Lecture 18-27 Flashcards
ecosystem def
community of organisms and their physical environment
= all organisms in an area + physical envr + biotic/abiotic interactions
biome def
a grouping of ecosystems sharing a similar set of plant characteristics under a similar environmental regime
what are the two major sets of biomes?
terrestrial: primarily influenced by temperature, precipitation, seasonality
marine: primarily influence by water depth and proximity to land
What effects impact the general pattern of distribution of terrestrial biomes across latitudes?
temperature, precipitation, seasonality
distribution of biomes with increasing latitude is echoed with increasing elevation
- at the equator, it is hot and wet with low seasonality - we get tropical rainforests
- at 30 degrees, it is very warm and dry with moderate seasonality - we get desert
Warm air holds more moisture, therefore there are no biomes that have very low temperatures and high precipitation
What happens to NPP when temperatures and precipitation increase?
The higher the NPP, the more plants because there is an increase in photosynthesis (more water and sunlight)
Net primary productivity (NPP) differs between terrestrial biomes in a manner consisten with difference in temperature and precipitation
evaporation def
the movement of water directly to the air from the soil and water bodies
affected by heat, humidity and wind speed
transpiration
the movement of water from root systems through a plant, and exit into the air as water vapour
affected by plant type, soil type, weather conditions, and cultivation practices
evapotranspiration
transpiration + evaporation
on average, between 3/5 and 3/4 of land precipitation is returned to the atmosphere via evapotranspiration
how does deforestation lead to reduced evapotranspiration?
removal of vegetation (e.g. deforestation) decreases evaportranspiration (ET), and increases groundwater recharge (R), and river discharge (D)
(see picture on slide 17 of lect. 18)
How is NPP correlated with actual evapotranspiration (AET)
AET is affected by both temperature and precipitation
high AET=warm and wet
low AET=dry and cold, or both
Associate biome to NPP/AET
a) low NPP, low AET
b) medium NPP, medium AET
c) high NPP, high AET
a) desert, tundra
b) broadleaf forest, boreal/montane forest, dry tropical forest, grassland
c) wet tropics, wet temperate
Which type of forest accounts for about 1/3 of Earth’s terrestrial NPP?
tropical forests
give an approximate order of the biomes according to how much NPP they account for in increasing order
tundra, shrublands, boreal forests, deserts, crops, temperate grasslands, temperate forests, tropical grasslands/savannas, tropical forests
Which has a higher total NPP between tropical and temperate forests?
On a daily basis, the NPP per unit area is similar between tropical and temperate forests, this means that the difference in yearly NPP between the two biomes is primarily related to the length of the growing season.
therefore, tropical forests have a higher total NPP since their growing season is much longer than temperate forests
What plant characteristics define biomes?
Size, shape, foliage structure and chemistry of plants determine many ecosystem properties and the nature of the other biota
list the three general plant forms
grasses, shrubs, trees
disturbance def
events causing removal of biomass (e.g. herbivory, wind, frost, pathogens, erosion, fire)
competition def
ability to acquire resources compared to neighbours
stress def
any condition that restricts plant production (e.g., shortage of light, water, nutrients, or low temperatures)
Explain the relationship of disturbance, competition and stress with the three general plant forms
grasses: low competition, high disturbance, low stress
trees: high competition, low-medium disturbance, low stress
shrubs: low competition, low disturbance, high stress
(review this)
ruderals def
allocate resources mainly to seed production, often annuals or short-lived perennials
high growth rate, short-lived leaves, short statured plants
example: grasses
good competitors def
high growth rate, short leaf-life, low seed production, high allocation to leaf construction
example: trees
stress tolerators def
allocate resources to maintenance and defenses
often evergreen, long-lived leaves, low growth rate
example: shrubs
forests
trees are dominant or (co-dominant) plant type
two different types, based on longevity of leaf:
1) deciduous (1 growing season): winter-deciduous (subtropical and tropical, leaf shed on dry periods), drought avoidance
2) evergreen (>1 growing seasons): broadleaf-evergreen (tropic rainforest, no distinct growing season, year-round PS). needle-leaf evergreen (growing season is short or nutrient availability contrains PS and plant growth), drought tolerance
How much monthly precipitation provides sufficient moisture for plant growth?
about 20 mm of monthly precipitation for each 10 degrees celcius in temperature
Walter climate diagrams
permits ecologically meaningful comparisons of climates between localities
illustrates seasonal periods of water deficit and abundance
each climate zone has a typical seasonal patterns of T and P
Temperate seasonal forest
dominated by deciduous trees
soil is rich in organic material
challenges: high seasonality (hot summers, cold winters)
deciduous leaves change colour and fall during autumn, thick bark (protection), shade-tolerant understory, lots of leaf litter
boreal forest
dominated by coniferous forests
soil is acidic and mineral-poor
challenges: shorter growing season, long cold winters
conical shaped conifers, dark coloured needles (less surface area –> less evaporation), waxy coating (reduced evaporation), seeds in protective cones
tundra
soil extremely rich and organic
challenges: short growing season, permafrost, extreme cold, poor drainage, very windy
shallow root systems, low to the ground, dark colours, grow close together, lots of lichen and moss, small leaves, wax fuzzy coating, most are perennials
temperature grassland
seasonality: moderate (hot summers, cold winters)
soil is extremely rich and organic
challenges: frequent fires, droughts, windy, grazing
narrow leaves, soft stems, extensive root systems, leaves contain silica, grow from near their base, wind pollination
tropical rain forest
soil is low in organic content
challenges: bacteria and fungi, risk of flooding and erosion of soil and leaching of soil nutrients
colourful plants/flowers attract pollinators (since no wind)
drip trips and waxy surfaces
broadleaf evergreens
smooth thin bark
subtropical desert
precipitation very low <25cm/year
soil is mostly sand (90-95%); low N and organic material; high CaCO3 (calcium carbonate) and phosphate
challenges: windy (no cover), extreme heat and drought and large temperature shifts (cold at night)
waxy coating, thick juicy leaves
white hairs
bloom at night
expendable stem
spines insteawd of leaves
What are the world’s most impacted biomes?
tropical dry forests and temperate grasslands
(56% terrestrial surface (minus permanent snow and ice) has low human impact)
Profound principles behind marine biomes
Life is short
things sink
it gets dark down there
and cold
What influecnes primary productivity in the ocean?
