"It was really a very black time for all of us," the former president of Friends of the Koala tells AAP.

The organisation was already inundated with injured and sick koalas, with years of drought battering vulnerable populations.

The group based at Lismore in northeast NSW had taken in more than 400 koalas in one year.

"Most of us already felt really bad about that. And then the bushfires came," Ms Irwin said

The region - the "green corner of NSW" - was completely unprepared for the chaos that followed.

"We had never before thought that bushfires are going to be a problem for us."

More than 700 homes and a million hectares of land - an area almost five times the size of the ACT - was torched in northern NSW, much of it prime koala habitat.

Thousands of koalas perished.

"If they weren't burnt to death, what we found was the radiant heat from the bushfires ... actually baked their organs," Ms Irwin says.

She recalled one family, whose property was a haven for a trove of koalas, desperately calling for help to save one.

"Whilst they were fighting to try and save their house, they could see the koalas coming down the trees and running and they couldn't catch them. All except this last one ran straight into the fire."

That koala ended up dying too.

In fact, all except three of the koalas the group managed to rescue, died.

Day after day of being seeing horrific injuries was heartbreaking for the welfare crew, but the grand scale of the fires nation-wide created an added level of grief.

An estimated three billion animals were killed and the habitats of even more, destroyed.

The period is "without doubt" the most traumatic chapter of Ros' life.

"It doesn't take much to take you back and to re-feel the emotions that you were going through then ... and immediately I feel my eyes watering."

That's a story Suzy Nethercott-Watson is all too familiar with.

She's been a wildlife volunteer for over two decades, and in 2018 set up a charity - Two Green Threads - to support her peers.

Trauma from dealing with graphic injuries, grief for not being able to save animals in care, and guilt at not being able to do more comes with the job.

But the fires were "the most horrendous culmination" of several tough years for the sector and overwhelmed many carers, leaving them feeling depressed.

"It was very hard not to think 'oh my god, I'm so helpless and hopeless and I can't do anything. I'm not making a difference'," Ms Nethercott-Watson tells AAP.

On top of that, being a carer comes with an added level of understanding of the desperate pain and panic many animals would have been feeling.

"In a way you, unfairly, project on yourself what they must be going through," she says.

A harrowing picture of a blackened kangaroo joey, scorched and stuck in a fence, took her to that dark place.

"It was horrendous even to a member of the public, in terms of the pure anguish that animal clearly experienced.

"But as a wildlife volunteer you know that little 2kg eastern grey joey should not have been without its mum and wouldn't survive without milk, even if it got through the fence and outran the fire.

"And you know how terrified it would have been."

Adding to the unprecedented stress of the period, was the fact that many wildlife volunteer groups felt unprepared.

They didn't have evacuation plans, and hadn't needed one before, says the International Fund for Animal Welfare's Nicole Rojas-Marin.

"No one was prepared for bushfires of that intensity and magnitude," she says.

And evacuating wildlife is not like evacuating pets - they can't be easily loaded in a car.

Some carers found they didn't have enough enclosures to transport their animals.

Others couldn't identify another safe place they could go, with the fires so widespread.

The situation forced them to make "impossible decisions", Ms Rojas-Marin says.

She heard numerous stories of volunteers staying to protect their homes and animals when they'd rather have evacuated to safety.

Other people set the animals up as best they could and hoped for a miracle as they left.

"That thought was so heartbreaking. Just picture yourself being in their position, having invested hours and hours of time, care and love into these animals," Ms Rojas-Marin says.

All three women are determined the sector is ready for the next, inevitable natural disaster, with research showing better preparation means better recovery.

Ms Rojas-Marin, through IFAW, is helping train volunteers and organisations like Friends of the Koala on how to prepare evacuation plans.

The group has established guidelines and templates to help carers prepare simple things: extra food, water, and medicine, back up carers, the equipment needed to transport the animals.

At the same time, Ms Nethercott-Watson is working on carers' mental preparation.

She is trying to convince carers to talk about their experiences and set healthy boundaries so they can keep doing the job for years to come.

"If you're around for longer, you can help more animals - because god knows they're going to need it."

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Australian Associated Press