Threats & Losses I

Question 1

What is a mass extinction?

Answer 1

extinction of a large number of species ( across taxa) within a short period of geological time

Question 2

There have been 5 mass extinctions

Answer 2

cretaceous ~65 MYA
- dinosaurs, many marine species,

permian ~250 MYA
- 50% of all animal families
-95%< of marine species
-many trees, amphibians, all trilobites

Question 3

What is the 6th mass extinction ?

Answer 3

pleistocene overkill Hypotheses
- correlated with human expansion over the planet
-exterminated many large mammals + island species

Question 4

how has human activity affected extinction rates in more recent times?

Answer 4

• best known for birds and mammals (larger + more easily spotted) (e.g. amateur bird watchers)
  extinction rates in modern times
  
  • 1600-1700: extinction rate of 1 species per decade
  • 1890-1950: 1 species every year

Question 5

according to the IUCN Red list of threatened species, there are _____ species threatened with extinction

Answer 5

41,000 species. 28% of all assessed species
-amphibian 41%
-mammals 27%
- conifers 34%
-birds 13%
-sharks & rays 37%
- reef corals 33%

Question 6

what is on of the most threatened ecosystem on the planet?

Answer 6

Freshwater systems
- faunal depletion in NA freshwater is 5x that of terrestrial fauna

WHY?
- highly populated
- heavily used for water, transit + food

Question 7

freshwater extinction rates

Answer 7

• approx. 1/3 are threatened with extinction
• over 10,000 fish species live in freshwater, 1/4 of vertebrate diversity
  BUT ecosystem covers only a small portion of Earth’s surface

Question 8

Marine extinction rates

Answer 8

few documented cases
- large predatory fish species and whale species have declined by 90% or more

Question 9

the highest extinction rate occurs on _______

Answer 9

ISLANDS!!
- half of all known extinctions since 1600 were island species

e.g. extinctions of birds on pacific islands in the wake of Polynesian colonization
- over 2,000 species (mostly flightless rails) are exticnt

Question 10

why are island species so susceptible to extinctions?

Answer 10

-highly specialized, unaccustomed to invasive species (e.g. mongoose, rats)
-small populations are more prone to chance extinction, smaller gene pool
-introduction of disease
- smaller chance of rescue effect

Question 11

drivers of biodiversity change ( threats)

Answer 11

increasing human population
great acceleration
- increased energy + water use

Question 12

the ecological footprint is a measure of what?

Answer 12

how much area of biologically productive land and water an individual, population or activity requires to produce all the resources as it consumes and to absorb the waste it generates

–> how much demand human consumption places on the biosphere

Question 13

what is biocapacity ?

Answer 13

the area of productive land available to produce resources or absorb carbon dioxide waste, given current management practices

Question 14

What is the biggest pressure on biodiversity world wide?

Answer 14

Habitat loss and degradation

Question 15

What is the biggest source of habitat loss in terrestrial ecosystems?

Answer 15

Conversion of wild lands to agriculture
Now accounts for 30% of land globally

Question 16

Why does FAO forestry data show a decreased rate of loss?

Answer 16

Rate of loss slowed between 1990-2020, due to reduced deforestation, + reforestation and the natural expansion of forest

Question 17

Contextualizing FAO slowed rate of loss

Answer 17

Many of the studied forest were cut hundreds of years ago, and may be regenerating only now

Question 18

Tropical rainforest land coverage

Answer 18

Occupy only 7% of earth’s land,but are estimated to contain > 50% of terrestrial species

Question 19

Importance of tropical moist forests

Answer 19

Regional importance in protection of water sheds
Global importance as Co2 sinks
Easily degraded + eroded

Question 20

Land change in tropical moist forest

Answer 20

60% is lost from small-scale cultivation (shifting cultivation)
Degraded for firewood
~20% destroyed through commercial logging
~10% destroyed for cattle ranching

Question 21

Reasons for land change in tropical deciduous forests

Answer 21

More suitable for agriculture & ranching than rainforest (easier to clear & burn)
Population density is 5x higher in dry forest areas

Question 22

Grasslands land change

Answer 22

Cover 3 x area of tropical forests
Have been almost completely destroyed by Humans
Ex: only 3% of tall grass persist in NA

Question 23

Wetlands land change

Answer 23

64% of the world’s wetlands have disappeared since 1900

Question 24

Wetlands (helpers et al. 2008)

Answer 24

• no area is unaffected by human influence and that 41% are affected by multiple drivers
• areas of little impact are near the poles

Question 25

Coral reef composition

Answer 25

High richness of organisms ~1/2 of the ocean’s fish species in only 0.2% of its surface area

Question 26

Coral reef land change

Answer 26

10% of coral reefs have been destroyed Bc: overfishing, over-harvesting, pollution, invasive species, climate change

Question 27

What is coral bleaching?

Answer 27

Corals stressed by changes in conditions such as Temperature, light or nutrients, they expel the symbiotic zooxanthellae living in their tissues and turn completely white