Effect of Drought on Migratory WaterfowlAnahuac National Wildlife Refuge

Presented by:Eric R. Maurer

ESSM 462http://theselfsufficientgardener.com/wp-content/uploads/2011/12/Wood_Duck_IF_02.jpg

• ObjectivesAssess the severity of the 2011 drought on waterfowl migration patterns in the Anahuac National Wildlife Refuge utilizing the Normalized Difference Vegetation Index (NDVI) and bird data collected from Global Biodiversity Information Facility (gbif.org)

• Background/Study AreaTexas Drought of 2011Anahuac National Wildlife Refuge

• MethodsDataProject Workflow

• ResultsNDVI mapsReview Geographically Weighted Regression

• Discussion/Conclusion

Outline

Objectives

• Assess the severity of the 2011 drought on waterfowl migration patterns in the Anahuac National Wildlife Refuge utilizing the Normalized Difference Vegetation Index (NDVI) and waterfowl data collected from Global Biodiversity Information Facility (gbif.org)

• Following methods were used: Image Processing, Raster Calculator/Band Math, Spatial Analyst, Data Conversion, Spatial Statistics

Background• In 2011, Texas went through an

exceedingly intensive drought. The record dry spell started in the Spring of 2011 and brought widespread extreme drought conditions to the state. The record drought conditions continued into Fall, and the 12-month rainfall total for October 2010 through September 2011 was far lower than the previous record, which was set in 1956.

(Nielsen-Gammon, 2011)

• Texas is located in the southern portion of the Central Flyway and provides crucial winter habitat for Anatidae species (Ducks & Geese) that migrate from the U.S. and Canadian prairies. Texas is unique in that it winters 90 percent of duck populations and 75 percent of snow goose populations found in the Central Flyway.

(Texas Conservation Projects)https://www.dnr.sc.gov:4443/wildlife/species/waterfowl/assets/flyway2.jpg

Anahuac National Wildlife Refuge: Chambers County, Tx.

Study Area

http://3.bp.blogspot.com/-Azn01ITAzQ4/UYMbf9S9hhI/AAAAAAAAF7E/NH9yGsvtYyQ/s1600/Anahuac-NWR%252C-4-13-13-4725.jpg

• Anahuac National Wildlife Refuge: Chambers County, TX

(29°36’37”N, 94°26’56”)

• Established in 1963 and consists of 34,000-acre of land and water

• Habitat:Coastal Marshes and Prairies

Methods

Normalized Difference Vegetation Index (NDVI)NDVI is defined as a standard vegetation index based on a plant’s absorption of chlorophyll in red visible light and reflection of near-infrared light. The index is obtained using the following equation:

NDVI = (NIR – RED) / (NIR + RED) where NIR is the brightness value recorded in the near infrared band and RED is the brightness value recorded in the visible red band in the imagery. (Enwright, Forbes, Doyle, Hunter, 2011)

Geographically Weighted Regression (GWR)GWR is a local spatial statistical technique used to analyze spatial

nonstationarity, defined as when the measurement of relationships among variables differs from location to location. (Fotheringham et al., 2002)

Data

• Using Texas Natural Resources Information System (tnris.org) I attained National Agriculture Imagery Program (NAIP) imagery for 2010 & 2012

• The NAIP data consists of 1-meter multispectral imagery (NC/CIR) Natural Color (NC) = red, green, and blue bands Color Infrared (CIR) = infrared, red, and green bands http://www.fsa.usda.gov/Internet/FSA_File/fourband_info_sheet_2011.pdf

• Along with NAIP imagery I also collected Texas counties, roadways and shoreline datasets from TNRIS

• Received the Anahuac National Wildlife Refuge shapefile from the U.S. Fish & Wildlife Services Geospatial Services (fws.gov)

• Gathered recorded duck and goose species from the Global Biodiversity Information Facility (gbif.org)

Project Workflow

Image Acquisition NAIP 2010 & 2012

Anahuac National Wildlife Refuge (FWR) shapefile

Clipped NAIP Images with FWR using Raster Processing tool

Calculated NDVI for 2010 & 2012 NAIP Images:

Spatial Analyst

Kernel Density of clipped Waterfowl Data

Data Conversion

Convert 2010 & 2012 Kernel Density using Raster to Point tool

Extract Values to PointsUse data conversion points to

extract raster values of the 2010 & 2012 NDVI

*Add a Log Density field to table: log(GRID_CODE + 1)

Geographically Weighted Regression

A linear regression used to model spatially varying relationships

*Dependent Variable = Log Density*Explanatory Variable = Raster Value

Collect and Process GBIF Waterfowl Data

Excel to Table,Display X,Y Data,

Clip Waterfowl Data w/ FWRExtract 2010 & 2012 points

2010 NAIP Image (CIR) 2012 NAIP Image (NC/CIR)

Clipped NAIP Images

2010 NDVI 2012 NDVI

NDVI Results

GBIF Waterfowl Data Results

2010 Waterfowl Data 2012 Waterfowl Data

Waterfowl Kernel Density Results

2010 Kernel Density 2012 Kernel Density

Raster to Points Results

2010 Raster to Points 2012 Raster to Points

Geographically Weighted Regression (GWR) Results

2010 GWR TableBandwidth 372,023.56

Residual Squares 16.33086273

Effective Number 2.006585982

Sigma 0.225557101

AICc -41.3081109

R2 0.002304906

R2 Adjusted -0.000823712

Dependent Field 0 Log density

Explanatory Field 1 RASTERVALU

Geographically Weighted Regression (GWR) Results

2012 GWR TableBandwidth 2,453.97

Residual Squares 105.8323246

Effective Number 69.37237764

Sigma 0.645967834

AICc 677.3216605

R2 0.393602144

R2 Adjusted 0.230130742

Dependent Field 0 Log density

Explanatory Field 1 RASTERVALU

Discussion/Conclusion• My assessment of the 2011 drought on the waterfowl migration patterns of the

Anahuac National Wildlife Refuge is inaccurate due to the GBIF waterfowl data used for this study.

• The waterfowl data collected was not distributed throughout the study area and many of the points were isolated to just a few locations causing this study’s results to be skewed.

• Improvements:Collect waterfowl data throughout the entire wildlife refuge, I would also extend the study to encompass a broader range of years.

Questions?