With about one million species at risk of extinction and the natural systems that sustain all living things in marked decline, the stakes have never been higher.

The COP15 conference, due to begin in Montreal, Canada, this week, is being billed as the biggest opportunity in a decade to turn that around.

Australian Conservation Foundation CEO Kelly O'Shanassy says issues don't get much bigger for humanity than being able to eat, drink and breathe.

That's essentially what the 15th gathering of parties to the United Nations Convention on Biological Diversity is about.

Almost 200 countries will meet in Montreal from Wednesday where they will be asked to agree on a landmark deal to safeguard nature, similar to the Paris agreement to tackle climate change.

One of the overarching ambitions is to protect 30 per cent of the planet's land and ocean areas by 2030, as a starting point.

Other targets up for negotiation deal with habitat restoration, pollution, sustainable food systems, how to fund the work and monitor progress.

Ms O'Shanassy says it simply won't be possible to fix the nature crisis without a Paris-style pact to mobilise global ambition and hold nations to account.

"One million species across the world are threatened with extinction, 75 per cent of land environments and 66 per cent of marine environments have been significantly affected by humans,'' she says.

"And this is the statistic that freaks me out ... 96 per cent of the mass of all mammals on Earth are humans and the animals we grow to eat. Every other mammal is the other four per cent."

The Labor government has already promised Australia will protect 30 per cent of its land and ocean areas by 2030.

Ms O'Shanassy hopes Environment Minister Tanya Plibersek will take a lead role in drumming up support for the target globally when she arrivals in Montreal for the second week of the conference.

"Of the 17 mega-diverse nations there's only two that are developed. The other is the United States and the US is not a signatory to the COP, so Australia is very important to this process," she says.

Quinton Clements is a policy expert with WWF-Australia and says the draft framework is a mess leading into COP15, which should have been held two years ago but was delayed by the pandemic.

He says one of the big hurdles is a decision by the COP's president, China, not to invite heads of government to Montreal, leaving the task to national delegations and their relevant ministers.

"Without heads of state, heads of government trying to really push this along ... there isn't that level of political ambition at this point," he says.

"Certainly the (UN) Secretary-General is looking at what can be done to try and get leaders to it ... virtually or in some kind of hybrid form.

"(Australian) organisations are reaching out to Prime Minister Albanese. We'd like to see him do something, whether it's attend a virtual event, or say something to indicate the importance of COP15."

Australian Associated Press