U.S. Department of Interior U.S. Geological Survey Landscape-scale assessments of climate impacts to tidal wetlands along the northern Gulf of Mexico Michael J. Osland U.S. Geological Survey, National Wetlands Research Center Lafayette, 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: nps.gov Source: tbep.org

Rainfall Temperature Dry Cold Wet Hot Herbaceous Salt Marsh Mangrove Forest Tidal Flats- No Plants Succulents Herbaceous Mesohaline Marsh Herbaceous Oligohaline Marsh Influence of climate on tidal wetland foundation species? ?

Vulnerability Assessment Sensitivity Exposure Adaptive Capacity

Ecological Tipping Points

Thresholds, stable states, resilience Stable Resilient Unstable Low Resilience Stable Resilient

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 cells 2.Determine mangrove forest presence or absence for each cell 3.Determine mangrove forest & salt marsh area for each cell (Florida) 4.Obtain 30-yr climate data for each cell ( ; 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 ( o C) 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 FL GA SC

Salt marsh sensitivity to winter climate change- induced mangrove forest range expansion Mean annual minimum temperature increase ( o C) that would lead to mangrove forest dominance

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

Rainfall Temperature Dry Cold Wet Hot Herbaceous Salt Marsh Mangrove Forest Tidal Flats- No Plants Succulents Herbaceous Mesohaline Marsh Herbaceous Oligohaline Marsh How do rainfall regimes affect tidal wetland ecosystems? Change in functional groups; ecosystem structure and function Change in plant coverage ?

Thresholds, stable states, resilience Stable Resilient Unstable Low Resilience Stable Resilient

Rainfall: Mean 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 established 2.Better understanding of historical change 3.Role of positive feedbacks/microclimate 4.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

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