Global Land Degradation Practice Flashcards

Introduction to Global Land Degradation

• Lecturer Profile:

  • Dr. Rosalind Henry: A lecturer in SBS whose research primary focuses on land use change modelling.

  • Research Interest: How land use is expected to change in the future in response to drivers such as population change and policy changes, and how those changes interact with biodiversity, food security, and human health.

• Lecture Overview:

  • Defining land degradation and its global drivers.

  • Ecological appearance across different ecosystems.

  • Consequences of degradation (ecological and human).

  • A preview of future topics: Global goals for reversing degradation, projections/models, and solutions found in global reports.

Defining Land Degradation

• Conceptual Distinction: Land degradation is exclusively human-driven. Changes in land condition resulting solely from natural processes are not classified as land degradation.

• IPCC Definition: "A negative trend in land condition caused by direct or indirect human processes, expressed as a long-term reduction or loss of at least one of the following: biological productivity, ecological integrity, or human value."

• IPBES Definition: "Refers to the many processes that drive the decline in biodiversity, ecosystem functions and services, and includes the degradation of all terrestrial ecosystems."

• Degraded Land Definition: Land in a state resulting from the persistent decline or loss of biodiversity and ecosystem functions.

• Forms of Degradation:

  • Forest Degradation: A reduction in biomass, productivity, or benefits derived from the forest.

  • Rangeland Degradation: Persistent loss of vegetation cover, specifically plants that support herbivores.

Global Statistics and Critical Thresholds

• Scale of Loss: At least $10^8\,ha$ (100,000,000 hectares) of healthy land are lost annually, which is roughly twice the area of Spain.

• Planetary Boundaries: Of the $9$ planetary boundaries defining a safe operating space for humanity, $4$ have already been exceeded. These breaches are linked to human-induced desertification, land degradation, and drought.

• Spatial Distribution: Land degradation occurs on every continent.

  • Europe: Degradation is primarily driven by land cover conversion (transforming natural state to unnatural state).

  • South America: Degradation is driven more by land management practices rather than just conversion.

• Soil Health: The UN estimates that $33\% \text{ of global soils}$ are already degraded.

Influential Global Bodies and Reports

• IPBES (Intergovernmental Science Policy Platform on Biodiversity Ecosystem Services):

  • Independent panel providing scientific assessments on biodiversity and ecosystems.

  • Report: Assessment Report on Land Degradation; emphasizes that degradation is a pervasive, systemic phenomenon occurring everywhere.

• IPCC (Intergovernmental Panel for Climate Change):

  • UN body assessing climate science to inform government policy.

  • Report: Special Report on Climate Change, Desertification, and Land Degradation.

  • Standard of Evidence: High confidence that unsustainable land management and land use changes are direct human causes of degradation.

• UNCCD (United Nations Convention To Combat Dessertification):

  • Established in the 1990s as the only legally binding framework to address drought and desertification (misspelled as "Dessertification" in the transcript).

  • Report: Global Land Outlook (2nd Edition); provides a more optimistic view focused on pathways for restoration.

Primary Drivers of Land Degradation

• Agriculture: The dominant sector driving global land degradation.

• Urbanization: Creation of anthropogenic landscapes.

• Forestry: Clearing of forests for timber or land.

• Pollution and Waste: Poor waste management and contamination.

• Livestock Management: High-intensity rearing and overstocking.

• Ground Zero Driver: Consumption: Underlying all specific activities is unsustainable consumption and consumerism in the developed world. Money and demand drive the destructive processes.

• Compound Effects: Land degradation interacts with climate change. Degradation leads to more emissions, which increases climate change, which then exacerbates further land degradation.

The Impact of Agricultural Expansion

• Population and Diet: Since 1961, the global population (now over $7.8 \times 10^9$) has seen a $32\% \text{ increase}$ in per capita calorie intake.

• Dietary Shifts: Meat and vegetable consumption have more than doubled. Dairy consumption increased by a factor of $1.2$.

• Production Increases: Crop production increased approximately $3.5\text{-fold}$, and animal product production increased $2.5\text{-fold}$.

• Footprint Inequality: The developed world (high-income countries) has the highest per capita consumption footprint. If the global population adopts the diet of the developed world, it will exceed Earth's capacity to deliver food.

Ecosystem Specifics: Forests and Peatlands

• Quantification Challenges: Estimates vary based on metrics (carbon loss vs. biomass loss vs. canopy cover).

  • Canopy cover may not reflect degradation happening underneath (loss of fauna or lower vegetation).

  • About $20\% \text{ of global forests}$ are degraded, while $30\% \text{ have been cleared}$.

• Intactness: Less than $30\% \text{ of global forests}$ remain intact, and only $40\% \text{ of forested area}$ is estimated to contain old-growth forest.

• Regional Drivers:

  • South America/Indonesia: Commodity-driven (soy and palm oil).

  • Tropical Africa: Shifting agriculture (clearing patches that lose productivity, then moving on).

  • Northern Hemisphere/China/Europe: Commercial forestry.

• Peatlands: Wetland areas where waterlogged conditions slow decomposition and store carbon.

  • Drainage: Draining peatlands for agriculture makes them CO2 emitters and increases wildfire risk.

