L26: The 6th Extinction

Question 1

What are the main causes of modern extinction?

Answer 1

1) Habitat loss and fragmentation
2) Invasive species
3) Overharvesting/ overhunting
4) Climate change

Question 2

Percentages threatened with extinction?

Answer 2

Globally, 12% of birds, 20% mammals, and 32% of amphibians are threatened with extinction.

Question 3

What are anthropogenic biomes?

Answer 3

Anthromes, also known as Anthropogenic Biomes, or Human Biomes, are the globally significant ecological patterns created by sustained interactions between humans and ecosystems.

Question 4

What are some components of the 6th mass extinction?

Answer 4

1) Evidence of defamation (Dirzo et al., 2014)
2) Evidence of risk and rate of extinction (Ceballos et al., 2015)
3) Minimum viable population (Flather et al., 2011).

Question 5

What is mass extinction?

Answer 5

Episode of relatively abrupt (few million of years) replacement of virtually all biotas.

Question 6

What is the 6th mass extinction?

Answer 6

The ongoing anthropogenic decline in biodiversity (Leaky and Lewis, 1995).

Question 7

6th mass extinction

Defaunation

Answer 7

Much like deforestation, means the loss of animals in all its myriad forms, including extinction, extirpation, or population declines.

Size selective defaunation gradient (larger mammals die out).

(Dirzo, 2014).

Question 8

What kind of behavioural/ physiological consequences can defaunation have?

Answer 8

Foraging

Movement

Diet

Habitat selection

Question 9

Defaunation

What kind of ecological consequences can defaunation have?

Answer 9

Short/ mid term:
Standing diversity
Structure

Long term:
Ecosystem processes (ecoservices)

Question 10

What kind of evolutionary consequences can defaunation have?

Answer 10

Phenotypic changes

Genetic structure

Question 11

What was the Kenya Long Term Exclosure Experiment?

Answer 11

Large wildlife are effectively removed by fences, as evidenced by mean different in dung abundance.

Positive effects for almost all small body consumers.

Negative impact on ticks.

Alteration of mutualism between ants and the dominant tree.

(Dirzo, 2014).

Question 12

What are the causes behind defaunation?

Answer 12

1) Habitat loss/ fragmentation including deforestation
2) Overexploitation of species for “meat”, medicine, or trophies.
3) Invasive species.

Question 13

Extinction is not only the loss of a species from the face of the Earth…

Answer 13

There’s a loss of critical ecosystem functioning in which animals play a central role that we need to pay attention to as well.

(Dirzo, 2014).

Question 14

What kind of habitat changes are being experienced in the global oceans?

Answer 14

Loss of coral cover

Increase in namer of marine wind turbines

Increase in container port traffic

Loss of mangrove area

Increase in seabed mixing contracts

Increase in number of dead zones

Question 15

Comparison of range contractions for select marine and terrestrial fauna

Answer 15

On many levels, defaunation in the oceans has, to data, been less severe than defaunation on land.

Question 16

Risk and rate of extinction

Answer 16

Rates of species extinction are difficult to determine on “natural conditions”.

The high rate of species extinction is largely a result of ecosystem degradation by humans.

Establishing species conservation priorities and recovery goals is often enhanced by extinction risk estimates.

Question 17

Biologist focusing on conservation at the population and species levels follow two main approaches:

Answer 17

The small population approach (minimum viable population): the population size required to provide probability of persistence for a given period of time.

The declining-population approach (also relevant for risk and rate of extinctions).

Question 18

What do we do the in declining population approach?

Answer 18

1) Confirm that the population is in decline
2) Study the species natural history and environmental factors that cause the decline
3) Apply the results of the diagnosis to manage for recovery

Question 19

Evolutionary implications of small population size

Answer 19

1) A small population is prone to inbreeding and genetic drift
2) The key factor is loss of the genetic variation necessary to enable evolutionary responses to environmental change.
3) Small populations and low genetic diversity do not always lead to extinction.

(Lomolino et al., 2011)

Question 20

What are the processes driving an extinction vortex?

Answer 20

Small population leads to…

Inbreeding/ genetic drift and therefore…

Loss of genetic variability and…

Reduction in individual fitness and population adaptibility leading to…

Lower reproduction/ higher mortality and….

A smaller population.

Question 21

What does a meaningful estimate of MVP require?

Answer 21

Determining the effective population size, which is based on the population’s breeding potential.

Question 22

What does Flather et al, 2011 conclude long term persistance requires?

Answer 22

Approximately 5000 adult individuals without taking into account taxonomy, life history or environmental conditions

Question 23

Case study of minimum viable population

Answer 23

(Berger, 1990)

Persistence of 120 bighorn sheep populations followed for up to 70 years in the US southwest.

All the populations with fewer than 50 individuals went extinct within 50 years.

Question 24

Define mass extinction

Answer 24

(Hallam & Wignall, 2002)

Mass extinction refers to “the extinction of a significant proportion of the world’s biota in a geologically insignificant period of time”.

Raup (1992) suggests that approximately half the earth’s surface must be environmentally affected in order for a mass extinction, on par with previous mass extinctions, to occur.