Victoria’s mountain ash forests naturally thin their trees. So why do it with machines? – The Conversation

Report on Forest Management and Sustainable Development Goals (SDGs)

Introduction

Global discussions have intensified regarding optimal forest management strategies amid climate change and increasing bushfire frequency. This report examines the implications of mechanical thinning in forests, with a focus on Victorian mountain ash forests, and emphasizes the relevance of Sustainable Development Goals (SDGs) in guiding forest management practices.

Mechanical Thinning in Forest Management

Mechanical thinning involves the removal of a proportion of trees using machinery to increase the size of remaining trees. It is commonly applied in timber plantations to accelerate timber development. The Victorian government’s new forest plan includes a “healthy forests” program likely to implement extensive mechanical thinning to reduce tree density and increase spacing.

Key Questions Raised by Mechanical Thinning

• What are the ecological effects of mechanical thinning?
• Could mechanical thinning be harmful to forest ecosystems?
• Is mechanical thinning necessary for maintaining forest health?

Current Knowledge on Thinning and Its Impacts

Effects on Wildfire Risk

Research indicates thinning can reduce severe wildfire risk in some forest types (e.g., certain US pine forests). However, in Australian eucalypt forests, thinning may have no effect or potentially exacerbate fire severity. Australian forestry manuals warn of increased fire risks associated with thinning.

Water Yield and Drought Resilience

Thinning has been shown to temporarily increase water yield and drought resilience in some forests, including tall eucalypt forests. However, these benefits are short-lived due to rapid plant regeneration in thinned gaps.

Environmental and Economic Costs

• Soil compaction and degradation
• Increased bushfire risk
• Habitat degradation for wildlife
• Carbon emissions from machinery
• High financial costs (approximately $A1830 per hectare in the US)

Natural Self-Thinning Process

Forests naturally undergo self-thinning, where tree density decreases over time as larger trees outcompete smaller ones for resources. This ecological principle shapes forests globally and reduces the need for human intervention.

Findings from Victorian Mountain Ash Forests

Natural Self-Thinning Quantified

A recent study quantified natural self-thinning in mountain ash forests, showing a 50-60% reduction in tree density from young (15 years post-fire) to old growth forests (over 120 years). Tree densities decreased from approximately 7000 to 1450 trees per hectare.

Variation by Species and Terrain

• Young forests dominated by thousands of wattles and eucalypts per hectare
• Old growth forests contain fewer than 100 eucalypts and about 20 wattles per hectare
• Tree density varies with slope, elevation, light, moisture, and soil properties

Importance of Tree Size Diversity

As forests mature, trees become larger and more varied in size, creating habitats essential for wildlife such as arboreal marsupials and birds, supporting SDG 15 (Life on Land).

Implications for Forest Management and SDGs

Benchmark for Restoration Practices

The study provides a natural benchmark for forest development without human intervention, guiding restoration efforts aligned with SDG 15 (Sustainable Management of Forests).

Risks of Mechanical Thinning

• Potential to increase bushfire risk and degrade habitats
• Compromises water security, impacting SDG 6 (Clean Water and Sanitation)
• Generates carbon emissions, affecting SDG 13 (Climate Action)
• Financial inefficiency and resource misallocation

Recommendations for Sustainable Forest Management

1. Prioritize ecological evidence-based management to avoid risky interventions like widespread mechanical thinning.
2. Allocate funding to restoration activities targeting areas where forest regeneration has failed, particularly after logging operations.
3. Recognize and support natural self-thinning processes to maintain biodiversity and ecosystem health.
4. Integrate forest management policies with SDGs, emphasizing climate resilience, biodiversity conservation, and sustainable resource use.

Conclusion

Effective forest management is critical under changing climate conditions. Evidence indicates that mechanical thinning is unnecessary and potentially harmful in Victorian mountain ash forests. Sustainable practices that align with the SDGs—particularly SDG 13 (Climate Action), SDG 15 (Life on Land), and SDG 6 (Clean Water and Sanitation)—should guide future forest management to enhance ecosystem resilience, conserve biodiversity, and ensure long-term forest health.

1. Which SDGs are addressed or connected to the issues highlighted in the article?

1. SDG 13: Climate Action
   • The article discusses forest management in the context of climate change and increasing bushfires.
2. SDG 15: Life on Land
   • The article focuses on sustainable forest management, biodiversity conservation, and restoration of native forests.
3. SDG 6: Clean Water and Sanitation
   • Thinning’s impact on water yield and drought resilience relates to water security.
4. SDG 12: Responsible Consumption and Production
   • Discussion on the cost-effectiveness and environmental impact of mechanical thinning relates to sustainable resource management.

2. What specific targets under those SDGs can be identified based on the article’s content?

1. SDG 13: Climate Action
   • Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters (addressing bushfire risks).
   • Target 13.2: Integrate climate change measures into policies and planning (forest management policies).
2. SDG 15: Life on Land
   • Target 15.1: Ensure the conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services (forest restoration and natural self-thinning).
   • Target 15.2: Promote the implementation of sustainable management of all types of forests (avoiding harmful mechanical thinning).
   • Target 15.5: Take urgent action to reduce the degradation of natural habitats (addressing habitat degradation from thinning and logging).
3. SDG 6: Clean Water and Sanitation
   • Target 6.4: Increase water-use efficiency and ensure sustainable withdrawals (related to water yield and drought resilience benefits from thinning).
4. SDG 12: Responsible Consumption and Production
   • Target 12.2: Achieve sustainable management and efficient use of natural resources (cost and environmental impact of thinning practices).

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

1. Indicators related to SDG 13 (Climate Action)
   • Frequency and severity of bushfires in forest areas.
   • Extent of forest area affected by climate-related hazards.
2. Indicators related to SDG 15 (Life on Land)
   • Forest tree density per hectare (e.g., reduction from 7000 to 1450 trees per hectare over time).
   • Proportion of native forest area restored or degraded (e.g., 20% of forests failed to regrow after logging).
   • Diversity of tree sizes and species composition in forests.
   • Habitat quality indicators for wildlife such as arboreal marsupials and birds.
3. Indicators related to SDG 6 (Clean Water and Sanitation)
   • Water yield measurements in forests before and after thinning.
   • Drought resilience metrics in forest ecosystems.
4. Indicators related to SDG 12 (Responsible Consumption and Production)
   • Cost per hectare of mechanical thinning operations.
   • Carbon emissions produced by forest management activities.
   • Soil compaction levels following mechanical thinning.

4. Table of SDGs, Targets and Indicators

Source: theconversation.com