An update of the Visual_HEA software to improve the implementation of the Habitat Equivalency Analysis method

- Method to size a mitigation area equivalent to that of a damaged area.
- Software to facilitate repetitive assessments of the size of mitigations for environmental damages.
- Use of a real case study of accidental environmental damage and mitigation calculation.

The Visual_HEA software tool was created in 2006 to facilitate the assessment of losses and gains in ecosystem services related to compensatory mitigation under the United States National Resource Damage Assessment Act (NRDA). Habitat Equivalency Analysis (HEA) is an ecological equivalence assessment method under NRDA that can be performed using the Visual_HEA software and for which it was named. The newers version - 2.6 - was recently enhanced and tested over several years to be adapted to the European context and to facilitate adherence to the Environmental Liability Directive (2004/35/EC) to compensate for environmental damages. Herein, enhancements, limitations, and a turnkey method of calculating variable gain and loss rates over space and time using the 2.6 version of the software are discussed. Major functionality enhancements include a quarterly discount calculation, increased decimal precision, gain calculations that extend into perpetuity, and the elimination of many small software “bugs”. A case study about the accidental pollution of the Mimizan River from a sodium hypochlorite spill at a paper mill illustrates the new functionalities of the software. The use of the HEA method to assess ecosystem services related to biodiversity offset has been widespread thanks to the development of this user-friendly software package. Furthermore, the HEA method implemented in Visual HEA_2.6 is recommended by the European Commission to enforce its Environmental Liability Directive and to size mitigations after accidental environmental damages.