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Air Resource Management Programs. Critical Loads and Target Loads: Tools for Assessing, Evaluating and Protecting Natural Resources Ellen Porter Deborah Potter, Ph.D. National Park Service U.S.D.A. Forest Service [email protected] [email protected] WESTAR Council - PowerPoint PPT Presentation
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Critical Loads and Target Critical Loads and Target Loads: Tools for Assessing, Loads: Tools for Assessing, Evaluating and Protecting Evaluating and Protecting
Natural ResourcesNatural Resources
Ellen Porter Deborah Potter, Ph.D.
National Park Service U.S.D.A. Forest Service
[email protected] [email protected]
WESTAR CouncilNovember 15-16, 2005
Air Resource Management Programs
• Why do we need them?• What are critical loads/target loads?• How are they developed?• How are they used?• Information needs
Overview
Why do we need them?
• Atmospheric Deposition Effects– Effects from nitrogen deposition
• Chemical changes in soils and trees • Nitrogen saturation in high-elevation soils;
runoff into lakes• Altered terrestrial and aquatic plant
communities
– Effects from sulfur deposition • acidification of lakes and streams• altered soil chemistry/nutrient cycling• mobilization of aluminum in soil• altered growth of spruce-fir forests
• Need for evaluation and assessment– How much deposition is too much?
“You’ve got to be careful if you don’t know where you’re going because you might not get there.”
Yogi Berra
History of Critical/Target loads
• Europe: – multi-national, coordinated approach (International
Cooperative Programmes) for critical loads research and implementation; critical/target loads used to set emissions reductions goals.
• Canada: – critical/target loads used to set emission reductions goals.
• U.S. Federal Land Managers (National Park Service, Forest Service, Fish and Wildlife Service): – use screening thresholds, limits of acceptable change, and
deposition analysis thresholds to assess deposition.
• U.S. EPA: – currently does not incorporate critical loads in air pollution
increments or standards.
Critical load/Target load
• Critical load: “The quantitative estimate of an
exposure to one or more pollutants below which significant harmful effects on specified sensitive elements of the environment do not occur according to present knowledge.” (Nilsson and Grennfelt 1988)
Critical loads can be developed for any pollutants.
Eff
ect
to s
pec
ific
res
ourc
e
Load (kg/ha/yr)
harmful effect
critical load
no harmful effect
Target loads
– Target Load: The level of exposure to one or more pollutants that results in an acceptable level of resource protection; may be based on political, economic, or temporal considerations.
“Protective” target loads vs
“Interim” target loads
Interim Target Load
Current deposition
Deposition reduction
Glide path
Dep
osit
ion
(k
g/h
a/yr
)
Time
Protective Target Load is set below critical load to ensure that critical load/harmful effect is not reached.An Interim Target Load is used if current deposition is above the critical load, to establish a glide path towards the critical load, and eventually, the protective target load.
Re-evaluate; adjust
Critical Load
Protective Target LoadCurrent deposition
Lo
ad (
kg/
ha
/yr)
Changes in soil chemistry
Change in plant communities
Episodic acidification
Forest health decline
Critical loads are defined for specific indicators and effects.
Chronic acidification
Scientists conduct empirical studies to identify resources sensitive to deposition
Scientists derive critical loads from empirical studies and modeling analyses.
Federal manager is guided by agency policy in selecting sensitive resources and indicators of change; defines ”harmful” changes to sensitive resources based on policy goals.
Decisions about interim or sustainable levels of N and S deposition on federal lands are made by federal manager, with consultation with air regulators and others if target loads will be used for emissions control strategies.
CRITICAL LOAD DEVELOPMENT
SCIENCE FEDERAL MANAGER
Lawrence and Huntington, USGS publication WRIR 98-4267
Ecosystem Approach
Critical Load Calculations
Simple, Steady-state, Mass-Balance Model
Empirical critical loads
Dynamic models
Input +/- Retention =Output
Observation, Observation, experimentexperiment
PnET, MAGIC, PnET, MAGIC, CENTURYCENTURY
ModelModel ExamplesExamples
Critical Load Calculations
Simple, steady-state,
Mass-Balance Model
Empirical critical loads
Dynamic models
total deposition rate (S, N)total deposition rate (S, N)
soil properties soil properties
soil solution chemistrysoil solution chemistry
vegetation vegetation (nutrient uptake, storage)(nutrient uptake, storage)
bedrock compositionbedrock composition
water chemistrywater chemistry(BCC, ANC, N, S)(BCC, ANC, N, S)
ModelModel Example Data InputsExample Data Inputs
Empirical Critical Loads
• Based on observed (actual) ecosystem response at known deposition rates, e.g., impacts to soil, water, plant and animal communities
• may consider results of field studies and mesocosm experiments to link cause and effect
• managers need a conservative loading rate that protects the most sensitive ecosystem components
http://swas.evsc.virginia.edu/Effects.pdf
Using the Critical Load Concept
Land Management Planning
Resource Planning Act
National Environmental Policy Act
State Implementation Plans
Regional Planning Organizations
New Source Review
Assess the success of air pollution regulatory programs (e.g., cap-and-trade programs)
Using Critical and Target Loads
To better evaluate and communicate how pollution is affecting natural resources and what is needed to protect and restore them…
To our own decision makers To the regulatory community
that sets the rules for controlling air pollution
To the public whose support is needed for positive change to
occur
Challenges
Synergistic effects Ecosystem complexity Lag time for ecosystem response Long-term ecosystem recovery / state Cost of complex models
(data gathering)
Increased communication and collaboration between land managers and scientists on resource management needs to meet resource protection goals.
Inventory and monitor sensitive resources; Identify / refine models for estimating critical loads in both aquatic and terrestrial ecosystems;Collaborate to use critical loads in air regulatory planning processes at the national, state, and local level.
Future Direction
SummaryUse loading rate models to …
identify and attain loading rates (e.g., kg N or S per ha per
year)
that will protect sensitive ecosystems and allowdegraded ecosystems to recover