Trade-offs between timber production and biodiversity in rainforest plantations: emerging issues and an ecological perspective
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During the past two centuries there have been three major paradigm shifts in the management of Australian rainforests and the use of their timbers: from felling native forests towards growing plantations; from viewing forests and plantations as mainly providers of timber to viewing them as sources of multiple benefits (e.g., timber, biodiversity, carbon sequestration, catchment protection, recreation, regional economic development); and from timber plantations being developed mainly by government on public land towards those established by private citizens, companies, or joint venture arrangements, on previously-cleared freehold land. Rainforest timber plantations are increasingly established for varied reasons, and with multiple objectives. Landholders are increasingly interested in the biodiversity values of their plantations. However, there are few guidelines on the changes to plantation design and management that would augment biodiversity outcomes, or on the extent to which this might require a sacrifice of production. This paper presents a conceptual framework for considering the interactions and trade-offs between biodiversity values and timber production within plantations of rainforest trees in the Australian tropics and subtropics, and discusses aspects of design and management that are likely to affect the outcomes. Three forms of trade-off are discussed: those related to plantation design and management, those connected with timber harvest cycles, and those involving landscape issues and site configurations (allocation of different areas for different primary goals). Existing knowledge suggests that plantation design, harvesting, and management regimes which maximise timber production will make a limited contribution to sustaining rainforest biodiversity. Different designs and management regimes may be able to produce better synergies between timber production and biodiversity, but to determine this will require: (1) implementation of a greater range of plantation designs, including those which purposefully aim for differing combinations of biodiversity and production, established in different landscape contexts; (2) quantitative assessments of both biodiversity and timber production made simultaneously at a range of these sites, at an appropriate stage of their development; and (3) a built-in research component, which includes biodiversity expertise, at the initial stages of large-scale tree-planting schemes. Measurements on existing sites, such as those planted during the CRRP scheme in the Wet Tropics, are providing some useful data, but a wider range of plantation designs and management regimes also needs to be established and monitored. Further development and application of site-based methods for quantitatively monitoring biodiversity values within mixed purpose plantation projects is also needed; these include assessment methods for plantations within environmental certification (e.g. eco-accreditation) schemes.
Reforestation in the Tropics and Subtropics of Australia Using Rainforest Tree Species