Perhaps it does. Sea level rise may change the spatial structure of marshes where up to some point, it would enhance habitat provision. With all the concern about sea level rise degrading marshes, what will really happen to marshes as habitats as the sea level rises in the coming years? Using a landscape ecology approach, we modeled how habitat properties such as area, edge density, fractal dimension and connectivity of salt marsh patches change with different rates of sea level rise. We found that moderate sea level rise retains and even improves habitat complexity. Marsh area, edge density and mean patch sized increased. Nearest neighborhood distance and juxtaposition between marsh patches and fractal dimension of the seaward edges remained constant. Patch size carrying capacity for select estuarine fishes also increased. Of course, patch connectivity improves when tidal barriers are removed to accommodate sea level rise. All these lead us to suggest that sea level rise may temporarily have positive effect for fish until rates of rise become so high that they drown the marshes or marshes are faced with coastal squeeze.

1. Impacts of Sea Level Rise on Fishes
Insightful
GeoInformatics
www.insightfulgeo.
ca

2. Source: IPCC, 2013
Sea level is expected to rise past historical levels in the next 100
years.
0
0.5
1
1.5
2
2.5
2000 2009 2018 2027 2036 2045 2054 2063 2072 2081 2090 2099
SeaLevel(m)
Year
SL Hist SL .5
SL 1 SL 1.5

3. Recent study show that sea level rise can drown and shrink
wetlands because of coastal squeeze.
0.5 1 1.5 2.0
Projected distribution of salt marsh areas at Year 2100 sea levels (m)
Source: Torio & Chmura, 2013

4. How will a shrinking marsh surface affect fish habitats within the
salt marsh?
Image source: http://ian.umces.edu/imagelibrary/displayimage-4192.html

5. To examine the impacts sea level rise on salt marsh as fish habitats,
the size, configuration and connectivity of salt marsh patches were
evaluated.
Patch size and configuration Connectivity

6. Results indicate that at moderate sea level rise, salt marsh area
increased resulting in more available fish habitats.
-At high sea level, 40% of the future marshes will be in
private properties!
0
10
20
30
40
50
60
70
0.00 0.32 0.50 1.00 1.50
ESLI
Constant Accretion
Accretion = SLR
Carrying Capacity (ESLI)

7. Not only the size but also the variability of marsh patches increased
with moderate sea level rise.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.00 0.32 0.50 1.00 1.50
Area(ha)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.00 0.32 0.50 1.00 1.50
Area(ha) Sea Level (m)
Constant Accretion
Accretion = SLR
Patch size standard deviation
Mean Patch Size

8. Apart from habitat size and variability, complexity of marsh edges
which provide refuge for small fishes also increased.
Edge Density Fractal Dimension

9. Furthermore, moderate flooding from sea level rise increased
connectivity between habitat patches.

10. Summary and conclusion
Moderate sea level rise resulted in
expansion of fish habitats. Moderate means
sea levels not exceeding 1 meter. Sea
levels exceeding this threshold resulted in
reduced habitat size, configuration and
fragmentation.