Myrtle rust (Puccinia psidii s.l.) on fruit of Rhodamnia sessiliflora, Queensland.
Sustainable forest management aims to maintain the productive capacity of native forests and plantations to provide the goods and services required by society while maintaining ecosystem health and vitality.
This criterion contains two indicators. The first considers the scale and impact of agents and processes affecting forest health and vitality, mainly pests and diseases, but also other environmental factors such as drought and extreme weather events. The second indicator considers the impacts of forest fire, and presents data on the area of forest burnt by planned and unplanned fires.
Forest health and vitality are affected by vertebrate browsers, invertebrates (mainly insects), pathogens and weeds, but also by other potentially damaging processes such as drought, river regulation, soil changes, extreme climatic events, and climate change. Australia's forests are adapted to many of these disturbances, and impacts are generally followed by periods of recovery.
Many pests and diseases, particularly native ones, exhibit cyclical patterns of impact on native forests, and are generally of minor overall concern. Active management of agents affecting forest health is directed mainly at the protection of commercial values in multiple-use public and private native forests and plantations, and the protection of biodiversity and other forest values in all forests. In most states and territories, forest health surveillance is carried out regularly, to detect and identify the extent and severity of problems. Forest health surveillance is mainly undertaken in plantations, with the aim of detecting disease, insect and vertebrate pests, weeds, and nutrient deficiencies, and monitoring the impacts of these on tree survival and growth.
Vertebrate animals, both native and exotic, can damage forests by browsing and ring-barking vegetation, contributing to soil erosion, competing for food and habitat, and killing native fauna. Insect pests in Australian forests include defoliating leaf beetle and moth larvae, psyllids, aphids, sawflies, weevils, bark beetles, wood wasps and wood borers. The exotic root-rotting pathogen Phytophthora cinnamomi and related species, which occur in all states and territories, kill a wide range of plant species, and a range of fungal leaf pathogens can have significant impacts on hardwood and softwood plantations. Weeds compete with native forest flora and can become locally dominant, reducing biodiversity and other values. Weeds can also affect tree establishment, growth and product yield in commercial forest plantations, and reduce the ease of human access.
A wide range of persistent or intermittent crown dieback syndromes occurs to some degree in native forests in all states and territories, often resulting in significant tree mortality and associated ecosystem impacts. These syndromes are usually caused by combinations of factors such as climatic stresses, poor land management practices, severe insect attacks, and an imbalance in insect predator levels; ameliorating their impacts through forest management can be difficult.
Other factors that can affect forest health include river regulation, dryland salinity, soil acidification and drought. Drought, in particular, can cause production losses in plantations, including by increasing the susceptibility of trees to disease and pests.
Fire is a major component of the ecology of most Australian forests. Eucalypt forests, in particular, accumulate large amounts of flammable fuel, and the various types of eucalypt forest burn naturally with a characteristic seasonality, frequency and intensity (known collectively as the 'fire regime'), followed by regeneration and regrowth. Flora and fauna species have a range of adaptations for surviving fire, and the absence of fire or changed fire regimes are threats to many ecosystems and specifically to forest health. However, wildfire can be very dangerous to life and property, especially in south-west and eastern Australia, where the combination of climate and vegetation is particularly conducive to producing catastrophic fire conditions.
Fire is also an important forest management tool in Australia. Planned fire of the appropriate intensity is used in fire-adapted forest types to reduce fuel loads and increase the ability to manage subsequent unplanned wildfire, to promote forest regeneration after wood harvesting, to promote the health of forest stands, and for biodiversity management. Forest fires, both planned and unplanned, burn annually across large areas of the woodland forests of northern Australia.
Understanding the role of climate change and climate variability is important for management of planned and unplanned fires. Projected climate change may exacerbate the risk of unplanned fire, and reduce the opportunity for safe use of planned fire.
Banksia seed pod open after a fire event, Scamander, Tasmania.
