AnnouncementsAnnouncements• No section this week, but No section this week, but we will have we will have

lecturelecture on Friday on Friday• Invasive species writing assignment due at Invasive species writing assignment due at

beginning of lecture this Wednesdaybeginning of lecture this Wednesday• Problem set will be handed out in lecture Problem set will be handed out in lecture

this Wednesdaythis Wednesday• Problem set is due Wednesday, November Problem set is due Wednesday, November

2424thth

• we will not have lecture that daywe will not have lecture that day• you can turn problem set into your TA’s box in you can turn problem set into your TA’s box in

the ES Program officethe ES Program office• for on-time turn-in, put it in your TA’s box by for on-time turn-in, put it in your TA’s box by

10am at the latest on November 2410am at the latest on November 24thth

Summary from FridaySummary from Friday

• Metapopulation TheoryMetapopulation Theory• subpopulationssubpopulations• maintenance of genetic diversitymaintenance of genetic diversity• source and sink populationssource and sink populations• controls on immigrationcontrols on immigration

• Invasive SpeciesInvasive Species• definition of termsdefinition of terms• why invasive species are successfulwhy invasive species are successful• problems with invasive speciesproblems with invasive species

How can they be stopped?How can they be stopped?

• Physical removalPhysical removal• slow and costlyslow and costly• leaves some to recolonizeleaves some to recolonize

• Chemical eradicationChemical eradication• can harm nativescan harm natives• expensiveexpensive

• BiocontrolBiocontrol• may not workmay not work• can create a bigger problem than you can create a bigger problem than you

solvesolve

Global ChangeGlobal Change

• What will the world be like in 100 years?• Population growth• Land use/cover change• Climate change

With this kind of exponential growth, when

will we reach carrying capacity?

Human Population GrowthHuman Population Growth

• The maximum biological carrying capacity for humans = 50,000,000,000• this figure assumes that all primary production

is consumed by people…is this possible?

Human Population GrowthHuman Population Growth

• The maximum biological carrying capacity for humans = 50,000,000,000• this figure assumes that all primary production

is consumed by people…is this possible?

So, what is a more meaningful estimate of carrying capacity?

Human Population GrowthHuman Population Growth

• The maximum biological carrying capacity for humans = 50,000,000,000• this figure assumes that all primary production

is consumed by people…is this possible?

So, what is a more meaningful estimate of carrying capacity?

8 to 16 billion people

Slowing the growthSlowing the growth

• What is the most effective way?• provide access to birth control• raise standard of living• education

Why does population matter?Why does population matter?

• More people will need space, food, and other materials• land clearing• habitat destruction• increased emissions of greenhouse gasses

• CO2 carbon dioxide

• CH4 methane

• N2O nitrous oxide

Land use and land cover Land use and land cover changechange

• DeforestationDeforestation

• DesertificationDesertification

Greenhouse gases and global warmingGreenhouse gases and global warming

• industrialization = higher emissions

• gases trap heat in the lower atmosphere

CO2

Secondary effects of warmingSecondary effects of warming

• Heat can alter hydrological cycles• melting of ice caps• rise in sea level

• evaporation• cooling in certain areas• movement of air: wind• storms

Human Population (size and resource use)

Industry Agriculture

CO2 increase

Nitrogen cycle

Land use and cover

change

Global climate change

Loss of biological diversity

Studying climate changeStudying climate change• Add CO2Add CO2• Add heatAdd heat

What happens?

