Illinois Natural History Survey - University of Illinois

INHS Reports Autumn 2000

The Critical Trends Assessment Program: Gathering Data on the Condition of Illinois' Ecosystems

The Critical Trends Assessment Program (CTAP: http://dnr.state.il.us/orep/inrin/ctap/ctaphome.htm) was initiated in 1991 to assess the current condition, future trends, and extent of Illinois ecosystems. Decisions, including how to save, enhance, and restore our heritage for future generations, are the responsibility of all Illinois citizens and require tremendous amounts of reliable information. Much new information is being collected now and CTAP is working on how best to package and deliver it. In 1994, Phase I of CTAP ended with the publication of a seven-volume report summarizing existing information on Illinois ecosystems.

As a direct result of the lack of standardized information reported during Phase I, four distinct but complementary components of CTAP Phase II were initiated:

1. Land cover mapping (using satellite imagery and computer technology) of the entire state.

2. Establishment of a small, highly skilled team of professional scientists (at the INHS) and a larger network of dedicated, well-trained "citizen scientists."

3. Use of professional scientists (biologists, geologists, hydrologists) to accumulate existing data in the form of Watershed Assessment Reports.

4. The development of a Web-based information delivery system, the Illinois Natural Resources Information Network.

Indicators of Ecosystem Quality

The toughest initial question when starting any monitoring program is, What aspects of the ecosystem should be monitored? Professional and EcoWatch staff have settled on a number of biological assemblages and physical and chemical attributes as indicators of ecosystem condition. The EcoWatch parameters were determined with input from the professional scientists so that both monitoring efforts complemented each other.

INHS CTAP scientists Jamie Ellis (left) and Connie Carroll
monitoring plants in Clinton County.

Some Emerging Trends

Professional biologists have finished their fourth year of monitoring, while some aspects of citizen monitoring have been ongoing since 1995. Some statewide and regional trends are evident even with this small amount of new information.

Streams: Most streams in the state have been channelized and are now fed by a system of tiles. Additionally, the protective tree canopy of many streams has been removed, increasing water temperature and changing the food base from that of tree leaves to algae. These modifications have left an estimated 75% of all streams with a fair-to-poor habitat quality rating. Consequences of this are that native fish and macroinvertebrate species have less suitable habitat on which to live and forage. Poor habitat conditions have also led to few sensitive ephemeroptera, plechoptera, and trichopetera (EPT--insects with a wide range of sensitivity to disturbance) species remaining in the northern 75% of the state, where historical records substantiate their presence. Both the Hilsenhoff biotic index (HBI--measures general stream disturbance) and the macroinvertebrate biotic index (MBI--collected by CTAP citizen scientists) indicate that most streams were at least moderately impaired by organic enrichment and overall disturbance. Even sites with high EPT scores often have biotic index scores indicating disturbance. The fish community in many CTAP streams was dominated by just 2 or 3 fish species, sometimes by 1 or more of the 15 introduced species found in the state.

Forests: Two hundred years ago, 38% of Illinois was forested. Today, 14% of the state's land area remains in forest. Forest cover is now slowly increasing, but the plant species composition of our oak- and hickory- dominated forests is changing due to the introduction of non-native species, habitat fragmentation, and fire suppression. The average CTAP site contained 58 native plant species, only three (5.2%) of which were introduced, but where introductions were present, they tended to crowd out native species. The shrub layer of forests was most dominated by introduced species. More than 70% of shrub stems counted by citizen scientists were of introduced species. Except for buckthorn and white mulberry, introduced trees were not a problem in the interior of most Illinois forests.

Grasslands: About 61% of the presettlement landscape of Illinois was prairie. Nearly 20% of the state is still characterized as grassland, although only 0.01% of the original prairie persists in a high-quality condition. CTAP sites contained an average of 20 plant species with 7.5 (37.5%) of them introduced. High-quality prairies have been demonstrated to support 100-140 different plant species. Of all terrestrial ecosystems, grasslands were the most heavily dominated by introduced species. Amazingly, 60 of 71 monitored sites had an introduced species as their most dominant (abundant, by percent coverage) plant. The major culprits in this takeover of grasslands were meadow fescue and Kentucky and Canadian blue grasses, all planted as forage or hay for livestock. On average, slightly less than two grassland-dependent bird species were encountered in CTAP grasslands. High-quality prairies have been shown to support 6-12 nesting species. Except for the Eastern Meadowlark, Brown-headed Cowbirds (a nest parasite of other birds) were detected more often than any grassland-dependent bird species.

Wetlands: During presettlement times approximately 23% of the state supported wetlands. Today, that number is 3.2% and still declining. Of the remaining wetlands, few remain in high-quality condition. Most are severely degraded due to introduced species invasion, siltation, changes in hydrology, runoff of roadway deicing salts, drainage activities, and grazing. CTAP wetland sites contained an average of 15 plant species, only 2 (13.3%) of them introduced. However, as with grasslands, when sites contained introduced species, they were usually dominated by them. Reed canary grass, the most commonly encountered introduced species, often completely dominated a site, replacing most native species and forming a near monoculture. It was the dominant species at 22 of 78 monitoring sites. Some sites were still diverse and contained a high proportion of native species. Southern Illinois wetlands, in particular, seem to be the least affected by introduced species. The number of wetland-dependent bird species found at the typical site was 1.3 species on average, whereas high-quality wetlands usually support 6-10 wetland-dependent species.

Enough data have been amassed to support the contention that the health of the state's ecosystems is not particularly good. Streams have been drastically affected by decline in habitat quality and heterogeneity, while terrestrial systems are in a pitched battle with introduced and invasive species. Habitat fragmentation has also been problematic, the results of which are exemplified by loss of habitat- and area-dependent bird species. Even in the aquatic setting, habitat fragmentation poses the question of whether our streams will ever again support a diverse fauna, owing to the distance sensitive species must traverse from relatively isolated patches of high-quality habitat.

Readers can look forward to a thematic issue of INHS Reports in 2001 where CTAP professional scientists will present in much greater detail the results of Illinois' first statewide effort to determine current ecosystem conditions.

R. Edward DeWalt, INHS CTAP Group

Charlie Warwick, editor