Contents Ecosystem Changes Chemical Recovery Biological Recovery Future Changes

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

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

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

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

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

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

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

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

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

Ecosystem Recovery from Acid Rain Clean Air Legislation Passed Emissions and Deposition Reduced Chemical Recovery  Biological Recovery From Acid Rain Revisited, pg. 16-17

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

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

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 20-25 years.

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.

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.

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