A phenology- and trend-based approach for accurate mapping of sea-level driven coastal forest retreat

Chen, Yaping; Kirwan, Matthew L.

doi:10.1016/j.rse.2022.113229

Cited by 24 publications

(24 citation statements)

References 69 publications

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“…The data that support the findings of this study are openly available in the Virginia Coast Reserve Long‐Term Ecological Research repository at https://doi.org/10.6073/pasta/4ae5ac3fbdb6a20dcdcb2ff36487d292%0A (Chen & Kirwan, 2023a), and https://doi.org/10.6073/pasta/4edf9b0d9d6660d354710748b2cf56f0 (Chen & Kirwan, 2023b).…”

Section: Data Availability Statementsupporting

confidence: 63%

“…We differenced the landcover maps in 1984 and 2020 to identify areas of forest change, and then estimated rates of lateral and vertical forest retreat based on unique patterns of forest boundary change. The step‐by‐step methodology is illustrated in Figure 2, modified from the framework in Chen and Kirwan (2022b) to quantify both lateral and vertical forest retreat. In brief, there are four patterns of forest loss depending on coastal tree line configuration: Interior loss (P1: emerging forest loss, tree line present only in 2020), Entire loss (P2: complete patch loss, tree line present only in 1984), Linear retreat (P3: parallel retreat with conjoint tree lines in 1984 and 2020), and Radial retreat (P4: concentric retreat with disjoint tree lines in 1984 and 2020) (Figure 2).…”

Section: Methodsmentioning

confidence: 99%

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Upland forest retreat lags behind sea‐level rise in the mid‐Atlantic coast

Chen,

Kirwan

2023

Global Change Biology

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Ghost forests consisting of dead trees adjacent to marshes are striking indicators of climate change, and marsh migration into retreating coastal forests is a primary mechanism for marsh survival in the face of global sea‐level rise. Models of coastal transgression typically assume inundation of a static topography and instantaneous conversion of forest to marsh with rising seas. In contrast, here we use four decades of satellite observations to show that many low‐elevation forests along the US mid‐Atlantic coast have survived despite undergoing relative sea‐level rise rates (RSLRR) that are among the fastest on Earth. Lateral forest retreat rates were strongly mediated by topography and seawater salinity, but not directly explained by spatial variability in RSLRR, climate, or disturbance. The elevation of coastal tree lines shifted upslope at rates correlated with, but far less than, contemporary RSLRR. Together, these findings suggest a multi‐decadal lag between RSLRR and land conversion that implies coastal ecosystem resistance. Predictions based on instantaneous conversion of uplands to wetlands may therefore overestimate future land conversion in ways that challenge the timing of greenhouse gas fluxes and marsh creation, but also imply that the full effects of historical sea‐level rise have yet to be realized.

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Section: Data Availability Statementsupporting

confidence: 63%

Section: Methodsmentioning

confidence: 99%

Upland forest retreat lags behind sea‐level rise in the mid‐Atlantic coast

Chen,

Kirwan

2023

Global Change Biology

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“…The average rate of relative sea level rise has increased from 2.45 mm yr −1 (1953-1983) to 4.7-6.2 mm yr −1 (1975-2021) (Ezer, 2023;Ezer & Atkinson, 2015). Concurrent with accelerating sea level rise rates, coastal forests migrated upslope and horizontal forest retreat rates accelerated from 3.1 m yr −1 (1985-2000) to 4.7 m yr −1 (2001-2020) in a portion of the Chesapeake Bay (Chen & Kirwan, 2022a). By 2100, 1,050-3,748 km 2 of uplands are projected to convert to marsh, largely at the expense of terrestrial forests and freshwater forested wetlands (Molino et al, 2022).…”

