Science of Sustainability FINAL

EVR 3021

Key stocks of carbon

Lithosphere/sediments (largest overall)

Hydrosphere/Oceans (Largest reactive pool)

Soil & Terrestrial Biosphere

Atmosphere

How carbon moves into ecosystems

Photosynthesis (autotrophic carbon fixation)

How carbon moves through ecosystems

Consumption, trophic transfer, decomposition, and organic carbon assimilation

How carbon moves out of ecosystems

Oxic and anaerobic respiration, leaching/runoff, volatile emissions, and combustion

Human impacts on carbon flows

Fossil fuel combustion and deforestation move stored carbon from long-term geologic/terrestrial stocks directly into the atmosphere, exceeding natural sink capacities

Redox reaction: Photosynthesis

carbon is reduced (gains electrons) as inorganic CO2 is converted to organic glucose

Redox reaction: Oxic respiration

Carbon is oxidized (loses electrons) using molecular oxygen (O2) as the terminal electron acceptor to release CO2

Redox reaction: Anaerobic Respiration

Occurs in oxygen-depleted environments using alternative terminal electron acceptors (e.g., nitrate, sulfate, or CO2)

Autrophic Ecosystems

Has GPP > Re (NEP > 0) and act as net carbon sinks

Heterotrophic ecosystems

Have Re > GPP (NEP < 0) and act as net carbon sources

GPP (Gross Primary Production)

Total rate of carbon dioxide fixed into organic matter by autotrophs before it is respired

Ra (autotrophic respiration)

respiration by primary producers/autotrophs

NPP (net primary production)

GPP - Ra

Organic carbon remaining after autotrophs respire

Rh (Heterotrophic respiration)

respiration by consumers and decomposers/heterotrophs

Re (ecosystem respiration)

Total respiration created by both autotrophs and heterotrophs

Re = Ra + Rh

NEP (Net ecosystem production)

GPP - Re = NPP - Rh

Net organic carbon accumulation rate in the ecosystem

cCorg = NEP + I + CM - Ex - Oxnb

organic carbon accumulation = net ecosystem production + imports + consumer movement - exports - nonbiological oxidation

Detection of climate change

demonstrating that climate has statistically changed

Attribution of climate change

establishing the specific cause-and-effect mechanisms of climate change—WHY the climate is changing

five pieces of evidence that show Earth is warming

1. rising global surface temperatures

2. ocean warming & heat content

3. shrinking ice sheets and glaciers

4. sea level rise

5. extreme weather/heat events

role of ice cores in climate science

allows scientists to read and measure levels of CO2 in years prior as air bubbles are trapped in glaciers

Key drivers of past climate shifts

Natural milankovitch orbital cycles aplified by carbon feedbacks

Key drivers of contemporary climate change

driven by anthropogenic GHG emissions (human-based)

Main three GHGs to worry about

1. carbon dioxide

2. methane

3. nitrous oxide (N2O)

which GHG traps the most heat?

methane

Relative heat-trapping strength of GHGs pound for pound

Nitrous oxide (~273xCo2) > Methane (~28-36x co2) > Carbon dioxide (1x baseline)

Global carbon budget major stocks

lithosphere / fossil reserves, oceans, soils/permafrost, terrestrial vegetation, and atmosphere

climate change mitigation

reduces GHG emissions or enhances sinks to prevent warming

climate change adaptation

adjusts human and natural systems to reduce harm from unavoidable warming

economic impacts of climate mitigation

economic damages of unmitigated climate change far exceed the costs of proactive mitigation

Positive (reinforcing) feedback loops

amplify initial changes

even number of O links

Negative (balancing) feedback loops

counteract changes to stabilize systems

odd number of O links

Impact of positive feedback loops

drives exponential growth or exponential decay, leading to instability or tipping points

Impact of negative feedback loops

provides stability, self-regulation, and equilibrium in a system

Key stocks of nitrogen

Atmosphere (78% of our air is N2 gas)

also soils, aquatic systems, and living biomass

Human impacts on nitrogen flows

doubled global reactive N fixation through Haber-Bosch process, agricultural crops, and combustion, leading to eutrophication, acid rain, and N2O emissions

Haber-Bosch Process

industrial synthesis combining atmospheric N2 and H2 under heat/pressure to form synthetic ammonia (NH3) fertilizer

biological n fixation (BNF) - terrestrial

conversion of atmospheric N2 to NH4+ by symbiotic bacteria or free-living soil microbes

biological n fixation (BNF) - Oceanic

fixation of dissolved N2 gas in surface oceans by marine cyanobacteria

nitrification

aerobic microbial conversion of ammonium to nitrite and then nitrate

NH4+ → NO2- → NO3-

denitrification

anaerobic microbial reduction of nitrate back to gaseous N2) and N2 gas

NO3- → N2O- → N2

Ammonification aka mineralization

decomposers break down organic N into inorganic ammonium

immobilization

microbes absorb inorganic N into cellular biomass, temporarily locking it from plant uptake

Epilimnion characteristics

warm, low-density upper water layer

well oxygenated, high light penetration

thoroughly wind-mixed

Hypolimnion characteristics

cold, dense bottom water layer

isolated from air, low light

susceptible to severe oxygen depletion (hypoxia)

Key stocks of phosphorus

sedimentary rocks, soils, aquatic sediments, and biota.

