The Past Matters: Using lake sediments to study the environmental effects of

multiple stressors

John P. SmolPaleoecological Environmental Assessment

and Research Laboratory (PEARL)Dept. Biology, Queen’s University,

Kingston, Ontario, CanadaSmolJ@QueensU.Ca

Important management questions

What were pre-disturbance conditions?

What is the range of natural variability?

Have conditions changed? How? How much? How fast? When? Why?

Can evidence of human activity be detected?

How much improvement can be expected?

0

10

20

30

40

50

60

70

<1 1 2 3 4 5 6 >6

Length of Study (Years)

Perc

enta

ge (%

)

n = 302

Environmental Monitoring and Assessment - 1981-1993

Smol (2008) Pollution of lakes and rivers: A paleoenvironmental perspective. 2nd ed.

Techniques to Assess Past Environmental Change

historical records

model hindcasts

natural archives

Photo: B. Cumming

Paleolimnology: reconstructing lake and river histories using the

physical, chemical, and biological information stored in sediments

allochthonousmaterial

e.g. pollen grains

autochthonousmaterial

e.g. algae & aquatic insects

Sediments: environmental archives

e.g. soil particles

e.g. aerially transported contaminants

Continuing Advances

• technology and methodology

• amount of information

• interpretation

Surface sediment gravity coring

Close-interval sectioning

24

68

1012

1416

1820

2224

2628

3032

3436

-5 0 5 10 15 20 25 30 35 40 45 50

214Bi

137Cs

210Pb

Cor

e D

epth

(cm

)

0

Dating the sedimentary sequences

• 210Pb & 137Cs (radioisotopes)

2002200119991998199619941992199019871985198119761972196519501946193619261920

1900189018701860185618501846

1910

2003200420052006Youngest

Oldest

Con

tinuo

us R

ecor

d

Activity (dpm/g)

~1963

From the Atmosphere

carbon particles from carbon combustion

fly ash from coal combustion

metals and other pollutants from

industry

From the Catchmentpollen mineral

particlesinsect

remainsbeetle wing

From the Aquatic System

diatoms chrysophytes chironomids

Photo: I Walker

Diatoms• Bacillariophyta• abundant and diverse• excellent environmental indicators• siliceous cell walls (frustules)

Freshwater diatoms

Photos: K. Laird and B. Cumming; in Smol (2008) Pollution of lakes and rivers: A paleoenvironmental perspective.2nd ed. Blackwell Publ., Oxford.

Select Study Lake

Collect Indicator Data

Sub-sample Sediments &Isolate Indicator of Interest

Analyze Data

Section & Date Sediment CoreSelect Coring Site & Retrieve Sediment Core

The Paleolimnological Approach

Photos courtesy of B. Cumming, I. Walker, Dell & Leica

210Pb

137Cs

14C

• Targets

• Trajectories

Users of Water

“The Real” Users of Water

What factors can be addressed using paleolimnology?

eutrophicationanoxia and fish habitat

climate changegroundwater qualityriver paleoecology

acidificationfire history

species invasionspeciation / evolution, etc.

Impacts of Cultural Eutrophication

- hypolimnetic anoxia- fish kills

- P release- ↑ accumulation and decay

- shoreline fouling -↑ plant growth- ↑ algal growth and toxins- taste and odour problems

- presence of undesirable species- aesthetic degradation

Three lake characteristicswe typically wish to track

1) Lakewater nutrient levels

2) Deepwater oxygen levels

3) Algal and cyanobacterial blooms

1) Trends in lakewater nutrients

Why not just measure total P in the sediments?

Many pitfalls and largely abandoned ~30 years ago

(this is not to say that sedimentary P has no value in other applications – very important in mass balance studies and determining processes, etc.)

So we have to use indirect proxy methods that are related to

lakewater total phosphorus (TP)

Research ongoing for over 30 years, but especially last 20 years

Surface areaDepthDevelopment Total phosphorusTotal nitrogenChlorophyll a

pHSecchi depthTemperatureConductivityOxygenAlkalinityAmmonium

Construction of a Transfer Function

lake surface sediment samples

environmental data

species response curves

Environmental variable (e.g. TP)

sp. 4sp. 1

sp. 2sp. 3 sp. 5 sp. 6

Abun

danc

e of

taxa

Dixit, S.S., Smol, J.P., et al. 1999. Assessing water quality changes in the lakes of the Northeastern United States using sediment diatoms. Can. J. Fish. Aq. Sci. 56: 131-152.

