13.1 Climate Change: Causes and Impacts on Biodiversity

This document outlines the definition of climate change, distinguishes between its natural and human-caused drivers, and details its significant impacts on the planet's flora and fauna.

• Climate Change: Long-term, gradual, and apparently irreversible changes in the climatic conditions of an area. This global phenomenon includes:

  • Average rise in global atmospheric temperature
  • Ocean acidification
  • Changes in seasonal duration and monsoon patterns
  • Extreme weather events like heatwaves, cold spells, flooding, and droughts

• Natural vs. Anthropogenic Change: While the Earth's climate has always changed naturally over millennia, the term "climate change" today primarily refers to the rapid, human-caused (anthropogenic) changes observed since the Industrial Revolution.

Causes of Climate Change

The Earth's climate is determined by the balance of energy entering and leaving the atmosphere. This balance can be disrupted by both natural and human factors.

Natural Factors

Natural processes that influence climate over long, often cyclical, periods.

• Volcanic Activity: Large eruptions release dust, ash, and sulfur dioxide, which can block sunlight and cause temporary cooling. They also release CO₂, a greenhouse gas, contributing to long-term warming.

• Solar Variability: The sun's energy output fluctuates in cycles. Periods of higher solar activity lead to more energy reaching Earth, causing temporary warming.

• Milankovitch Cycles: Long-term, cyclical changes in Earth's orbit and axial tilt that affect the amount of solar radiation received.

  • Eccentricity: The change in the shape of Earth's orbit from more circular to more elliptical over a 100,000-year cycle.
  • Obliquity (Axial Tilt): The variation in the tilt of Earth's axis (between 22.1° and 24.5°) over a 41,000-year cycle.
  • Precession: The "wobble" of Earth's axis of rotation over a 26,000-year cycle.

• Ocean Currents: Oceans transport heat globally. Changes in circulation patterns, like El Niño (warmer Pacific waters) and La Niña (cooler Pacific waters), cause significant short-term shifts in global weather patterns.

• Natural Greenhouse Gas Emissions: Processes like organic decay, respiration, and wetlands naturally release greenhouse gases such as carbon dioxide (CO₂) and methane (CH₄).

Anthropogenic (Human-Caused) Factors

Human activities, particularly since the Industrial Revolution, that have accelerated climate change by increasing atmospheric greenhouse gas concentrations.

• Burning of Fossil Fuels: The combustion of coal, oil, and natural gas for energy, industry, and transportation is the largest source of human-caused CO₂ emissions, enhancing the greenhouse effect.

• Deforestation and Urbanization:

  • Deforestation: The clearing of forests removes "environmental buffers" or carbon sinks (trees absorb CO₂). Burning forests releases stored carbon.
  • Urbanization: The expansion of cities often involves clearing vegetation and creating "urban heat islands" where surfaces absorb more heat.

• Industrial Processes and Agriculture:

  • Industry: Cement production and chemical processes release CO₂ and other greenhouse gases.
  • Agriculture: Livestock farming releases significant amounts of methane (CH₄), while the use of fertilizers releases nitrous oxide (N₂O).

• Waste Management: Landfills produce methane as organic waste decomposes.

• Transportation: Vehicles, air travel, and shipping are major sources of CO₂ emissions.

• Aerosols and Chemicals: Industrial pollutants can have mixed effects. Some aerosols reflect sunlight (cooling), while others like black carbon (soot) absorb it (warming). Chlorofluorocarbons (CFCs) are potent greenhouse gases that also damage the ozone layer.

Impact of Climate Change on Biodiversity

Biodiversity refers to the variety of life in an area, encompassing all flora (plants) and fauna (animals). Climate change severely disrupts the delicate balance of ecosystems.

Impact on Flora (Plants)

• Changes in Growing Seasons: Altered temperatures are making growing seasons longer in some regions and shorter in others, affecting key plant life cycle events like flowering and fruiting.
• Increased Stress from Extreme Weather: More frequent and intense droughts, floods, and storms damage or kill plants by creating unfavorable soil and water conditions.
• Migration of Plants: As climates shift, plant species may migrate as their seeds disperse to new, more suitable regions, while some may disappear from their original habitats.

Impact on Fauna (Animals)

• Loss and Shifting of Habitats: Rising temperatures and environmental changes force animals to move to find suitable climates and resources. For example, melting sea ice eliminates the hunting grounds for polar bears.

• Food Chain Disruption: The decline or extinction of a species due to climate change has cascading effects. The loss of a specific plant impacts the herbivores that eat it, which in turn affects their predators.

• Disruption of Life Cycles: Temperature-sensitive biological cycles like breeding, hibernation, and migration are disrupted. Animals may emerge from hibernation too early or late, leading to a mismatch with food availability. This is often referred to as Phenological Mismatch.

• Ecosystem Imbalance and Extinction: Rapid climate change can overwhelm the ability of species to adapt, leading to extinction and disrupting the entire ecosystem.

• Invasive Species: As species migrate to new areas, they can become invasive, outcompeting native species for resources and harming the local ecosystem.

• Species Adaptation: While some species may adapt evolutionarily, the current rate of climate change is too fast for many to keep up, increasing their risk of extinction.