Detecting Ecological Effects of Development in the Wappingers and Fishkill Watersheds

Detecting Ecological Effects of Development in the

Wappingers and Fishkill Watersheds

Karin Limburg, Karen Stainbrook, Bongghi HongSUNY College of Environmental

Science & Forestry

(1974!)

Ecosystem health, qu’est-ce que c’est? - a concept that’s been around a long time, currently enjoying a comeback

• maintenance of “biotic integrity”

• resistance and/or resilience of systems in the face of disturbance

• absence of factors that degrade ecological population, community, and ecosystem structure and function

Assessing watershed health:

The idea: organisms and ecosystems integrate and reflect the insults (or lack thereof) resulting from watershed-level processes

Some techniques have proven robust after 25+ years of testing; others in development

Low Human influence High

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Ecosystem indicators of human disturbance should ideally be sensitive to these factors, and not confounded by natural ones

(or at least possible to tease out the differences)

Indicators of ecosystem health can (should?) evaluate changes at levels of

•Population•Community/habitat•Whole-system

Metrics may not all be additive, although many schemes designed that way

What we looked at:• physical habitat characterizations

• water chemistry

• biotic community structure (fish and bugs)

• ecosystem function

Total of 33 sites

tributarymainstem

Physical habitat – involved making many measurements of flow, stream dimensions, substrate types, vegetative cover, bank characteristics, riparian zone, etc

Water chemistry: four synoptic surveys conducted May - August – get high and low flow conditions

The idea: to characterize the nutrient environment that indicates whether or nor an ecosystem will be eutrophic or just “well balanced” (very few, if any, sites here expected to be oligotrophic…)

Water chemistry parameters we measured:

• Dissolved O2, pH, temperature, conductivity in the field

• Chlorophyll, TSS, particulate C & N, total N & P, NO3, NH4, TDN, SRP, TDP, DSi, DOC, TDS in the lab

Indexes of biotic integrity (IBI): collected fish by electrofishing 100 m of stream –

Noted species, abundances, lengths & weights, obvious diseases, etc.

Macroinvertebrate (stream insect) IBIs: collected 3 representative kick-samples, identified insects to lowest “reasonable” taxonomic unit

Ecosystem-level measurements:

Community metabolism

Food web linkages

Some results: how “healthy” are the Wappingers and Fishkill Creek watersheds?

Let’s look at a few diagnostics…

Land use patterns

Environmental quality patterns

Biological indicators

…includes changes over time

Assessments at different spatial scales(relates to the degree of influence)

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Amount of land in different uses varied at different spatial scales

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Conductivity – a measure of the ionic strength of water

Correlates strongly with human disturbance (population density, road density, nitrates, etc.)

Getting recognition as a bellwether of aquatic disturbance

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Water quality score Habitat score Nutrient score Physicalcharacteristics

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Index of Biotic Integrity (IBI) Scores

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Cumulative watershed area (km2)

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ITR H' EPT DOM PMA FBI BAP

Aquatic insect metrics

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Presence of “threshold effects”?

”under-built” ”overbuilt”

Last bits: some time trends.

• Land use change, 1992 vs. 2001

• Changes in Fishkill biotic indexes

• Some projections about % impervious surfaces (from models)

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EPT FBI BAP ITR IBI FSR

Biotic metric

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1988 2001

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Comparing bio-indicator scores in Fishkill: across the board improvement since 1988!

Percent impervious surface:

Current conditions in Wappingers watershed

A simulated look at the future, with new housing generated, but classified as “low intensity”

(i.e., with relatively low percent impervious surface)

Simulated future, with new housing, but with it classified as “high intensity”

Lots more impervious surface

Can also begin to make crude forecasts of effects, too…

Summary: how is the “health” of the two watersheds?

• Land use cover: similar at large scale, but Fishkill seems more developed near the sites of stream studies

• Stream quality indicators: Fishkill worse off

• Biological indicators: Fishkill worse off

• Yet, Fishkill in 2001 has better bio-scores than in 1988

Finally, future development will likely increase things like impervious surfaces and thus increase stream degradation

Thank you!

Funded by Hudson River Foundation and National Science Foundation