One of the most important and least understood concepts related to biological resources is our planet's biodiversity--the vast variety of organisms that inhabit the earth. Even today, the majority of organisms remain unknown to modern science. Although about1.5 million species of animals and plants have been discovered and described, somewhere between 4 and 30 million species are thought to exist on earth. The biodiversity of our planet and our State is threatened by man-caused pollution of our atmosphere and water, and by destruction of the habitats that plants and animals require to survive.
Because each species contains unique biological and genetic information, conservation of species may be critical to the future quality of our lives. All living species have potential significance to humanity, many in unknown but, perhaps significance to humanity, many must also learn to value the biodiversity of our planet and State for its own sake, quite apart from its possible direct benefits to humanity.
Natural Habitats
Illinois is divided into 14 natural divisions, based on the topography, the kinds of geologic materials exposed at and near the ground surface, soil characteristics, rainfall and water availability, and the kinds of native animals and plants found there. Portrayed in this exhibit are some of the distinctive habitats and/or communities of plants and animals found in each division.
Living Organisms
Many species of plants and animals are restricted to a single natural division, or to a particular habitat within that division.The photographs and captions in this exhibit show some of the less familiar organisms found in Illinois and describe how and where they live and what they require to survive. Many of these plants and animals are unfamiliar because their habitats have always been rare in Illinois or because their habitats have been severely reduced by human activities.
Biodiversity in Illinois
On first impression, Illinois seems to be little more than flat plains covered with corn and soybean fields and occasional cities and villages. However, Illinois actually has a surprising variety of plants and animals. Lying at the junction of the eastern forest, western great plains, southern coastal plain, Ozark uplift and northern forest biomes (groups of plants and animals that commonly live together), our state is a meeting ground for organisms that are characteristics of these different geographical areas and habitats. Illinois is host to some 25,000 species of insects,over 3,000 species of plants, 200 species of fish, 100 species of birds, about 100 species of reptiles and amphibians, 79 species of fresh water mussels, and even 29 species of crayfish. This display of specimens from the collections of the Illinois Natural History Survey provides examples of some of the many different animals and plants--from bats to butterflies to orchids--that live in Illinois. The Natural History Survey's collections, and others across the country, help us identify plants and animals and compare today's flora and fauna with those of earlier times.
Yesterday and today
During the billions of years of earth's history, many events have shaped the face of what is now Illinois. Dinosaurs, wooly mammoths,trilobites, tully monsters and huge numbers of other animals andplants that once inhabited the area in ancient times have become extinct through natural causes. Some of the major stages in the evolution of life and the geologic history of Illinois and the surrounding region are portrayed here.
Fossils show that Illinois lay beneath a warm, shallow sea 420 million years ago. Later, in dank tropical marshes 300 million years ago, dragonflies with 3-foot wing spans droned among ferns and horsetails as tall as trees. These plants were the raw materials for Illinois' abundant coal resources.
During the last million years, Illinois has been buried repeatedly beneath glaciers (sheets of compacted snow and ice hundreds of feet thick) that advanced and melted as the climate cooled and warmed. These vast ice sheets and torrents of meltwater shaped and molded the land surface into the flat plains and gentle hills characteristic of modern Illinois. During the dry arctic-likewinters while the ice was here, sediments deposited by summer meltwater streams dried out. Strong winter winds blowing across the sediment-choked bottomlands of the major river systems gathered up clouds of dust that blanketed the tundra-like land with silty deposit called loess (pronounced "luss"). Loess and other materials exposed at the land surface are the parent materials from which Illinois' rich soils formed.
Today, the people who live and work in the State are themselves significant controllers of Illinois' landscape and the diversity of its plants and animals. Clearing of forests, draining of wetlands,urban development, highway construction and other human activities have drastically reduced the diversity of habitats in Illinois and the overall biodiversity of the state.
Geologic Influences on Biodiversity
The geology of a region exerts a major influence on its biodiversity.Geologic processes--glaciation, weathering, erosion, deposition of eroded materials, and movements of the earth's crust--shape the land surface, affect local environmental conditions, and determine many soil properties.
Soil is the altered material at and near the earth's surface that forms through the long continued interactions of plants and animals with geological materials. The nature of the soil at a particular place depends on interactions among the parent materials (the geologic materials being altered); the climate; plants and animalsthat live on and in the soil as it forms, and the local relief or slope of the land surface. When these factors remain stable for many years, the soil characteristics become increasingly dependent on the effects of soil organisms and climate and less dependent on the nature of the parent materials. The factors that control soil formation also influence the nature of habitats and the diversity of living organisms.
Because they have been developing for the relatively short 14,000 years since the last continental glaciers finally melted away, the present-day soils in Illinois still reflect the underlying parent materials. Our State's complex geologic history has left a wide variety of these materials exposed at the surface. That, in combination with the climatic, topographic and biological variables, has given Illinois its wide variety of soil types. Photographs and captions in this display illustrate some of the important geologic characteristics that influence soil formation in several of our State's natural divisions.
Water, Climate and Biodiversity
Illinois is a water-rich state. Its landscape is dotted with numerous lakes, reservoirs and ponds, and crossed by the Rock, Illinois, Sangamon and other rivers. Lake Michigan and the Mississippi, Ohio and Wabash Rivers mark our State's boundaries. Water can be found beneath the surface of our State as well--filling the pores and spaces in layers of rock or sand, and gravel. In Illinois, groundwater resources are extensive but not limitless. Although much more is available than is used, our groundwater resources are located unevenly throughout the State and vary widely in quality.
Variety characterized the climate of Illinois, both geographically and within seasons. We enjoy a continental climate with relatively cold, dry winters and warm, wet summers and with four distinct seasons. Temperatures can soar into the 60s for a day in the middle of winter, and sometimes snowflakes can be seen in the air in early May. The diversity of our State's flora and fauna reflects the climate's variability. Cypress swamps found in relatively warm, wet, southern Illinois are more commonly found in the Gulfcoast states. Other plants and animals typical of more northerly or mountainous parts of North America remain in parts of northern Illinois.
The distribution of water resources and the climate have strongly influenced Illinois' recent development. Population centers usually form where water for drinking and transportation is readily available.The spring and summer climates, ideal for agriculture, provide a long growing season and abundant rainfall. The figures and photographs in this display illustrate the geographical variability of the water resources and climate in Illinois.