AnnouncementsAnnouncements• Invasive species writing assignment due now Invasive species writing assignment due now • No section this week, but No section this week, but we will have we will have

lecturelecture on Friday on Friday• Make sure to get the problem set todayMake sure to get the problem set today• Problem set is due Wednesday, November Problem set is due Wednesday, November

2424thth

• we will not have lecture that daywe will not have lecture that day• you can turn problem set into your TA’s box in the you can turn problem set into your TA’s box in the

ES Program officeES Program office• for on-time turn-in, put it in your TA’s box by for on-time turn-in, put it in your TA’s box by

10am at the latest on November 2410am at the latest on November 24thth

Summary from MondaySummary from Monday• Global changeGlobal change

• Population growthPopulation growth• why it matterswhy it matters• carrying capacity for humanscarrying capacity for humans• how to slow the growthhow to slow the growth

• Land use and land cover changeLand use and land cover change• deforestationdeforestation• desertificationdesertification

• Climate changeClimate change• increased COincreased CO22 emissions by human activity emissions by human activity• studying climate changestudying climate change

Global change Global change community community changechange

• Different species have different responsesDifferent species have different responses• elevated COelevated CO22 and C4 vs. C3 plants and C4 vs. C3 plants

Global change Global change community community changechange

• Different species have different responsesDifferent species have different responses• elevated COelevated CO22 and C4 vs. C3 plants and C4 vs. C3 plants

• water use and drought-tolerant plantswater use and drought-tolerant plants• heat stressheat stress

Temperature

Succ

ess

optimum

potential survival,

but stressed

potential survival,

but stressed

intolerant intolerant

Global change Global change community community changechange

• Different species have different responsesDifferent species have different responses• elevated COelevated CO22 and C4 vs. C3 plants and C4 vs. C3 plants

• water use and drought-tolerant plantswater use and drought-tolerant plants• heat stressheat stress

Global change Global change community community changechange

• Different species have different responsesDifferent species have different responses• elevated COelevated CO22 and C4 vs. C3 plants and C4 vs. C3 plants

• water use and drought-tolerant plantswater use and drought-tolerant plants• heat stressheat stress

• With a change in community, biodiversity With a change in community, biodiversity may…may…• increaseincrease• decreasedecrease• stay the samestay the same

What is biodiversity?What is biodiversity?

Biodiversity = variation in living thingsBiodiversity = variation in living things• Genetic diversityGenetic diversity• Species diversitySpecies diversity

• Species richness: # of speciesSpecies richness: # of species• Species evenness: how #’s are Species evenness: how #’s are

distributeddistributed• Growth-form diversityGrowth-form diversity• Community diversityCommunity diversity

• How is biodiversity measured?How is biodiversity measured?

Measuring BiodiversityMeasuring Biodiversity

• Count the # of species presentCount the # of species present• Count the # of families representedCount the # of families represented• Look for different “functional groups”Look for different “functional groups”

Biodiversity Hotspots

Distribution of BiodiversityDistribution of Biodiversity

• general increase from poles to equatorgeneral increase from poles to equator

Bird species in North America

Diversity increases from pole to equator

for many species.

Why?

Diversity in the TropicsDiversity in the Tropics• 50-80% of today’s species live in tropical 50-80% of today’s species live in tropical

rainforestrainforest

• high temp. and rainfall in tropicshigh temp. and rainfall in tropics• many species rely on treesmany species rely on trees

• however, tropical forests in Africa not as however, tropical forests in Africa not as diverse as those elsewhere diverse as those elsewhere other drivers of other drivers of biodiversity aside from climatebiodiversity aside from climate

Distribution of BiodiversityDistribution of Biodiversity

• general increase from poles to equatorgeneral increase from poles to equator

Must also consider:Must also consider:• history history • productivity of the systemproductivity of the system• habitat structurehabitat structure• specialization of species specialization of species • survival of specialistssurvival of specialists

HistoryHistory• Most of Earth’s land mass was once Most of Earth’s land mass was once

tropicaltropical• Evolution of flowering plants in tropics Evolution of flowering plants in tropics

increased diversity of:increased diversity of: plants insects mammalsplants insects mammals

• When Earth’s climate cooled, some When Earth’s climate cooled, some species at high latitudes went extinctspecies at high latitudes went extinct

ProductivityProductivity• Tropics are near the equatorTropics are near the equator• Sun’s rays are direct Sun’s rays are direct high high

productivityproductivity• More energy at the bottom of the More energy at the bottom of the

food chain means more species can food chain means more species can be supportedbe supported

