Transcript We are the National Park Service

National Park Service
Critical Loads for Atmospheric Deposition:
Assessing, Evaluating and Protecting Natural
Resources
Tamara Blett
Air Resources Division – National Park Service
CANS Workshop
Feb 2006
Development/Use of Critical Loads
DEVELOPMENT
(what is the CL?)
Scientists
IMPLEMENTATION
(how can the CL be
used to protect parks &
wilderness areas?
Regulators
Land Managers, (NPS/FS), EPA
Definitions…
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)
• 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.
Critical loads and target loads can
be developed for any pollutants.
Preserve and Protect
“…conserve [natural and cultural resources]…as will
leave them unimpaired for the enjoyment of future
generations.” (NPS Organic Act)
“Wilderness areas…shall be administered…in such a
manner as will leave them unimpaired for future use
and enjoyment as wilderness…” (Wilderness Act of
1964)
“…preserve, protect and enhance the air quality in
national parks, national wilderness areas, national
monuments, national seashores…” (Clean Air Act as
amended in 1977)
“In cases of doubt the land manager should err on the side of
protecting the air quality-related values for future generations.”
(Senate Report No. 95-127, 95th Congress, 1977)
[Rocky Mountain NP should be managed for] “…preservation of the
natural conditions and the scenic beauties thereof.” (1915 park
enabling legislation)
Defining the critical load
1)
2)
”The maximum amount of pollution into an
ecosystem that does not cause significant damage
to system resources, survival, structure or function”
“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)
This first CL definition used in some European approaches… request that we
use the *second definition for sensitive U.S. systems and this modeling effort
Indicators and Thresholds….
Rocky Mountain National Park: Continuum of Impacts to Ecological Health
N Load (kg/ ha /yr)
Ecosystem endpoints for CL: Conceptual Diagram
Changes in soil &
water chemistry
Surface water N
saturation
Change in aquatic plant
species composition
Changes in
tree chemistry
Effects on aquatic
animals (episodic
acidification)
Change in alpine
plant species
Forest decline
(acidification effects
on trees)
Lethal effects on fish, other
aquatic animals (chronic
acidification)
Critical loads are defined for specific indicators and endpoints
CRITICAL LOAD DEVELOPMENT
SCIENCE
FEDERAL MANAGER
Federal manager is guided by
Scientists conduct
empirical studies to identify
resources sensitive to
deposition
Scientists derive critical
loads from empirical studies
and modeling analyses.
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.
Science/Policy Integration Recommendation- March
2004 FLM CL Workshop
4 box model is useful conceptual
framework for considering S and N
Critical Loads
Acidif.
Aquatic
Terrestrial
Nutrient
“Sensitive Elements” and “Effects”
• “Specified sensitive elements”: ecosystems
sensitive to nitrogen and/or sulfur deposition,
e.g.,
– Poorly buffered lakes, streams, soils
– Ecosystems that evolved under low nutrient
conditions and/or with short growing season (e.g.
deserts or alpine areas)
• “Harmful effects”: changes in the natural
functioning of an ecosystem, e.g.,
– Loss of acid-neutralizing capacity affecting biota
(growth, viability, condition, etc)
– Unwanted enrichment by nitrogen resulting in
changes in natural vegetative community