Illinois Natural History Survey - University of Illinois

Statewide Summaries

 

The RRAs include 45% of the bottomland, 43% of the
nonforested wetland, and 34% of the upland forest in Illinois
while occupying less than 20% of the state's total area.

Thirty Resource Rich Areas (RRAs) (Figure 1) were identified using the methods described in Methodology. In total they cover 19.8% of the state (Table 1), encompassing seven of the state's 36 million acres. However, the actual area of biologically important natural resources is less than the total area of the RRAs. This results from the use of watersheds as the unit of analysis. In most RRAs, the existing natural resources occupy a concentrated portion of the watershed, or core area, often along riparian corridors. While nearly half the area within the RRAs is in agricultural production, less than 15% of the state's total cropland occurs in the RRAs. The RRAs include over one-third of the woodlands and nearly half the wet lands in Illinois (Table 1).

The RRAs range dramatically in size from 15,144 to 626,795 acres (Table 2). The largest RRAs are Big Rivers, the Southern Till Plain, and the Middle Il linois River. The smallest RRAsSugar River, Thorn Creek, Des Plaines River, Illinois Beach, and the DuPage Riverare found in the northern part of the state, the latter four in highly urbanized areas. RRAs are distributed throughout the state and occur generally on the main stems of the larger rivers or in the southern part of the state.

Landcover

Bottomland, nonforested wetland, and upland forest are well represented in the RRAs. The RRAs include 45.1% of the bottomland, 42.6% of the nonforested wetland, and 33.9% of the upland forest in Illinois, while occupying less than 20% of the total area in the state. Landcover classes with the lowest percentages in RRAs were cropland (14.9%), grassland (20.2%), and urban (20.6%). Within the RRAs cropland was the dominant landcover class (45.4%), followed by upland forests (19.8%) and grassland (18.3%).

Table 1. Landcover Composition for Resource Rich Areas and for Illinois. The "Forest - total" category is the combination of upland and bottomland forest classes and the "Wetlands - total" category is the total of nonforested wet land and bottomland forest.


Landcover
Class
%State Acreage
Included in RRAs
Composition
of RRAs
Composition
of Illinois
Acres in
RRAs
Acres
Statewide

Upland Forest
(Forest - total)
Bottomland Forest
Nonforested Wetlands
(Wetland - total)
Urban and Built-Up
Cropland
Grassland
Water
33.9
(35.8)
45.1
42.6
(44.6)
20.6
14.9
20.2
47.9
19.8
(25.7)
5.6
1.1
(6.8)
5.4
45.4
18.3
4.5
11.6
(14.0)
2.5
0.5
(3.0)
5.2
60.4
18.0
1.8
1,416,602
(1,815,373)
398,771
77,552
(476,323)
389,463
3,246,905
1,308,331
319,439
4,179,367
(5,064,576)
885,209
182,245
(1,067,454)
1,886,912
21,773,580
6,489,045
666,266

Total 19.8%
of state
100.0%
of sites
100.0%
of state
7,157,063 36,062,624

 

Natural Areas Inventory, Biologically Significant Streams, and Natural Heritage Sites

The Resource Rich Areas include 76% of all Illinois Natural Areas Inventory (INAI) acreage and 55% of all INAI sites in the state. The distribution of INAI sites relative to RRAs is depicted in Figure 2. The Driftless Area and the Karst/Cave Area have the highest INAI acreages (Table 2). The greatest number of INAI sites occurs in Shawnee Hills, followed by Chain O' Lakes-Fox River, Cache River, Big Rivers, and Illinois Ozarks.

Forty-eight percent of all Biologically Significant Stream (BSS) mileage lies within RRA sites. The Shawnee Hills and Embarras River RRAs have the highest BSS mileage with 126 and 112 miles respectively (Table 2). Eight RRAs have no BSS streams. The distribution of BSS streams relative to RRAs is depicted in Figure 3.

Chain O' Lakes-Fox River ranked highest in occurrence of Heritage points with 476, followed by three RRAs in southern IllinoisCache River (298), Shawnee Hills (255), and Illinois Ozarks (227). The number reflects a combination of significant communities, endangered and threatened species loca tions, geological features, and colonial nesting bird sites (rookeries).