Regional Scale Diatom Calibration Set

2) Deepwater oxygen levels?

Use organisms that need oxygen, and live in the deep waters

http://www.nzfreshwater.org/food.html

Chironomid head capsules as indicators

Chironomus

Chironomus mentum

5 mm

(Photo: D. Bos)

0

2

4

6

8

10

12

0 2 4 6 8 10 12

Measured VWHO

Infe

rred

VW

HO

Predictive O2 Model Based onAquatic Communities

(modified from Quinlan & Smol 2001)(from Ontario lakes)

3) Algal and cyanobacterial blooms

Photo Todd Sellers

Fossil Pigments

Example #1: The effects of urbanization and shoreline

development on water quality

Clerk, S., Hall, R., Quinlan, R., and Smol, J.P. 2000. Quantitative inferences of past hypolimnetic anoxia and nutrient levels from a Canadian Precambrian Shield lake. J. Paleolimnology 23: 319-336.

Peninsula Lake andthe Deerhurst Resort

Peninsula Lake, Huntsville, Ont

1867

1885

1870-90

1895

Late-1800s –early-1900s

First pioneers

Railway to area

Development of local industries

Deerhurst Resort

Significant logging

Sewage Treatment

Lake area = 822.9 ha

Mean depth = 9.9 m

Maximum depth = 34.1 m 1972

Diatoms indicate striking eutrophication and recovery

Similarly chironomids indicate marked changesin deepwater oxygen levels

‘Natural’ conditions: Before European settlement in the region

1700

1750

1800

1850

1900

1950

2000

0.05.010.015.0

Deep-water oxygen

1700

1750

1800

1850

1900

1950

2000

0.0 5.0 10.0 15.0

Phosphorus

Total phosphorus (µg/L) Dissolved oxygen (mg/L)

low high high low

A decline in water quality

1700

1750

1800

1850

1900

1950

2000

0.05.010.015.0

Deep-water oxygen

1700

1750

1800

1850

1900

1950

2000

0.0 5.0 10.0 15.0

Phosphorus

Total phosphorus (µg/L) Dissolved oxygen (mg/L)

low high high low

Turning the corner

1700

1750

1800

1850

1900

1950

2000

0.05.010.015.0

Deep-water oxygen

1700

1750

1800

1850

1900

1950

2000

0.0 5.0 10.0 15.0

Phosphorus

Total phosphorus (µg/L) Dissolved oxygen (mg/L)

Europeansettlement

sewagetreatment

low high high low

What factors can be addressed using paleolimnology?

eutrophicationanoxia and fish habitat

climate changegroundwater qualityriver paleoecology

acidificationfire history

species invasionspeciation / evolution, etc.

Acidification: Timing of changes

• Study changes at decadal scale

timing of acidification

• Cape Breton Highlands National Park:

“low” SO42- deposition

6 lakes

• Kejimkujik National Park:

“high” SO42- deposition

8 lakes

2002

1995

1975

1955

1935

1915

1895

1875

1855

1835

18151800

4.5 5.0 5.5 6.0

Pebble

loggit

ch

4.5 5.0 5.5 6.0

Peska

wa

4.5 5.0 5.5 6.0

Kejimku

jik

4.5 5.0 5.5 6.0

Pesko

wesk

5.0 5.5 6.0 6.5

Big Dam

Wes

t

5.0 5.5 6.0 6.5

Frozen

Oce

an

5.0 5.5 6.0 6.5

Grafton

5.0 5.5 6.0 6.5

Big Dam

East

5.0 5.5 6.0 6.5

Beave

rskin

2002

1995

1975

1955

1935

1915

1895

1875

1855

1835

18151800

4.5 5.0 5.5 6.0

Pebble

loggit

ch

4.5 5.0 5.5 6.0

Peska

wa

4.5 5.0 5.5 6.0

Kejimku

jik

4.5 5.0 5.5 6.0

Pesko

wesk

5.0 5.5 6.0 6.5

Big Dam

Wes

t

5.0 5.5 6.0 6.5

Frozen

Oce

an

5.0 5.5 6.0 6.5

Grafton

5.0 5.5 6.0 6.5

Big Dam

East

5.0 5.5 6.0 6.5

Beave

rskin

5.0 5.5 6.0 6.5

Big Dam

Wes

t

5.0 5.5 6.0 6.5

Frozen

Oce

an

5.0 5.5 6.0 6.5

Grafton

5.0 5.5 6.0 6.5

Big Dam

East

5.0 5.5 6.0 6.5

Beave

rskin

Acidified ~1925

Forest Fire?

