Global Ecology and Climate Change Study Guide

Course Logistics and Grading

• Current Status of Grades:

Introduction to Global Ecology and Biogeochemistry

• Global Ecology Overview: Focuses on Climate Change and the widespread environmental problems caused by humans changing the environment on a global scale.

• Atmospheric Emissions: Human activity has increased emissions of:     * Pollutants     * Dust     * Greenhouse gases

• Study Objective: A major focus is studying the environmental effects of human activities and understanding global biogeochemical cycles.

• Biogeochemistry Definition: The study of the physical, chemical, and biological factors that influence the movement and transformation of elements.

• Source Attribution: Visuals in the presentation are courtesy of the Center for Snow and Avalanche Studies, Silverton, CO.

Global Biogeochemical Cycles and Essential Elements

• Four Important Elements:     * Carbon (C): Described as the chemical backbone of life on Earth. It is critically important for biological activity, energy transfer (ATP), and the construction of biomass. Carbon is indispensable for life due to its ability to combine with many other elements to form specialized molecules for cell functions.     * Nitrogen (N): Essential for Amino acids and Proteins.     * Phosphorus (P): Essential for tissues, cell repair, and genetic material (RNA and DNA).     * Sulfur (S): Essential for amino acids and enzymes.

• Environmental Roles: These elements are vital for biological activity but also act as pollutants in the global environment.

The Global Carbon Cycle: Pools and Fluxes

• Carbon Dynamics: Carbon moves between atmospheric, terrestrial, and oceanic pools over periods of weeks to decades. Changes in this cycle are currently influencing Earth’s climate.

• Terminology:     * Pool/Reservoir: The amount of an element in a component of the biosphere.     * Flux: The rate of movement of an element between pools (e.g., terrestrial plants are a pool; photosynthesis is a flux).

• Measurement Units:     * Gt (Gigatons): A billion metric tons.     * Petagrams (Pg): $1\,\text{Pg} = 2,204,622,621,849\,\text{pounds}$.

• Major Pool Sizes (measured in Pg):     * Rocks: $60 \times 10^6$ (The most stable pool; 99% of global C is in sediments and rock).     * Deep Ocean Waters: $38,000$     * Soils: $1,500$ (Contains twice as much C as plants).     * Surface Ocean Waters: $920$     * Atmosphere: $760$     * Vegetation: $650$     * Benthic Sediments: $150$     * Detritus: $11$     * Marine Biota: $3$

• Major Flux Rates (measured in Pg/year):     * GPP (Gross Primary Production): $123$     * Respiration: $120$     * Fossil Fuels: $10.6$     * Land Use Change: $0.9$     * Atmosphere-Ocean Flux: $91$ (up to atmosphere), $92$ (down to ocean).     * Ocean Mixing: $92$ (up to surface), $101$ (down to deep ocean).     * Transport in Rivers: $0.8$     * Marine Biota to Deep Ocean: $11$     * Deep Ocean to Benthic Sediments: $0.2$     * Detritus to Deep Ocean: $50$     * Deep Ocean to Detritus: $39$

Dynamics of the Carbon Cycle

• Oceanic Processes:     * Surface water takes up $CO_2$ from the atmosphere via diffusion (moving from high to low concentration).     * Carbon is transferred to deeper water as organic detritus and carbonate shells.     * Upwellings: Bring carbon-rich water to the surface, releasing $CO_2$ back into the atmosphere.     * Surface depth: $75-200\,\text{m}$ (site of most biological activity).

• Terrestrial Processes:     * $CO_2$ is exchanged with the atmosphere primarily through photosynthesis and respiration.     * Pre-Industrial era: Terrestrial and atmospheric fluxes were roughly equal, resulting in no net change in atmospheric $CO_2$.

Anthropogenic Impacts and Greenhouse Gases

• Atmospheric Carbon Forms: Primarily Carbon Dioxide ($CO_2$) and Methane ($CH_4$).

• Greenhouse Gases: Influences the atmospheric absorption of infrared radiation and reradiation from the Earth's surface.

• Human-Induced Changes:     * Sources: Land-use change (mostly deforestation via cutting and burning) and burning fossil fuels.     * Historical context: Before the mid-19th century, deforestation was the main anthropogenic flux.     * Recent trends: Anthropogenic emissions of $CO_2$ almost tripled between 1970 and 2018.

