Delegates from the International Union for Conservation of Nature meet every four years for a thorough review of world flora and fauna at risk, which currently stands at thousands of species.

"We want this congress to be the event that brings together solutions for biodiversity," French Environment Minister Nicolas Hulot said in a statement released by the IUCN.

Hulot was also in Marseille on Friday to outline his own plans for preserving France's environmental diversity and "raise consciousness" about the stakes for the planet.

"We have become a weapon of mass destruction" for the planet, Hulot said during his visit, saying the "moment of truth" was at hand.

Scientists have given a dire prognostic about the fate of thousands of species in the coming years, victims of climate change and human encroachment on their natural habitats.

Some say the planet is already undergoing a "mass extinction event", the first since the dinosaurs disappeared about 65 million years ago, and only the sixth in the last half-billion years.

An update of the Red List last year found that of the 91,523 species assessed, nearly 26,000 were classified as "threatened" -- of which roughly 5,500 were "critically" imperilled.

Next year's IUCN congress coincides with the formal implementation of the landmark 2015 Paris climate accord, which aims to cap global warming at "well under" 2 Celsius (3.6 degrees Fahrenheit) and 1.5 C if possible.

That goal has been thrown into doubt after US President Donald Trump said he would pull out of the deal signed by nearly 200 nations.