Jeffrey W. Hollister and Bryan Milstead

Linking landscapes to ecosystem services: Landscape structure as an indicator and predictor of water clarity in New England lakes

Atlantic Ecology Division, National Health & Environmental Effects Research Lab,Office of Research and Development, U.S. Environmental Protection Agency, Narragansett, RI 02882

INTRODUCTION:INTRODUCTION: Lakes provide ecosystem services such as recreation, clean water, aesthetics, wildlife habitat, and nutrient attenuation. While numerous methods exist to monitor these services (e.g. visitor counts, opinion surveys, water quality monitoring, etc.) they are labor intensive to collect and difficult to implement in broad-scale monitoring programs. An alternative is to use linkages between landscapes and ecosystem services to monitor services over large areas.

1) Inverse Distance Weighted Source Proportion =

2) Weighted Flow Accumulation

Water Clarity as an Ecosystem Service IndicatorWater Clarity as an Ecosystem Service Indicator::

As ecosystem services are inherently anthropocentric, it is important to understand how individual lakes are perceived by humans. To examine this idea we generated a word cloud from narrative descriptions of lakes classified as “Appealing” by National Lakes Assessment field crews. Obviously, water clarity is of prime importance in perceptions of a lake’s appeal.

Water clarity, measured simply by Secchi depth, is also an excellent predictor of recreational and aesthetic quality of lakes as well as habitat suitability for charismatic species (e.g. Common Loon, Gavia immer).

Lastly, water clarity is related, in part, to nutrient loads derived from the surrounding landscape.

Data:Data: To begin our work on landscape structure and water clarity, we have compiled data on lakes in New England from the following:

Elevation – 10m National Elevation Dataset

Land Cover – 2001 National Land Cover Dataset (NLCD)

Lakes – National Hydrography Dataset Plus (NHDPlus)

Measured Water Quality – National Lakes Assessment (NLA)

Lake Basins – National Lakes Assessment Basins

Nutrient Loads – USGS SPARROW

Landscape Metrics: Landscape Metrics:

As water moves across the landscape it either picks up materials (e.g. nutrients or sediments) in source patches such as agricultural or developed land or those materials are removed in sink patches such as wetlands or forested land. To account for this, we first converted the 2001 NLCD into sinks and sources of nutrients and other materials likely to impact lake clarity.

2001 National Land Cover Dataset Classes

Source - Developed, Low Intensity- Developed, Medium Intensity- Developed, High Intensity- Barren Land- Cultivated Crops

Sink - Deciduous Forest - Grassland/Herbaceous- Evergreen Forest - Pasture/Hay- Mixed Forest - Woody Wetlands- Scrub/Shrub - Emergent Wetlands

Neither - Open Water- Perennial Ice/Snow

To examine different aspects of the landscape structure of sources and sinks we calculated Inverse Distance Weighted Source Proportion (1) and Weighted Flow Accumulation (2).

1AllCells

-1sSourceCell

Distance

Distance

Landscape Structure/Water Clarity Associations:Landscape Structure/Water Clarity Associations:

We compare these to measured Secchi depth to determine if source composition, proximity and/or connectivity is related to water clarity.

AcknowledgementsAcknowledgements:: Wordle.net and Nate Silver of FiveThirtyEight.com both deserve mention. We took the word cloud idea from Nate Silver’s blog post on health care reform and used Wordle.net to generate the word cloud.

CONCLUSIONS:CONCLUSIONS: Initial results suggest little additional information is provided by the weighted flow accumulation in relation to lake clarity. We plan to continue research on weighted flow accumulation and examine how different weights for different classes impact the metric.

As we gain a better understanding of how landscape structure impacts ecosystem services, we should be able to inform future efforts to identify source patches that due to their configuration on the landscape contribute nutrients in amounts disproportionate to their size.

Flow Direction

Weighted Flow Accumulation (WFA)

Example 1Sources & Sinks

Weighted Flow Accumulation (WFA)

0 0 0

102

31 0

1 1 1

-1-1-1

01 1

-1 -1 -1

111

01 1

0 0 0

000

51 1

Flow Direction

Example 2Sources & Sinks

Example 1: Lake WFA = 3Proportional Lake WFA = 3/8 = 0.375

Sources add nutrients or sediments = 1

-1

Lake = 0

Example 2: Lake WFA = 5Proportional Lake WFA = 5/8 = 0.625

Sinks remove nutrients or sediments =

0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10 12

Minimum Secchi Depth (m)

Pro

bab

ility

of

Loon

Pre

senc

e,

give

n X

>X

c

1.0

1.5

2.0

1 2 3 4 5

ln (Total Phosphorus + 1)

ln(S

ecch

i Dep

th +

1)

0 0.1 0.2 0.3 0.4 0.5

2.5

3.5

4.5

5.5

ln(N

/P +

1)

0 0.1 0.2 0.3 0.4 0.5 0.6

2.5

3.5

4.5

5.5

0 0.1 0.2 0.3 0.4 0.5

0.5

1.5

2.5

3.5

ln(C

hlor

oph

yll a

+ 1

)

0 0.1 0.2 0.3 0.4 0.5 0.6

0.5

1.5

2.5

3.5

0 0.1 0.2 0.3 0.4 0.5

1.0

1.5

2.0

Weighted Flow Accumulation

ln(S

ecch

i Dep

th +

1)

0 0.1 0.2 0.3 0.4 0.5 0.6

1.0

1.5

2.0

Inverse Distance Weighted Source Proportion

USial2010-3-31.ppt