7. Environmental carrying capacity

This is the 7th lesson of the course 'Poverty and Environment ' taught at the Faculty of Social Sciences and Humanities, Rajarata University of Sri Lanka

1. P.B. Dharmasena
0777 613234, 0717 613234
[email protected], [email protected]
https://independent.academia.edu/PunchiBandageDharmasena
https://www.researchgate.net/profile/Punchi_Bandage_Dharmasena/contributions
http://www.slideshare.net/DharmasenaPb
Poverty and Environment
Course code: ECON/EMGT 4214
Friday from 8.30-12.30 a.m
Lesson 7 –Environmental Carrying Capacity
P.B. Dharmasena
0777 613234, 0717 613234
[email protected], [email protected]
https://independent.academia.edu/PunchiBandageDharmasena
https://www.researchgate.net/profile/Punchi_Bandage_Dharmasena/contributions
http://www.slideshare.net/DharmasenaPb

2. Environmental carrying capacity
P.B. Dharmasena
0777 -613234, 0717 -613234
[email protected], [email protected]
https://independent.academia.edu/PunchiBandageDharmasena
https://www.researchgate.net/profile/Punchi_Bandage_Dharmasena/contributions
http://www.slideshare.net/DharmasenaPb

3. What is Carrying Capacity?
•Is the maximum
population a habitat can
support indefinitely
•Population exceeds it,
for long periods,
degrades its
environment and
reduces future carrying
capacity

4. Carrying capacity of environment
1.Generallycarryingcapacityreflectsabilityofbearingorcontaining
somethinginmaximumcontinuously
2.Therefore,carryingcapacityofanenvironmentwithregardtoa
biologicalspeciesisthemaximumpopulationsizeofthespeciesthat
theenvironmentcansustainindefinitely,giventhefood,
habitat,waterandothernecessitiesavailableintheenvironment.
3.Inpopulationbiology,carryingcapacityistheenvironment'smaximal
load,whichisdifferentfromtheconceptofpopulationequilibrium.
4.Withregardtothehumanpopulation,morecomplexvariablessuch
assanitationandmedicalcarearesometimesconsideredaspartofthe
necessaryestablishment.
5.Aspopulationdensityincreases,birthrateoftendecreasesanddeath
ratetypicallyincreases.
6.Thedifferencebetweenthebirthrateandthedeathrateisthe"natural
increase".
7.Thecarryingcapacitycouldsupportapositivenaturalincrease,or
couldrequireanegativenaturalincrease.

5. 1.Carryingcapacityisthenumberofindividualsanenvironment
cansupportwithoutsignificantnegativeimpactstothegiven
organismanditsenvironment.
2.Belowcarryingcapacity,populationstypicallyincrease,while
above,theytypicallydecrease.
3.Afactorthatkeepspopulationsizeatequilibriumisknownas
aregulatingfactor.
4.Populationsizedecreasesabovecarryingcapacityduetoarange
offactorsdependingonthespeciesconcerned,
5.butcanincludeinsufficientspace,foodsupply,orsunlight.
6.Thecarryingcapacityofanenvironmentmayvaryfordifferent
speciesandmaychangeovertime
7.duetoavarietyoffactors,including:
foodavailability,
watersupply,
environmentalconditionsand
livingspace.

6. 1.Severalestimatesofthecarryingcapacityhavebeenmadewitha
widerangeofpopulationnumbers.
2.UNreport(2001)saidthattwo-thirdsoftheestimatesfallinthe
rangeof4billionto16billion(withunspecifiedstandarderrors),
withamedianofabout10billion.
3.Morerecentestimatesaremuchlower,particularlyifresource
depletionandincreasedconsumptionareconsidered.
4.Theapplicationoftheconceptofcarryingcapacityforthehuman
populationhasbeencriticizedfornotsuccessfullycapturingthe
multi-layeredprocessesbetweenhumansandtheenvironment,
whichhaveanatureoffluidityandnon-equilibrium,andfor
sometimesbeingemployedinablame-the-victimframework.
5.Supportersoftheconceptarguethattheideaofafinitecarrying
capacityisjustasvalidwhenappliedtohumansaswhenapplied
toanyotherspecies.
6.Animalpopulationsize,livingstandards,andresourcedepletion
vary,buttheconceptofcarryingcapacitystillapplies.
7.Wasteandover-consumptionespeciallybywealthypeopleand
nations,isputtingmorestrainontheenvironmentthan
overpopulation.

