According to ISO 19011 Annex A.3, auditors that intend
to examine environmental management systems:

• Need to have environmental management
  knowledge and skill, and

• Be able to apply environmental management methods, techniques, processes, and practices.

They must have the knowledge and skill needed to examine
environmental management systems and to generate appropriate
audit findings and reach valid conclusions.

The following examples illustrate the kind of knowledge and skill that
environmental management auditors need to have. They should:

1. Understand environmental terminology.

2. Understand ecosystems and biodiversity interactions.

3. Understand environmental media (e.g. air, water, land etc.).

4. Understand measurement and monitoring sciences.

4.1. Understand environmental metrics and statistics.

4.2. Understand measurement and monitoring techniques.

5. Understand risk management methods and techniques.

5.1. Understand environmental impact evaluation methods.

5.1.1. Understand significance evaluation methods.

5.1.2. Understand life cycle assessment methods.

6. Understand product stewardship concepts and methods.

7. Understand pollution prevention and control techniques.

8. Understand waste management practices and processes.

8.1. Understand reuse, recycling, and treatment methods.

8.2. Understand source reduction and waste minimization.

9. Understand how hazardous substances are being used.

10. Understand greenhouse gas emission management.

10.1. Understand greenhouse gas accounting methods.

11. Understand environmental performance evaluation methods.

12. Understand environmental reporting and disclosure issues.

13. Understand renewable energy and low carbon technologies.

14. Understand environmental design concepts and practices.

15. Understand natural resource management methods.

Please note that these are only examples. No attempt has been made
to provide an exhaustive list of environmental management auditor
knowledge and skill requirements. You're free to add your own.

OTHER KNOWLEDGE AND SKILL EXPECTATIONS

Quality Management Auditing Knowledge and Skills

Records Management Auditing Knowledge and Skills

Continuity Management Auditing Knowledge and Skills

Occupational Health and Safety Auditing Knowledge and Skill

Information Security Management Auditing Knowledge and Skill

Transportation Safety Management Auditing Knowledge and Skill

OTHER RELATED PAGES

Introduction to ISO 19011 Standard

Plain English ISO 19011 Auditing Definitions

Brief Overview of ISO 19011 Auditing Standard

ISO 19011 Standard Translated into Plain English

ISO 14001 2015 Standard Translated into Plain English

How to Audit an Environmental Management Audit Program

How to Plan and Perform Environmental Management Audits