D4.3: Climate Change

Where does Earth's temperature come from?

Short-wave radiation from Sun enters atmosphere, some are reflected back into space but most are absorbed by Earth & re-emitted as long-wave radiation

Maintenance of Earth's Temp

Earth's temp is maintained by a layer of gases like CH4 and CO2 which retain heat

-without them, Earth's average temp would be < 0 C

-anthropogenic sources from human activities release large amounts of such gases

Anthropogenic

Human-induced changes on the natural environment

Main Greenhouse Gases (2)

CO2, CH4

CO2

produced through cell respiration (naturally) and combustion of biomass and fossil fuels (mostly anthropogenic)

-removed through photosynthesis an dissolution in oceans

CH4

Produced Through:

-emissions from marshes and wetlands

-organic waste in landfills

-extraction of fossil fuels

-melting of permafrost in polar regions

Most Abundant Atmospheric Gases

O2 and N2

-not considered greenhouse gases bc they do not absorb longer-wave radiation

Water Vapors

Released by evaporation of oceans and plant transpiration, accelerated by global warming, removed via rain and snow

Retain heat when condensed as clouds, act as a heat sink, then radiates it back to Earth's surface

*why temp drops faster at night with clearer skies due to less heat retention*

Weather (6)

determined by temp, humidity, precipitation, visibility, wind, and atmospheric pressure

-all of these are influenced by heat

-persistent heat increases influence long-term weather and climate patterns

Positive Feedback

amplifies the process that created the result

*seen in global heating*

Positive Feedback in Global Heating (5)

-Albedo

-Permafrost and CH4 release

-CO2 and ocean warming

-frozen CH4 in oceans

-forests and fires

Albedo

Amount of radiation that is reflected back into space

-snow and ice, or light colored surfaces, have high albedo

-oceans/forests, or dark-colored surfaces, have low albedo

Melting polar ice caps expose darker ocean, decreases albedo and increases heat absorption, speeding up ice cap melting

*process repeats*

Permafrost

permanently frozen layer of soil beneath the surface of the ground

Permafrost and CH4 Release

permafrost contains frozen organic matter, or detritus'

-once melted, CH4 is released from decay, CH4 further accelerates global warming

*prrocess repeats*

CO2 and Ocean Warming

Gas solubility in water decreases with increases in temperature

-increase in atmospheric CO2, increase global temp, warming oceans

*process repeats*

Frozen CH4 in Oceans

Frozen CH4 can cap (when CH4 is trapped within lattice of H2O molecules) methane stores in oceans

-warming oceans dissolve hydrate caps, releasing CH4, which further warms oceans

*process repeats*

Forests and Fires

Higher temps make forests drier and more prone to fires

-burning forests release CO2 (further increases temps)

-damaged forests reduce carbon capture capacity as well

Tipping Point

occurs when environment changes and feedback cycles overwhelm ecosystem resilience

Boreal Forests

cold temps slow down cell respiration, reducing decomposition rates

-photosynthesis stores CO2 as biomass

But warmer temps and decrease snowfall increase droughts, leading to more intense and frequent forest fires

-fires release CO2 from biomass, decrease carbon storage, and forests may shift from being carbon sinks to carbon sources

Landfast Ice

sea ice that is fastened to land and does not move w/ wind or currents

Pack Ice

Ice that floats on water rather than being attached to land

Importance of Landfast Ice

Essential for emperor penguins for stable habitat, specifically breeding sites

-fluctuating climate causes ice to break and reform, making habitat unreliable, which causes errors regarding situating nesting sites, which impact fledgling survival

ex. ross island ice break-up in 2018 led to lots of fledgling death :(

Importance of Pack Ice

Essential for walrus resting areas

-female walruses use ice to avoid pups being trampled by adult males

expanding floating pack (sea) ice increases feeding site range but forces walruses to travel farther

-increased travel for feeding and thermoregulation requires more energy

Ocean Stratification

Warmer, less salty (less dense) water floats on top of colder, saltier (denser) water