Availability of nutrients (N,P, Fe, Si)
Amount of sunlight
Ocean stratification
Heat arrives at the ocean surface from above
90% of radiation entering ocean is absorbed in the top 100 m
Warm water is less dense than cold; warm water on top of cold is a stable configuration
Surface +/-200 m is well mixed and separated from deeper water
Surface currents and deep currents behave differentlt, although they are linked
Top layer floats on top and cold water below (warm water is less dense)
Ocean layers
top 150m: warm, nutrient-depleted surface water
150-250m: thermocline
bottom: cold, nutrient-rich deep water (because not much competition for the nutrients)
productivity in temperate oceans (according to seasons)
winter: short days, little light (no phtosynthesis), low productivity (missing warm temperature), not much thermocline (all cold in the winter)
spring: phytoplankton bloom, but quickly uses up the nutrients and then low productivity, solar radiation available for photosynthesis, not much thermocline so mixing occurs
summer: strong thermocline means that when nutrients are used up, there is a low productivity, strong thermocline keeping cold nutrient rich water below
fall: thermocline breaks down, bringing nutrients up from below, so we have a short-lived phytoplankton bloom, thermocline begins to disappear, secondary bloom
Comparing productivity of polar midlatitude, and tropical ocean regions
polar regions: extremely high rate of productivity during the summertime
tropical regions: steady, low rate of productivity year-round
middle latitude: large peak in productivity during the spring and a lesser peak in productivity during the fall
What are the marine biomes, and how are they distributed?
Light availability:
- euphotic: top layer of ocean, most sunlight
- photic
- aphotic: no more light
Water depths
- pelagic: open water, not on the bottom, surface all the way bottom excluding the floor
- benthic: floor of the ocean
- abyssal: on the bottom, but very deep
Distance from land:
- intertidal: mangroves
- neritic (continental shelf): coral reefs, kelp forests
- oceanic: all the rest of the ocean away from the continental shelf
Euphotic zone
topmost part of the ocean where light is the strongest
where nearly all of primary production from photosynthesis occurs
photic zone
upper part of the ocean where light penetrates
aphotic zone
Lower part of the ocean where very little or no light penetrates
No living plants
High pressure, low temperatures
Animals survive by eating detritus or other animals
Must adapt to living with no light
Is NPP high or low in open ocean
NPP is lower in the open ocean relative to the shore because nutrients are low
Where does photosynthesis peak in the ocean?
Approx 100m below the surface
Photosynthesis is inhibited at the very top since there is too much light
Lower light levels restrict photosynthesis down here
Benthic zone
Any sea bottom surface
Low oxygenation of water
Low temperatures
Animals here feed on detritus or other animals
Little or no plant life (depending on water depth)
Abyssal zone
Subdivision of benthic zone
Floor of the deepest parts of the ocean
Incredible water pressure
Absolutely no light
Very cold temperatures
Hard to survive
Pelagic zone
open ocean of any depth
Why is depth is a key factor in determining the distribution of the dominant marine biomes?
Depth determines:
- Light intensity (photic zone=high light; photosynthesis>respiration)
- Temperature
- O2 concentration (depends on temperature and balance between photosynthesis and respiration)
- Pressure
- Nutrient concentrations (atmospheric input at surface; nutrients consumed and tied up in organisms near the surface, released in aphotic zone by bacterial decomposition)
Organic matter in relation to depth
Organic matter is high near the surface, and is depleted and nutrient concentrations are enriched with increasing depth.
Most life is in shallow ocean where photosynthesis happens. When things die, they usually get consumed before sinking too low
Oxygen in relation to depth
oxygen is high at depth due to deep current sources and low temperature (conveyor belt)
How are nutrients brought to photic zones?
Upwelling along continental margins brings nutrient rich waters into the photic zone; high nutrients, oxygen and light support high productivity
As you go deeper, what happens to:
a) light/temperature
b) salinity/density
c) nitrates/carbon
d) oxygen
a) decreases
b) increases
c) increases
d) decreases, and then increases
Why is distance from land a key factor in determining the distribution of the dominant marine biomes?