Key findings are a condensed version of the Key points presented at the start of individual indicators in this criterion.
In general, native insect pests and pathogens caused only low-severity damage to forest ecosystems over the reporting period. Most of the observed damage to forests was caused by exotic pests and pathogens that have become established in Australia. Occasional outbreaks caused damage that adversely affected commercial values, particularly in plantations.
Quambalaria shoot blight caused damage in spotted gum plantations in Queensland, and fungal leaf pathogens caused occasional significant defoliation in plantations in Tasmania, Victoria, Queensland and Western Australia. Teratosphaeria (Kirramyces) leaf spot emerged as a major problem for eucalypt plantation establishment in the central-coast region of Queensland. Spotted gum canker became a health issue for Corymbia species in New South Wales. Spring needle cast remained one of the major problems affecting the radiata pine plantation estate, and Dothistroma needle blight had an impact on radiata pine plantations in Victoria and New South Wales.
Phytophthora cinnamomi and a number of other Phytophthora species remained a threat to a wide range of plant species, predominantly in regions with an average annual rainfall of more than 600 millimetres. Spread of this pathogen is controlled with soil and water hygiene protocols, monitoring of quarries used in road-building, intensive monitoring to designate disease risk areas, and the use of management zones to protect threatened flora.
Myrtle rust (Puccinia psidii78), a strain of guava or eucalypt rust, established and spread in New South Wales, Queensland and Victoria. Rust spores can be spread by the wind, and myrtle rust has a wide host range within the Myrtaceae family, but the likely impact of myrtle rust on Australia's forests is still unclear.
A number of tropical cyclones caused significant damage to native forests and plantations in Queensland during the reporting period, including cyclone Larry in March 2006, cyclone Ului in March 2010, and cyclone Yasi in February 2011. Cyclone Yasi was the largest and most powerful on the eastern coast of Australia since 1918, and the extensive cyclone damage impacted industry confidence in the viability of future forest plantations in coastal regions of Queensland.
Native and plantation forests affected by drought, fire and cyclones were colonised by pests such as bark beetles and ambrosia beetles during the reporting period. The pine-killing Sirex wood wasp remained a significant issue, although it had only localised adverse impacts. Sirex was detected for the first time in Queensland in this reporting period.
Drought affected large areas of the south-eastern states of Australia during much of the early part of the reporting period, and large areas of Western Australia for most of the reporting period, with significant impacts on forest health. Projected drier and warmer conditions in the rest of this century and beyond could make forests more susceptible to some pests and diseases.
The Australian plantation industry is a significant user of biological control agents. Chemical pest and disease control methods used in plantations are highly regulated, and the Australian plantation forestry sector has been estimated to spend less than 1% of the total Australian spending on pesticides.
An estimated 39.0 million hectares of forest was burnt by fire in Australia in the period 2006-07 to 2010-11. This estimate combines data derived from MODIS satellite imagery for northern Australia, with data provided by states and territories for southern Australia, and includes some areas of northern Australia that were burnt more than once during this period. A total of 77% of the forest area burnt was in the Northern Territory and Queensland. The reported forest area burnt increased by 14.3 million hectares compared with 2001-02 to 2005-06, with the increase mostly in the Northern Territory and Queensland.
From 2006-07 to 2010-11, unplanned fires (wildfire) burnt an estimated 31.6 million hectares (81% of total forest burnt), and planned fires burnt an estimated 7.4 million hectares of forest (19% of total forest burnt).
In southern Australia, all states and the ACT experienced serious bushfires over the reporting period. The most extensive bushfire activity was in Victoria, especially areas near Melbourne, with the Black Saturday bushfire of 2009 being exceptionally serious.
Projected climate change could exacerbate the risk and impact of unplanned fire, and reduce the seasonal time 'window' in which planned fires can be used for management, especially in southern Australia. National fire research priorities are identified in the National Bushfire Management Policy Statement for Forests and Rangelands.
A planned fuel reduction burn in native production forest in Victoria.