4. Contents Ecosystem Changes Chemical Recovery Biological Recovery
Future Changes

5. Ecosystems are dynamic
I. Ecosystem Changes
Ecosystems are dynamic
They are constantly responding to a changing environment.
Examples of natural disturbances:
- hurricanes/wind storms
- fire
- ice storms
- drought
- insect damage
Damage from the ice storm of 1998

6. they go through a process of recovery.
I. Ecosystem Changes
When ecosystems are relieved from
a stress such as acid rain,
they go through a process of recovery.
Photo by Joseph Mehling

7. of an ecosystem must happen before
II. Chemical Recovery
Chemical recovery
of an ecosystem must happen before
biological recovery
can take place.
Hubbard Brook Acid Rain Story: Part III

8. If emissions reductions are sufficient, then:
II. Chemical Recovery
If emissions reductions are sufficient, then:
Sulfate concentrations in soil and stream water decrease
Nitrate concentrations in soil and stream water decrease
Inorganic aluminum concentrations in soil and stream water decrease
pH of soil and stream water increases (less acidic)
acid-neutralizing capacity increases (soil is more “buffered”)
base cations (nutrients) increase

9. III. Biological Recovery
Chemical Recovery
leads to
Biological Recovery
Biological recovery usually occurs in stages...
Hubbard Brook Acid Rain Story: Part III

10. Stream macroinvertebrates
III. Biological Recovery
Stream macroinvertebrates
may recover within three years…

11. may take a decade or more to reestablish.
III. Biological Recovery
Lake zooplankton
may take a decade or more to reestablish.

12. III. Biological Recovery
Fish populations
should recover in
five to ten years

13. Trees probably take decades.
III. Biological Recovery
Trees probably take decades.

14. Ecosystem Recovery from Acid Rain
Clean Air Legislation
Passed
Emissions and
Deposition Reduced
Chemical Recovery  Biological Recovery
From Acid Rain Revisited, pg

15. IV. Future Changes
To what extent must emissions be reduced to allow ecosystems in the Northeast to fully recover?
To answer this question, HBES scientists used a computer model called PnET-BGC to estimate the relationship between emissions, deposition and chemical recovery at the HBEF.
Hubbard Brook Acid Rain Story: Part III

16. Results of the model suggest that
IV. Future Changes
Results of the model suggest that
deeper reductions in emissions beyond those mandated in the 1990 Clean Air Act Amendments
are necessary to achieve ecosystem recovery.
Photo by Joseph Mehling

17. In specific, results from the model suggest that
IV. Future changes
In specific, results from the model suggest that
an 80% reduction in electric utility emissions of sulfur dioxide beyond the requirements of the CAAA
would cause headwater streams like those found at the HBEF to become biologically favorable to organisms again within the next years.

18. IV. Future Changes
The only way to determine the effects of legislation on ecosystem recovery is to
continue long-term monitoring of deposition, surface waters and ecosystems.
The Hubbard Brook Experimental Forest is one of 26 sites in the U.S. that monitor ecological processes over long periods of time as part of the Long-Term Ecological (LTER) Network. The HBEF has been an National Science Foundation-funded LTER site since 1988.

19. With continued funding, HBES researchers will continue to monitor ecosystems in the Northeast.
Their findings help us to understand our relationship with the natural environment.

20. For more detailed information on ecosystem recovery:
Acid Rain Revisited,
a Science Links publication of the Hubbard Brook Research Foundation