~1878

Logging?

CO32-

Acidification ~ 1940

Ginn et al. Hydrobiologia 586: 261-275

Acidification: Timing (Kejimkujik)

2003

1995

1975

1955

1935

1905

1875

1855

1835

~1800

5.0 5.5 6.0 6.5

Cradle

5.0 5.5 6.0 6.5

Lake

of Is

lands

5.0 5.5 6.0 6.5

Dunda

s #4

5.0 5.5 6.0 6.5

Whit

e Hill

5.0 5.5 6.0 6.5

Deer

5.0 5.5 6.0 6.5

Warr

en

2003

1995

1975

1955

1935

1905

1875

1855

1835

~1800

5.0 5.5 6.0 6.5

Cradle

5.0 5.5 6.0 6.5

Lake

of Is

lands

5.0 5.5 6.0 6.5

Dunda

s #4

5.0 5.5 6.0 6.5

Whit

e Hill

5.0 5.5 6.0 6.5

Deer

5.0 5.5 6.0 6.5

Warr

en

• No acidification trends in 15 of 16 lakes.

• Diatom changes from climatic causes?

Ginn et al. Hydrobiologia 586: 261-275

Acidification: Timing (Cape Breton)

Acidification: Cape Breton’s Glasgow Lake?

Glasgow Lake:

Rogue signal?

or

Sentinel of acidification?

0.0-0.250.25-0.51.0-1.252.0-2.253.0-3.254.0-4.245.0-5.256.0-6.257.0-7.258.0-8.259.0-9.25

10.0-10.2511.0-11.2512.0-12.2513.0-13.2514.0-14.2515.0-15.2516.0-16.2517.0-17.2518.0-18.2519.0-19.2520.0-20.2521.0-21.2522.0-22.2523.0-23.3524.0-24.2525.0-25.2526.0-26.2527.0-27.2528.0-28.2528.75-29.029.0-29.25

0 20 40 60

Astrion

ella r

alfsii

var a

merica

na (o

ver 4

5um)

0

Eunoti

a exig

ua

0

Frustul

ia rho

mboide

s

0

Eunoti

a bilu

naris

var m

ucop

hila

0

Aulaco

seira

pergl

abra

0

Eunoti

a bide

ntula

0

Eunoti

a pec

tinali

s var

pecti

nalis

0 20

Brachy

sira b

resbis

sonii

0

Encyo

nema m

inutum

0 20

Aulaco

seira

lirata

0 20 40

Tabell

aria f

loccu

lossa

strai

n IIIp

0 20

Eunoti

a inc

isa

0 20

Aulaco

seira

dista

ns

5.0 5.3 5.6 5.9 6.2 6.5

Diatom

-infer

red pH

-1.0 -0.8 -0.6 -0.4 -0.2 0.0

Diatom

-infer

red lo

g Gran

-alka

linity

-2.0-1.00.01.02.03.0

PCA Axis 1

Site Sco

res

210PbDate

~1400

2003

1980

1935

~1800

1870

~1650

~1200

~1000

Core Depth (cm)

Relative Abundance (%)

0.0-0.250.25-0.51.0-1.252.0-2.253.0-3.254.0-4.245.0-5.256.0-6.257.0-7.258.0-8.259.0-9.25

10.0-10.2511.0-11.2512.0-12.2513.0-13.2514.0-14.2515.0-15.2516.0-16.2517.0-17.2518.0-18.2519.0-19.2520.0-20.2521.0-21.2522.0-22.2523.0-23.3524.0-24.2525.0-25.2526.0-26.2527.0-27.2528.0-28.2528.75-29.029.0-29.25

0 20 40 60

Astrion

ella r

alfsii

var a

merica

na (o

ver 4

5um)

