Tuesday, 23 December 2014

Is short-rotation plantation forestry in Asia sustainable?

Sustainable management of agricultural and forestry systems is one of the most important challenges facing people all over the world. As we strive to feed, house and provide for a rapidly growing and increasingly affluent global population, we need to produce more. At the same time we need to make sure that the production systems we use don’t diminish our ability to produce in the future.

Much of the public commentary about the sustainability of plantation forestry has not been informed by good science. A new ACIAR Technical Report (Sustainable plantation forestry in South-East Asia) has changed the debate. This report is the first comprehensive scientific study on the sustainability of fast-grown plantations of eucalypts and acacia trees.
Eucalypts and acacias have been planted in Asia for over 60 years. They were first introduced to help address shortages of fuelwood and timber. Their suitability to a wide range of environments and good growth rates make them ideal for planting by smallholders and plantation companies.

Over the past 30 years, ACIAR has helped ensure that the use of these trees in Asia is based on good science. Working collaboratively with partner-country colleagues, Australian forestry scientists have helped Asia develop the techniques to grow eucalypts and acacias as short-rotation plantations to produce wood for pulp mills. The area of eucalypt and acacia plantations grown with rotations of 5-8 years in Asia has now grown to more than 7 million hectares.

Since the 1980s, there have been critics of the use of these trees in plantation forestry or social forestry schemes. They have been blamed for negative environmental effects such as reduction in water yield and depletion of soil nutrients. In addition, the critics consider the practice of repeated planting of short-rotation plantations of exotic trees to be unsustainable.

In forestry, sustainability is a complex issue, with both technical and time dimensions. One of the most important dimensions is whether or not the productivity of the site is maintained over time. If the yield of wood products declines from one rotation of trees to the next, then the practices used are not sustainable.

Dr Nuyen Hoang Nghia and Mr Stephen Midgley, who have collaborated for 25 years on ACIAR projects in Vietnam, inspect a plantation of Acacia auriculiformis near Hue in central Vietnam. (Photo: Tony Bartlett/ACIAR).

The new report, written by former CSIRO forestry scientists Drs Chris Harwood and Sadanandan Nambiar, includes reviews of actual inventory data from successive rotations of fast-grown plantations in five countries: Indonesia, Malaysia, Vietnam, China and Thailand.

The purpose was to see how the final yields from these plantation crops vary over time. The researchers found that, in most situations, the mean yields are actually increasing over time, rather than decreasing. However, as pointed out clearly in the report, there are a range of other issues that, if not addressed, will impact on plantation yields in the future. These include the way the sites are managed between and during rotations, and the increasing incidence of disease.

The report emphasises that sustainability is not a destination but a journey, and that further research and creative partnerships are required for successful progress.

By Tony Bartlett, ACIAR Research Program Manager for Forestry

More information: 

Sustainable plantation forestry in South-East Asia (2014), ed. C.E. Harwood and E.K.S. Nambiar. ACIAR Monograph No. 84, Australian Centre for International Agricultural Research.

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