About Environmentally Sensitive Areas

Environmentally Sensitive Areas (ESAs) are land and water areas containing natural features or ecological functions of such significance as to warrant their protection in the best long-term interest of the people and environment of Halton. 

ESAs are part of The Greenlands System in the Halton Official Plan, which restricts the alteration of physical and/or biological features in these areas. While the general boundaries of ESAs are documented, precise boundaries are established through an Environmental Impact Assessment (EIA) (Adobe Portable Document Format (PDF)1.7MB) which may be required when development is proposed near an ESA.

Environmentally Sensitive Areas Consolidation Report

ESAs are documented through the Halton Region Environmentally Sensitive Areas Consolidation Report, April 2005.

Information in this document is current to 2002.

Halton Region Environmentally Sensitive Areas Consolidation Report April 2005 Adobe Portable Document Format (PDF)2.8MB

top of page


ESAs were first identified through a two-year program that involved a summer biological study and a hydrogeological study. Members of the Ecological and Environmental Advisory Committee contributed to the program by sorting through the available data, developing selection criteria, investigating candidate sites and selecting final ESAs. 

As a result, 38 ESAs were identified and documented in Halton's 1978 ESA Study. Two years later, 37 of these ESAs were embodied into the Official Plan for the Region of Halton.

Halton Region has maintained its commitment to protecting these natural areas through continued protection and further study, including a review and updates to ESA designation criteria and ESA Updates in 1995 and 2002, which provided improved mapping and knowledge about the ESAs, recommended additions and deletions to existing ESAs and identified 10 new ESAs. 

ESA designation does not imply that land will be purchased or expropriated by a public agency. It does mean that altering the physical and/or biological features of ESAs is restricted. Some ESA land is owned by public agencies but much of it is private property. Responsible stewardship of ESAs is the best possible protection that we can provide for these special areas. 

top of page

ESA Selection Criteria

Primary Criteria

  1. Areas that exhibit relatively high native plant and/or animal species richness in the context of Halton Region.
  2. Areas that provide links among two or more adjacent natural systems.
  3. Areas that contain a relatively high number of native plant communities in the context of Halton Region.
  4. Areas that contain large (in a Regional context), relatively undisturbed expanses of natural, native plant communities.
  5. Areas that contain remnant native plant communities that are rare within Halton Region or that are not represented in other ESAs.
  6. Areas that contain plant and/or animal species that are rare provincially or nationally.
  7. Areas that contain representative earth science features and/or processes typical of those which were instrumental in creating Halton's landscape.
  8. Areas that are determined to contribute significantly to local and/or regional groundwater recharge.
  9. Areas that are determined to be significant groundwater discharge areas.
  10. Areas that contribute significantly to groundwater quality.
  11. Areas that contribute to maintaining surface water quality.

Secondary Criteria

  1. Areas that contain regionally rare plants.
  2. Areas that contain high quality assemblages of native plant and/or animal species.
  3. Areas that are recognized as highly aesthetic themselves or that provide designated viewpoints.
  4. The location of the area, combined with its natural features, make it particularly suitable for scientific research and conservation education purposes.

top of page