0

Eunoti

a exig

ua

0

Frustul

ia rho

mboide

s

0

Eunoti

a bilu

naris

var m

ucop

hila

0

Aulaco

seira

pergl

abra

0

Eunoti

a bide

ntula

0

Eunoti

a pec

tinali

s var

pecti

nalis

0 20

Brachy

sira b

resbis

sonii

0

Encyo

nema m

inutum

0 20

Aulaco

seira

lirata

0 20 40

Tabell

aria f

loccu

lossa

strai

n IIIp

0 20

Eunoti

a inc

isa

0 20

Aulaco

seira

dista

ns

5.0 5.3 5.6 5.9 6.2 6.5

Diatom

-infer

red pH

-1.0 -0.8 -0.6 -0.4 -0.2 0.0

Diatom

-infer

red lo

g Gran

-alka

linity

-2.0-1.00.01.02.03.0

PCA Axis 1

Site Sco

res

210PbDate

~1400

2003

1980

1935

~1800

1870

~1650

~1200

~1000

210PbDate

~1400

2003

1980

1935

~1800

1870

~1650

~1200

~1000

Core Depth (cm)

Relative Abundance (%)

Acidified ~1925 – but why only this lake?Gerber et al., 2008, Hydrobiologia

Acidification: Cape Breton’s Glasgow Lake

-0.6 1.0

-1.0

1.0

Gran-alkalinity

PH

TP

ZmaxZmean

Surface Area

Volume

Watershed AreaVolume:Watershed Area

Relative Area

Retention Time

Pre-industrial pH

Mica Hill

Warren

Cradle

Branch

Lake of Islands

Dundas 3

Dundas 4

White Hill

Gull

Indian

Two Island

Glasgow

John Dee

Long

Round

Deer

High volume, slow flushing, very low alkalinty

Critical sulphate load = 0 kg/ha

Sentinel of acidification in Cape Breton

Gerber et al. 2008, Hydrobiologia

Acidification: Cape Breton’s Glasgow Lake?

What can we learn from these studies?

1) Lake ecosystems can respond quickly (in both directions)

2) Paleolimnology can be used to identify problems, suggest solutions and to monitor improvements

Many paleolimnological studies were completed around the world, showing eutrophication and acidification were detrimentally affecting lake ecosystems.

However, nothing ever seems to be as simple as it first appears to be.

The threat of “multiple-stressors”

Be prepared for surprises

“Aquatic Osteoporosis”: The widespread threat of

calcium decline in fresh watersAdam Jeziorski, N. D. Yan, A.M. Paterson, and John P. Smol

M. A. Turner, D. S. Jeffries, W. Keller, R. C. Weeber, D. K. McNicol, M. E. Palmer, K. McIver, K. Arseneau, B. K. Ginn, and B. F. Cumming

Jeziorski et al. (2008) Science 322: 1374-1377

Lake [Ca] Decline

Calcium – why do we care?

Alkaline earth metal

Essential nutrient, critical to the survival, development and biogeographic distribution of biota

Ca concentrations are currently falling in many softwater regions of North America and Europe

Lake [Ca] Decline

1975 1980 1985 1990 1995 2000

Cal

cium

Con

cent

ratio

n (m

g·L-

1 )

1.0

1.5

2.0

2.5

3.0

3.5

(A. Paterson, Ontario MOE)

[Ca] of the Dorset “A” Lakes

Ca Decline/“Aquatic Osteoporosis”

Declines in lakewater calcium (Ca) concentrations have been observed in many regions of Eastern N.A. and Europe

Due to a lack of baseline data, some of the questions currently being raised are only answerable using paleolimnological techniques

Mechanism of Ca Decline

AtmosphericDeposition of Ca

MineralWeathering

Forest Growth/Tree Harvesting

Leaching

Inputs Outputs

Exchangeable Soil Calcium

Acid Rain

Identifying an Indicator for Calcium Thresholds

Crustacean Zooplankton

Crustacean zooplankton have a direct dependence upon Ca (used as a structural material in the carapace)

Species-specific [Ca] differences (and by extension Ca requirements)

Leave identifiable remains that preserve well in sediments (head-shields, carapaces, ephippia)

Daphnia – the Miner’s Canary ?

[Calcium]

1.5 mg/L

Daphnia spp.

Bosmina spp.