Section: Study Areamentioning

confidence: 99%

Biophysical Drivers of Coastal Treeline Elevation

Molino,

Carr,

Ganju

et al. 2023

JGR Biogeosciences

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Sea level rise is leading to the rapid migration of marshes into coastal forests and other terrestrial ecosystems. Although complex biophysical interactions likely govern these ecosystem transitions, projections of sea level driven land conversion commonly rely on a simplified “threshold elevation” that represents the elevation of the marsh‐upland boundary based on tidal datums alone. To determine the influence of biophysical drivers on threshold elevations, and their implication for land conversion, we examined almost 100,000 high‐resolution marsh‐forest boundary elevation points, determined independently from tidal datums, alongside hydrologic, ecologic, and geomorphic data in the Chesapeake Bay, the largest estuary in the U.S. located along the mid‐Atlantic coast. We find five‐fold variations in threshold elevation across the entire estuary, driven not only by tidal range, but also salinity and slope. However, more than half of the variability is unexplained by these variables, which we attribute largely to uncaptured local factors including groundwater discharge, microtopography, and anthropogenic impacts. In the Chesapeake Bay, observed threshold elevations deviate from predicted elevations used to determine sea level driven land conversion by as much as the amount of projected regional sea level rise by 2050. These results suggest that local drivers strongly mediate coastal ecosystem transitions, and that predictions based on elevation and tidal datums alone may misrepresent future land conversion.

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“…The climate there is characterized by hot, humid summers and cool winters. The Chesapeake Bay region is a hotspot for sea‐level‐driven coastal forest retreat, driven by rapid SLR across a gently sloping coastal plain topography (Schieder et al ., 2018; Chen & Kirwan, 2022a,b). The 20 th century relative SLR rates in the Chesapeake Bay region ( c .…”

Section: Methodsmentioning

confidence: 99%

“…Our predictive certainty regarding ghost forest formation is poor due to a lack of understanding of the physiological processes underlying tree death from SLR, and due to the lack of vegetation dynamic models developed for shoreline ecosystems (McDowell et al ., 2022; Yoshikai et al ., 2022). Predictions are further complicated by the confounding impacts of SLR and other climate change factors such as rising atmospheric CO 2 levels (Chen & Kirwan, 2022a,b). Our poor capacity to predict the rate of ghost forest formation impedes assessment and mitigation of ecosystem services and terrestrial habitat losses due to SLR (Kirwan & Gedan, 2019; Ward et al ., 2020).…”

Section: Introductionmentioning

confidence: 99%

Modeling the mechanisms of conifer mortality under seawater exposure

et al. 2023

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Summary Relative sea level rise (SLR) increasingly impacts coastal ecosystems through the formation of ghost forests. To predict the future of coastal ecosystems under SLR and changing climate, it is important to understand the physiological mechanisms underlying coastal tree mortality and to integrate this knowledge into dynamic vegetation models. We incorporate the physiological effect of salinity and hypoxia in a dynamic vegetation model in the Earth system land model, and used the model to investigate the mechanisms of mortality of conifer forests on the west and east coast sites of USA, where trees experience different form of sea water exposure. Simulations suggest similar physiological mechanisms can result in different mortality patterns. At the east coast site that experienced severe increases in seawater exposure, trees loose photosynthetic capacity and roots rapidly, and both storage carbon and hydraulic conductance decrease significantly within a year. Over time, further consumption of storage carbon that leads to carbon starvation dominates mortality. At the west coast site that gradually exposed to seawater through SLR, hydraulic failure dominates mortality because root loss impacts on conductance are greater than the degree of storage carbon depletion. Measurements and modeling focused on understanding the physiological mechanisms of mortality is critical to reducing predictive uncertainty.

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A phenology- and trend-based approach for accurate mapping of sea-level driven coastal forest retreat

Cited by 24 publications

References 69 publications

Upland forest retreat lags behind sea‐level rise in the mid‐Atlantic coast

Upland forest retreat lags behind sea‐level rise in the mid‐Atlantic coast

Biophysical Drivers of Coastal Treeline Elevation

Modeling the mechanisms of conifer mortality under seawater exposure

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