Table 2. Illinois Natural Areas Inventory (INAI), Biologically Significant Streams (BSS), and Natural Heritage occurrences for Resource Rich Areas.


Name of
Resource Rich Area
Total
acres
INAI
acres
# INAI
sites
BSS
miles
# Heritage
occurrences

Driftless Area 191,814 30,556 19 22.4 109
Sugar River 15,144 2,993 2 4.5 24
Chain O Lakes-Fox River 285,844 9,442 72 35.6 476
Illinois Beach 49,172 4,252 15 0 155
Kishwaukee River 64,386 362 3 15.0 8
Rock River 206,215 5,416 20 17.5 101
DuPage River 51,653 1,576 7 0 17
Mississippi-Lower Rock 457,449 18,590 17 44.2 74
Des Plaines River 43,470 2,115 11 0 61
Thorn Creek 20,614 927 5 0 13
Prairie Parklands 152,669 10,037 18 23.8 85
Kankakee-Iroquois 231,005 6,731 17 63.3 67
Peoria Wilds 277,847 1,859 24 0 51
Nauvoo 150,316 7,409 9 0 36
Mackinaw River 125,008 1,139 4 26.9 7
Middle Illinois River 575,515 13,474 38 0 134
Vermilion River 132,252 1,998 14 58.0 44
Big Rivers 626,795 10,514 61 28.9 150
Embarras River 447,925 5,009 15 112.5 50
Sangamon River 53,734 880 2 15.5 8
Upper Wabash River 170,654 2,212 4 76.4 8
Southern Till Plain 584,788 6,903 15 48.8 31
Karst/Cave Area 291,305 26,230 27 2.9 92
Lower Wabash River 163,894 4,639 12 75.5 34
Kaskaskia Bottoms 197,654 1,681 10 31.1 28
Middle Fork Big Muddy 114,908 388 1 0 2
Illinois Ozarks 466,755 17,010 59 33.1 227
Shawnee Hills 477,112 8,638 83 125.9 255
Cache River 443,616 18,444 63 52.8 298
Cretaceous Hills 87,928 1,940 19 14.1 74

Totals 7,157,441 223,364 *659 928.7 2,719

* Natural Areas occurring in more than one RRA are counted only once.

Natural Heritage Communities

Of the 968 significant community occurrences in Illinois, 58% are located in RRAs (Table 3). Several community types are well represented in the RRAs, particularly caves, primary types, savannas, and wetlands. The distribution of significant community types relative to the RRAs is illustrated in Figures 4­-7 Figures 8-­11.

Table 3. Occurrence of Significant Community Types in Resource Rich Areas and in Illinois.


Community TypeOccurrences
Statewide
Occurrences
in RRAs
Percent of each type
included in RRAs

Forest 190 80 42.1
Floodplain Forest 62 36 58.1
Wetland 188 133 70.7
Prairie 312 147 47.1
Savanna 54 40 74.1
Cave 49 44 89.8
Lake 42 25 59.5
Primary (glade, cliff, lake shore) 71 55 77.5

Total 968 560 57.9

State and Federally Owned Land

The number of state owned entities in RRAs varies from 0 to 9 (Table 4). The Middle Illinois River RRA has by far the most state-owned acreage with 31,630 acres, although this represents only 5.5% of its area. Illinois Beach has the highest percentage of area that is state owned (6.3%).

Federal ownership is concentrated in southern Illinois where the Shawnee Na tional Forest is located (Shawnee Hills, Illinois Ozarks, Cretaceous Hills, and Cache River) and in the Driftless Area and Prairie Parklands RRAs (Table 4). State and federal lands are shown relative to the RRAs in Figure 12.

Table 4. State and Federally Owned Lands in Resource Rich Areas.