3 Paleolimnological Case Studies

Plastic Lake (Ontario) - Received little acid deposition and the lake did not acidify; [Ca] = 1.4 mg/L

Little Wiles Lake (NS) - Naturally acidic; [Ca] = 1.0 mg/L

Big Moose Lake (NY) - Experienced a steady pH decline throughout the 1950s (peak acidification) to 4.5 and has subsequently recovered to >5.5; [Ca] = 1.5 mg/L

Plastic Lake (ON, Canada)

Located on the Canadian Shield Received little acid deposition and the lake did

not acidify 2006 [Ca] = 1.4 mg/L

Little Wiles Lake (NS, Canada)

Located off the Canadian Shield Naturally acidic 2006 [Ca] = 1.0 mg/L

Big Moose Lake (NY, USA)

Located on the Pre-Cambrian Shield in Adirondack Park of NY

Experienced a steady pH decline throughout the 1950s (peak acidification) to 4.5 and has subsequently recovered to >5.5

2006 [Ca] = 1.5 mg/L

3 acidification scenarios, similar Daphnia responses

Low calcium levels are now widespread on Shield lakes

About 1/3 of shield lakes surveyed have declined in Ca levels to below the 1.5 mg/L level

About 2/3 are now below the 2.0 mg/L level

n = 770 (Jeziorski et al., 2008)

Ecosystem Implications:Daphniid Cascade

Algae Daphniids InvertebratePredators

Waterfowl, Fish

X

Ecosystem Implications:Other Biota

Potentially sensitive biota include: Mussels (shell) Gastropods (shell) Crayfish (exoskeleton) Macrophytes Waterfowl (dietary, egg shells)

Also indirect effects such as: pH resilience Metal toxicity

The Limnologist’s Canary?

Climate change:

The new “threat multiplier”

www.ccepr.org/liu/researchCC_en.html

Environment Canada, SOE Report No. 92-2

Cape Herschel, Ellesmere Island

Cape Herschel Field Station; July 9, 2007

Cooler temperatures

Warmer Temperatures(Smol 1983, 1988)

Douglas, M.S.V., Smol, J.P., and Blake, W., Jr. 1994. Marked post-18th century environmental change in high Arctic ecosystems.

Science 266: 416-419.

• unprecedented ecosystem change in ~4 k yr

Douglas et al., 1994, Science

~ 150 yr BP

~ 3900 yr BP

Cape Herschel, Ellesmere I., Elison Lake

(Douglas, Smol & Blake; Science 1994)

1850 210Pb

Cape Herschel, Ellesmere I., Col Pond

Douglas and Smol, 1999

PredictedResponsesto ClimateChange

Warmer:diverse, complex

Cooler:few taxa, simple

Interpretation of data: warming scenario

Douglas and Smol, 1999

Smol, J.P., Wolfe, A.P., Birks, H.J.B., Douglas, M.S.V., Jones, V.J, Korhola, A., Pienitz, R., Rühland, K., Sorvari, S., Antoniades, D., Brooks, S.J., Fallu, M-A., Hughes, M., Keatley, B.E., Laing, T.E., Michelutti, N., Nazarova, L., Nyman, M., Paterson, A.M., Perren, B., Quinlan, R., Rautio, M., Saulnier-Talbot, É, Siitonen, S., Solovieva, N., and Weckström, J.

Climate-driven regime shifts in the biological communities of arctic lakes.

(2005) Proc. Nat. Acad. Sci. 102: 4397- 4402.

(From Smol, Wolfe et al. 2005, PNAS)

Climate-Related Ecological Thresholds in High Arctic Lakes and Ponds

Ice and snow cover

Substrates, such as mosses

Thermal stratification

Water chemistry, such as nutrients

Are similar patterns occurring in temperate lakes?

(http://www.cccma.ec.gc.ca/hccd/)

Year (AD)

Winter

Win

ter T

empe

ratu

re (º

C)

-20

-18

-16

-14

-12

-10

-8 y = 0.0216x - 16.136

2.3ºC increase in 106 years

Kenora 100-year Temperature Record

February

Febr

uary

Tem

pera

ture

(ºC

)

Year (AD)

-22

-20

-18

-16

-14

-12

-10

-8

-6

-4 y = 0.0437x - 16.561

4.6ºC increase in 106 years

-96º -95º -94º -93º

49º

50º Kenora

Rühland et al submittedEnvironment Canada data

Lake of the Woods

Whitefish Bay Ice Cover Record“The longer & colder a winter is, the earlier lakes freeze & the later they thaw.”

