U.S. Department of InteriorU.S. Geological Survey

Landscape-scale assessments of climate impacts to tidal wetlands along the northern Gulf of Mexico

Michael J. OslandU.S. Geological Survey, National Wetlands Research CenterLafayette, Louisiana

Gulf of Mexico tidal wetlands are abundant and diverse

Mangrove trees and shrubs

(mangrove forests)

Graminoid plants

(salt marsh)

Succulent plants (salt marsh)

Algal mats (salt flats)

Foundation species play an important ecological role

Species that create habitat and facilitate the

development of entire ecological

communities

Foundation species support ecosystem goods and services

• Coastal protection/resilience• Carbon sequestration• Fish and wildlife habitat• Nutrient and sediment removal• Trophic linkages to coastal ecosystems• Seafood • Recreation

Source: nola.com

Source: nola.com

Source: nps.gov

Source: tbep.org

Rainfall

Tem

pera

ture

DryCold

Wet

Hot

Herbaceous Salt Marsh

Mangrove ForestTidal Flats-

No Plants

Succ

ulent

s

Her

bace

ous

Mes

ohal

ine

Mar

sh

Her

bace

ous

Olig

ohal

ine

Mar

sh

Influence of climate on tidal wetland foundation species?

?

Vulnerability Assessment

Sensitivity

Exposure

Adaptive Capacity

Ecological Tipping Points

Thresholds, stable states, resilience

StableResilient

UnstableLow

Resilience

StableResilient

Zones of Instability

Osland et al. In press, Ecology

Identification of zones of instability- sensitive to

climate change

Two Studies

1. Winter climate change: salt marshes vs. mangrove forest

2. Rainfall change: Ecological transitions across a rainfall gradient

Mangrove individuals present

Winter climate is an important driver of salt marsh-mangrove forest interactions in the southeastern U.S.

Mangrove individuals present

How might winter climate change impact mangrove forest-salt marsh interactions?

1. Divide the coast into a grid of cells2. Determine mangrove forest presence or absence for each cell3. Determine mangrove forest & salt marsh area for each cell (Florida) 4. Obtain 30-yr climate data for each cell (1970-2000; Maurer et al. 2002)5. Develop species distribution and relative abundance models

Mangrove individuals present

The tipping point: salt marsh vs. mangrove forest

Osland et al. 2013, Global Change Biology

Salt marsh sensitivity to winter climate change-induced mangrove forest range expansion

Mean annual minimum temperature increase (oC) that would lead to mangrove forest dominance

Amount of salt marsh area within each state that would become vulnerable to mangrove forest replacement

TX

LA

FLGA SC

Salt marsh sensitivity to winter climate change-induced mangrove forest range expansion

Mean annual minimum temperature increase (oC) that would lead to mangrove forest dominance

Study #2: Ecological transition across a rainfall gradient (in press, Ecology)

Rainfall

Tem

pera

ture

DryCold

Wet

Hot

Herbaceous Salt Marsh

Mangrove ForestTidal Flats-

No Plants

Succ

ulent

s

Her

bace

ous

Mes

ohal

ine

Mar

sh

Her

bace

ous

Olig

ohal

ine

Mar

sh

How do rainfall regimes affect tidal wetland ecosystems?

Change in functional groups; ecosystem structure and function

Change in plant coverage

?

Thresholds, stable states, resilience

StableResilient

UnstableLow

Resilience

StableResilient

Rainfall: 1970-2000Mean Annual Precipitation (mm/yr)

Plant cover transitions along the rainfall gradient

Osland et al. In press, Ecology

Estuarine level analyses

Osland et al. In press, Ecology

Zone of instability: sensitive to small changes in freshwater availability

Zones of instability: small changes in macroclimatic drivers could lead to landscape-scale ecological

change

Red= high sensitivity to changes in winter temps

Blue = high sensitivity to changes in freshwater availability

What should be done within sensitive areas (zones of instability)?

1. Monitoring networks should be established2. Better understanding of historical change3. Role of positive feedbacks/microclimate4. Implications for good and services?5. Implications for adaptation to sea level rise and

other stressors? Resilience? 6. Can management and restoration efforts be

optimized to maximize adaptation?7. Future-focused models should incorporate

macroclimatic drivers

Zones of Comparative Stability

Green = Potential refuge for salt marsh ecosystem good and services

What should be done within stable areas?

1. Gauge whether these areas can serve as refuges

2. What other aspects of future change may affect ability to serve as refuges?

3. Any barriers to adaptation to sea level rise (e.g., urbanization & other stressors)?

4. How can management and restoration efforts be optimized functionality as refuges?

Thanks to many colleagues that contributed to this research

• Richard Day• Nicholas Enwright• Tom Doyle• Camille Stagg• Jim Grace• Chris Gabler• Steve Hartley• Andy From• Jennie McLeod• Meagan McLemore• Erik Yando• Ken Krauss• Mark Hester• Jonathan Willis

For more info: mosland@usgs.gov