State Lands* Federal Lands**

Name of
Resource Rich Area
# of
Parks
# Cons
Areas
# of
Forests
# of
FWA
State
acres
% of
RRA
Federal
acres
% of
RRA
Driftless Area 1 0 0 1 3,354 1.7 40,6122 1.2
Sugar River 0 0 0 0 0 0.0 0 0.0
Chain O Lakes-Fox River 2 0 0 0 5,338 1.9 0 0.0
Illinois Beach 1 0 0 0 3,092 6.3 726 1.5
Kishwaukee River 0 0 0 0 0 0.0 0 0.0
Rock River 3 0 1 0 4,706 2.3 0 0.0
DuPage River 0 0 0 0 0 0.0 0 0.0
Mississippi-Lower Rock 2 0 0 1 1,493 0.3 15,694 3.4
Des Plaines River 0 0 0 0 0 0.0 0 0.0
Thorn Creek 0 0 0 0 0 0.0 0 0.0
Prairie Parklands 2 1 0 0 7,324 4.8 26,904 17.6
Kankakee-Iroquois 1 1 0 0 6,415 2.8 0 0.0
Peoria Wilds 0 4 0 1 9,570 3.4 1,589 0.6
Nauvoo 1 0 0 0 140 0.1 0 0.0
Mackinaw River 0 0 0 1 1,397 1.1 0 0.0
Middle Illinois River 1 5 1 2 31,630 5.5 21,499 3.7
Vermilion River 1 0 0 1 5,944 4.5 0 0.0
Big Rivers 1 1 0 0 9,547 1.5 37,901 6.0
Embarras River 3 0 0 3,226 0.7 0 0.0 1
Sangamon River 0 0 0 0 0 0.0 0 0.0
Driftless Area 1 0 0 1 3,354 1.7 40,6122 1.2
Upper Wabash River 1 0 0 0 3 0.0 0 0.0
Southern Till Plain 0 0 0 1 554 0.1 682 0.1
Karst/Cave Area 1 0 0 1 3,364 1.2 0 0.0
Lower Wabash River 1 1 0 0 1,261 0.8 0 0.0
Kaskaskia Bottoms 1 0 0 1 6,916 3.5 494 0.2
Middle Fork Big Muddy 0 0 0 1 22 0.0 0 0.0
Illinois Ozarks 1 1 1 1 18,668 4.0 81,266 17.4
Shawnee Hills 2 1 0 0 2,060 0.4 136,817 28.7
Cache River 3 2 0 0 11,924 2.7 53,741 12.1
Cretaceous Hills 1 0 0 0 619 0.7 11,999 13.6

Totals 30 17 3 12 138,567 0.6 429,924 6.0

* Parks, Cons Areas (Conservation Areas), Forests, and FWA (Fish and Wildlife Area) refer to state lands.
** Federal Land figures for Shawnee National Forest are based on ownership boundaries rather than the more general proclamation boundary.


 

Natural Divisions

All 14 natural divisions are represented in the thirty RRAs. The Coastal Plain, Shawnee Hills, and Lower Mississippi Bottomlands divisions are par ticularly well represented (Table 5). The Western Forest-Prairie and Grand Prairie are the least represented; these divisions have been extensively converted from presettlement conditions to agricultural use (Schwegman, et al. 1973). Figure 13 illustrates the relationship of natural divisions to the RRAs. Many RRAs are comprised of a single natural division, such as Chain O' Lakes-Fox River, Kishwaukee River, DuPage River, Thorn Creek, Kankakee-Iroquois, Mackinaw River, Sangamon River, Kaskaskia Bottoms, and the Middle Fork of the Muddy River. Others are composites of several divi sions, particularly the Mississippi-Lower Rock and Big Rivers RRAs.

Table 5. Natural Divisions in Illinois and in Resource Rich Areas. Natural divisions are listed from lowest to highest area in Illinois.


Name of Natural Division Percent of
Illinois
Percent of Division
Contained in RRAs
Wisconsin Driftless 1.0 37.3
Lower Mississippi Bottomlands 1.0 79.7
Illinois and Mississippi River Sand Areas 1.1 61.4
Ozarks 1.1 63.7
Coastal Plain 1.3 85.2
Shawnee Hills 2.5 81.6
Upper Mississippi and Illinois River Bottomland 3.3 64.5
Rock River Hill Country 4.2 14.8
Middle Mississippi Border 4.3 35.6
Wabash Border 4.8 34.0
Northeastern Morainal 6.8 22.6
Western Forest-Prairie 12.2 4.4
Southern Till Plain 19.8 15.2
Grand Prairie 36.1 8.6

 



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