Using Land to Mitigate Climate Change: Science, Policy, Benefits, and Drawbacks
Introduction to Land-Based Climate Change Mitigation (Richard J. Harper, Murdoch University)
This lecture provides a comprehensive and in-depth overview of the critical role land plays in global climate change mitigation efforts, specifically focusing on the principles and applications of carbon farming. It delves into the foundational scientific principles that underpin carbon sequestration and emission reduction in terrestrial ecosystems, alongside the intricate policy frameworks designed to support these activities. The discussion highlights the substantial environmental and economic benefits achievable through land-based offsetting approaches, such as enhanced ecosystem services and new economic opportunities for landholders. Furthermore, it critically examines the potential drawbacks, challenging tradeoffs, and emerging issues that must be addressed for the sustainable and equitable implementation of various land-based mitigation strategies.
Speaker Background
Richard J. Harper, currently the Associate Dean Research in Agricultural Science at Murdoch University, has held a distinguished professorship there since . His academic and research leadership builds upon a significant career in science and policy roles with the Western Australian Government from to . This extensive background provides him with a unique perspective, bridging cutting-edge scientific research with practical policy implementation in environmental management and agricultural science. His primary research areas indicate a deep commitment to climate-related issues:
Carbon mitigation: This area specifically investigates the potential of diverse natural systems—including forests, agricultural soils, coastal mangroves, and various shrublands—to sequester atmospheric carbon. His work spans both the scientific understanding of carbon cycling in these systems and the development of effective policy instruments to incentivise and regulate mitigation efforts.
Forests and water: Research in this domain focuses on the intricate interactions between forest ecosystems and hydrological cycles, examining how forest management can influence water availability and quality, a critical consideration in arid and semi-arid regions.
Soil water repellency: This research addresses a significant agricultural challenge, exploring the causes and management strategies for soil conditions that hinder water infiltration, impacting crop productivity and ecosystem health, often indirectly related to land management practices that can influence carbon storage.
His expertise has been recognized through his service on several influential national and international committees, reflecting his broad impact:
The Intergovernmental Panel on Climate Change (IPCC) AR5: Contributing to the Fifth Assessment Report, which compiles and assesses the most recent scientific, technical, and socio-economic information produced worldwide relevant to understanding climate change.
The Emissions Reduction Assurance Committee (under the CFI Act): This Australian federal committee plays a vital role in ensuring the integrity and effectiveness of carbon credit methods under the Carbon Farming Initiative (CFI) Act, providing scientific and technical advice.
The Threatened Species Scientific Committee (under the EPBC Act): This committee advises the Australian government on species and ecological communities at risk, connecting biodiversity conservation with land management, which is often intertwined with carbon farming initiatives.
The IUFRO Forests and Water Taskforce: An international taskforce focused on advancing scientific understanding and policy recommendations regarding the critical relationship between forests and water resources globally.
Overview of Carbon Farming
Around the world, both the agricultural sector, which is a significant emitter of greenhouse gases, and the broader economy are increasingly committing to ambitious emission reduction targets, such as net-zero by or earlier. Carbon farming is positioned as a cornerstone mitigation activity within these strategies, encompassing a diverse array of approaches designed to reduce net greenhouse gas emissions from agricultural and land management systems. These approaches include:
Reforestation and afforestation: Planting new trees on land that has not been forested for a long time or land that previously had no forest.
Improved forest management: Practices that enhance carbon storage in existing forests, such as thinning, extended rotations, or managing for increased biomass.
Soil organic carbon sequestration: Enhancing the carbon content in agricultural soils through practices like minimum tillage, cover cropping, organic amendments, and improved pasture management.
Livestock management: Reducing methane emissions from ruminant livestock through feed supplements, improved genetics, and manure management.
Savanna burning: Controlled burning regimes in northern Australian savannas to reduce fire intensity and frequency, thereby lowering overall greenhouse gas emissions.
Nitrous oxide reduction: Implementing practices that minimize nitrogen fertilizer use and improve its efficiency, reducing ext{N} ext{_}2 ext{O} emissions from agricultural soils.
This robust strategy has been a consistent and evolving feature of Australia's climate change policies over the last three decades, evolving from early pilot programs to comprehensive legislative frameworks like the Carbon Farming Initiative and the Emissions Reduction Fund.
Offsetting Emissions Using the Land
The Agriculture, Forestry, and Other Land Uses (AFOLU) sector occupies a unique and critical dual role in addressing climate change. On one hand, it is a significant producer of greenhouse gas (GHG) emissions, contributing approximately of global anthropogenic emissions, primarily through deforestation, livestock enteric fermentation, manure management, rice cultivation, and synthetic fertilizer application. On the other hand, it possesses substantial unrealized potential for both mitigating these emissions and actively offsetting emissions from other sectors by acting as a carbon sink. Land-based mitigation methods, when carefully planned and implemented, can offer substantial additional benefits, often referred to as co-benefits, beyond just carbon accounting, including:
Improved water management: Practices like riparian zone restoration, enhanced soil organic matter, and appropriate tree planting can improve water infiltration, reduce runoff, prevent erosion, and enhance water quality in rivers and streams.
Biodiversity conservation: Reforestation, protection of native vegetation, and ecologically sensitive agricultural practices can create habitats, improve ecosystem connectivity, and contribute to the recovery of threatened species.
Additional income streams for landholders: Beyond carbon credits, landholders can benefit from increased agricultural productivity due to healthier soils, revenue from ecotourism, or payments for ecosystem services.
However, it is crucial to carefully consider potential tradeoffs, as large-scale land-based mitigation efforts can introduce complexities, particularly concerning:
Water availability: Extensive tree planting, especially in water-stressed regions, can lead to increased water consumption by vegetation, potentially impacting groundwater levels and water resources for other uses.
Food security: Converting productive agricultural land for carbon sequestration (e.g., planting forests on croplands) could reduce food production capacity, raising concerns about food supplies and prices.
Flexibility in land-use decisions: Long-term carbon contracts or commitments can limit a landholder's future flexibility to change land use in response to market demands, environmental changes, or personal circumstances.
These tradeoffs necessitate integrated planning and robust policy frameworks that balance climate mitigation goals with other vital societal and environmental objectives.
Greenhouse Gases Beyond CO
While carbon dioxide () is undeniably the primary focus of climate change discussions due to its sheer volume and long atmospheric lifetime, it is crucial to acknowledge and account for other potent greenhouse gases that contribute significantly to global warming. These non- gases have a much higher impact per molecule than over specific timeframes:
Methane (): This gas, primarily emitted from livestock (enteric fermentation), wetlands, rice paddies, and fossil fuel production, has a Global Warming Potential (GWP) greater than over a -year period. While its atmospheric lifetime is shorter than (around years), its high warming potential makes its reduction crucial.
Nitrous oxide (): Primarily derived from agricultural soils (due to fertilizer use), industrial processes, and combustion, is an even more potent GHG, with a GWP greater than over a -year period. It also has a longer atmospheric lifetime of approximately years.
In analyses, carbon inventories, and carbon markets, these gases are not treated in isolation but are converted and presented as (carbon dioxide equivalent). This conversion provides a standardized metric for comparing the climate impact of different GHGs based on their GWP, allowing for a common unit for reporting emissions, setting targets, and trading carbon credits. Essentially, it normalizes various greenhouse gases to a single measurement unit, making it easier to quantify and manage overall climate impact.