Lesson 7 Environmental carrying capacity

This is the 7th lesson of the course - Foundation of Environmental Management taught at the Faculty of Social Sciences and Humanities, Rajarata University of Sri Lanka

1. 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
Foundation of Environmental Management
Course code: EMGT 2114

2. Course Content
1.Concepts of Ecology and Environmental
Biology
2.Biogeochemical Cycles (C, N, P etc.)
3.Ecosystems and Energy Flow
4.Ecosystem Functions and Ecosystem
services
5.History of Environmental Management
6.Biodiversity
7.Environmental Carrying Capacity

3. Environmental carrying capacity
Population is increasing

4. 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

5. Carrying capacity of environment
1.Generallycarryingcapacityreflectsabilityofbearingorcontaining
somethinginmaximumcontinuously
2.Therefore,carryingcapacityofanenvironmentwithregardtoa
biologicalspeciesisthemaximumpopulationsizeofthespeciesthatthe
environmentcansustainindefinitely,giventhefood,habitat,waterand
othernecessitiesavailableintheenvironment.
3.Inpopulationbiology,carryingcapacityistheenvironment'smaximal
load,whichisdifferentfromtheconceptofpopulationequilibrium.
4.Withregardtothehumanpopulation,morecomplexvariablessuch
assanitationandmedicalcarearesometimesconsideredaspartofthe
necessaryestablishment.
5.Aspopulationdensityincreases,birthrateoftendecreasesanddeath
ratetypicallyincreases.
6.Thedifferencebetweenthebirthrateandthedeathrateisthe"natural
increase".
7.Thecarryingcapacitycouldsupportapositivenaturalincrease,orcould
requireanegativenaturalincrease.

6. 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.

7. 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.

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

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

10. 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

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

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

13. 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.

14. •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

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

16. 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)

17. Three Key Characteristics of Populations
•2. Density: measurement of population per unit area or
unit volume
Pop. Density = # of individuals
unit of space
17
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

18. Three Key Characteristics of
Populations
02 June 2010 Populations.ppt 18
•Dispersion: describes
their spacing relative to
each other

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

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

21. 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 21Populations.ppt

22. 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.)

23. 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 23

24. 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

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

26. 02 June 2010 Populations.ppt 26

27. 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

28. 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.

29. 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

30. 2 Life History Patterns
2. “K” Strategists
long life span
large body size
reproduce slowly
have few young
provides parental care
Ex: humans, elephants

31. 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

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

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