  • Loss: $99\% \text{ of peatlands in non-boreal regions}$ are lost. In the UK, East Anglia fens dropped from $3,400\,km^2 \rightarrow 10\,km^2$.

Ecosystem Specifics: Grasslands and Savannahs

• Conservation Status: Temperate grasslands are one of the most endangered biomes.

• Biodiversity: Tropical grassy biomes harbour nearly $50\% \text{ of the vascular plant richness}$ found in tropical forests.

• The Albedo Effect: Grasslands have high reflectance (albedo). Evidence suggests the temperature-lowering benefit of their albedo outweighs the carbon-fixing benefits of planting trees on that same land.

• Cerrado (Brazil): A biodiversity hotspot with endemic species being degraded by monocultures of Eucalyptus and Pine, which exhaust water resources and require heavy fertilizer/pesticide inputs.

• Scotland Case Study: Grassland loss (mackeres/meadows) has led to an $80\% \text{ decline}$ in the Great Yellow Bumblebee and a >50\% \text{ decline} in Curlews.

Soil Erosion Processes

• Types of Water Erosion:

  1. Splash Erosion: Rain hitting bare soil and dislodging particles.

  2. Sheet Erosion: Large areas of surface soil being swept away.

  3. Rill Erosion: Formation of small channels as water moves through tracks or paths.

  4. Gully Erosion: Large depressions/channels forming in the landscape.

• Arable Specific Erosion:

  • Tillage Erosion: Soil moving down slopes due to plowing. This results in thinned soil on hilltops (lower yield) and accumulated soil at the bottom (potential for high productivity but also higher water erosion).

  • Harvest Erosion: Soil that sticks to crops (e.g., potatoes) and is removed from the field. It affects $8\% \text{ of global lands}$ and remains poorly understood.

Carbon Sequestration and Soil Mechanics

• Carbon Reservoirs: Soils hold $2\times \text{ the carbon}$ of the atmosphere and $3\times \text{ the carbon}$ found in all vegetation. European soils contain approximately $75 \times 10^9 \text{ tonnes}$ of organic carbon.

• The Importance of Roots:

  • Annual crops (arable) have shallow roots, whereas natural vegetation has deep roots that stabilize soil.

  • Chemical Recalcitrance: Roots contain lignin and suberin, resistant to microbial decomposition.

  • Physicochemical Protection: Root-derived carbon forms organo-mineral complexes that protect organic matter.

  • Physical Protection: Roots promote the formation of soil aggregates.

• Clearing Effects: Clear-cutting forests reduces soil carbon by an average of $10\%$. Global forest loss since 2000 has resulted in a loss of potential sequestration of $972 \times 10^6 \text{ tonnes of carbon}$ ($972$ million tons) by 2050.

Global Economic and Environmental Consequences

• Sedimentation: Soil running into waterways reduces clarity, kills aquatic plants, and causes algal blooms.

  • Lake Victoria: Algal blooms linked to sedimentation killed $400,000\text{ fish}$.

  • Costs: River dredging in Europe costs $900,000,000\,Euro/year$. US erosion costs are $3.76 \times 10^{10}\,Euro/year$ ($4\,billion\,\text{GBP}$) for water erosion and $9.8 \times 10^9\,USD$ for wind erosion.

• Dust Creation: Wind erosion releases $5,000\,Tg$ of mineral dust annually.

  • Colorado River Basin: Receives $5\times$ more dust than $200$ years ago, causing snowmelt to occur $31\text{ to }51\text{ days}$ earlier, affecting water supply.

• Albedo Loss: Dust landing on snow reduces its albedo, accelerating melting and climate change.

Human and Socio-Economic Impacts

• Food Security: Land degradation is projected to reduce crop yields by $10\% \text{ by } 2050$, potentially increasing food prices by $30\%$.

• Health and Nutrition: Degraded soils produce food with lower nutritional value (micronutrient/vitamin deficiency).

• Poverty and Conflict: Poor populations are more dependent on ecosystem services and agriculture, making them more vulnerable. For every $5\% \text{ loss in GDP}$ caused by degradation, there is an associated $12\% \text{ increase}$ in the likelihood of violent conflict.

• Human Health Outcomes: Linked to cardiovascular diseases, respiratory issues (from dust), and mental health.

  • DALYs (Disability-Adjusted Life Years): Developing countries experience significantly higher DALY loss per $1,000$ people due to degraded environments compared to European countries.

• Vulnerable Groups:

  • Women and Children: Disproportionately affected by water scarcity and waterborne diseases.

  • Mental Health: Exposure to natural landscapes (as opposed to urban/degraded ones) is linked to faster recovery from stress and better childhood development.

• Cultural Identity: There is a strong spatial overlap between high biodiversity and high linguistic/cultural diversity. The loss of indigenous species (which provide $50\% \text{ of smallholder food in Africa}$) erodes cultural heritage.

Questions & Discussion

• Prompt: Dr. Henry asked the group what they think of when they hear the term "land degradation."

• Discussion Points:

  • The students discussed it amongst themselves.

  • Dr. Henry addressed the fact that there are multiple definitions (IPCC/IPBES).

  • The class discussed "Ground Zero" drivers: Overconsumption, money, construction/development, and agricultural farmland conditions.