climate Change and its Kyoto Protocol, include provisions that enable greenhouse sinks, or the sequestration of carbon in soils and vegetation to be used by Parties as one strategy to fulfil their obligations. The Kyoto Protocol, which is yet to be ratified by Australia, also allows for trading in emission reductions, and this opens the possibility that investment in carbon sinks may help underwrite broader natural resource management objectives. This paper describes a study that examined the possibilities for improved land management in Western Australia arising from the development of carbon sinks. This considered (a) the likelihood of a carbon market developing and the likely depth of that market as a result of current national and international policies, (b) the data available to provide estimates on different types of sinks and (c) the likely benefits of wide-scale sink investment. The study was designed to quantify an upper limit to sink potential. It was estimated that the total amount of carbon that could be sequestered by revegetating 16.8 Mha of cleared farmland was 2.2 Gt CO2-e, and 3.3 Gt CO2-e by destocking 94.8 Mha of Western Australian rangelands. It was considered that there were insufficient data to produce estimates of sequestration following changes in tillage practice in cropping systems or the revegetation of already salinized land. We conclude that carbon sinks are only likely to become profitable as a broad-scale stand-alone enterprise when carbon prices reach A$15/t CO2-e. However, below this price their value can be significant as an adjunct to reforestation schemes that are aimed at providing other products (wood, pulp, bioenergy) and land and water conservation benefits. Irrespective of this, carbon sinks provide an opportunity to both sequester carbon in a least-cost fashion and improve soil and watershed management.