Invasive Species

As of January 1, 2012, the Department of Environment no longer exists as a standalone unit. The integrated model that replaces it is critical to incorporate sustainability so that it is a part of every policy decision and capital investment. Starting in 2012, each department and sister agency became engaged in creating a more sustainable Chicago. 

Threat of Invasive Species

Chicago’s natural areas comprise less than 3% (3,800 acres) of the entire City area, but represent all basic types of northeastern Illinois ecosystems. Our wetlands, forests, savannas, and prairies provide habitat for more than 400 species of mammals, birds, reptiles, amphibians, and fish. Today, these important natural areas and the wildlife that depend on them are threatened by the spread of invasive species. Invasive species alter the local ecology and out-compete native species for resources, causing irreparable harm and millions of dollars in damage. Thus, the City of Chicago, sister agencies, homeowners, and land managers must work together to reduce the threat of invasive plants in our region.


A native species is one that occurs naturally in a particular place without human intervention. Species native to North America are generally recognized as those occurring on the continent prior to European settlement.

An organism is considered non-native when it has been introduced by humans to a location outside its native or natural range.

An invasive species is one that is usually non-native to an ecosystem and whose introduction causes or is likely to cause economic or environmental harm or harm to human health, for example, by:

  • out-competing native species for resources and pollinators
  • altering the ecology of natural areas
  • weakening or damaging equipment and infrastructure
  • spreading pathogens and parasites

Reproducing rapidly, invasive species spread over large areas of the landscape and have few, if any, natural controls, such as predators or diseases, to keep them in check.

Climate Change:

Chicago’s climate has already begun to shift and will continue to do so in the face of global climate change. Since 1980, the average temperature has risen by about 2.6°F. Trees and plants flower earlier in the spring and frosts occur later in the fall. There have been several major heat waves in recent years, and the amount of winter ice on Lake Michigan is decreasing. Heavy rainstorms are also increasing in frequency.

As our climate shifts, so do our delicate ecosystems. Many native species will become extinct or migrate to more suitable land, and many non-native species will move in. By regulating these species and raising awareness about their threat, the City of Chicago is taking aggressive, preventative actions today to protect our native ecosystems and limit the spread of harmful invasive species.

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Asian Carp

Asian carp, which include bighead, silver, black, and grass, are serious threats to the Great Lakes. The City of Chicago has been a strong advocate for preventing Asian carp introductions to the Great Lakes. For instance, we introduced an innovative invasive species ordinance in 2003 that made it illegal to release Asian carp into the environment in Chicago. (See below for more information on the updated ordinance.) Also in 2003, in partnership with the United States Fish & Wildlife Service (USFWS), the City hosted the Aquatic Invasive Species Summit (AIS) to determine a comprehensive solution to the exchange of species between the Great Lakes and Mississippi River basins through the Chicago Sanitary and Ship Canal (CSSC) conduit.

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Invasive Species Ordinance

The City of Chicago’s Invasive Species Ordinance, which passed City Council in 2007, makes it unlawful to possess certain invasive species on the regulated list. This ordinance replaced the 2003 Asian carp ordinance. The 2007 list consisted of aquatic invasive plants and animals. In 2009, the regulated list was updated to include land-based invasive plants. While there are many more invasive species that could cause harm in the region, the current list prioritizes species that are in trade, not yet prevalent in the city, and pose the greatest threat to our natural areas. The City of Chicago worked with scientists, industry leaders and other stakeholders to compile these regulated species lists.

Posted below are documents with information about the Ordinance and specific invasive species. 

Past Press Releases:

Supporting Information Facts

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