P rotecting the Forests of the Chesapeake Watershed: Use Best Tools …

Protecting the Forests of the Chesapeake Watershed:Use Best Tools …

John ScrivaniResource Information

April 16, 2007 Update

Methodology Update Bring forward the five layers developed for Version 1.0

Streams, shorelines, and floodplain forests and forested wetlands Forests in headwaters and on steep slopes Forest protecting drinking water supplies Large contiguous blocks of forest; and Sustainable, managed working forests

Add layers representing habitat integrity at the landscape scale (12-digit hydrologic units)

Index of Terrestrial Habitat Integrity Modified Index of Biotic Integrity (Aquatic systems from INSTAR)

Compute forest conservation value via weighted overlay with 60% weight on habitat integrity

Methodology Update

For comparison, compute forest conservation value for current conserved lands

Compute layer of forest conversion rates from Phase 1 FIA data

Compute weighted overlay of forest conservation value and forest conversion rates to identify higher value lands under higher threat of conversion

Streams, shorelines, floodplain forests and forested wetlands

National Hydrography Dataset (NHD) 1:100K

Buffered to 500m

Refined by NWI, NLCD

Headwaters and steep slopes National

Watershed Boundary Dataset (NWBD) 1:24K (DCR)

Divides buffered to 1km

Ranked by % slope

Forests protecting drinking water supplies

Surface water source protection areas (VDH)

Zones 1 & 2

Large contiguous blocks of forest

VANLA (DCR)

Managed working forests

Index of Terrestrial Habitat IntegrityComposite of four layers:

The Natural Cover Index (INC) is based on the proportion of a watershed that is represented by natural vegetation

The River-Stream Corridor Integrity Index (IRSCI) is the

proportion of the river-stream corridor that is covered by natural vegetation

The Habitat Fragmentation/Road Index (IHF) addresses

habitat fragmentation by roads and reflects degradation of water quality, and terrestrial and aquatic ecosystems from associated development

The Imperviousness Index (IP) is the proportion of a

watershed that is identified as impervious cover

Figure 1. Natural Cover Index (INC)0.86 - 1.00

0.72 - 0.85

0.56 - 0.71

0.36 - 0.55

0.04 - 0.35

Figure 2. River-Stream Corridor Integrity Index (IRSCI)0.86 - 1.00

0.72 - 0.85

0.56 - 0.71

0.36 - 0.55

0.04 - 0.35

0.25 - 0.39

0.17 - 0.24

0.10 - 0.16

0.06 - 0.09

0.04 - 0.05

0.00 - 0.03

Figure 3. Habitat Fragmentation/Road Index (IHF)

Figure 4. Imperviousness Index (IP) 26.10 - 42.15

16.80 - 26.09

10.64 - 16.79

6.27 - 10.63

3.07 - 6.26

1.43 - 3.06

0.55 - 1.42

0.00 - 0.54

Figure 5. Index of Terrestrial Habitat Integrity (ITHI )91 - 100

81 - 90

71 - 80

61 - 70

51 - 60

41 - 50

31 - 40

21 - 30

11 - 20

0 - 10

< 0

Figure 6. Modified Index of Biotic Integrity (mIBI ) 21 - 24

17 - 20

15 - 16

13 - 14

11 - 12

8 - 10

Overlay Model - Forest Conservation Value

After an initial equal-weighting overlay it was deciding to set the relative weights:

• 30% Modified Index of Biotic Integrity (mIBI)• 30% Index of Terrestrial Habitat Integrity (ITHI )• 20% large forest blocks • 5% Streams, shorelines, floodplains and forest wetlands • 5% headwaters and steep slopes• 5% drinking water source protection areas • 5% managed working forests

The resulting values ranged from 1 to 10.

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Figure 7. Forest Conservation Value

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Figure 8. Forest Conservation Value of Non-conserved Lands

Cumulative Acres of Forest by Decreasing Conservation Value Score

Score Acres Cumulative Acres

10 3,019 3,019

9 284,393 287,412

8 1,531,436 1,818,847

7 2,390,522 4,209,369

6 1,138,582 5,347,951

5 256,895 5,604,846

4 53,921 5,658,767

3 13,312 5,672,079

2 81 5,672,160

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Figure 9. Forest Conservation Value with Threat of Forest Conversion

Acreage Distribution of Forest Conservation Value Scores weighted with Conversion Threat.

Score Acres Cumulative Acres

11 2,790 2,790

10 15,198 17,988

9 17,447 35,436

8 50,180 85,615

7 97,349 182,964

6 2,137,013 2,319,977

5 2,187,282 4,507,259

4 1,120,239 5,627,498

3 38,685 5,666,183

2 5,887 5,672,070

Thank you !10

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