Sandy beach ecosystems and climate variability Omar Defeo, Leonardo Ortega, Eleonora Celentano, Diego Lercari, Gastón Martínez

• World’s coastlines total almost 106 km

• Sandy beaches dominate open coastlines

• Accreting beaches are the exception (<10%)

• > 80 % are experiencing some erosion

Sandy beaches

tides waves sand

Sandy beaches: main physical factors

1

Weeks

Months

Years

Decades

Centuries

Tim

e

Space (km)10 100 1000

Climate changeand sea-level rise

Beach mining

Exploitation

Coastal engineeringand urban development

Pollution, nourishmentand grooming

Recreation and ORVs

Sandy beaches provide irreplaceable ecosystem services to society

Environment and biota are being threatened by several drivers acting at multiple temporal and spatial scales

Severely under-represented in climate change ecology

Sandy beach threats

Do sandy beaches respond to climate change in ways that are consistent with expectations of hypotheses from general climate-change ecology?

Defeo et al 2009, 2013, Schoeman et al 2014

• Beaches are caught between rising sea and expanding human activity

• Retreat is not possible in most cases because of urban development

• Beach and dunes reduced/lost

Sea level rise

COASTExpanding population Coastal squeeze

The physical environment: coastal squeeze

Coastal squeeze + erosion: negative socio-economic effects

Coastal squeeze: negative socio-economic effects

Uruguayan coast:

Increase in temperature, and in the frequency, intensity and speed of onshore winds

y = 0.28x + 1.63R²= 0.44***

1.2

1.4

1.6

1.8

2.0

2.2

-0.4 0.1 0.6 1.1Sea surface temperature anomalies (ºC)

Win

d sp

eed

anom

alie

s (m

.s-1

) 2007

20112008

2006

1989

1990

1993

1988

y = 0.28x + 1.63R²= 0.44***

1.2

1.4

1.6

1.8

2.0

2.2

-0.4 0.1 0.6 1.1Sea surface temperature anomalies (ºC)

Win

d sp

eed

anom

alie

s (m

.s-1

) 2007

20112008

2006

1989

1990

1993

1988

Increase in temperature, onshore winds and extreme events

y = 0.45x - 879.54R2 = 0.80***

10

12

14

16

18

20

22

24

1991 1995 1999 2003 2007 2011

Year

Swas

h w

idth

(m)

Long-term increase in wave height, swash width, and decrease in beach slope EROSION

Ortega et al. 2013, Defeo et al. 2013

Hall 2011, Defeo & Castilla 2012, Defeo et al. 2013

Climate fluctuations affect the social-ecological system

Habitat Fauna

Society

Loss of intertidal habitat, catchability, fishing days and $$$

10

12

14

16

18

20

22

24

1985 1986 1987 1990 2009 2010 2011

January

February

10

12

14

16

18

20

22

24

1985 1986 1987 1990 2009 2010 2011

January

February

Num

ber o

f fis

habl

e da

ysPerception of fishers: fishing days

Much less Less Normal More Much more

0

> 95% of species, abundance and biomass made up by three taxa:• Crustaceans (isopods, amphipods, hippids, mysids, decapods)

• Molluscs (bivalves and gastropods)• Polychaete worms

Sandy beach macrofauna

Excirolana

Mesodesma

Glycera

How do they respond to How do they respond to the beach environment the beach environment and climate variability?and climate variability?

Mesodesma donacium

Mesodesma mactroides

4ºS

50ºS

24ºS

41ºS

Mesodesma donacium

Mesodesma mactroides

4ºS

50ºS

24ºS

41ºS

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1969 1974 1979 1984 1989 1994 1999 2004

Cat

ch (t

on)

Peru

0

4000

8000

12000

16000

20000

1965 1970 1975 1980 1985 1990 1995 2000 2005

Cat

ch (t

on)

Chile

0

4000

8000

12000

16000

20000

1965 1970 1975 1980 1985 1990 1995 2000 2005

Cat

ch (t

on)

Chile

Almost collapsed fishery stocks, despite management strategies (area-based + co-management) that succeeded in other benthic fisheries (Chile, Uruguay)

0

2000

4000

6000

8000

10000

12000

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

2009

Year

Abu

ndan

ce (i

nd/m

)