NO IN ATMOSPHERE

human impacts on phosphorus flows

mining P rock for fertilizers and agricultural runoff/sewage discharge cause aquatic nutrient pollution

key sources of P into water

agricultural fertilizer runoff, soil erosion, livestock manure, municipal wastewater effluent, and urban stormwater

role of mycorrhizal fungi

symbiotic relationship w/plant roots, expand surface area to extract immobile soil P in exchange for plant sugars

role of sediments in P dymanics

oxic bottom water keeps iron oxidized, binding P in sediment

Hypoxic conditions reduce iron, releasing bound P into the water column

Harmful algae blooms (HABs)

causes excess nutrient loading (N and P), warm temps, stagnant water, and abundant sunlight

Limiting nutrient definition

the specific nutrient in shortest supply relative to demand that restricts biological growth

typically limiting nutrient in freshwater

P

typically limiting nutrient in marine systems

N

Biodiversity

number and variety of Earth’s organisms

multiple scales: genetic diversity, species diversity, ecosystem diversity

Fragmentation

separating of a species’ habitat into 2 or more segments, essentially isolating them and harming their overall survival

Corridors

purposeful connections between fragments of a fragmentated habitat, reconnecting a species with more land and raising their chances of survival

Pointsource Pollution

pollution that comes from a single point, easy to identify

nonpoint source pollution:

comes from many dispersed sources

hard to pinpoint the exact source

three phases to conserve endangered species:

1. identification

2. protection

3. restoration

critical habitat

vital to the survival of protected species

keystone species

key to the survival of an ecosystem

biodiversity hotspots

relatively small areas of land

contain many endemic species

at high risk from human activities

Suggestions for Conserving Biodiversity:

set targets to achieve goals.

• protect 50% of habitat in a region

• maintain connectivity (corridors)

• focus more on biodiversity than climate change

• demonstrate value of nature to humans

• convince people that biodiversity can be achieved

Species triage

methodology to most effeciently utilize inadequate resources to maximize species and/or habitat conservation, according to various critera that have been proposed

Sustainable food system

a food system that delivers food security and nutrition for all in such a way that the economic, social, and environmental bases to generate food security and nutrition for future generation are not compromised

two challenges to a sustainable food system

increased production

decreased negative environmental impact

What is the argument for how industrial agriculture helps to preserve biodiversity?

That because modern agriculture takes up less room, it is more sustainable and helps preserve biodiversity (which isn’t true btw)

what are the critiques to the modern agriculture argument?

the problem is that while it uses less room, the crops are condensed which will overuse the soil and nutrients and create an overreliance on pesticides and similar tools that can cause pollution

Agroecology

The application of ecological principles to agricultural systems

Thirteen principles of Agroecology

1. Recycling

2. Input reduction

3. Soil Health

4. Animal health

5. Biodiversity

6. Synergy

7. Economic diversification

8. Co-creation of knowledge

9. Social values and diets

10. Fairness

11. Connectivity

12. Land and natural resource governance

13. Participation

Industrial Agriculture - common traits

• high fossil fuel use

  • industrial fertilizer

  • machinery

  • transportation

• low biological diveristy (monoculture)

• ethical concerns

• high yields

Sustainable agriculture - common traits

• Lower fossil fuel use

  • Natural fertilizer

  • Labor intensive

  • Reduced food miles

• High biological diveristy (polyculture)

• Decentralized (lots of small farms)

• Farms act like ecosystems

  • closed material cycles

  • ecosystem services

Urban Ecology

the study of the structure & function of man-made environments, how the living and nonliving parts of those environments relate to each other and the quantification of the flows of energy, materials and nutrients, etc., required to sustain urban systems.

Land sparing

concentrates high-yield farming into small areas to leave land for wild conservation

Land sharing

integrates sustainable farming throughout wild landscapes

Integrated pest management

combining biological, cultural, physical, and targeted chemical tools to manage pest populations sustainably

Ecology In Cities

studies organisms living in urban patches

Ecology Of Cities

studies the entire city as an integrated urban ecosystem

Urban Ecosystems vs. Oyster Reefs

both are dense, fixed biological structures that filter fluid flows, alter microclimates, consume inputs, and build habitat

EROI (Energy Return on Investment)

Ratio of usable energy delivered to the energy expended to extract it.

What are the EROI trends for petroleum?

declining as easy reserves deplete

soil permeability

Determined by grain size and pore structure

high permeable soils or low permeable soils

High permeability in sandy soils; low permeability in clay soils.

Urban River Characteristics

Urban rivers feature flashy flow hydrographs, high nutrient loads, and extreme diurnal dissolved oxygen swings.

Phytotechnology

Using vegetation to clean up, contain, or remediate polluted soil and water.

Four stages of wastewater treatment

1. Preliminary (screening large solids)

2. Primary (physical settling of sludge)

3. Secondary (biological microbial digestion)

4. Tertiary (nutrient removal & disinfection).

Nitrification-Denitrification in wastewater

Converts harmful dissolved ammonium/nitrate into harmless N2 gas.

Free water surface

Free Water Surface has open water exposed to air

cheaper

easier construction and maintenance

more diverse habitat (open water)

Subsurface flow wetlands

Subsurface Flow passes water through gravel

higher rate of contaminate removal

more space efficient (50 sq ft./person for secondary treatment)

avoids odors, mosquitos

protected from cold

Life Cycle Assessment (LCA)

A technique to assess environmental impacts associated with all the stages of a product's life from cradle-to-grave

Four stages of LCA

1. Identifying the goal and scope

2. Inventory analysis (outline input & output, etc)

3. Impact assessment

4. Interpretation

Why Use LCA?

Identifying inefficiencies in process

comparing products/services

Cradle-to-grave

Life cycle of an object from creation to end of use

cradle-to-cradle

Life cycle of an object from creation to end of use, where at the end of use stage the outputs become the inputs again for reuse