7. Carrying Capacity
Time
Population size
Graph line = Population
size at a specific time
Dotted line = Carrying Capacity

8. Carrying Capacity
•When a population is BELOWits carrying
capacity, it will INCREASEin size
•Birth rate exceeds death rates
Time
Population size

9. Carrying Capacity
•But if it increases too much and rises ABOVE
its carrying capacity, it will DECREASEin size
•Death rate exceeds birth rate
Time
Population size

10. Carrying Capacity
•This happens over and over… but the increases
and decreases get smaller and smaller…
Time
Population size

11. Carrying Capacity
•Until eventually, the population size BECOMES
STABLE AT THE CARRYING CAPACITY
•Birth rate = death rate
Time
Population size

12. Carrying Capacity
•Carrying capacity can also have a broader
meaning. It can be defined as the number of
living things (plants and animals) any area of
land or water can support at any one time.
•Different organisms will have different
carrying capacities in the same area. Thus, the
carrying capacity of an ecosystem affects
everything that lives in it.

13. •Population: all the individuals of a
species that live together in an area
•Demography:the statistical study of
populations, make predictions about how
a population will change
POPULATIONS
& CARRYING CAPACITY

14. Three Key Characteristics
of Populations
•Size, number of
individuals (N)
•Density (N/ area)
•Dispersion,
–Random, uniform,
clumped,
•(appropriate scale)

15. Three Key Characteristics of
Populations
•1. Size: number of individuals in an area
–Characterized by (N)
Growth Rate:
Birth Rate (natality) -Death Rate (mortality)
(How many individuals are born vs. how many die)

16. Three Key Characteristics of Populations
•2. Density: measurement of population per unit area or
unit volume
Pop. Density = # of individuals
unit of space
16
4 Factors that affect density
1. Immigration-movement of individuals into a population
2. Emigration-movement of individuals out of a population
3. Density-dependent factors-Biotic factors in the environment that have
an increasing effect as population size increases
Ex. Disease, competition, parasites
4. Density-independent factors-Abiotic factors in the environment that affect
populations regardless of their density
Ex. Temperature, storms, habitat destruction, drought

17. Three Key Characteristics of
Populations
02 June 2010 Populations.ppt 17
•Dispersion: describes
their spacing relative to
each other

18. Dynamic characteristics
of populations
•Age distribution,
–proportions of young, middle-aged, old
–Differs in growing, stable, decreasing populations

19. Immigration
Emigration
Natality MortalityPopulation
+
+
-
-
Factors That Affect Future Population
Growth

20. Changes in populations
•Growth
–Expansion of species’ populations may lead to
evolution of new species
•Decline
–Shrinking species’ populations may lead to
extinction
•Small populations
•Narrowly specialized species
02 June 2010 20Populations.ppt

21. Changes in populations
•ΔN = +B +I –D –E
–+B = births (birth rate)
–+I = immigrants (immigration rate)
––D = deaths (death rate)
––E = emigrants (emigration rate)
–(For many [most] natural populations I and E
are minimal.)

22. Other factors that affect population
growth
Limiting factor-any biotic or abiotic
factor that restricts the existence of
organisms in a specific environment.
–EX.-Amount of water
Amount of food
Temperature
02 June 2010 Populations.ppt 22

23. Other factors that affect population
growth
•Carrying Capacity-the maximum population
size that can be supported by the available
resources
•There can only be as many organisms as the
environmental resources can support

24. Carrying Capacity
Carrying Capacity (k)
Number
Time
J-shaped curve
(exponential growth)
S-shaped curve
(logistic growth)

25. 02 June 2010 Populations.ppt 25

26. Logistic model
•Logistic model works, to a point.
–Real organisms have time lags for growth, time to
develop eggs, flowers, etc.
•seasonality, longevity
–Real populations may exceed carrying capacity.
•Easter Island
•PribloffReindeer
•Kaibab Deer

27. Easter Island –An Example
•Discovered by Polynesians ~ A.D. 1000
•Population grew to several thousand
–Used trees for canoes to hunt dolphins
–Used wood for cooking
–Also ate birds, eggs, vegetables
•Resources (trees) depleted
–No canoes, no dolphins
–Warfare over land, food resources
•Population fell to ~ 100 when discovered by
Dutch, Easter Sunday 1722.

28. 2 Life History Patterns
1. “R” Strategists
short life span
small body size
reproduce quickly
have many young
little parental care
Ex: cockroaches, weeds,
bacteria

29. 2 Life History Patterns
2. “K” Strategists
long life span
large body size
reproduce slowly
have few young
provides parental care
Ex: humans, elephants

30. Two general types of
Life History Strategies
Life History traitr-adapted,
Opportunistic
K-adapted,
Equilibrium
Offspring Many, small (high r)Fewer, large (low r)
Offspring survivalLow High
Parental care Rare Common
Reproductive age Early Later
Reprod. “seasons”1-few Many
Habitat Unstable, temporaryStable, permanent
Competitiveness Low High
Population regulationDensity independentDensity dependent
Population fluctuationIrruptive Stable near K

31. Life History Strategies
•Survivorship curves of Opportunistic and
Equilibrium species
–Opportunistic have Type III
–Equilibrium have Type I

32. Life History Strategies
•Fluctuating populations of two interacting populations
–Based on pelts sold by Canadian trappers to the Hudson Bay
Company, ~1840-1940.