0

2000

4000

6000

8000

10000

12000

1981

1983

1985

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007

2009

Year

Abu

ndan

ce (i

nd/m

) Mesodesma mactroidesUruguay-Brazil-Argentina

Sandy beach clams – Pacific – Atlantic South America

Sandy beach clams: mass mortalitiesMass mortalities of this cold-water clams during the last 2 decades decimated populations

throughout entire distribution ranges in the Atlantic and Pacific:

1. Important SOCIAL-ECOLOGICAL SYSTEMS: fisheries and human livelihoods affected

2. Community structures and ecosystems drastically changed

3. Possible causes: fishing PLUS temperature increase, algal blooms, diseases

Brazil – Uruguay – Argentina

Peru - Chile

Fiori et al. 2004, Fiori & Defeo 2006, Oderbrecht et al 2009

0

2000

4000

6000

8000

10000

12000

19601963196619691972197519781981198419871990199319961999200220052008

Year

Abu

ndan

ce (I

nd.m

-1)

-3

-2

-1

0

1

2

3

AM

O (c

umul

ativ

e su

m)

Atlantic Multidecadal Oscillation

Reg

ime

shift

Reg

ime

shift

Mass mortalities

Increase in temperature

Defeo & Castilla 2012, Ortega et al. 2012, 2013, Schloeman et al. 2014

SSTA

Atlantic yellow clam: mass mortalities and increasing temperature

Mass mortalities: negative socio-economic effects

Mass mortalities that began in late 1993

Closed fishery until 2008, without showing evidence of stock recovery, particularly in the adult (harvestable) stock

Ortega et al. 2012, 2013, Defeo et al. 2014

Pacific surf clam: mass mortalities, ENSO and fishery collapse

Ortega et al. 2012

ENSO affected landings in Peru and Northern Chile: closed season in Peru since 1999…

Unit price: another significant predictor of long-term trends

ENSO

Ecological effects of climate variability: tropicalization

0

20

40

60

80

100

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

Mesodesma mactroides

Donax hanleyanus

Emerita brasiliensis

Adu

lt ab

unda

nce

(%) Ex

perim

enta

lm

anag

emen

t

80

60

40

Jun ´81

20

100

Dec ´81 Jun ´82 Dec ´82 Jun ´83 Oct ´83

Freq

uenc

yby

num

ber

(%)

Donax

peruvianus

Emerita analogaOthers

Mesodesma donacium EL NIÑO

´ ´ Jun ´82 Dec ´82 Jun ´83 Oct ´83

(%)

Others

Massive mortalities of yellow clam

1. Increasing SST

2. Phytoplankton biomass,

composition and

intensity of blooms

3. Benthic community

structure

4. Population abundance

5. Persistence of invasive

species

6. Range shifts

Changes being assessed:

Blooms

Climate change and transitional waters

Basset et al. 2013, Schoeman et al. 2014

Changes in:

• Temperature• Precipitations• Sea level• Water runoff

Hypotheses to be tested:

• Spp composition shifts• Expansion of exotic species

(Corbicula)?• Increase in mortality of

marine species

Uruguay

Environment EcosystemProcesses, functions

Biodiversity

Abundance/structure

Managementtools

TimeSpace SpeciesSizesEffort

Fisheries

Tourism

Protection to extreme events

Long term management policies

Sandy beach management requires the integration of ecology with socio-economic and institutional factors

Governance modes and institutional

structuresGovernment-based

Co-managementDecentralized

UNCERTAINTY

Ecological, Statistical, Socio-economic, Governance

Sandy beaches as social-ecological systems

Services

1. Different lines of evidence support a climate change interpretation as a primary causal agent in sandy beaches

2. Effects on the environment:

a. Coastal squeeze (sea level rise and urbanization)

b. Changes in beach morphodynamics: erosion

c. Increase in swash width

3. Effects on macrofauna:

a. Biodiversity loss: a major driver of ecosystem change (regime shifts)

b. Across taxa: similar effects in parallel communities (Atlantic and Pacific)

Conclusions: sandy beaches & climate variability

Conclusions: sandy beaches & climate variability

1. Biophysical changes affected socio-economic issues: sandy beaches as social-ecological systems

2. Effects of climate variability swamped management measures

3. Long-term policies, early warning systems (e.g. red tides) and co-governance of SES are needed

4. Institutional adaptive capacity to cope with climatic and human drivers of change

Gutierrez et al. 2011 - Nature