OPTIMAL STRATEGIES FOR ECOLOGICAL RESTORATION UNDER CLIMATE CHANGE

1
OPTIMAL STRATEGIES FOR ECOLOGICAL RESTORATION
UNDER CLIMATE CHANGE Koel Ghosh, James S.
Shortle, and Carl Hershner Agricultural
Economics and Rural Sociology, Pennsylvania State
University Center for Coastal Resources
Management, Virginia Institute of Marine Science
B Purpose of Study The study determines
optimal strategies for natural resource
adaptation under climate change using the
Submerged Aquatic Vegetation (SAV) Restoration
Program in the lower Chesapeake Bay as a case
study.
E Study Region
A Introduction Natural ecosystems like
forest, wilderness, and wetlands provide valuable
habitat and ecological services intimately linked
with sustenance of life on earth. The survival of
species depends on the availability of migration
corridors and the existence or emergence of
suitable habitats. Climate change will affect
fundamental ecological processes and the spatial
distribution of terrestrial and aquatic species.
A crucial issue in facilitating ecosystem
adaptation to climate change is managing land use
and landscapes to preserve migration corridors
and potentially emergent habitats.
Fig. 5 The study region is Hampton Roads in
southeast Virginia. The right-hand map divides
the region into segments for the study.
CASE STUDY
C Submerged Aquatic Vegetation The diverse
assembly of underwater grasses found in the
shallow water of the Chesapeake bay are called
Submerged Aquatic Vegetation (SAV). SAV provides
important habitat for the fish and shellfish
population of the bay and contributes to
improving water quality by removing excess
nutrients. The increased nutrient and sediment
input from development in the surrounding
watershed resulted in a dramatic bay wide decline
in all SAV species in the late 1960s and 1970s.
Compared to historical estimates of 200,000
acres, a 1984 aerial survey of the bay
documented only 38,000 acresprompting a SAV
restoration plan that would ensure the future of
SAV in the Chesapeake Bay.

• F Methodology Steps
• Understand the impact of sea-level rise on
  existing SAV and future SAV restoration
  opportunities.
• Identify adaptation strategies for SAV
  restoration under climate change--strategies are
  a portfolio of choices regarding extent of
  restoration at current sites and future sites.
• Account for uncertainty in future sea-level rise.
  This is done by considering alternative
  scenarios of sea-level rise that can occur in the
  future. Associated with each state is the
  likelihood of that state occurring.
• Account for the social cost of other land and
  water uses excluded by SAV restoration.
• Bring it all together in a mathematical model.
• Solve the model using Discrete Stochastic
  Programming (DSP).

Fig. 1 Eelgrass (Zostera marina) dominates
the lower Chesapeake Bay.
Fig. 2 The blue crab, symbolic of the life and
culture in the Chesapeake Bay region, uses the
bay grass beds as nursery area.
G Data Bathymetry maps points of equal
water depth. Data was obtained by combining
bathymetry information (from the Chesapeake Bay
Program) with GIS data coverage of current and
historic SAV, suitable shellfish aquaculture
area, and tidal marsh inventory data (from
Virginia Institute of Marine Science) in GIS
software ArcInfo.

• D Climate Change and SAV restoration
• The distribution of SAV is influenced by
  salinity, temperature, light penetration, water
  depth, water wave and current actions, and bottom
  sediment. Climate change can affect any of these
  conditions, either by itself or by interacting
  with other environmental stressors.
• This study looks at the impact of climate-induced
  sea-level rise on SAV distribution and
  restoration opportunities. Sea level rise will
  alter the water depth at current SAV sites.
  Existing SAV will migrate from the deeper waters
  to the shallower waters near the shore.
• As the sea moves inland, current tidal marshes on
  the coast may become suitable as SAV growing
  sites.
• There is incomplete information regarding both
  the magnitude and the likelihood of sea-level
  rise. These uncertainties must be reflected in
  the methodological framework.

Fig. 4 The bathymetry bands and coverage area of
existing SAV, historic SAV, tidal marshlands, and
aquaculture suitable areas are shown for segment
6.
MHWMean High Water MTL Mean Tide Level MLW
Mean Low Water T Low Tide L Light

• H Usefulness of the study
• This methodological framework also can be used
  for research on the economics of planned
  ecosystem adaptation to climate change (in
  addition to SAV).
• The study is of practical value as it will aid
  Chesapeake Bay region planners in evaluating
  ecological restoration strategies and developing
  forward-looking land-use plans that enhance
  autonomous adaptability of marine ecosystems.

Fig.3 The suitable water depth for SAV is below
the low tide line (T) to about 2 meters in depth
(L). The SAV fringe (arrow) decreases as the
tidal range increases with sea-level rise.
Source Chesapeake Bay Program
Acknowledgements1. Support is provided by the
Global Change Research Program, Office of
Research and Development, U.S. Environmental
Protection Agency (Cooperative Agreement
R-83053301). 2. Tamia Rudnicky at Virginia
Institute of Marine Science helped organize the
GIS data for the analysis.