Streamside forests reduce nutrient pollution of aquatic

ecosystems

Donald E. Weller, Thomas E. Jordan, and Matthew E. Baker

Smithsonian EnvironmentalResearch Center

Ecosystem services• Terrestrial

– Wildlife habitat– Carbon sequestration– Forest products

• Aquatic– Aquatic food chain– Control temperature– Pollutant regulation– Nutrient removal

Field studies of nitrogen removal

Distance from field toward stream (m)

Nitr

ate

conc

entr

atio

n (m

g N

/l)

Mid-Atlantic removal results

National stream and river restoration

Riparian restorations1990-2003

> 20,000projects

> $5 billion

Buffer prevalence varies widely

Problems “scaling up” . . .Watershed results mixed

Transect results striking

?

(Mal)adaptive management

Knowledge

Evaluation

Measurement

Implementation

Overlay sources and streams on elevation

Identify downhill transport pathways

transportpathwayfor 1 pixel

Quantify width & aggregate paths

Well-buffered pathway

Not so well-buffered

New geographic analysis

sources flowpaths sinks

Prioritizing management efforts

>375 m250 m120 m20 m

<20 m

Buffer Width

Chesapeake Bay example

321 watersheds3 physiographic

provinces focus on cropland

and buffersempirical models for

stream nitrate

Benefits differ among regions

Physiographic provinceCP PD AM

Nitr

ate

conc

entra

tion

(mg

N/l)

0

1

2

3

4

buffer leakage

restored bufferremoval

current bufferremoval

non-crop

Stream Nutrient Levels

<no buffers

<current buffers

<complete buffer

<no cropland

Overall reductions

Physiographic provinceAll

Nitr

ate

conc

entra

tion

(mg

N/l)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

buffer leakage

restored bufferremoval

current bufferremoval

non-crop

16%

32%

68%

Policy implications• Protect riparian areas

– Conserve existing forest buffers– Restore missing forest buffers

• Outreach and education• Focus incentive funding

– Regional targeting– Site level targeting

• Implement adaptive management– Improve models for estimating benefits– Measure outcomes