With less energy, only 8 niches exist

With more energy, 16 niches are possible

Habitat StructureHabitat Structure• diverse structure diverse structure more biodiversity more biodiversity

• multi-aged stands of treesmulti-aged stands of trees• epiphytesepiphytes• gapsgaps

• physical structure providesphysical structure provides• feeding surfacesfeeding surfaces• nesting sitesnesting sites• microclimatesmicroclimates

SpecializationSpecialization• constant presence of food in tropicsconstant presence of food in tropics• migration not necessary in tropicsmigration not necessary in tropics• certain specialized feeding strategies certain specialized feeding strategies

that are not possible in temperate that are not possible in temperate regions work in the tropicsregions work in the tropics

Survival of SpecialistsSurvival of Specialists• temperate regions have been temperate regions have been

glaciated several times in the past 2 glaciated several times in the past 2 million yearsmillion years

Survival of SpecialistsSurvival of Specialists• temperate regions have been temperate regions have been

glaciated several times in the past 2 glaciated several times in the past 2 million yearsmillion years

• with every ice age, glaciers scour with every ice age, glaciers scour temperate regions and primary temperate regions and primary succession must take placesuccession must take place

• generalists are more successful than generalists are more successful than specialists in temperate zonesspecialists in temperate zones

Why is biodiversity Why is biodiversity important?important?

Genetic diversityGenetic diversity• Long term survival requires Long term survival requires

responsiveness to small changes in responsiveness to small changes in the environmentthe environment

• Prevent genetic bottleneckPrevent genetic bottleneck

Genetic diversity

Population size

Time

Conserving a viable Conserving a viable populationpopulation

Goal of conservation: maintain a MVPGoal of conservation: maintain a MVP

MVP: minimum viable populationMVP: minimum viable population• it is difficult to know what this number isit is difficult to know what this number is

With too few mating pairs:With too few mating pairs:• inbreeding depression:inbreeding depression: lowered fitness of lowered fitness of

offspringoffspring• genetic drift:genetic drift: random loss of alleles from random loss of alleles from

the the genetic poolgenetic pool

Why is biodiversity Why is biodiversity important?important?

Species DiversitySpecies Diversity• Ethical ReasonsEthical Reasons

• some believe in a universal right to existsome believe in a universal right to exist• aesthetic, spiritual, or other intrinsic aesthetic, spiritual, or other intrinsic

valuevalue

• Practical ReasonsPractical Reasons• medicinesmedicines• pest controlpest control• ecosystem servicesecosystem services

AnnouncementsAnnouncements• Pick up the problem set from your TA Pick up the problem set from your TA

if you don’t have it alreadyif you don’t have it already• Problem set is due Wednesday, Problem set is due Wednesday,

November 24November 24thth by 10am in your TA’s by 10am in your TA’s boxbox

• No section this weekNo section this week

Summary from WednesdaySummary from Wednesday• Global change drives community changeGlobal change drives community change• BiodiversityBiodiversity

• increases from poles to equator increases from poles to equator • higher temp. and rainfall in tropicshigher temp. and rainfall in tropics

• other drivers:other drivers:• historyhistory• productivityproductivity• structurestructure• specializationspecialization• survival of specialistssurvival of specialists

• Why is biodiversity important?Why is biodiversity important?

Ecosystem ServicesEcosystem Services

• Primary production for food, forage, fiberPrimary production for food, forage, fiber

Ecosystem ServicesEcosystem Services

• Primary production for food, forage, fiberPrimary production for food, forage, fiber• Control of water dynamicsControl of water dynamics

• flood controlflood control• water purificationwater purification

Ecosystem ServicesEcosystem Services

• Primary production for food, forage, fiberPrimary production for food, forage, fiber• Control of water dynamicsControl of water dynamics

• flood controlflood control• water purificationwater purification

• PollinationPollination

Ecosystem ServicesEcosystem Services

• Primary production for food, forage, Primary production for food, forage, fiberfiber

• Control of water dynamicsControl of water dynamics• flood controlflood control• water purificationwater purification

• PollinationPollination• Regulation of nutrient distributionRegulation of nutrient distribution• COCO22 uptake and C sequestration uptake and C sequestration

but how does biodiversity matter?

