lecture 4 - threats to biodiversity: habitat change Flashcards
7 environmental ethics?
- All species have a right to exist
- All species are interdependent
- People have a responsibility to act as stewards of the earth
- people have a responsibility to future generations
- Respect for human life and huma diversity is compatible with a respect for biodiversity
- People benefit from aesthetic and recreational enjoyment of biodiversity
- People benefit from the knowledge the natural world provides
indirect human threats to biodiversity?
increasing human pop + consumption: agriculture aquaculture commercial + residential development natural resource use international trade transportation + roads
direct human contributions/threats to biodiversity loss?
habitat loss fragmentation habitat degradation (pollution) climate change over exploitation invasive species disease
resulting loss of biodiversity bc of human activities?
extinction of sp. + pops
degradation of ecosystems
erosion of genetic diversity + evolutionary potential
loss of ecosystem services
erosion of support systems for human societies
what is the root of major threats to biodiversity?
human pop growth
how has human population growth changed? what does it lead to?
- Incredible exponential growth
- Development of health and medicine that allowed for more survival - our population boomed
- Decrease in species abundance as human pop grows
what did the living plant index find? is it impacted by “noise” in the data?
- 68% decline in abundance: decline in fitness and health of these plant pops.
- Clearly noise in our estimates of pop size - when averaged and looked at statistically, the decline is still statistically significant and far from value of no change
why is there a current mass extinction?
- Multiplier effect - 100 sp over 100 yrs = 10,000 sp
- Already way past our estimate of sp on earth over 200 yrs
- Hard to imagine bc geological time scale is so long - however, extinction occurring at an accelerated rate
- Previous great extinctions were over much longer periods of time
what is a mass extinction
A mass extinction is a sharp spike in the rate of extinction of species caused by a
catastrophic event or rapid environmental change. Scientists have been able to
identify five mass extinctions in Earth’s history, each Of which led to a loss Of more
than 75 percent Of animal species.
is the ecological foot print per capita high in all places with high human pop?
- Per capita - per person
* For how many people in india or china - relatively low, especially compared to USA and CAD
what did industralization result in?
an increase in atmospheric carbon + nitrogen
still increasing exponentially
what human cause changes are levelling off? (still increased)
stratosphereic ozone
domesticated land
what have CO2, nitrous oxide, stratospheric ozone, and domesticated land lead to?
decrease in sp abundance
how is total ecological foot print measured? why is it higher in cities? where is it highest?
• Measured by millions of hectres
• Allocation of resources- more focused in cities bc of high density of people
• Supporting infrastructure should be considered
USA, india, china
what is habitat destruction? why does it occur?
• Removal or conversion of the natural habitat
Mostly for agriculture - our single greatest reason for converting land
what biomes are most impacted by habitat destruction
- Globally: temperate broadleaf and mixed forests most impacted
- Areas suited for intense agriculture are more used - land that is desirable
why arent tropical rainforests used for agriculture?
• Tropical Rainforests - most productivity but not as used - more vegetation - when removed not lots of nutrients left in soil bc they use it!!
○ Lots of microbial breakdown and decomp in soil bc of climate - no buildup of organic matter in soil
Erosion - not lots of depth of soil bc of lack of organic matter
what other regions are not utilized for agriculture/ habitat destruction? why?
• Colder regions not as used/exploited - tundra least used
○ Also dryer regions ie deserts
• Also areas w more settlement
•
how is deforestation important? what trend does it follow? why does it occur + why is it impactful?
• One of the greatest threats to habitats
• Trend - areas of pristine forests getting deforested
○ Economic value
○ Wood used for warmth
○ takes decades to regrow forests - lots will regrow but it will take time
○ Cascading kind of effect - Ie building a road leads to other roads, hunting etc - fragmentation of the forest
how are coral reefs impacted?
• Symbionts - zooxanellnae
• Near coasts/continental shelves bc of light
○ Close to land where humans fish, etc,
○ Runoff
• Bleaching
Massive problem
define deforestation
When habitat is removed or converted to a different type of land cover
what experiments have been done on algae and corals?
○ Create lab tests - select for algae that can survive at higher temps in plates - propogate them and keep raising temps and selecting for them over time - then have them associate w corals - didn’t work in the end, but an attempt was made - a different approach to conservation
○ Organisms do not evolve at a rate that keeps up with the changes in warming
define habitat fragmentation. how is it impactful?
• The habitat is broken up into fragment - reducing cont. connected area
• Impacts biodiversity greatly
- Maintaining patches
- Experimental treatment - if they cant use the reduced habitat for breeding, survival, etc, - there will be a decline in abundance
○ Resource use can be more impactful than just reduce of land
○ Ie butterflies cant eat all plants - some are toxic - coevolution
○ Pulses - ecological data tends to be noisy - need lots of replicates and statistical analysis
describe edge effects. what are sizemic lines?
eduction in area unaffected by the edge
- Outer edge is impacted more by wind, etc - Exposure = more light hitting plants at the edge - facilitates growth of plants that are unable to grow under canopy - Ex. Road is direct interferenced, but the surface area is reduced by the edges created, and the patches are smaller (+ can stop certain organisms from moving from patch to patch) - Sizemic lines - take a long period of time to grow back - changes the use of the landscape bc some predators know how to used these for faster movement + to track animals
what changes occur in land use as societies develop
pre-settlement- natural ecosystem
frontier- frontier clearings
subsistence - agriculture and small scale farms
intensifying- protected recureational lands, urban areas, some intensive agriculture, some small scale farms, some frontier clearings
intensive - protected recreational lands, urban areas
intensive agriculture
what is our agricultural footprint: how much global productivity used, dominant human uses, fertilizer use, forest clearing,
- Humans use 1/3 to 1/2 of global productivity
- Dominant human uses are croplands and pastures (cover approx 40% of earths surface)
- Fertilizer use has increased 700% and irrigated 70% in the last 40 years
- 7-11 million km2 of forest has been cleared in last 300 years
greatest source of nitrogen?
• Greatest source of nitrogen is production - chemically synthesized process to fertilize crops
what country used to account for most deforestation? net deforestation rates?
brazil, rates have decreased here
rates inscreased in southeast asia
no net reduction in deforestation rates
Habitat Destruction in Tropical Rain Forests?
number of native mammal sp. going down in tropical and temperate
impacts of reduced area + fragmentation in brazil study?
residency sp richness community competition nutrient retention success rate abundance was variable btwn studies
