Marking World Environment Day, state Greens leader Samantha Ratnam on Wednesday flagged a motion for an inquiry which has the backing of fellow upper house crossbenchers Fiona Patten, Andy Meddick and Clifford Hayes.

"It really is alarming and every day we're hearing stories of more parts of our ecosystem really under threat and many party of our ecosystem on the brink of collapse," Ms Ratnam told reporters at parliament.

"It's important that we all do everything we can and that takes every level of government."

Ms Patten said the issue had reached a drastic point.

"We need to take urgent action," she told reporters.

The inquiry is yet to be voted on, but if it gets up, it will examine the decline of Victoria's ecosystems, the extinction crisis and measures to restore habitats and populations of threatened and endangered species.

Marking World Environment Day in parliament on Wednesday, Mr Hayes pointed to the latest United Nations report on biodiversity.

"It has found that up to 1 million of the earth's estimated 8 million plant, animal and insect species are at imminent risk of extinction due to our relentless pursuit of economic growth," he said.

Australian Associated Press