Lecture 25 Human Impacts on Organisms Flashcards

1
Q

Human impacts on the environment

A
  • Humans have been transforming environments for millennia
  • Recent decades have experienced drastic acceleration of modification
  • All biomes have experienced 20-50% conversion to human use

slide 3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Threats to Biodiversity

A

Local and global scale processes lead to biodiversity loss

slide 4-6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Land Use Change: Habitat Loss

A
  • Widely considered most important threat to biodiversity: If species have
    nowhere to go, then do the other threats matter?
  • Contributes to 73% of species
    that have become extinct,
    endangered, vulnerable,
    or rare
  • Agriculture is biggest
    contributor, but also:
    mining, logging, trawling,
    urbanization
  • Most severely impacts:
    large-bodied, wide-ranging,
    specialist, migratory species;
    endemics

slide 7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Habitat Loss: Freshwater Aquatic

A
  • Dams, reservoirs,
    channel modification,
    flow regulation affect
    most of world’s rivers
  • Wetlands filled in for
    agriculture and
    development

slide 8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Habitat Loss & Fragmentation: Deforestation

A
  • 130,000 km2 of tropical forest are cleared each year
  • Global forest area has been cut in 1/2 over last 300 years
  • 50+ nations have lost 90-100% of their forest cover

Deforestation alters
hydrology, nutrients
in soil, and
microclimate

slide 10-13 and 15

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Habitat Loss: Coral Reefs

A
  • 70% of coral reefs have been damaged by human activities
  • At current rate, 40-50% of reefs could disappear in next 30-40 years

slide 9

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Deforestation: Madagascar

A
  • More than 90% of
    rainforest habitat has
    been cleared
  • 90% of species are
    endemic
  • Largest percentage of
    species threatened or
    endangered in the world
  • Humans are responsible
    for extinction of 17
    species and 8 genera

slide 14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Habitat Fragmentation

A
  • Habitat is destroyed leaving
    smaller unconnected areas
  • Smaller habitat fragments have
    higher extinction probability
  • Creates “edge habitat” that favors
    certain kinds of species (“edgeadapted”)
  • As patch size decreases, species
    that specialize in forest interior
    decline

Patches may function like a metapopulation, but dispersal can be dangerous!

Long-term ecological
research studies have
helped us understand
how populations are
responding to habitat
loss and fragmentation

slide 16-22

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Habitat Loss & Degradation: Agriculture

A

11% of the Earth’s land surface is used
for crop production, 26% for livestock

  • More than 80% of North American grasslands
    have been converted to agriculture & other uses
  • More than just habitat loss!
  • Crop harvesting removes nutrients from soil à
    reduction in future plant productivity
  • Nutrient addition (next week)
  • Fire often used to clear land à CO2 release

slide 23-25

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Habitat Loss & Degradation: Urbanization

A
  • More than ½ of humans
    live in cities
  • By 2030, 5 billion people
    expected to live in cities
  • Leads to loss of species
    across all taxa and trophic
    levels

slide 26-29

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Habitat Loss & Degradation: Urbanization

A
  • Many species are tolerant of urbanization… but most are not
  • Many urban-tolerant species are non-native
  • Urbanization leads to global biotic homogenization of ecological communities

slide 30

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Habitat Degradation: Urban Heat Island Effect

A

slide 31

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Overharvesting

A
  • Overharvesting
    (overexploitation): of wild
    organisms at rates exceeding
    the ability of their
    populations to persist
  • Not just food – many species
    poached because of economic
    value
  • Most severely impacts:
  • Species with restricted
    habitats
  • Large organisms with low
    reproductive rates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Overharvesting: Hunted to Extinction

A

slide 33-37

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Overharvesting: Hunted almost to Extinction

A
  • Northern elephant seals - only 20 individuals in 1890s
  • Rebounded to >150,000 today (but very low genetic variation)

slide 38-39

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Overharvesting: Fishery Collapse

A
  • Fish populations once thought to be inexhaustible now decimated
  • Particularly effective and damaging harvesting technologies: long-line, trawlers
  • Industrial-scale fishing operations

Fishing down the food web:
As fish stocks of top trophic
levels (predatory fish)
decline fisheries are looking
to lower trophic levels

slide 40-43

17
Q

Overharvesting: Poaching

A
  • African elephants declining in most
    of Africa for last 50 years, largely
    because of ivory
  • International ban on sale of ivory
    led to increased poaching (illegal
    hunting)
  • 2006-2015: elephants dropped
    from 525,000 to 415,000 (22%
    decline)
  • If this continues – elephants could
    become extinct in wild!
18
Q