input of nutrients to photic zone
- nutrients in airborne dust
- nutrients from rivers and estuaries
- nutrients from coastal upwelling
Intertidal zone
Where land and ocean overlap
Abundant sunlight
Constant wave action supplies nutrients and oxygen
Food is abundant
Varied substrate provides hiding places and surfaces to cling to
Neritic zone
seaward from the low tide line, the continental shelf out to the shelf break
Well oxygenated water
Low water pressure
Stable temperature and salinity levels
Home to photosynthetic life
Oceanic zone
Beyond the continental shelf
Larger creatures
Life decreases with increasing depth
Widest array of life (because it is a very broad area)
Upwelling def
process in which deep, cold water rises toward the surface (drive up cold deep ocean water filled with nutrients)
Perks to intertidal zone
Abundant sunlight
Abundant nutrients and oxygen (waves, proximity to land)
Varied substrate for hiding places and surfaces to cling to
Challenges to intertidal zone
rapidly changing conditions - exposure to surface and sun varies, salinity
Abundant sunlight can lead to desiccation
Waves can carry you away
Competition for space, light, food
Exposed to predators when tide is out
Name some adaptions to life in intertidal zone
sticky podia (seastars)
Byssal threads (mussels)
close shells tightly (barnacles)
Holdfast root system - attaches to rocks and mussels (kelp)
CaCO3 structure, red colour
Cluster and secrete mucus (snails)
Neritic zone characteristics
Shallow, sunlit waters
Plentiful nutrients from land and upwelling
Most productive and economically significant parts of ocean
90% global catch of shellfish and finfish from here
Where is productivity the highest and lowest in marine environments?
highest: continental shelves
lowest: open ocean
Species def
a group of genetically similar organisms that can interbreed and produce fertile offspring
(def does not apply to asexual organisms)
species diversity
typically measured as species richness: # of species within a habitat
How does species richness change towards the tropics?
increases toward the tropics
1) tropics have greater land mass: more area, therefore more species (however, polar regions have fewer species than similar areas in lower latitudes)
2) harsher climates at the poles
3) tropical regions have more stable climates (but also applies to top of mountains)
4) species-energy hypothesis: greater exposure to solar energy –> greater productivity –> more species can be accomodated in food webs
5) higher speciation rates (driven by energy), greater accumulation of species over evolutionary time
What are the functional differences between terrestrial and marine biomes?
precipitation/temperature:
- key controlling factors in terrestrial biomes
- precipitation unimportant and temperature less important in marine biomes
Variation in seasons:
- high variation between seasons in terrestrial
- low variation between seaons in marine
Organism adaptions:
- terrestrial: organisms exposed to extremes of climate; adapted to moisture/temp. regimes
- organism adaptions similar in all marine biomes
materials:
- terrestrial: fall but largely remain in the ecosystem; recycled
- marine: sink=become inaccessible to organisms at a given depth; “biological pump”
nutrients:
- terrestrial: via soil and atmosphere
- mainly from atmosphere (precip. and dust); proximity to land is important
Effect of gravity on terrestrial vs. marine organisms
Land plants tend to have structures to live with gravity (structures that are harder to breakdown and decompose)
Gravity is not a factor when you are in the water, structure is squishy, as a result get eaten more easily and quicker
What does water availability depend on?
Residence time in the reservoir
Temporal availability
Spatial availability
Proximity to human need (availability vs. access)
Residence time def
length of time water remains in a reservoir differs
averages can be deceiving
- different reservoirs of the same type can have different residence times
How is freshwater classified based on residence time?
renewable:
- water in the reservoir is continuously recharged (<1 year)
- significant withdrawals do not typically cause depletion within the reservoir
- can be depleted if withdrawals are significant enough
non-renewable
- reservoirs which are not recharged on human time scales, or recharge so slowly that significant withdrawals will cause depletion within the reservoir
Temporal availability
not all freshwater is equally accessible year round
- rainfall patterns vary seasonally
major changes in seasonal rainfall patterns
- rainy season and dry season
Spatial availability
rainfall patterns differ globally
majority of precipitation in the equatorial region (30 degrees north and south of the equator)
frequency of terrestrial reservoirs differs (both for green and blue water)
local proximity (location of freshwater resources must be within reach of the human activities requiring the water resources
available freshwater resources and population is unevenly distributed in Canada (issues with water security)
Available water
how much water is available for potential usage
accessible water
how much available water we can actually access for use
- spatial and temporal location
- economic access
- culturally and politically acceptable access
Equation for renewable sources available in a stable state
RFWS(land)=P(land)=ET(land)+R
RFWS(land): terrestrial renewable fresh water supply
P(land): precipitation over land
ET(land): evapotranspiration from land (green water)
R: runoff to sea (blue water)
Classification of water usage
water for survival: water needed for basic survival (drinking, cooking, hygiene)
water for economic purposes: agriculture, industry
environmental water: water needed to support ecosystems, services and species
water for survival
estimated 2.2 billion ppl globally do not have access to safe drinking water at home (3.5 million ppl die annually from contaminated water)
access to safe drinking water is not shared globally
water distribution issues (even technologically advanced countries)
lack of investment in water infrastructure is a major issue (even in developed nations)
many existing water systems are aging and inefficient
lack of safe drinking water has been used as a political took (insufficient infrastructure for poor or indigenous cultures) –> Canada
Water for economic usage
many of the world’s largest rivers now run dry at some point during the year –> often a result of mismanagement and overallocation
agricultural fields in many places around the globe are unproductive for lack of water (lying fallow)
What happens to a lake when it suddenly gets warm, and then cold?
The available oxygen in the thin layer mixes in the entire lake. The oxygen becomes so diltuted that fish drown in the lake due to lack of oxygen
where does saltwater infiltration occurs in areas previously occupied by freshwater
Where rivers dry up at freshwater/marine interface
freshwater pressure generated by flow (holds back salt water)
reduced freshwater flow (saltwater moves into terrestrial areas –> saltwater intrusion)
Environmental water
salt water is generally fatal to freshwater species
can also infiltrate groundwater sources
terrestrial freshwater
derived from precipitation
divided between organic (green) and inorganic (blue) reservoirs
How much renewable freshwater resources derived from precipitation do we use?
