HEADWATERS ECONOMICS GEOGRAPHIC DATA LIBRARY DOCUMENTATION

TITLE: 
Geodataset Name: 		NA_TNC-ecoregions
Geodataset Type: 		SHAPE
Geodataset Feature: 		POLYGON

GENERAL DESCRIPTION: 
This dataset contains The Nature Conservancy Terrestrial Assessment Units as of September 12, 2006. 

DATA SOURCE(S):  		The Nature Conservancy

Scale of Original Source Maps:	1:7,500,000
Date of Original Source Maps:	2006

GEODATASET EXTENT:  	North America
 
FEATURE ATTRIBUTE TABLES CODES AND VALUES: 

ITEM			ITEM DESCRIPTION
ECO_NUM			Unique Ecoregion Number Identifier
ECO_CODE		Unique Ecoregion String Identifier
ECO_NAME		Name of the Ecoregion

DATA LINEAGE SUMMARY: 
Developed originally by Olson, D. M. and E. Dinerstein (2002), Bailey (1995) and Environment Canada (Wiken, 1986), these data layers were modified by The Nature Conservancy (TNC) to be used in its Biodiversity Planning exercises in the process known as Ecoregional Assessments. Several Ecoregions were modified from the originals by TNC staff developing the aforementioned assessments. The modifications are based on ecological, bio-physical and political rationales; most changes are noted in the accompanying documentation (attributes). Ecoregions in Canada and Mexico were modified mainly at the border with US territory, where TNC modified-Bailey (1995) ecoregions crossed over the country boundaries and the Olson, D. M. and E. Dinerstein (2002) and (Wiken, 1986) were replaced where the TNC modified-Bailey (1995) overlayed them. This is the primary data set used in the definition of an assessment area for the terrestrial ecoregional assessment analytical process for the World. This is an updated version from a data layer created in 2004. Data subject to continual revision and updates. A major revision of which ecoregions were part of which ERAs was conducted in December 2005.

MAP PROJECTION PARAMETERS 
PROJECTION 			ALBERS CONICAL EQUAL AREA
DATUM 				NAD83
UNITS 				METERS
SPHEROID 			GRS1980
PARAMETERS
1st standard parallel		29 30  0.000
2nd standard parallel		45 30  0.000
central meridian		-96 00  0.000
latitude of projection's origin	37 30  0.000
false easting (meters)		0.00000
false northing (meters)		0.00000

DATA SOURCES CONTACT(S): 
Name: 			ConserveOnline
Web site: 	  	http://conserveonline.org/
          
HEADWATERS ECONOMICS CONTACT: 
Name:			Headwaters Economics Geographic Data Library
Abbr. Name:		HEGDL
Address:		Headwaters Economics
                        566 Highland St.
                        Helena, Montana 59601
Web site:		http://www.headwaterseconomics.org
Contact Person:   	Patty Gude	
Phone:   		(406)599-7425	
Email:   		patty@headwaterseconomics.org