Download Sandy beach ecosystems and climate variability

Sandy beach ecosystems and climate variability
Omar Defeo, Leonardo Ortega, Eleonora Celentano, Diego Lercari, Gastón Martínez
Sandy beaches
• 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: main physical factors
tides
waves
sand
Sandy beach threats
Sandy beaches provide
irreplaceable ecosystem
services to society
Centuries
Climate change
and sea-level rise
Coastal engineering
and urban development
Decades
Beach mining
Time
Environment and biota
are being threatened by
several drivers acting at
multiple temporal and
spatial scales
Pollution, nourishment
and grooming
Years
Exploitation
Months
Severely underrepresented in climate
change ecology
Recreation and ORVs
Weeks
1
10
100
1000
Space (km)
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
The physical environment: coastal squeeze
• 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
COAST
Expanding
population
Coastal squeeze
Sea level rise
Coastal squeeze + erosion: negative socio-economic effects
Coastal squeeze: negative socio-economic effects
Increase in temperature, onshore winds and extreme events
Ortega et al. 2013, Defeo et al. 2013
Wind speed anomalies (m.s-1)
Uruguayan coast:
Increase in temperature,
and in the frequency,
intensity and speed of
onshore winds
Long-term increase in wave
height, swash width, and
decrease in beach slope Î
EROSION
2.2
y = 0.28x + 1.63
1.6
1988
1993
1990
1.4
1.2
-0.4
1989
0.1
0.6
Sea surface temperature anomalies (ºC)
Sw ash w idth (m )
y = 0.45x - 879.54
2
R = 0.80***
20
18
16
14
12
10
1991
1995
1999
2003
Year
2008
2006
24
22
2011
2.0 R²= 0.44***
1.8
2007
2007
2011
1.1
Climate fluctuations affect the social-ecological system
Society
Habitat
Fauna
Hall 2011, Defeo & Castilla 2012, Defeo et al. 2013
Number of fishable days
Loss of intertidal habitat, catchability, fishing days and $$$
24
January
22
February
Perception of fishers: fishing days
20
18
16
14
12
0
10
1985
1986
1987
1990
2009
2010
2011
Much less
Less
Normal
More
Much more
Sandy beach macrofauna
> 95% of species, abundance and biomass made up
by three taxa:
• Crustaceans (isopods, amphipods, hippids, mysids, decapods)
• Molluscs (bivalves and gastropods)
• Polychaete worms
How do they respond to
the beach environment
and climate variability?
Mesodesma
Excirolana
Glycera
Sandy beach clams – Pacific – Atlantic South America
4500
4000
Peru
Catch (ton)
3500
4ºS
3000
2500
2000
1500
1000
500
0
24ºS
1969
1974
1979
1984
1989
1994
1999
2004
20000
Mesodesma
donacium
Chile
Catch (ton)
16000
41ºS
50ºS
Mesodesma
mactroides
12000
8000
4000
0
Mesodesma mactroides
Uruguay-Brazil-Argentina
10000
8000
1965
1970
1975
1980
1985
1990
1995
2000
2005
6000
4000
2000
Year
2009
2007
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
1983
0
1981
A b u n d a n c e (in d /m )
12000
Almost collapsed fishery stocks,
despite management strategies
(area-based + co-management) that
succeeded in other benthic fisheries
(Chile, Uruguay)
Sandy beach clams: mass mortalities
Mass 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
12000
10000
8000
3
2
1
6000
0
4000
-1
2000
-2
0
-3
AMO (cumulative sum)
Regime shift
Mass mortalities
Abundance (Ind.m-1)
Atlantic Multidecadal Oscillation
Regime shift
Atlantic yellow clam: mass mortalities and increasing temperature
2008
2005
2002
1999
1996
1993
1990
1987
1984
1981
1978
1975
1972
1969
1966
1963
1960
Year
Increase in temperature
TA
S
S
Defeo & Castilla 2012, Ortega et al. 2012, 2013, Schloeman et al. 2014
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
ENSO affected landings in Peru and Northern Chile: closed season in Peru since 1999…
Unit price: another significant predictor of long-term trends
ENSO
Ortega et al. 2012
Ecological effects of climate variability: tropicalization
Experimental
management
100
Adult abundance (%)
Massive mortalities of
yellow clam
80
Changes being assessed:
1. Increasing SST
2. Phytoplankton biomass,
Donax hanleyanus
composition and
Emerita brasiliensis
60
intensity of blooms
3. Benthic community
40
Mesodesma mactroides
20
4. Population abundance
5. Persistence of invasive
0
1982
Frequency by number (%)
structure
1984
1986
1988
1990
1992
1994
1996
1998
2000
species
6. Range shifts
Mesodesma donacium
100
EL NIÑO
80
Donax
peruvianus
60
40
20
Emerita
analoga
Others
Jun ´81
´
Dec ´´81
Jun ´82
Dec ´82
Jun ´83
Oct ´83
Blooms
Climate change and transitional waters
Changes in:
•
•
•
•
Temperature
Precipitations
Sea level
Water runoff
Uruguay
Hypotheses to be tested:
• Spp composition shifts
• Expansion of exotic species
(Corbicula)?
• Increase in mortality of
marine species
Basset et al. 2013, Schoeman et al. 2014
Sandy beaches as social-ecological systems
Governance modes
and institutional
structures
Long term
management policies
Government-based
Co-management
Decentralized
Environment
Ecosystem
Processes, functions
UN
C
Ec
olo
gic
al,
S
Biodiversity
ER
TA
INT
Y
tat
isti
cal
,S
oci
o
-ec
on
om
ic,
G
ove
rna
Abundance/structure
Management
tools
Time
Space
Species
Sizes
Effort
Services
Fisheries
Tourism
Protection to
extreme events
nce
Sandy beach management requires the integration of
ecology with socio-economic and institutional factors
Conclusions: sandy beaches & climate variability
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
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