30%
Water scarcity index (WSI)
means to quantify water poverty
physical availability of renewable water
can be quantified on a percentage scale
also accounts for social, economic, and environmental factors
R(WS)=W/Q
where,
R(WS)=renewable water supply
W=water withdrawal from all sources
Q=discharge
What is the discrepancy between pop. and accessibility to water? (supply and need)
Areas with most freshwater do not necessarily overlap with areas of greatest pop.
Name 3 strategies to addressing issues with discrepancies between supply and need in freshwater resources
Capturing runoff
Moving remote water
“producing” more water
Capturing runoff
dams and reservoirs
- manmade structures designed to hold precipitation not immediately used by human activities
- largest can supply local water needs for 2-3 years without replenishment
- modifications can be made for electricity generation
consequences:
- permanently disrupt natural pop. in freshwater ecosystems (migratory fish species in particular)
- displaced local communities
- flooded reservoirs
- international conflicts
flooded reservoirs
newly created “blue space” often floods considerable plant life
- decomposition releases large amounts of methane (from plant life dying from flooding)
- newly created wetlands may be a source of methane
displaced communities due to dams
human habitation frequently located next to rivers
history of displacing poor and indigenous communities for reservoir formation
Moving remote water
moving water from a water-inaccessible area to an area where it will be accessible for human use (pipelines, trucks/ships)
Water pipelines
Mainly short pipelines from reservoirs to nearby human activities
Long pipelines currently not economically feasible
Use implies:
- water unavailability in the long term at the end of the pipe
- water availability in the long term at the beginning of the pipe
- enough energy to power the mechanical pumping of the water
- fair political agreements between suppliers and consumers over the long term
trucks and ships to move water
smaller scale transport of freshwater into water-deficient area
- usually a response to a temporary scarcity of water
- has become the primary source of water distribution in some chronically water scarce regions without the resources for pipe construction
How is water availability linked to poverty?
lack of reliable in-home drinking water is a direct contributor to poverty
for people lacking tap water
- sources are often far away
- water delivery often irregular and inconvient
children and women typically tasked with collect water
- interferes with education
Making more water
when there is not enough precipitation to capture, or other water cannot be brough in remotely
- extract non-renewable sources
- recycled water
- desalination
groundwater extraction
to help meet shortfall in renewable freshwater
- can extract non-renewable sources
some groundwater resources refresh rapidly from precipitation (shallow groundwater)
most groundwater sources refill over 100-1000 years (cannot be replaced within a human life)
groundwater
- water held underground in soil or spaces between rocks
overextraction of groundwater
when water is withdrawn from a groundwater reservoir faster than it can be replaced over an extended period of time
overextraction can lead to the disappearance of accessible sources of freshwater
- some surface sources of water supplied by groundwater reservoirs
Consequences of groundwater extraction
overextraction
groundwater takes up physical space (supports soils, a component of elevation)
removal of groundwater sources can result in land subsidence (decrease in elevation)
4 types of recycled water
treated water: water which has been chemically treated to remove contaminates for the purpose of use as drinking water
greywater: wastewater (generally household) that does not contain toxic chemiclas or human fecal matter (water from sink, bath, dishwasher, etc.)
reused water: waste water that has been chemically treated for reuse (treatment can vary in intensity)
untreated water: water that has not been treated to remove harmful contaminants
challenge with recycled water
can be difficult to convince pop. that recycled water is safe to drink
desalination
removal of salt from salt water, to produce freshwater
feasible for a community located close enough to a significant source of salt water
limitations to desalination
Costly to build
Require location next to a supply of saltwater
Extremely energetically costly over the long term (produces GHG)
Require constant maintenance (prone to expensive repairs)
Have a limited capacity (even the most sophisticated cannot currently provide all the drinking water a community needs)
Produce hyper-concentrated solutions of salt (toxic waste that needs disposal)
Designing models to predict the future - System modeling
1) We must determine all the factors that influence what one is trying to forecast
2) We need to qtfy how the interactions occur (interaction/behavior equations). These interactions are then expressed as mathematical equations describing how each qty varies with time
3) We often must estimate the inital conditions (or starting values) of the different relevant factors
4) We then solve these mathematical equations
Range of responses to environmental problems
doing nothing
mitigation: action of reducing the severity or seriousness of an environmental problem
adaptation: reducing our vulnerability to impacts by increasing our resilience or capacity to deal with them
Why do we come up with scenarios?
Challenges of scenarios: near infinite number of possibilities; no way to know which is correct, which could be reasonable
–> scenarios are not predicitions; they allow investigations of the implications of various developments and actions (what-ifs)
Problem specific to climte modeling: given the complicated nature of Earth system models, only a few scenarios can be properly evaluated, and every group must use similar scenarios to permit comparisons.
–> we must arbitrarily choose a few scenarios that simultaneously capture the range of possible futures while being meaningful and useful for planning
How do we come up with scenarios?
A consensus must be established on a limited set of different enough scenarios to learn from those differences and estimate associated uncertainties
For coordinated efforts at an international level, this is generally taken care of by a dedicated organization
Drivers of IPCC scenario making
geophysical driving forces: GHG and aerosol emissions land use, Earth system response
socio-economic driving forces: population, technology development, and associated energy needs and geophysical implications (emissions, land use, etc.)
societal/policy drivers: emphasis on sustainability, regional rivalry, inequality, fossil fuel intensive development
- types of possible responses (mitigation, adaptation, agreed-upon targets)
institutional context
- need for a range of outcomes to grasp the many issues
- working groups coordination: scientific basis, impacts, response
Milestone centric information presentation
What will climate change look like when a particular threshold is reached, such as 2 degree warming
Predicted changes
Patterns of temperature changes:
- more over land than over water
- more at high latitudes and in winter than at low latitudes or in summer
- more at night than during the day
evaporation inccreases, but patterns of precipitation change: contrast between wet and dry regions and seasons will generally increase (to a first order, dry regions get drier, wetter regions will get more precipitation)
overall predictions are very dependent on scenarios –> we can change the outcome
Some changes are expected to proceed more slowly and last considerably longer, such as for sea levels
How will climate change impact ecosystems?