-mixing occurs between layers via currents, winds, and tides, but the greater the difference in density, the more difficult the mixing, increasing "ocean stability"

Ocean Stability

When mixing btwn ocean layers is more difficult

Warming climate increases ocean stability by warming surface temp, melting ice, and decreasing salinity

-produces stronger stratification, limiting heat, oxygen, and CO2 transport to deeper ocean layers

Stratification and Global Warming

increased stratification (ocean stability) adds to global warming by keeping CO2 at the surface

-warmer waters absorb less CO2 and O2 as molecules gain more kinetic energy, making it harder for them to remain dissolved

reduced mixing affects marine life

Ocean Carbon Cycling

Sunlight reaches surface, enables photosynthesis and food chain activity

-carbon from detritus and waste moves to deep ocean through gravity and organism movements

-deep currents also move nutrients upward

Nutrient Upwelling

Nutrient upwelling cycles contribute to ocean primary production and energy flow through marine food chains

Range Shifts

Species are relocating to areas with more tolerable climate conditions

Montane Species

live in mountains and experience temperature increases at all elevations

-migrate upslope to find optimal climate conditions

-high-elevation species cannot move any higher and face habitat limitations

*competitive exclusion forces species to seek new niches as competitors arrive*

Climate Change and Montane Species

Climate change model predict extinction for higher elevation species, disproportionate number of threatened species are found at higher elevations

Tropical montane species are more sensitive to temperature changes as they are more use to a narrower range than temperate species

ex. king of saxony bird of paradise

King of Saxony Bird of Paradise

rising temperatures push them to seek a cooler, moist, more tolerable range at higher altitudes

-moving upslope, they encounter more limited habitats and those already at highest elevations lack higher grounds

Shifts in Latitude Ranges

Shifts in latitude ranges affect population distributions, Northern hemisphere species tend to shift northward

ex. American Beech

American Beech

tree that is expanding into Southern Canada as winters become milder, impacts local ecosystems by changing forest composition

-compete w/ native species that are less tolerant of warmer temps

-also affect wildlife as beech nuts are essential food source for black bears, squirrels, and various bird species

Ocean pH Change

over 500 billion tons of CO2 have been dissolved in ocean since Ind. Rev

ocean pH has decreased from 8.179 to 8.069, indicating 30% acidification

Impact of Acidification on Corals

corals require carbonate ions (CO3 2-) from seawater to make calcium carbonate skeleton

-dissolved CO2 reacts w/ H2O to form carbonic acid (H2CO3)

Basically the reaction between H2O and increased CO2 from global warming reduces the availability of carbonate ions for corals, making it difficult for them to build skeletons

Coral Bleaching

Corals have mutualistic relationship w/ zooxanthellae

-warm water causes coral to eject zooxanthellae as way of self-preservation (results in bleaching)

**zooxanthellae contain pigments that provide corals w/ their colors, loss of zooxanthellae exposes coral's white skeleton through translucent skin

Impact of Coral Bleaching

Corals are known as ecosystem "engineers" (basically keystone species)

-their disappearance impacts marine ecosystems as habitat loss for marine species and food chain disruptions, resulting in loss of biodiversity

Carbon Sequestration

capturing of Co2 from atmosphere and storing it through geological and biological processes

Carbon Sequestration Processes (3)

1. photosynthesis (carbon fixation)

2. biomass storage in vegetation, wood, and burial of undigested detritus

3. carbon uptake by aquatic organisms (building shells)

Human Approaches to Carbon Sequestration (3)

Afforestation, reforestation, restoration of peat

Afforestation

Planting trees in areas where they do not exist, done by countries to meet climate change goals

ex. EU and Canada do this

Reforestation

Forest regeneration: restocking of depleted forests, often after clearcutting

-involves replanting trees, usually a monoculture of commercially valuable species :(

