Download mangroves - Department of Environmental Science and Policy

HOW TO GET THERE FROM
HERE: ECOLOGICAL AND
ECONOMIC DYNAMIC OF
ECOSYSTEM SERVICE
PROVISION
SANCHIRICO AND SPRINGBORN, 2011
Amanda Luna Mera
ECL 212B
About the authors
James N. Sanchirico
• PhD in Agricultural and Resource
Economics by UC Davis
• Research interests: analysis of policy
design and implementation for marine
and terrestrial species conservation,
the development of economicecological models for forecasting the
effects of resource management
policies, and the control and
prevention of invasive species.
Michael Springborn
• PhD in Environmental Science and
Management by UC Santa Barbara
• Research interests: Environmental
and resource economics, decisionmaking under uncertainty
PURPOSE
To include an Ecological Model
into a fishery model (Economic
Model) where mangroves provide
habitat and protection to certain
species.
The model maximizes NPV from fishing and
mangrove conversion and conservation.
• The goal of the study was to inform decisions on how to value and
conserve habitats (mangroves) and to determine the optimal fish
catch.
• The Bioeconomic model integrates ecological and economical
understanding of the fishery-habitat linkages
• The system considers how multiple types of habitats impact the
dynamics of the fish population.
• mangroves
• seagrass
• coral reefs
METHODOLOGY
The model shows multiple ecosystem service
provision in a production function framework.
Optimal habitat
development
Optimal Biological
Stock Harvesting
•Restorable resource
•Renewable resource.
• The efficient long-run optimal locus was identified in the
production frontier
The ecological model is embedded in an
economic framework
Mangroves -inputs - contribute to fish production
Choice variables
State variables
Fishing catch
Fish stock
Mangrove conversion
Proportion of Mangrove
conserved
• The production function determines:
• Fish population changes over time in response to availability
and use of mangroves habitats and other ecological
processes.
• Market approach- calculating fisheries production as the gross
revenues of all fish associated with mangroves.
• Assumes absolute dependence of the fish population on mangroves.
Density-dependence is considered in the
recruitment and the use of mangroves.
• The environmental
parameters influence
both population size and
intrinsic growth rates.
• The mangroves have
obligate and facultative
use.
Species use different habitats at different stages in their lifes.
• Seagrass for juveniles- mangroves for future
development – coral reef for adults.
The objective production function included the
habitat alternatives for the fish stock
Mangroves - inputs for
fish production
- Fish population
changes in response to
availability and use of
mangrove habitats.
Density-dependence
processes are included
too.
Economical Function
Ecological Production
Function
• The Ecological Economic Model was composed of:
Estimates the fisheries’
production value of
mangroves as the gross
revenues of all fish
associated with
mangroves.
Assumes the population
depends completely on
mangroves.
The model shows that the association between
fish and mangroves can be facultative or obligate.
The value of
mangroves is
less.
Facultative
Not all
survivorship
depends on
mangroves
If mangroves are
removed
Obligate
The population
is entirely
dependent on
recruits from the
mangroves
The fish population
will fo extinct.
RESULTS
The Economic Model maximizes the NPV from fishing,
and mangrove development and protection.
• The model allows a social planner to chose the level of mangrove
conversion and fish catch in each period.
Profits
Conversion
costs
Benefits
In situ value of
mangroves
prov. Coastal
protection
• Mangroves contribute to the value of the system:
• Indirectly= production of fish
• Directly= protection of coastal area
The Optimal interior steady-state for fish stock and
mangroves
• The optimal extent - M*
balances
• BM (returns from
development)
• PM (returns from storm
protection)
• FM (returns from fishing)
Mangroves
Fish stock
• The optimal stock on the reef
occurs when the returns in
perpetuity from harvesting
another fish minus the
opportunity cost is equal to
the rate of return of selling
the fish and investing the
revenues in capital markets.
The optimal policies depended on the nature of
the species-habitat relationship.
The optimal fish stock depends which values are
taken into account by the planner
• If all values are considered (fish production and storm
protection) the resulting optimal fish stock would be lower.
Mangroves affect long-run equilibrium
• The unexploited steady-state equilibrium is derived as a
function of the mangrove coverage to show how mangroves
affect long-run equilibrium
The extent of mangroves connected to the reef
depends on whether they are restored or cleared.
• The mangrove dynamics are:
• Dt= effort devoted to mangrove conversion at time t
• Positive= clearing for development
• Negative= restoration
• F(Dt)= time rate of change in mangroves
• This function considers that restoring mangroves may be more
difficult than clearing them.
The FOC incorporate the harvest, conversion, fish
population and mangrove coverage levels.
• The First Order Conditions were obtained using Langrangian
values.
• The shadow prices for the harvest, conversion, fish population
and mangrove coverage levels were determined jointly.
• The dynamics of the shadow prices over time depend on the
ecological and economic conditions in the ecosystem.
The Optimal State was identified in two
scenarios – with and without storm protection.
Case 1- Omitting storm
protection values
• Overshooting mangrove
equilibrium is part of the
solution.
• Additional benefits earlier
from fishing
•Faster recovery rates of pop.
• Differences in the trade-off curve
between the obligate and
facultative setting.
• Species won’t go extinct
without mangroves.
•
Case 2- Including storm
protection values
•The fish stock levels are
similar across the obligate
and facultative settings.
•The fishery is more
productive
•Overshooting is optimal
when the relationship is
obligate
The optimal PES schedule is interdependent on
the ecological and economical context
Optimal
•Correspond to the
optimal fish catch
trajectory
PES for
mangroves
• Depend on the
relative value of the
sectors using the
mangroves.
• Different habitat
uses
• PES are
interdependent
• Change over time
• Greater when
ecosystems are
degraded
Dynamic
The Fisherman’s WTP to forgo development depends on the marginal value to the
fishery forman additional unit of mangrove at time t.
CONCLUSIONS
The poor understanding of ecosystems is a
limiting factor in resource management decisions.
• The ecosystem production functions  dynamic process
models
• Map the structure and operation of the biological and physical components
of the ecosystems into the provision of services.
Mangroves are an input of several services
-Fish habitat
-Storm protection
Fish populations and mangroves can have an obligate or facultative
relationship
• The planning and management decisions must be based on detailed
knowledge of ecological production functions and the economic
conditions.
The incentives to achieve an efficient trade-off
between fish biomass and mangrove habitat
conservation are dynamic.
• The model developed considers different types of species habitat
dependency
• Allows variation in the extent of the habitat to affect the growth
rate and the long-term fish level.
CRITIQUE
The study found a numerical solution for an
optimal transition to a point in the trade-off curve
• The finding was new in the discussion on ecosystem services
provision.
• Highlights the need for detailed knowledge about the ecological
production functions along with the economic conditions of the
individuals and species who receive the benefits.
• The model succeeds in incorporating not only the ecological and
economic components of the system, but also the relationships
and interdependences.
• The sensitivity analysis explored the implications of the economic
and ecological parameters.
• This allowed to make fit into the model more realistic species-habitat
interactions.