Self: changing life history traits in terms of your physiology
Time: adjusting life cycle events to match the new climatic conditions
Space: dispering to areas with suitable habitat
Phenotypic plasticity
the ability of a single genotype to produce alternate phenotypes in an environmentally dependent context
a fundamental mechanism by which species respond to a changing environment
flexibility in phenotype –> the more flexible, the more they will be able to change to adapt to their environment
Plants and physiological adaption to climate change
open-top chambers supplied three levels of warming (+0, +2, and +4 degrees C above ambient) over 3 years
optimal temperature for CO2 assimilation was strongly correlated with daytime temperature (as temperature increased, their optimal temperature for growth increased as well)
direct impacts of climatic warming on forest productivity, species survival, and range limits may be less than predicted
Invertebrates and physiological adaption to climate change
populations with different thermal histories (cool vs. warm), compared physiological adjustments following exposure to warming
warm-acclimated individuals had a higher thermal threshold (exposed to global warming –> had higher critical temperatures)
given the relatively gradual rate of global warming, marine organisms may be able to adaptively adjust their physiology to future climate
How does warmer water impact fish size?
Warmer waters could lead to smaller fish
1) warmer water contains less oxygen
2) fish require more oxygen at higher temperatures: since fish are ectotherms (cold-blooded), their metabolism is sensitive to temperature-and increases rapidly with temperature
3) larger fish cannot compensate when oxygen declines
What is the gill-oxygen limitation theory?
Growth of gill surfaces cannot keep up with the oxygen demand of growing 3D bodies
Gill surface area does not increase in constant proportion with fish body weight. Fish size is constrained by capacity to take up O2. When O2 declines, fish size much decline.
What is Allen’s Rule in relation to birds and mammals?
Appendages of endotherms will be larger in warmer climates –> dumping of heat loads
Increased bill (beak) size with increasing temperatures
In mammals, larger tails, ears, legs
Reptiles and behavioural adaption to climate change
Reptiles bask in sun to attain physiologically active body temperature. Activity in hot weather may result in body temperatures exceeding critical thermal maximum, leading to death.
Retreat to cool refuges rather that risk death by overheating (quickly reach critical temperature)
However, in thermal refuges limited foraging, decreased growth, maintenance, and reproduction (hiding makes it so that they are not mating, not eating, not taking care of offspring)
Phenotypically plastic adjustments to thermoregulatory behaviour increase their vulnerability to extinction
Polar bears behavioural adaption to climate change
Polar bears use ice to hunt. However, ice is decreasing so they have to eat terrestrial organisms on land (caribou, geese, rodents, and grazed vegetation)
rare occurence
Lead to decrease in body condition and survival rates (lose weight)
Phenology definition
the study of recurring plant and animal life cycle stages that are influenced by environmental changes, especially seasonal variations in temperature and precipitation driven by weather and climate
has been principally concerned with the dates of first occurrence of biological events in their annual cycle
examples:
- the date of emergence of leaves and flowers
- the first flight of butterflies
- the first appearance of migratory birds
- the date of leaf colouring and fall in deciduous trees
- the dates of egg-laying and amphibia
How is climate change impacting phenological adaptations?
Some seasonal biological activities are occurring weeks earlier now than several decades ago
Life events are happneing earlier in the year
The advance in phenology is 3x stronger in birds and butterflies than in flowering plants
birds and phenological adaption to climate change
individual adjustment to egg-laying date (earlier in the year when temperatures are higher in the spring)
yet this does not change the date of spring migration (relies on endogenous rhythms not affected by climate climate)
in consequence, laying eggs in the wrong place
birds and phenological adaption to climate change
individual adjustment to egg-laying date (earlier in the year when temperatures are higher in the spring)
butterflies and phenological adaption to climate change
certain butterfly species are shifting their migration timing and arriving earlier
causes of pop. size decreasing: deforestation, climate change, loss of milkweed
Plants and phenological adaption to climate change
leafs unfolding earlier in the year
cherry blossom flowering earlier
phytoplankton and phenological adaption to climate change
blooms becoming earlier (shifts about 10 days)
phytoplankton are at the basis of the food web –> affects other trophic levels (they need to change with it)
Why is adapting not enough to adjust to climate change?
climate warming has not systematically affected morphological traits, but has advanced phenological traits
adaptive for some species but imperfect (consistent selection for earlier timing)
other organisms need to change with them sinec organisms rely on each other
How does climate change impact the distribution of species and biomes?
biomes are changing (some getting bigger, some smaller)
tropical conifer forests, tundra, and montane grassland and shrubland biomes showed the largest net decline in area
Biomes are changing into other biomes
- In response to poleward and upward (in elevation) movement of biomes, species distributions have often moved with them. For some, this expands their range.
- New home = new friends and new enemies (biotic interactions from organisms moving to new locations)
What is happening to the Arctic biome with climate change?