Control of ecosystem Control of ecosystem servicesservices

RedundancyRedundancy• more than one species has a similar more than one species has a similar

“job”“job”• if one goes extinct, the others if one goes extinct, the others

compensatecompensateAtta sexdens Atta cephalotes

Control of ecosystem Control of ecosystem servicesservices

RedundancyRedundancy• more than one species has a similar more than one species has a similar

“job”“job”• if one goes extinct, the others if one goes extinct, the others

compensatecompensate

Leaf-cutter ants are responsible for the Leaf-cutter ants are responsible for the decomposition of decomposition of 20%20% of the leaves in of the leaves in South American rainforests!South American rainforests!

Control of ecosystem Control of ecosystem servicesservices

• Keystone speciesKeystone species• a single species with impacts on an a single species with impacts on an

ecosystem that are disproportionate to ecosystem that are disproportionate to its biomassits biomass

• if removed, the ecosystem changes a lotif removed, the ecosystem changes a lot

Keystone SpeciesKeystone Species

A healthy kelp forest A healthy kelp forest with sea otters with sea otters presentpresent

When sea otters are When sea otters are eliminated, urchins eliminated, urchins take overtake over

Island BiogeographyIsland Biogeography

Islands are great for studying Islands are great for studying population ecology because:population ecology because:

• They are isolatedThey are isolated• You can potentially quantify all occurring You can potentially quantify all occurring

speciesspecies

Patterns of Biodiversity on Patterns of Biodiversity on IslandsIslands

• Large islands have more species than Large islands have more species than small islandssmall islands

Larger islands have more species

Patterns of Biodiversity on Patterns of Biodiversity on IslandsIslands

• Large islands have more species than Large islands have more species than small islandssmall islands

Why is this true?Why is this true?

A larger area will support more species, and larger populations of a single

species

Patterns of Biodiversity on Patterns of Biodiversity on IslandsIslands

• Large islands have more species than Large islands have more species than small islandssmall islands

• Islands close to the mainland have more Islands close to the mainland have more species than islands further awayspecies than islands further away

Controls on immigrationControls on immigration

Distance to source populationDistance to source population

main

lan

d

Lots of immigration

Little immigration

Patterns of Biodiversity on Patterns of Biodiversity on IslandsIslands

• Large islands have more species than Large islands have more species than small islandssmall islands

• Islands close to the mainland have Islands close to the mainland have more species than islands further more species than islands further awayaway

• With more physical diversity, and With more physical diversity, and island will have more speciesisland will have more species• more habitats provide more nichesmore habitats provide more niches

Patterns of Biodiversity on Patterns of Biodiversity on IslandsIslands

• Large islands have more species than Large islands have more species than small islandssmall islands

• Islands close to the mainland have Islands close to the mainland have more species than islands further more species than islands further awayaway

• With more physical diversity, and With more physical diversity, and island will have more speciesisland will have more species• more habitats provide more nichesmore habitats provide more niches

• Small islands are unlikely to have top Small islands are unlikely to have top predatorspredators• not enough prey available as foodnot enough prey available as food

Do islands have high Do islands have high diversity?diversity?

• if biodiversity increases with area, if biodiversity increases with area, how can islands be diverse? how can islands be diverse?

Patterns of Biodiversity on Patterns of Biodiversity on IslandsIslands

Required for high biodiversity on islands:Required for high biodiversity on islands:• evolution of new species requires evolution of new species requires

isolationisolation• long geologic time periodlong geologic time period• high temperature and rainfallhigh temperature and rainfall• topographic complexitytopographic complexity

Designating a “Designating a “biodiversity hotspotbiodiversity hotspot”:”:• many many endemicendemic plant species plant species• impacted by humansimpacted by humans