News of the failure to build the promised Western Grassland Reserve on the city's boundary follows last week's warning from biodiversity experts that 1 million species around the world face extinction because of humans.

In 2009, Premier John Brumby enriched developers and landowners who had property just outside Melbourne's western town boundary, re-zoning 41,000 hectares of grassland and farm properties for housing.

This land had been protected by previous governments as "green wedge" zones.

To offset the environmental legacy of turning these open spaces into housing sprawl, Labor promised to buy 15,000 hectares of land for the Western Grassland Reserve.

It would protect "one of Victoria's most endangered ecosystems", Mr Brumby said at the time and "provide ongoing protection to areas with significant biodiversity values and ... offset the extension to Melbourne's urban growth boundary".

The pledge passed into law in 2010, with legislation pledging creation of the reserve by 2020.

But with next year's deadline looming, just 9 per cent of the land needed has been bought by the state.

Local biodiversity experts say the land purchased and the farmland that was meant to be bought is languishing in a degraded state, with serrated tussock and other weeds smothering native grasses.

"This is one of the most depressing place I've been in my life," said RMIT's Sarah Bekessy, after a visit to one section of reserve last week.

Less than one per cent of Victoria's original grasslands remain, with the rest cleared for agriculture and housing.

Professor Bekessy has long campaigned for these remaining grasslands surrounding Melbourne to be better protected, because they are home to endangered species including the southern brown bandicoot, growling grass frog, legless lizard and earless dragon.

"It's an ecosystem that we might see go extinct literally in our lifetimes," Professor Bekessy said.

She commended Labor for having committed a decade ago to the western reserve - "any attention is better than nothing" - but said it now had to fulfil its promise.

"This reserve should have been a chance to showcase [Victoria's] ecosystem. Right now, it's hardly a place to take your kids, and definitely not somewhere that's going to inspire people to think 'I am going to save this'."

The reserve was to be bought with money from developers as they cleared land for housing. But the money never flowed at the rate predicted in 2009.

Creating the grasslands was promised under the federal Environment Protection and Biodiversity Conservation Act.

But the lack of consequences for the Victorian government's failure to deliver has revealed Canberra's lack of power where the environment is concerned.

The current Environment Mminister, Lily D'Ambrosio, recently told Parliament that the government remained "committed" to buying land as it becomes available.

"The government has been acquiring land only through voluntary sales, at a time when the owner is ready to sell," Ms D'Ambrosio said in Parliament in response to questions from Sustainable Australia MP Clifford Hayes.

The government has bought 1335 hectares of land for the Western Grassland Reserve, and recently agreed to buy another 153 hectares. Ms D'Ambrosio said the government was negotiating to buy another 3000 hectares within the reserve area.

But Mr Hayes said at this rate it would take a century to fulfil Mr Brumby's pledge, not 10 years.

"Governments make grand promises of environment or heritage protection when they want to get something through, but afterwards the promises quietly slip away," Mr Hayes said.

Australian Conservation Foundation policy analyst James Trezise said grasslands didn't have the profile of forests, rivers or reefs, but were critical to many Australian species surviving.

He said Canberra had little or no powers "to compel the Victorian government to meet their end of the bargain and ensure nature is protected alongside urban development".

Federal Greens senator for Victoria, Janet Rice, said the federal government, having allowed Victoria to rezone thousands of hectares for housing, had simply left it to the state to police their own promise.

"This is a recipe for disaster," she said and "a classic example of how federal environment laws and offsets are failing to protect the environment".

The Greens want an overhaul of federal environment laws, and the creation of a national Environment Protection Authority.

- The Age