Threats Flashcards
What are the biggest threats to freshwater biodiversity?
overexploitation
water pollution
flow modification
destruction or degradation of habitat invasion by exotic species
(Dudgeon et al, 2006)
What are some of the biggest challenges for protecting freshwater biodiversity?
Assessments of freshwater biodiversity are very incomplete (data deficient).
Humans compete drastically over freshwater resources.
Freshwaters are ‘receivers’ of land effluents.
A lot of freshwaters span multiple cities/countries without an overall management plan (i.e., it differs by jurisdiction) and control of the land, water, and inputs is needed for freshwater conservation.
(Dudgeon et al, 2006)
What are the biggest effects of humans on Earth’s ecosystems?
Land and water transformation
Alterations of biogeochemical cycles (CO2, H2O, N)
Extinctions
Invasive species
(Vitousek et al, 1997)
Explain stress, stressors, and stress response.
Stress is a condition in which an organism’s homeostasis is threatened or disturbed as a result of the actions of intrinsic or extrinsic stimuli, called stressors.
The actions of stressors, are twofold: they produce effects that threaten or disturb the homeostatic equilibrium, and they elicit a coordinated set of behavioural and physiological responses thought to be compensatory and/or adaptive, enabling the animal to overcome the threat, i.e., the stress response.
(Wendelaar, 1997)
Homeostasis
Homeostasis refers to the relatively stable state inside the body of an animal. Animal organs and organ systems constantly adjust to internal and external changes in order to maintain this steady state.
https://ecampusontario.pressbooks.pub/animalphysiology/chapter/1-3/#:~:text=Homeostasis%20refers%20to%20the%20relatively,to%20maintain%20this%20steady%20state.
How will climate change impact your study species?
Will cause range shifts for species where possible.
Fishes: less oxygen will be available and fewer cool/coldwater habitat for fish that need them. They’ll need to find cooler deep waters. Temperature and flow are also key factors that influence hatch timing for fishes. A reduction in body size is occurring with consequences for energy demand relative to supply (Currie & Evans, 2021).
Turtles:
Harder to tell because they’re so long-lived its been hard to study.
However, snapping turtle sex is determined by temperature. Mixed sex ratios only occur when temperature varies. When temperature is consistently high only females are produced. This will ultimately lead to extinction. Less dependable river flows will also impact nesting success.
How will climate change impact my study ecosystem(s)?
Receding glaciers and reduced snowpack cause earlier freshet and altered flow regimes.
Enhanced evaporation leading to reduced water levels - more evaporation = warmer atmosphere because more water in it = more evaporation = positive feedback loop.
Increased CO2 and acidity levels.
Lower [DO] with higher temperatures.
More algae production with longer growing season, higher water temperatures, and longer ice-off season.
More frequent severe weather events such as droughts, floods, temperature extremes, and storms.
(ENSC 3106 Notes; BIOL 4503 Notes)
HIREC
Human Induced Environmental Change
How does urbanization, tilling, and drainage (e.g., of wetlands) alter the natural flow regime?
There is an increase in magnitude and duration of high flows which results in bank erosion and channel widening as well as downward incision and floodplain disconnection.
Reduced infiltration into soils causes reduced baseflows.
(Poff et al, 1997)
How do levees and channelization impact the natural flow regime?
They reduce overbank flows which restricts the channel causing downcutting, prevents floodplain erosion and deposition, and reduces channel migration and the formation of secondary channels.
(Poff et al, 1997)
How does groundwater pumping alter the natural flow regime?
It lowers water table levels which causes streambank erosion and channel downcutting after the loss of vegetative stability.
(Poff et al, 1997)
How do dams and weirs alter the natural flow regime?
They capture sediment moving downstream which causes downstream channel erosion and tributary headcutting as well as bed coarsening.
Reduce the magnitude and frequency of high flows which causes deposition of fines in gravel, stabilization and narrowing of the channel, and reduced formation of point bars, secondary channels, oxbows, and changes in channel planform.
(Poff et al, 1997)
Urbanization
It is predominantly the process by which towns and cities are formed and become larger as more people begin living and working in central areas.
(Wikipedia)
Urban
A human settlement with a high population density and an infrastructure of built environment (i.e., human-made conditions not natural).
(Wikipedia)
Anthropocene
Term assigned to current geological epoch that is a result of humans drasticly altering the environment.
Started ~2 centuries ago with creation of steam engine.
Transformation of land
Increased greenhouse gases
Pollution
Ocean acidification
(Crutzen, 2006)
