Northeastern Coastal Zone

By Roger F. Auch ¹

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Ecoregion Description

 

The Northeastern Coastal Zone is a north to southwest trending ecoregion covering approximately 37,158 km² (14,347 mi²) in eight states (Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, and New Jersey) (fig. 1). The ecoregion was glaciated in the recent geologic past, which caused it to have more irregular topographic relief than the neighboring Atlantic Coastal Pine Barrens to the southwest, but it is not as hilly and mountainous as the Northeastern Highlands to the west and north.  The soils tend to be rocky and nutrient poor (U.S. Environmental Protection Agency, 1997).  Natural vegetation is dominated by hardwood and mixed forests, but also includes more limited coastal and inland wetlands.  The Northeastern Coastal Zone’s climate consists of cold winters and warm summers, with 1,000 to 1,500 mm (40-60 in) of precipitation occurring in an average year.

The Northeastern Coastal Zone’s land cover is dominated by forested and developed land that, according to our estimates, together account for more than 70 percent of the ecoregion (fig. 2a and 2b).  Large areas of developed land are found in the northern portion of the New York metropolitan area, east along Long Island Sound to New Haven, Connecticut, and northward along the Connecticut River to Springfield, Massachusetts (fig. 1) (Vogelmann and others, 2001).  Another ring of development encircles the upper reaches of Narragansett Bay in Rhode Island (metropolitan Providence), whereas greater Boston has radial lines of urbanization to Worchester, Massachusetts, in the west; Nashua, New Hampshire, to the northwest; and toward Cape Cod, Massachusetts, in the south to southeast.  Portland, Maine, forms the last urban node in the extreme northeast.  According to aggregated county-level data, the ecoregion’s population increased by more than one million people between 1970 and 2000, reaching 15,269,068 (U.S. Bureau of the Census, 1973; U.S. Census Bureau, 2003). Water, wetlands, and agriculture are secondary land covers classes commonly found across the ecoregion but in smaller, less frequent concentrations than forested and developed land (fig. 3a and 3b).  The only notable concentration of agricultural land is found in the Connecticut River Valley, north of Hartford.

 

Contemporary Land Cover Change (1973 to 2000)

 

The Northeastern Coastal Zone had moderately low amounts of land cover change compared with other Eastern U.S. ecoregions during the study period (fig. 4).  A total of 5.7 percent of the ecoregion changed at least once during the study period (table 1).  The amount of change estimated by time interval shows that the two intervals between 1973 and 1986 appeared to have considerably lower change than the two intervals between 1986 and 2000 (table 2). Normalizing the amount of change to annual rates to avoid unequal time intervals shows that the 1986 to 1992 period had the highest rate of change (fig. 5).  The variability in land cover change across the ecoregion was low and relatively steady during the study period, as indicated by the margin of error in our statistical estimates, ranging from +/- 0.20 percent to +/- 0.40 percent (table 2). 

The dominant land cover classes, forest and development, experienced the most net change during the study period (table 3, fig. 6).  Developed land increased an estimated 4 percent (1,510 km²) to approximately 27 percent of the ecoregion’s area, one of the highest percentages of developed land of any eastern ecoregion.  Much of the new development came from forest loss, with a decrease of 3.7 percent (1,361 km²) during the study period (fig. 7).  Agricultural land cover decreased by 0.8 percent, and although this may appear to be a small amount of farmland loss, it represents a loss of approximately 10 percent of the estimated agricultural land present in the ecoregion in 1973 (fig. 8).  Other, more minor land cover changes included slight decreases in wetlands and slight increases in mechanically disturbed lands and mining (fig. 9).  Increased development was the primary reason for these changes (i.e., wetlands converted to development, increased aggregate mining for construction materials, and forest land being cleared—mechanically disturbed—for pending development).

The ecoregion gained an estimated 1,510 km² of new developed land between 1973 and 2000.  The vast majority (approximately 87 percent) of the net decrease in forest, agriculture, and wetlands land cover classes were losses to development (fig. 10).  Another 115 km² of forest was converted to mining land uses, mostly for construction aggregates to help maintain or increase the built land infrastructure, although this change did not rank in the top five conversions for every time interval (table 4).  Conversions from forest to mining are not always a permanent loss, as some of these areas revert back to grassland/shrubland or even forested land once mining operations cease.  The forest to mechanically disturbed changes mapped in the Northeastern Coastal Zone were primarily driven by land clearing for new development, although in a few locations some forest harvesting for wood products did occur. Secondary changes included a grassland/shrubland transition to forested land that appears in the two time intervals between 1980 and 1992.  This may have been related to vegetation succession on abandoned farmland or on lands where timber harvest had happened in the recent past (fig. 11).  Also, minor changes from forest to agriculture and agriculture to forest land cover classes occurred but they made it into the top five changes only twice (1973 to 1980 and 1986 to 1992) during the four time intervals. In both cases, the conversion was forest to agriculture, as agriculture to forest did not place in the top five changes during any time interval (table 4).

The main story of land cover change in the Northeastern Coastal Zone ecoregion during our study period was increased urbanization, primarily through unidirectional land cover conversion to developed land uses.  The change was relatively low, but steady, over time.  The great majority of this new development came from forested land and a lesser extent from farmland.

 

References

 

U.S. Bureau of the Census, 1973, 1970 Census of population, v.1, characteristics of the population: Washington, D.C., U.S. Government Printing Office, various state parts.

U.S. Census Bureau, 2003, American FactFinder, Basic Facts, economic characteristics- employment, income, poverty, and more; general characteristics- population and housing, accessed May 25, 2006, at http://factfinder.census.gov/servlet/BasicFactsServlet?_basicfacts= [Use “basic facts” table option, select the above subjects, select for “county”, then “state” for individual counties.]

