The recently-released state of the environment report 2021 - a scorecard from the nation's leading experts - paints a bleak picture for threatened species, the farming sector and tourism.

Deakin University professor of wildlife ecology and conservation Euan Ritchie said the compounding threat of climate change and invasive species outlined in the findings was "really bad news" for the south-west.

The report notes a 10-20 per cent decrease in post-1997 rainfall levels in southern Victoria where changes in seasons have been most pronounced.

Former head of the Warrnambool campus and ecology expert Rob Wallis said the decreasing water availability in rivers, associated waterways and wetlands had placed the south-west in a far worse position than other regions.

"The aquatic environment has been the most affected and the state of our rivers in the south-west is a lot worse than anywhere else," he said.

Professor Ritchie said the report's findings meant large-scale fish kills similar to those observed in Peterborough's Curdies River could become more frequent.

"Blue-green algal blooms occur in part due to the amount of rainfall and water flowing through those systems," he said.

"That was of course mentioned in the state of environment report - that the amount of water supposed to be allocated for the environment has not been met.

"If you don't have water flowing through systems and they become shallower, warmer and full of nutrients in part because of agricultural practices, you can have these really horrific blooms.

"That's symptomatic of the fact we're not taking care of our aquatic systems very well and as a result the wildlife suffer."

The lack of rainfall and warming temperatures could spell trouble for the region's beloved marine mammals.

In south-east Australia, summer extremes have increased faster than averages since 2000.

That's caused a sharp uptick in the frequency of very high temperatures - the average number of days per year on which the temperature reached 45 °C somewhere in Victoria increased from 0.3 in 1961-2000 to 2.0 in 2001-20 and 2.6 in 2011-20.

Professor Ritchie said the findings emphasised the importance of protecting Southern Right Whale migration.

"I suspect it would impact the whales because one of the reasons why they're off the coast of Warrnambool or Portland is because of the upwelling, so really productive marine environments and cold water," he said.

"Warming waters could potentially decrease the productivity which has been mentioned as a concern for penguins and other seabirds.

"If the temperatures warm that can lead to a decrease in productivity of those marine environments and affect the food chain."

He said the worrying trend also held implications for keystone species.

"If the ocean continues to warm then areas including around south-west Victoria where we have kelp - a really important keystone species for the marine environment because it provides so much structure and habitat for other species - will begin to disappear and that's really bad news for the environment," Professor Ritchie said.

"Kelp itself is quite good at capturing and storing carbon so you've got this double whammy in a sense that because of increasing temperature you're losing kelp and kelp's ability to store carbon."

Professor Ritchie said the pressures of climate change were not limited to marine life and could make conservation efforts for threatened inland species more difficult.

"We may have more extreme events, you may have these situations where you have extended droughts, hot periods, fires then you have really heavy rainfall periods," he said.

"One of the devastating things that can happen after fires is heavy rainfall including in Victoria and that then flushes ash and sediment and so forth into our marine and fresh water aquatic environments and that can smother the animal and plant life and cause them death.

"In south-west Victoria we do have populations of native marsupials which are really important like potoroos, bandicoots and so forth that are already being impacted by introduced species like foxes and feral cats.

"We know there's potentially an interaction there with fire and so therefore if we're having increased fire days on top of invasive species, compounded by climate change, that doesn't bode very well for our native marsupials or animals."

Sudden cold-snaps and severe frost warnings - including that issued for the south-west this week on our coldest start for the year - could also become more common.

"As climates get drier, that means they're actually more prone to frost," Professor Ritchie said.

"It's to do with the combination of dryness as well as huge fluctuations in temperature. Yes, temperatures are overall on the rise but what's happening really is the climate is becoming destabilised.

"You have this overriding trajectory of increased temperatures but as part of that you also have these wild fluctuations and extremes like real cold snaps, intense heat events and those isolated incidents which may only happen over a day or so can actually have a more devastating impact than the long-term trend.

"You can imagine scenarios in south-west Victoria where really intense cold or hot periods - which are really oppressive to people and wildlife - can lead to the death of livestock or failure of crops."

Volcano produce owner Ben Pohlner experienced first-hand the consequences, having lost an entire crop of seedlings when the mercury plummeted to -0.9 degrees on Wednesday morning.

Corangamite Shire Council recently pledged $800,000 to address climate change, promising a "stronger focus" on emissions reduction.

The amount was allocated in its 2022-23 financial budget.

Professor Ritchie said proactive steps were necessary to protect the tourism sector.

"If you're seeing your environment being degraded because of extreme fires that is at some point going to have an impact on tourism," he said.

"If you're going to see a beautiful forest and it's all burned down, less people are going to visit - that's just a fact.

"That goes for the marine environment as well. If you want to go diving on a beautiful kelp forest and it's all barren because the waters are too warm and all the kelp has disappeared, then that's the same."

Professor Wallis said all steps should be taken to protect the small victories.

"The report substantiates what us as scientists have believed for some time - it documents the decline of species and biodiversity," he said.

"Historically, if you look at the records there are mammals in the region we've lost. Unless we actively manage the conservation of the ones we have now, we can't just assume they'll be there forever.

"There's been a reduction and therefore it makes it all the more important for us to conserve those forest patches, those natural areas, the marine parks and so forth.

"The Warrnambool Field Naturalist Club for example has been working on a patch of privately-owned forest on the Cobden Road that adjoins another patch which altogether stretches 100 hectares. They're crucial refuges for threatened species in the region.

"There's been some good news stories too - species are getting found where we thought they'd disappeared. There's a beautiful little marsupial which they found at the 'Maam', a little wetland reserve opposite Premier Speedway.

"Warrnambool Coastcare Landcare recently got funding to do a study and found a little White-footed Dunnart was living there which was fantastic news because I thought it'd disappeared from the region forever."

Professor Ritchie said change required a collective approach from all sectors.

"Many farmers are doing regenerative agriculture, restoring areas and doing the best they can," he said.

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