Arctic tundra being increasingly covered by deciduous shrubs
Commonly assumed to increase carbon (C) storage, however, most C in the Arctic is stored in soils
Shrub expansion will cause changes in soil processes that have the potential to promote soil C losses that substantially exceed C gains in plant biomass
Increased shrub growth means deeper permafrost mel in Arctic landscapes
Net release of carbon by replacing tundra with shrubs. As permafrost disappears, all the dead matter decomposes and is introduced into the atmosphere
What plants are increasingly common in the Antarctic?
vascular plants have increased in abundance due to greater seed germination and survival in warmer temperatures
How is a change in species distribution (in birds for example) created a contracting range?
southern range boundary is shifting faster –> even though moving north, southern boundary moving faster
What happends to species if they cannot shift their range fast enough?
Projected that large areas of the globe (28.8%) will require velocities faster than the more optimistic plant migration estimates from a landscape before anthropogenic fragmentation
Plant migration may not keep pace with the unprecedented rate of current climate change
–> decreases in populations, extirpation or even extinction
What is the change in biotic interaction between caribous and shrubs?
Increased shrub growth threatens caribou
Shrubs crowding out lichens (key winter food for caribou)
Shrubs collect snow; deep snow makes it hard for caribou to reach lichens beneath
Increasing shrubs also speeds up rate of warming
- snow trapped by shrubs insulates soil, keeping it warmer over winter (prolongs the length of the season, which makes it more conducive for shrub production –> positive feedback loop)
- arctic microbes increase processing of organic matter in soil, making soil even better for shrubs, further increasing the shrubs’ capacity to warm the soil
What is the change in biotic interactions between polar and brown bears?
ecology of brown bears in arctic offers evidence that these habitats are unlikely to provide sufficient food for polar bears (food is limited)
brown bears have been shown to displace polar bears from feeding sites
What is the change in biotic interactions between birds and caterpillars?
Current phenology is changed under climate change:
- nesting period is shortened (ends earlier)
- caterpillar stage is shortened and pushed much earlier (ending is at the beginning of nesting period)
- leafing is extended, and flowering is shortened (ends earlier)
Changes in biotic interactions between zooplankton and predators
example:
daphnia feed on phytoplankton, main herbivore. They are an important food source. They have a small change in morphology that makes them less eaten.
However, CO2 increases prevents daphnia to smell their predators. Cannot have morphological change. Decreases their ability to defend themselves –> population decline
What is the change in biotic interactions between plants and herbivores?
Elevated CO2 reduces plant nutritional quality for herbivores by increasing leaf carbon-nitrogen ratios
Consequently, herbivores will need to consume more plant tissue to meet their nutritinal demands
Being eaten more than being produced –> net negative to plant biomass
Name 3 ecoevolutionary feedbacks that impact selection on plant traits due to climate change
1) higher temperatures –> higher insect growth rates, increasing plant damage
2) warmer winter temperatures reduce overwinter mortality among herbivores and increase foraging during prolonged growing seasons
3) climage change may disrupt herbivore-predator interactions
What are the changes in biotic interactions between plants and pollinators?
Climate change decreases flower size (droughts), inhibits pollen and nectar production (elevated CO2), which all impact pollinators
What are changes in biotic interactions between plants and mycorrhizal associations
Majority of studies showed that elevated CO2 had a positive influence on plant-mycorrhizal relationships
HOW???
Changes in disturbance regimes: wildfire, drought, and insects
cliamte change increases the risk of fire in areas where decades of total fire suppression have resulted in buildip of dead fuels
Wildfire increasing in frequency, size, season length
- longer, more intense summer droughts stressing trees
- stressed trees are more susceptible to beetles attacks, which leave standing dead fuels in their wake
Changes in disturbance regimes: arctic wildfire and shrubs
wildfires consume lichens
also facilitate rapid increases in shrub cover through nutrient release and soil warming
(positive impact on shrubs –> benefits shrubs)
increase in shrubs in the Tundra adds to warmer and drier conditions –> increases fires
climate change also increases shrub-promoting microbes which warm the soi making it more favourable for shrub growth
Changes in disturbance regimes: mountain pine beetle
endemic (naturally occuring) in lodgepole pine forests
female beetles drill into bark of mature pine, lay eggs. Larvae hatch, feed on sapwood, overwinter. Disrupt water and nutrient flow, kill tree. Spring: adults emerge, fly to new trees, cycle restarts
Beetles prefer mature lodgepole pine –> because of fire suppression, we have lots of mature pine.
Beetle larvae are killed by severe winter cold snaps –> survival is enhanced by warmer winters (climate change).
Carbon sequestration is an important forest ecosystem service. Trees fix CO2 while they grow, release it as they decompose. So, with an increase in pines dying due to pine beetles, forests become a source of CO2 (instead of a sink).
Positive feedback loop (increasing pine beetle infestation kills trees –> increasing temperature rise –> increasing beetle reproduction)
What has happened with the mountain pine beetle since 2004?
Infestation peaked in 2004
On a provincial level, the annual kill declined rapidly since then
- the amount of available habitat has diminished, as the beetle has already destroyed most of the mature lodgepole pine
- the rate of spread in other areas of the interior has been somewhat varied, due to diverse terrain and forests with greater diversity of timber species.
How do plants show evidence of declines due to climate change?
decreases in species richness of 10-32%
changes in temperature most significantly explained tree cover changes
How do butterflies show evidence of declines due to climate change?
drought limits the growth of milkweed and increases the frequency of catastrophic wildfires (monarch pop. goes down since they are picky and like eating milkweed)
temperature extremes trigger earlier migrations before milkweed is available
severe weather has killed millions of butterflies
Evidence of declines due to climate change in marine environments?