Invasive Species

A
  • Introduced species are
    moved (intentionally or
    accidentally) from native
    range to a new region by
    humans
  • Species introductions are
    nothing new… but global
    connectivity of the world
    today makes them more
    common
  • Introduced species become invasive species when they have a negative
    ecological impact on native species & often cause economic harm
  • Outcompete native species for resources or habitat
  • Consume native species
  • Introduce pathogens to naïve populations
  • Contributed to
    40% of extinctions
    since 1750
  • Cost billions in
    damage and
    control
  • > 50,000
    introduced
    species in USA!

slide 45-47

19
Q

Unintentional Introductions: Brown Tree Snake

A
  • Introduced to
    Guam after WWII
    in military cargo
  • 12 species of
    birds, 6 species
    of lizards have
    gone extinct
20
Q

Unintentional Introductions: Chestnut Blight

A
  • American Chestnut was dominant tree in eastern
    North American deciduous forests prior to 1910
    (>40% of trees were chestnut)
  • Fungus imported with Asian Chestnut tree
  • American chestnuts no longer exist as mature
    trees but only as stumps barely hanging onto
    existence and unable to reproduce
21
Q

Intentional Introductions: Kudzu

A

Introduced to control erosion and as an ornamental plant

slide 50

22
Q

Human-Wildlife Interactions

A

Habitat loss, transformation, and environmental change force species into new regions
where they may have closer contact with humans leading to conflict and disease

slide 51

23
Q

Human-Wildlife: Conflict

A

Threats to crops, property, livestock, and human safety lead to increased
persecution of species & contribute to decline

24
Q

Human-Wildlife: Disease

A
  • Organisms become more
    susceptible to disease in
    degraded ecosystems
  • Humans unintentionally
    spread disease to wildlife
    and vice versa
  • Habitat loss and
    fragmentation alters
    abundance and dispersal
    of pathogens and their
    animal hosts and vectors

slide 53

25
Human-Wildlife: Zoonotic Disease
* ¾ of emerging human diseases are zoonotic diseases transmitted to humans from other animals * May be transmitted by direct or indirect contact, or via a vector (intermediate species, often parasites) * Examples: Rabies, plague, Chagas’, salmonella, sleeping sickness, Malaria, Lyme, Nipah, ebola, zika, monkeypox, avian flu, intestinal worms…
26
Zoonotic Disease: Lyme
* Caused by bacterial parasite Borrelia burgdorferi * Transmitted by blacklegged tick (Ixodes scapularis) * Forest loss and fragmentation leads to higher densities of infected ticks * Found in NYC!!!
27
6th Mass Extinction?
* Extinction is a natural phenomenon occurring since life first evolved * Extinction rate now is alarmingly high compared to past * More than 1,000 species extinct in past 400 years: 100 to 1,000 times background rate * We will lose many species before we even know they exist! slide 56-58
28
Extinction Vortex
* Small populations are particularly vulnerable to threats * Extinction vortex: downward population spiral of small populations because of the combined effects of inbreeding and genetic drift * Effects of inbreeding and drift become more harmful as the population shrinks! slide 59
29
Extinction Vortex: Prairie Chicken
* Greater Prairie Chicken used to be common in Eastern US * Numbered in the millions in 1800’s * Introducing new genetic variation rescued population from downward spiral slide 60
30
Extinction Vortex: MVP
* Minimum Viable Population (MVP): the size a population must be to assure long-term survival * Vertebrate estimates ~1000 per population, invertebrates ~10,000 * Depends on life history and dispersal ability * If below MVP, extinction vortex or catastrophes can eliminate the population slide 61
31
Extinction Vortex: Effective Population Size
* How do we know if a population is too small (below MVP)??? * Not all individuals in a population breed successfully * Actual genetic variation of a population is a subset of the total population * Effective population size (Ne) estimates the size of a population based on only successfully breeding individuals
32
Extinction Vortex: Effective Population Size
* Effective population size more accurately reflects the genetic diversity (and adaptive potential) of a population * Ne can be used to conduct a population viability analysis to quantify the risk of extinction * MVP can be used to know how much habitat must be preserved * Larger parks needed for larger animals! slide 63-66
33
Extinction Debt?
Extinction Debt: the future extinction of species due to events in the past, owing to a time lag between an effect and the subsequent disappearance of species By some estimates more than 80% of expected species losses are yet to come! slide 67