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Ms Higgins, of London, last year urged the United Nations to better safeguard the planet by developing a law against the proposed new crime of "ecocide".
Ecocide is defined as "extensive damage, destruction to, or loss of ecosystems", including by commercial corporations.
Last week she took part in an Open Forum and gave a public lecture, on aspects of "The Law of Ecocide", at the University of Otago, where she was hosted by the Faculty of Law and the Research Cluster for Natural Law Resources.
There was growing support for the proposed new law and it was likely to be enacted within five years, Ms Higgins said in an interview.
New Zealand risked being left behind by international public opinion unless the country showed "moral leadership"over the proposed law, she said in an interview.
A widely-publicised mock trial, involving an "ecocide" charge, will be held in the London Supreme Court later this month.
Ms Higgins said current international law failed to protect the environment against extensive pollution and other environmental damage.
She advocates adding "ecocide" to the four international Crimes Against Peace: Genocide, Crimes Against Humanity, War Crimes, and Crimes of Aggression.