Seagrass meadows are one of the most productive ecosystems in the world, ranked ahead of coral reefs
20% of the world’s seagrass has been lost
sea level rise –> increased coastal water depths, changes in tidal variation, increased seawater intrusion
decrease in popultions due to more highly saline conditions and icreased water depth
in addition to habitat loss, manatees in subtropical waters of the southeastern US suffering from increased hurricane occurrence
How did the golden toad go extinct?
reproduction synchronized to precipitation patterns
shift to dyer climate, led to mismatch with reproductive cycles
first known extinction of a land animal due to climate change (timing of reproduction did not change with climate)
How did the bramble cay melomys go extinct?
small roden only found on a single island off of Australia
habitat=dense vegetation near shoreline
cause of extinction: loss of habitat due to sea rise
firest extinction of a mammal due to climate change
What are some ways to mitigate the impacts of climate change?
saltmarshes and mangroves both protect the immediate vicinity during storms, as well as populations further inland by preventing storm surges salination, inland flooding
if mangroves were lost, 15 million more people would be flooded annually across the world
protection of mangroves will reduce impacts of climate change (invest in protecting coastal biomes)
biodiversity may modulate the impacts of climate change on ecosystem functions
- in grasslands, increased plant diversity promoted the effect of positive climatic drivers, such as elevated CO2 levels, nutrient addition and warming
- diversity may increase ecosystem stability to drought and climate extremes
- potential of biodiversity to enhance increased productivity or modulate any reduction in productivity caused by climatic drivers
Factors influencing action on environmental issues?
how well established is the nature of the problem?
how well understood are the cuases and the effects?
what are the likely impacts and their severity?
how distant in time and space are the impacts?
are there available solutions? if not, how quickly can they be developed?
who, or how many, must be involved in the solution(s)?
what are the economic implications of inaction and of action?
how immediate are the benefits of a response?
what is less complex: mitigation or adaptation?
Which human activities release GHG?
Energy (73.2%)
Agriculture, forestry, land use
Waste
Industry
How is energy use and CO2 release correlated?
Most of the needed energy comes from fossil fuels that release CO2, as only fossil fuels are currently capable of meeting the world’s baseload requirement
What is required for any kind of stabilization in GHG emissions?
a reduction of >90% of emissions
The Kaya Identity
A convenient way to look at carbon emissions from energy use and to study our ability to reduce them is to use the Kaya Identity:
C = P *Y/P * E/Y * C/FF * FF/E
where,
C=carbon emissions
P=population
Y=output (income, GDP)
E=energy used
FF=fossil fuels used
Kaya Identity: Y/P
Per capita income (and consumption)
Capitalism in action: the more efficient or productive wins and is rewarded by increased wealth that can be used to buy the more things we can produce
Kaya Identity: E/Y
Energy intensity, or amount of energy required to generate a unit wealth
The Kaya Identity: C/FF
Carbon emitted per fossil fuel burned. This has been historically reduced by 0.3%/yr as we switched from coal to oil, and now to natural gas that emits less CO2 per energy produced
Kaya Identity: FF/E
Fossil fuels used per unit energy produced
Kaya Identity: solutions to population (P)
population control: difficult issue that clashes with many values, religions, and local realities
for example, in many developing countries, having many children is what provides a social net to aging parents. the best proven population control mean is increased education and wealth
Kaya identity: solutions per capita consumption (Y/P)
Reduce standard of living: hard to achieve in countries with a higher standrd of living, and not compatible with the aspirations of people in poorer (or even richer) countries
Kaya Identity: solutions to energy (E/Y)
Energy efficiency and conservation
Improve efficiency in energy production and in energy use
Reduction in consumption and/or buying goods or services requiring less energy to produce
Some possibilities here especially in transportation and utilities, but a long-term sustained increase in efficiency back to and beyond 1.5%/yr will require a lot of work
Kaya Identity: solutions carbon and fossil fuel (C/FF and FF/E)
Alternative energies and emissions control are simpler social choices, but many technical challenges must be (and are being) solved
Technological approaches
Reduce emissions at the source
Compensate for the warming or stimulate natural processes of sinks (geoengineering)
What is solar radiation management
aims to reflect a small proportion of the Sun’s energy back into space
sunshades: aiming more of the energy back into space by increasing the albedo
stratospheric aerosols: do it in space, in the atmosphere (dump sulfates into the atmosphere) to reflect sunlight back into space
increase cloud albedo: takes care of the temperature, but not CO2 concentrations (ocean acidification, impact on plants)
- enhance upwelling
Carbon dioxide removal
devise ways to accelerate sinks of CO2
examples:
- enhance downwelling
- carbonate addition
Geoengineering approaches
all of the geoengineering approaches that can provide significant effect have serious consequences
there is growing consensus that geoengineering approaches are worth studying, but should not be our plan A
however, if a sudden catastrophe is in progess (e.g., the beginninf og a runaway warming,) their use could be justified
Extinction
extinction is the natural fate of most species (99% of all species which have ever evolved are now extinct) –> in the past, includes species that evolved into other species
normal rates of extinction
- 0.1 species per million species per year
ecosystems must be able to lose species and remain stable in the long term
- population size impacts extinction risk
- natural and normal part of ecosystems –> need to persis even when species go extinct
Population Size
population of individuals (genetic diversity)
- population health is much more related to genetic diversity
smaller population (greater change of individuals being born with a combination of deleterious recessive alleles)
recessive alleles are much more common to be expressed in smaller populations (recessive phenotypes)
Genetic bottleneck
due to loss of population (loss of genetic diversity) –> causes a genetic bottleneck as well
recovery of individual in a population does not restore lost genetic diversity
- genetic diversity generated over long periods of time through survivable rare genetic mutations
Quaternary extinction event (QEE)
began 130 000
majority of extinctions occurred between 13 000- 8 000
global trend in selective extinctions in mammals over 44kg
pattern in extinction trends
lowest overall rate of extinctions (African continent)
further away from africa –> greater % of species lost
What was ocurring globally during the QEE?
