Plant Diversity in the Chicago Region

Despite the skyscrapers, expanses of concrete, heavy industry, and large population centers, the Chicago Region has a very diverse composition of plants (flora). See Table 1 below. There are almost 2,700 individual species of vascular plants found within this area of 30,557 square kilometers (11,798 square miles). Compare that to the only 1,400 species that occur in the similarly sized country of Belgium (30,510 sq. km). For a closer-to-home comparison, the state of West Virginia is about two times the size of the Chicago Region (62,361 sq. km) and there are only 2,344 vascular plant species recorded in that state. Of the nearly 3,000 taxa of vascular plants found in the Chicago Region, 55% of those plants are native.

Considering the land area and number of species in the Chicago Region, the area's diversity of vascular plant species (represented as the number of species per unit of area) is much higher than for many other temperate areas (Table 2). In fact, the species diversity of the Chicago Region is closer to values found in the tropics where diversity tends to be at its highest (Table 3).

Part of the reason the Chicago Region's flora is so diverse has to do with the geographic and geologic features of the area.

Table 1. Facts about the Chicago Region vascular flora.

Chicago Region vascular plants	Number	Comment
Vascular plant taxa (species, subspecies, varieties)	approximately 3000	almost 2700 species
Families represented	164
Genera represented	895
Native plant taxa	approximately 1650	55% of flora
Species endemic to Chicago Region (grow nowhere else in world)	2	plus 5 Great Lakes endemic taxa
Threatened or endangered taxa	700	23 % of flora, but 42 % of native taxa
Non-native (alien) taxa	approximately 1350	45 % of flora
Invasive taxa	approximately 150	5 % of flora, 11% of all non-native taxa
Also read about disjunct plants, habitats, or biology.