D. M. Livingstone (2005)

• Ice-free period increased by 27.7 days since 1964

• Corresponds to increased temperatures

1960 1970 1980 1990 2000 2010180

190

200

210

220

230

240

250

260y = 0.6556x + 203.64

Year AD

# ic

e-fr

ee d

ays

1960 1970 1980 1990 2000 2010180

190

200

210

220

230

240

250

260

1

2

3

4

5

6

# ic

e-fr

ee d

ays

Year AD

Temperature (ºC

)R = 0.77

# Ice-free DaysAnnual Temperature

Data from Ministry of Natural Resources, Kenora, Ontario, Canada

Rühland, Paterson & Smol 2008: Global Change Biology

Heavier diatoms sink to bottom

Stratified water columnMixed water column

Lake water properties & warmingLength of ice-free season- timing of ice-off & ice-on

Timing, duration, strength of the spring freshet & spring overturn

Timing, duration, strength of thermal stratification – depth of mixed epilimnion

Warming & related factors favour small, planktonic Cyclotella taxa

Taxon-specific shifts: Cyclotella-Aulacoseira-Fragilaria

Small planktonic diatoms favoured

Taxon-specific shift: Cyclotella-Aulacoseira

Aulacoseira islandica

Aulacoseira islandica

Aulacoseira granulata

5 μm

Whitefish Bay – Reference site Taxon-specific Relationships

Rühland, Paterson, Smol 2008: Global Change Biology

Kenora Temperature Record

Annual Temperature Cyclotella spp Aulacoseira spp

Annu

al T

empe

ratu

re (º

C) R

elative Abundance (%)

1900 1920 1940 1960 1980 2000 20201.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0

10

20

30

40

50

R = 0.73

1900 1920 1940 1960 1980 2000 20201.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

10

20

30

40

50

60

Year AD

R = - 0.65

Rühland, Paterson, Smol 2008: Global Change Biology

1970 1980 1990 2000118

120

122

124

126

128

130

132

134

0

10

20

30

40

50

1970 1980 1990 2000118

120

122

124

126

128

130

132

134

10

20

30

40

50

60Ic

e-O

ut D

ay o

f Yea

r

Relative Abundance (%

)

Year AD

R = - 0.76

R = 0.77

Whitefish Bay – Reference site Taxon-specific Relationships: Ice-out record

Ice-out day of year Cyclotella spp Aulacoseira spp

How will this affect other algae and cyanobacteria?

Blue-greens like it hot!

Stratified and/or less ice

Mixed water column

Stratified and/or less ice:

Exacerbates blooms

If we are seeing these changes in deep lakes, what is happening to the very shallow lakes?

Large Small

Let’s return to the Cape Herschel High Arctic Ponds

Based on our paleoenvironmental data, the Cape Herschel High Arctic ponds have been permanent water bodies for thousands of years.

But they have started to change profoundly over the last century or so, consistent with climate warming.

What has happened to these ponds over the last few years? (The warmest years on record in this part of the Arctic.)

Smol, J.P. and Douglas, M.S.V. 2007. Crossing the final ecological threshold in high Arctic ponds. Proceedings of the National Academy of Sciences 104: 12395-12397.

The final ecological threshold?

July 16, 2007; Cape Herschel

Smol & Douglas (2007) PNAS 104: 12395-7.

Camp Pond, 16 July 2007

July 12, 2007

Smol & Douglas (2007) PNAS 104: 12395-7.

Smol & Douglas (2007) PNAS 104: 12395-7.

1980’s

2005 - 2009

T ice cover evaporation water levels conductivity

Smol & Douglas (2007) PNAS 104: 12395-7.

increasedevaporation

Even though average precipitation increasing

Smol & Douglas (2007) PNAS 104: 12395-7.

Crossing Ecological Thresholds

permanent ponds ephemeral ponds

larger, deeper ponds shallower, exposed shorelines

(and of course other marked changes in the physical, chemical and biological characteristics of the sites)

ephemeral ponds dry landephemeral ponds dry land

permanent ponds

2 x CO2

4 x CO2

The Arctic in a “Greenhouse Dominated” World?

Estimated summer temperatures by ca 2090

http://www.natural-health-information-centre.com/image-files/head-in-sand.jpg

Not really an option

Lessons from the Past

2) We tend to be overly optimistic –things are generally worse and more complicated than we initially imagined.

1) The recurring patterns of “unintended consequences”

Multiple stressors

Limnological Sampling

neolimnology paleolimnology

a continuum of time scales

HOURS

DAYS

SEASONS

YEARS

DECADES

CENTURIES

MILLENNIA

Paleolimnology: extending the sampling window back in time

From : Smol (2008) Pollution of lakes and rivers: A paleoenvironmental perspective.2nd ed. Blackwell Publ., Oxford