Climate: ice age with periods of glaciation and inter-glaciation periods
Many species which went extinct during the QEE had previously survived similar global climate change
Modern homo sapiens began migrating out of Africa (100 000 years ago)
Climate change overlaps with human migrations in some locations
- Either factor alone may not have been enough to cause extinctions (combo of both increased extinction rate)
QEE: Overkill hypothesis
humans overhaversting is the primary driver in mammal extinctions during the QEE
Evidence supporting:
- Timeline for human migration coincides with extinction events
- Extinctions occurred rapidly (<1000 years)
- Only large animals affected (preferred food source)
- African species mainly unharmed (co-evolved with Homo sapiens)
Evidence against:
- Some species hunted did not go extinct (bison, moose)
- Australian extinctions started before human migrations
QEE ecological impacts
complete change in plant diversity
global increase in fire frequency correlating to loss of grass-specialist grazer species
fewer grazers, more grass and more fuel for wildfires
increased fire frequency (global carbon cycle)
What are some lessons learnt from the QEE
Extinctions in animal species can effect both biotic/abiotic systems, and local/global systems
Even small human populations can engage in overharvesting significant enough to cause extinctions
Effects of overharvesting are worse when they occur at the same time as environmental stressors
- large populations are more resilient to stressors such as climate change
What are some common patterns in modern overharvesting of wildlife populations?
Selective exploitation apex predators
Removal largest animals from a community
Targeting of species perceived as “most valuable”
Eradication of species which are viewed as undesirable
Wildlife viewed as resources
Selective exploitation of apex predators
Frequently viewed as “pest species”
- killed to conserve “desirable” wildlife and domestic species
Apex predators exert a top-down control on many terrestrial ecosystems (example: explosion of pop. of white-tailed deer)
- deer are herbivores
- preferred plant species extremely rare in areas with deer overpop.
- can change entire plant community (and dependent species)
Brainworm impacts due to overpopulation of deer
Brainworm: nemoatode worm which infects brain tissues in cervids. Larvae are laid in deer feces.
- Snail consume the larvae
- New cervid hosts consume the snails on grass they eat
Deer carry the parasite asymptomatically
- brainworm is endemic in many pop. of white-tailed deer
- Can still pass the parasite on to other species
Deer are spreading brainworm to moose since deer are moving into territory that is historically occupied by moose
Moose are highly susceptible to brainworm
- causes severe neurological symptoms that lead to death
Removal of large animals
Large animals are dispropotionaly overharvested compared to small animals
Large animals more likely to be food for people
Predators of “desirable species” (eliminated as pests)
Large animals can have as significant effect on an ecosystem as an apex predator (even if they are a primary consumer)
Removal of bison impacts
bison prefer grasses over non-grass species. they will selectively consume grasses, allowing other plants to grow (many of these non-grass species produce flowers)
removal of bison from their historic range has resulted in an increase in grasses at the expense of non-grass species
bison also affect the microbiome of the soil (bison feces)
Removal of whales
Whales consume food in the upper layers of the ocean. Whale poop and dead bodies bring nutrients to the lower levels of the ocean
Whales travel considerable distance –> move nutrients to distant locations
The Krill paradox
loss of main kirll predator (whales) should have led to increase in krill numbers (classic top-down model)
instead, krill numbers declined with whale populations
bottom-up model: krill dependent on nutrient input from whale poops
- In other words, whales are the predator and the source of food for krill
Removal of desirable species
some species are seen as particularly desirable to harvest
examples: food, fashion (plume trade in 1800-1900s), rare hardwoods, medicinal plants, rare plant species, trinkets
Removal of undesirable species
some species have always been seen as less desirable (ugly appearance, little economic use)
undesirable species have the opposite problem of desirable species: no one is concerned when pop. are overharvested
example: arthropods are frequently a target of uncontrolled overexploitation –> however, they are food sources, pollinators, decomposers (critically important to ecosystems)
Wildlife viewed as resources
Until the early 20th century, all wildlife was viewed as resources to be managed. In the 21st century, this view shifted towards wildlife having intrinsic value –> yet exceptions to this modern framework are forests and fisheries
wildlife as resources; fisheries impacts
seabirds are dependent on oceanic fish for survival
- evidence many species can no longer find enough food to support populations
- switching what they are consuming due to lack of fish
loss of fish stocks have also affected nutrient cycling in terrestrial systems (salmon fertilization) – eggs travel down streams/rivers and collect nutrients – bears eat the fish, consume and excrete the nutrients in their terrestrial ecosystems.
- correlation between salmon run size and plant health
- greenness of plant canopy indicates levels of nutrients (coming from salmon)
Give an example of species evolved due to selection pressure from overharvesting
1) Pop of mice has moved into a new area where the rocks are very dark. Some are black and some are tan.
Tan mice are more visible to predatory birds –> eaten at higher freuqnecy.
Because black mice had a higher chance of leaving offspring than tan mice, the next generation contains a higher fraction of black mice than the previous generation
2) African elephants with tusks selectively targeted by poachers. Increase incidence of tuskless individuals in heavily hunted populations
Impacts of overharvesting
nutrient cycling
changes to the carbon cycle
top-down and bottom-up to species assemblages
evolution