• Absorption Proportions:     * Oceans: Absorb $25-30\,\%$ of human $CO_2$ emissions.     * Land: Absorbs $30\,\%$.     * Atmosphere: $40-45\,\%$ remains in the atmosphere.     * Future Trend: The proportion taken up by land/ocean will likely decrease as they cannot keep pace with the rate of atmospheric increase.

• Methane ($CH_4$):     * Anthropogenic Sources: Fossil fuel use, agriculture (especially rice), livestock, and burning forests/crops.     * Natural Sources: Emitted by anaerobic methanogenic bacteria in wetlands and the rumens of ruminant animals.     * Potency: $CH_4$ is $25$ times more effective as a greenhouse gas than $CO_2$.     * Atmospheric Lifespan: Approximately $10-12$ years.     * Oxidation Equation: $CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$

Global Climate Change: Observations and Evidence

• Definition: A directional change in climate over a period of at least three decades.

• Temperature Increase: Average global surface temperature increased by $0.97\,^\circ\text{C}$ between 1880 and 2018.

• Associated Phenomena:     * Widespread retreat of mountain glaciers.     * Thinning of polar ice caps.     * Melting permafrost.     * Sea level rise at a rate greater than any in the past $3,000$ years.

• Disturbances:     * Australian Bush Fires: Human-induced climate change increased the risk of weather conditions driving these fires by at least $30\,\%$.     * Saiga Antelope Mass Die-off (2015): In Kazakhstan, $220,000$ antelope (60% of the population) died suddenly. They were infected with Pasteurella multocida, a bacterium normally harmless that became deadly blood poisoning when exposed to unusually warm and wet weather.

Ecological Responses and Range Shifts

• Observed Responses:     * Earlier bird migrations.     * Local extinction of amphibian and reptile populations.     * Earlier leaf-out of vegetation.

• Geographic Range Shifts (Chen et al. 2011):     * Species are shifting to higher elevations at an average rate of $36.1\,\text{feet}$ ($11.0\,\text{meters}$) per decade.     * Species are moving to higher latitudes at about $10.5\,\text{miles}$ ($16.9\,\text{kilometers}$) per decade.

• European Butterfly Study (Parmesan and Yohe 2003):     * $63\,\%$ of species shifted ranges northward.     * Only $3\,\%$ shifted southward.

Biological Impacts and Extinction Risks

• Lizard Populations (Sinervo et al. 2010):     * Extinctions in Mexico linked to warmer spring temperatures limiting foraging time during breeding seasons.     * Projections predict $39\,\%$ of global lizard populations will go extinct by 2050 due to physiological stress.

• Migratory and Marine Animals:     * Prey shifts: Fish and whales may need longer journeys to find prey, resulting in new feeding behaviors.     * Phenological Mismatch: Birds arrive earlier in spring, but the plants and invertebrates they depend on for food may not yet be available.

• Forest Composition (Western North America):     * Mountain Bark Beetles: Now complete two life cycles per year and are found at higher latitudes and elevations.     * Forest Fires: Have doubled since 1984 due to warmer weather and lower moisture content in fuel.

• Adaptation Constraints: Evolution may be too slow for the rapid pace of climate change. Dispersal is the primary escape mechanism, but it is constrained by habitat fragmentation and dispersal barriers.

Future Projections and Global Climate Mitigation

• Paris Agreement: Aims to keep the rise in global average temperature "well below" $2\,^\circ\text{C}$ above pre-industrial levels.

• Lifestyle Emissions: Approximately two-thirds of global greenhouse gas emissions are linked to private households. Transport, food, and energy sectors each contribute about $20\,\%$ to lifestyle emissions.

• Ten Personal Lifestyle Actions (United Nations ActNow):     1. Save energy at home.     2. Walk, bike, or take public transport.     3. Eat more vegetables.     4. Consider your travel.     5. Throw away less food.     6. Reduce, reuse, repair, recycle.     7. Change your home's source of energy.     8. Switch to an electric vehicle.     9. Choose eco-friendly products.     10. Speak up.

• Ethical and Philosophical Perspectives:     * Native American Proverb: "We do not inherit the Earth from our ancestors, we borrow it from our children."     * Wendell Berry: "To damage the earth is to damage your children."     * Summary Philosophical Note: The Earth was not given by parents but loaned by children.