Clearcutting

all or most trees in a designated area are cut down and removed, leaving land mostly or completely bare

Restoration of Peat

Forming ecosystems like wetlands, bogs, and moors which constitute the world's largest carbon sinks (which happen to be useful for fuel, heating, and fertilizer)

Global Peatlands initiative aims to protect, maintain, conserve, and restore peatlands

-requires restoration of water levels, prevent drainage, and re-establish native species

Phenology

Study of seasonal timing in animal and plant behavior, such as leaf budding and egg laying

Photoperiods and Temperature Patterns

examples of variables that influence timing of biological events

Photoperiods

period during which an organism is exposed to light within 24 hours

-varies according to seasons, but remains stable annually

-unaffected by climate change and serves as a reliable environmental signal

Photoperiods influence the timing of plant...

growth and flowering

includes both short vs long days and impact budburst and bud set

Short Days

trigger flowering of autumn plants like chrysanthemums and poinsettias

Long Days

trigger flowering of crops like lettuce and spinach

Budburst and Bud Set in Deciduous Trees

-shorter days (in fall) slow growth, leading to bud set, when bud set encloses branch ends, protecting apical meristem

some species bud set relies on day length, while others depend on decreasing temperature or both

warming temperatures trigger budburst mostly, which initiates new leaf growth

Bird Migration

Birds migrate on resource availability (food/nesting sites)

-changes in day length serve as primary signal for migration, which triggers physiological and behavioral changes

-both fat accumulation for energy reserves, increase feeding, and sometimes molt of feathers

Shorter days (fall) prompt southward migration, while longer days (spring) prompt northward migration

Molting

shedding of old, worn out feathers to grow new ones

Nesting Behavior of Birds

photoperiods help birds time their nesting

-increase day length prompts nest-building, courtship, and egg-laying

aligns hatching with peak food availability so that insects, seeds, and other resources are abundant to maximize survival rate of chicks

Disruption of Nesting Behavior

nesting behavior of birds (photoperiod) is synced w/ peak food availability

-but the presence of seeds, fruits, and insects are temperature-dependent

climate change alter food availability (bc change temp) while photoperiods remain unchanged, creating conflict

Great Tits

A bird that feeds their young caterpillars

-warmer weather has caused caterpillar biomass to peak earlier, leading to fewer and lighter chicks per brood

Reindeer

photoperiod triggers their migration (increased daylight=migrate northward)

Reindeer consume arctic mouse-ear chickweed, plant whose growth is triggered by temperature

-but warmer growth has caused their growth to occur earlier, misaligning it w/ reindeer migration which decreases reindeer survival

Photoperiod/Climate Change General Idea

Climate changes bring disruptions when temperature acts as a cue in one population and a photoperiod acts as a cue in another

Insect Life Cycles

Warmer temperatures accelerate life cycles of pests like the spruce bark beetle

-they normally have a 2-year life cycle as cold winters and short growing seasons limit their reproductive rate

But warming conditions allow larvae to develop faster, shortening life cycle to a single year, doubling reproductive rate

Impact of Shorter Insect Life Cycles

Shorter life cycles = more reproduction, leads to widespread infestation, attacking and killing spruce trees which weakens forest health/resilience

-has produced large-scale tree die-offs as spruce bark beetles bore into bark, disrupting water/nutrient flow

Tree death releases stored CO2 into atmosphere, further contributing to climate change

Climate Change and Evolution

climate change initiates evolutionary changes by altering environmental conditions

Tawny Owls

exhibit 2 main color forms, (grey and brown), heritable traits that aid w/ camouflage

-in areas where winters are long, gray forms are more common as they provide better camouflage against snow (enhancing fitness)

Climate change has caused their habitat to decrease in snow, reducing advantage of grey forms

-expose to snow-free landscapes gives brown form the advantage, increasing their fitness, which causes a shift in the allele frequencies

now brown forms are more common, acting as evidence of natural selection in response to changing environment

*example of microevolution*