U.S. Environmental Protection Agency, 1997, Descriptions of level III ecological regions for the CEC report on ecological regions of North America, accessed April 12, 2006, at http://www.epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads

Vogelmann, J. M., Howard, S.M., Yang, L., Larson, C.R., Wylie, B.K., and Van Driel, N., 2001, Completion of the 1990s national land cover data set for the conterminous United States from Landsat thematic mapper data and ancillary data sources: Photogrammetric Engineering & Remote Sensing, v. 67, p. 650-662.

 

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Table 1.  The percentage of the ecoregion that experienced change

 

[Most of the sample pixels remained unchanged (94.3 percent) whereas 5.7 percent changed at least once through the study period]

 

	Overall	Number of changes
	spatial change	1	2	3	4
Percent of ecoregion	5.7	5.1	0.6	0.1	0.0

 

 

 

Table 2.  Rates of change by time period and 85 percent confidence interval

 

	Period
	1973-1980	1980-1986	1986-1992	1992-2000
Total change (% of ecoregion)	1.3%	1.1%	2.1%	2.0%
Margin of error (85% confidence level)	+/-0.3%	+/-0.2%	+/-0.4%	+/-0.4%
Average annual rate of change (%/year)	0.2%	0.2%	0.3%	0.2%

 

 

 

Table 3.  Land cover classes, estimated ecoregion percent and area

 

	1973		1980		1986		1992		2000		Net change 1973-2000
Land-use/land-cover class	km²	%	km²	%	km²	%	km²	%	km²	%	km²	%
Water	3956	10.6	3961	10.7	3960	10.7	3962	10.7	3962	10.7	6	0.0
Developed	8606	23.2	8893	23.9	9106	24.5	9622	25.9	10109	27.2	1502	4.0
Mechanically disturbed	27	0.1	49	0.1	41	0.1	55	0.1	104	0.3	77	0.2
Mining	147	0.4	172	0.5	183	0.5	197	0.5	205	0.6	58	0.2
Barren	88	0.2	87	0.2	90	0.2	89	0.2	87	0.2	-1	0.0
Forest	18791	50.6	18492	49.8	18299	49.2	17901	48.2	17429	46.9	-1361	-3.7
Grassland/Shrubland	107	0.3	135	0.4	154	0.4	149	0.4	159	0.4	52	0.1
Agriculture	3038	8.2	2981	8.0	2940	7.9	2802	7.5	2731	7.3	-307	-0.8
Wetland	2399	6.5	2388	6.4	2386	6.4	2380	6.4	2372	6.4	-27	-0.1
Non-mechanically disturbed	0	0	0	0	0	0.0	0	0.0	0	0.0	0	0.0

 

 

Table 4.  Leading land cover changes by time interval

 

		Area changed	% of all
From class	To class	(km2)	changes
Forest	Developed	223	47
Agriculture	Developed	52	11
Forest	Mechanically disturbed	40	9
Forest	Mining	31	7
Forest	Agriculture	26	6
Other classes	Other classes	98	21
		470	100
Forest	Developed	162	40
Agriculture	Developed	38	9
Forest	Mechanically disturbed	36	9
Forest	Mining	23	6
Grassland/Shrubland	Forest	22	5
Other classes	Other classes	124	31
		405	100
Forest	Developed	368	48
Agriculture	Developed	119	15
Forest	Mechanically disturbed	45	6
Grassland/Shrubland	Forest	38	5
Forest	Agriculture	31	4
Other classes	Other classes	173	22
		774	100
Forest	Developed	369	50
Forest	Mechanically disturbed	95	13
Agriculture	Developed	71	10
Forest	Mining	32	4
Mechanically disturbed	Developed	22	3
Other classes	Other classes	154	21
		743	100
Forest	Developed	1,123	47
Agriculture	Developed	280	12
Forest	Mechanically disturbed	215	9
Forest	Mining	115	5
Forest	Agriculture	96	4
Other classes	Other classes	563	24
		2,392	100

 

 

 

Figure 1.  The Northeastern Coastal Zone’s Land Cover Trends sample blocks (the yellow hollow 10 km x 10 squares) overlay the USGS 1992 National Land Cover Database.

 

 

 

Figure 2a (above).  Forested land cover as observed along an old stone fence in eastern Connecticut. Figure 2b (below).  Older, linear housing on the outskirts of Southbridge, Mass., with forest beyond, a typical scene in Ecoregion 59. Photos Roger Auch

 

 

 

 

Figure 3a (above).  Marina located on Long Island Sound near Stamford, Conn. Figure 3a (below).  Farmhouse and fields in southeast New Hampshire. Photos Roger Auch

 

 

 

 

Figure 4.  The overall spatial change in all Eastern U.S. ecoregions.  Each bar chart shows the proportion of the ecoregion that experienced change on 1, 2, 3, or 4 dates.

 

 

 

Figure 5.  Change by time interval normalized to annual rates.

 

 

 

Figure 6.  Estimated net percentage change by land cover class.

 

 

 

Figure 7.  New home site being cleared from forested land in rural southeast New Hampshire. Photo Roger Auch

 

 

Figure 8.  Newer housing subdivision built on former farmland about 10 miles northeast of Hartford, Conn. Photo Roger Auch

Figure 9.  Aggregate mining operation located in south-central Massachusetts.

Photo Roger Auch

 

 

 

 

 

Figure 10.  Net forest, agriculture, and wetland losses in hectares.

 

 

 

Figure 11.  Old farm field about 10 miles west of Portland, Maine, undergoing succession into grass and shrubland.  Undisturbed, this field will eventually return to forest. Photo Roger Auch