Study Notes on Major Global and Environmental Changes

UNIT SIX

MAJOR GLOBAL AND ENVIRONMENTAL CHANGES

6.1. Persistent Environmental Changes

Objectives

• Describe the nature and characteristics of persistent environmental changes.

• Distinguish between the nature and characteristics of persistent and emerging environmental changes.

6.1.1. Habitat Destruction

• Definition: Habitat is a subset of physical environmental factors that permit a particular species to survive and reproduce at any given point in time.

• Main Source: Humans are the major modern source of habitat loss, fragmentation, and biodiversity loss around the planet due to landscape modification.

Methods of Landscape Alteration by Humans

1. Land use change through agriculture and urban development.

2. Deforestation leading to loss of forests.

3. Drainage of wetlands altering ecosystems.

4. Mining operations disrupting the land.

5. Infrastructure development (roads, buildings, etc.) fragmenting habitats.

Natural Occurrences Affecting Habitat

• Natural disasters such as floods, volcanic eruptions, earthquakes, and temperature shifts can change landscapes and cause habitat destruction.

• The introduction of invasive species into environments is a major factor contributing to the extinction of native species.

Impact on Organisms

• Access to appropriate habitat profoundly affects organisms' distribution, abundance, survival, reproduction, and long-term persistence.

• Although some species may prefer disturbed environments, others may survive in degraded habitats without reproducing.

• Habitat degradation can take a long time to impact species; e.g., the loss of large trees with cavities threatens many forest species worldwide.

6.1.2. Agricultural Intensification

• Definition: The process of increasing agricultural output per unit of input (labor, land, time, fertilizer, seed, and feed or cash).

  • Successful in increasing productivity with improved seeds, high doses of inputs, heavy machinery, and irrigation but failed to tackle some environmental issues.

Negative Effects of Agricultural Intensification

• Loss of biodiversity: Monocropping and reliance on a few crop varieties have led to a drastic reduction in agricultural diversification. Today, only 15 crop species and 8 livestock species provide 90% of human food supply.

• Reduction of soil quality: Increased use of synthetic fertilizers has harmed soil quality and led to nitrate pollution.

• Pesticide hazard: Persistent pesticides pollute soil, air, and water and bioaccumulate in food chains, causing health issues such as cancer in animals.

• Soil salinization: Irrigation practices have resulted in toxic soil due to sodium ion accumulation.

• Increased pests and diseases: Indiscriminate pesticide use leads to pest population surges and disease spread in crops.

• Soil compaction: Heavy machinery contributes to soil compaction, affecting soil health and crop yields.

Agricultural Challenges in Sub-Saharan Africa

• Intensive use coupled with poor land management leads to low agricultural yields, characterized by:

  • Significant depletion of soil nutrients.

  • Unsuitable land management techniques.

  • Excessive soil erosion.

  • High costs of agricultural inputs.

Sustainable Practices for Agricultural Intensification

• Recommended practices include:

  • Improving fertilizer and water use efficiency through innovative breeding programs.

  • Integrated soil and pest management strategies.

  • Agroforestry which enhances food security sustainably compared to monoculture systems.

• Aim: Balance the demand for food with the need for biodiversity conservation.

6.1.3. Overexploitation of Resources

• Definition: Over-exploitation occurs when natural resources are harvested at excessive rates without sufficient attention to regeneration.

• Consequences: Rapid depletion of stocks leading to economic or ecological extinction not only by humans but also through introduced species – predators and herbivores.

Examples of Overexploitation

• Overfishing: Occurs when a fish stock is fished below the level that can sustain future catches.

• Overgrazing: When land is grazed beyond its capacity to recover, damaging soil health.

• Over-logging: Forests logged faster than they can naturally reforest, leading to biodiversity loss.

• Over-drafting: Water resources such as aquifers over-extracted faster than they can recharge.

• Mineral exploitation: Technological advancements enable deeper mining, increasing the depletion rates of minerals like phosphorus and copper.

Economic Implications of Oil Depletion

• Rising oil demand leads to:

  • Business decline.

  • Increased living costs in developing nations.

  • Uncertainty in transportation sectors.

6.1.4. Invasive Alien Species

• Definition: Invasive alien species are organisms that encroach upon ecosystems beyond their historic range, often causing harm.

  • They compete effectively and can dominate environments, displacing native species.

Characteristics of Invasive Species

• Often have special adaptations (e.g., modifying leaves into thorns, altering reproduction strategies) that aid in their survival and proliferation.

Causes of Invasive Species Expansion

• Climate change exacerbates the spread of invasive species. For example, flooding disrupts soil profiles and promotes invasive plant establishment.

• Disturbances such as floods can be a double-edged sword, sometimes allowing beneficial control of aquatic invasives.

Habitat Classification of Invasive Species

• Terrestrial Invasive Species: Adaptable, can change phenotypically under different conditions, e.g., mayapple and purple loosestrife.

• Aquatic Invasive Species: Often outcompete native species, leading to ecosystem instability and reductions in biodiversity. They can be categorized as:

  1. Floating weeds: Reside on water surfaces, e.g., duckweed.

  2. Emergent plants: Grow in waterlogged areas, needing support structures, e.g., mangroves.

  3. Submerged plants: Grow entirely underwater, impacting native aquatic ecosystems.

Phases of Invasion in Ecological Context

1. Introduction: Dispersed weeds establish beyond their historical range.

2. Naturalization: New populations integrate with local flora, influenced by environmental conditions (abiotic factors).

3. Colonization: Founding populations expand to form self-sustaining colonies, competing with natives.

4. Dispersal: Influenced by biological and environmental factors affecting colonization.

Impacts of Invasive Plants

• Leads to biodiversity loss, species extinction, and damaging ecological processes.

• Disrupts relationships within ecosystems, such as pollination and seed dispersal.

• Potentially endangers human health and livability through habitat degradation.

6.2. Poverty – Environment Nexus

Objectives

• Outline the connection between poverty and the environment.

• Recognize the cause-effect relationship between land degradation, deforestation, and poverty.

• Familiarize with land management options to reduce land degradation.

Definitions

• Poverty: A multidimensional concept reflecting lack of access to capital assets for livelihood.

• Environment: Encompasses both renewable and nonrenewable natural resources.

  • Poverty-Environment Nexus: A cycle of mutual reinforcement between poverty and environmental harm, leading to further degradation and exacerbation of poverty.

The Cycle of Poverty and Environmental Degradation

• Poverty leads to exploitation of resources, resulting in environmental degradation, which in turn exacerbates poverty, creating a vicious cycle.

• Dynamics: The relationship is influenced by geographic location and socio-economic contexts.

• Poverty-Environment Mainstreaming: Seeks a balance between resource preservation and poverty alleviation.

6.2.1. Poverty and Land Degradation

• Definition: Land degradation is a decline in land conditions impacting biodiversity, ecosystem functions, and productivity due to human-driven processes (direct and indirect).

• Major components:

  1. Soil degradation

  2. Biological degradation

  3. Vegetation alterations

  4. Water resources degradation

Impacts of Land Degradation

• Lead to decreased agricultural productivity, thus increasing food insecurity.

• Primarily affects impoverished communities but is driven by both poor and affluent households.

Management Strategies for Land Degradation

• Soil Management: Addressing soil issues such as runoff, salinization, and compaction.

• Vegetation Management: Preventing overgrazing and maintaining tree density and diversity.

• Water Management: Mitigating over-extraction and managing flooding.

• Integrated Options: Consider ecosystem health factors such as biodiversity loss and urbanization.