Broad-scale restoration of landscape function with timber, carbon and bioenergy investment

Salinization threatens up to 17 million ha of Australian farmland, major fresh water resources, biodiversity and built infrastructure. In higher rainfall (>600 mm yr-1) areas of south-western Australia a market-based approach has resulted in the reforestation of 250,000 ha of farmland with Eucalyptus globulus pulpwood plantations. This has had significant collateral environmental benefits in terms of reducing salinity and restoring landscape function in several key water supply watersheds. This success has not been replicated in the lower (300-600 mm yr-1) rainfall areas of this region, which is a global biodiversity hotspot. Wood yields are lower and there is often a land-holder preference to maintain existing agricultural activities. Several new forest products, such as sequestered carbon and biomass for renewable energy generation, are being evaluated as it is considered that a multi-product approach is more likely to be profitable than timber production alone. Carbon sequestration may occur both as an adjunct to wood production systems and also where restoration of biodiversity is the primary aim. The development of full markets for these products is dependent on the establishment of national emissions and renewable energy policies and targets, and in the case of liquid biofuels further technological development. Three broad approaches to integrating trees into the dryland farming systems are being assessed viz. (a) belts of trees with farming maintained in the alleys, (b) blocks of trees located on areas of water accumulation or of high recharge, and (c) short phases (3-5 years) of trees alternated with cropping. Both the alley and phase farming systems offer the prospect of producing biofuels from farmland without either using food-grains or displacing farming production. Paradoxically, for systems that are attempting to stabilize landscape hydrology, a major issue for reforestation is water management and this can be manipulated through species selection, tree placement and canopy management. If inappropriate species or planting densities are used, in relation to a site’s water supply, the trees will die. Although this is an aim of the phase farming system, for the other systems, avoidance of annual and periodic drought is a prime consideration