Exploring Drivers of Change in Forest Ecosystems from the Tree to the Globe – US Forest Service (.gov)

Impact of Human Activities and Natural Disturbances on Forest Ecosystems and Carbon Stocks

Introduction

Human activities and natural disturbances are significantly influencing tree population dynamics and forest carbon stocks. While the United States has experienced a slow decline in its forest carbon sink due to these factors, global carbon stocks are increasing substantially. Understanding these impacts is crucial for informing the future potential and limitations of forest ecosystems, aligning with the Sustainable Development Goals (SDGs), particularly SDG 13 (Climate Action) and SDG 15 (Life on Land).

Forests as a Climate Change Mitigation Strategy

Forests play a vital role in mitigating climate change by reducing greenhouse gas emissions, contributing to the global target of net zero emissions by 2050 (SDG 13). To assess this potential, empirical data on current forest conditions and the drivers of ecosystem changes are essential.

Research Findings on Forest Demographics and Disturbances

1. Forest Demographic Index Development: Scientists at the Northern Research Station developed a standardized forest demographic index using remeasurement data from the National Forest Inventory (NFI).
2. Population Decline Observations: Significant population declines were observed in most tree species studied, with severe, size-dependent declines among subalpine species in montane forests of the western United States. These changes reflect shifts in forest size-structure driven partly by natural disturbances such as fire, insects, and disease.
3. Impact of Insects and Disease on Carbon Sequestration:
   • Forests affected by recent insect disturbances sequestered 69% less carbon in live trees compared to undisturbed areas.
   • Forests affected by recent disease disturbances sequestered 28% less carbon in live trees compared to undisturbed areas.

Global Trends and Future Implications

Despite increased frequency and severity of natural disturbances, global data indicates an overall increase in forest carbon stocks. This highlights the resilience and potential of forests to contribute to climate mitigation efforts, supporting SDG 13 and SDG 15.

Conclusion and Relevance to Sustainable Development Goals

• Understanding the combined effects of human activities and natural disturbances is essential for managing forest ecosystems sustainably (SDG 15).
• Forests remain a critical component in achieving climate action goals by enhancing carbon sequestration (SDG 13).
• Continued monitoring and research will inform policies to maximize the role of forests in sustainable development and climate resilience.

1. Sustainable Development Goals (SDGs) Addressed or Connected

1. SDG 13: Climate Action
   • The article discusses climate change mitigation through forests as a critical strategy to reduce greenhouse gas emissions to net zero by 2050.
2. SDG 15: Life on Land
   • The article focuses on forest ecosystems, tree population dynamics, natural disturbances, and carbon stocks, all of which relate to sustainable management of forests and biodiversity conservation.

2. Specific Targets Under Those SDGs Identified

1. Under SDG 13: Climate Action
   • Target 13.2: Integrate climate change measures into national policies, strategies, and planning. The article’s emphasis on understanding forest ecosystem changes to inform mitigation efforts aligns with this target.
   • Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters. The article’s analysis of natural disturbances (fire, insects, disease) impacting forests relates to this target.
2. Under SDG 15: Life on Land
   • Target 15.1: Ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services. The article’s focus on forest carbon stocks and population dynamics supports this target.
   • Target 15.2: Promote sustainable forest management to halt deforestation and restore degraded forests. The article’s discussion on forest demographic changes and disturbances is relevant here.

3. Indicators Mentioned or Implied to Measure Progress

1. Forest Carbon Stocks and Stock Changes
   • The article mentions measuring carbon stocks in live trees and changes due to disturbances, which corresponds to indicators such as Indicator 15.2.1 (Forest area as a proportion of total land area) and Indicator 13.2.2 (Total greenhouse gas emissions per year).
2. Forest Demographic Index
   • The use of a standardized forest demographic index based on national forest inventory data implies measurement of tree population dynamics, size-structure changes, and species decline, which can be linked to indicators under SDG 15 related to biodiversity and forest health.
3. Impact of Natural Disturbances
   • Quantification of carbon sequestration reduction due to insect and disease disturbances (e.g., 69% less carbon sequestration with insect disturbance) implies monitoring indicators related to forest degradation and ecosystem resilience.

4. Table: SDGs, Targets and Indicators

Source: fs.usda.gov