While rain has arrived in some drought-affected areas, it has been too late for many native trees.

Unprecedented dry conditions this year have been killing trees that have survived previous droughts.

To find out the scale of the problem, scientists have launched a citizen science program called the Dead Tree Detective.

With help from the public around Australia, they hope to map the environmental damage of 2018's record dry.

On Gordon Williams's farm near Armidale in northern New South Wales, it's not just the animals that are desperate for relief from the dry conditions.

Trees are struggling to draw water from the ground, and some are dying.

Gordon Williams has seen trees die on his property in this year's drought. ( ABC New England: Lara Webster )

Mr Williams points to a stand of trees bleaching in the sun.

"See that little rocky hill? You can see quite a lot of dead [trees] poking through."

Up close, the farmer peels back the bark of a dead tree.

"This is a good example of something that has probably largely died from drought stress.

"The trees have been through four or five years of below average rainfall. The trees may have been a bit stressed anyway and the drought is the last straw for them," Mr Williams said.

Understanding how trees cope in drought

Professor Belinda Medlyn has launched a citizen science project called the Dead Tree Detective. ( Supplied: Belinda Medlyn )

Belinda Medlyn, an expert in tree mortality at the University of Western Sydney, said this drought had seen a significant rise in tree deaths.

"This year has been extremely severe actually," Professor Medlyn said.

"We've had anecdotal reports from a number of places in New South Wales where it has actually been severe enough for trees to start dying."

Professor Medlyn wants to gather better data about what is happening to trees during droughts. But with the impact so dispersed around Australia, she needs the help of the public.

She has recently launched a citizen science project called the Dead Tree Detective.

"People can go and upload pictures of trees that have died recently or look like they're about to die so that they can let us know here [when] they see signs of trees dying that seem unusual," Professor Medlyn said.

To better understand how trees cope with environmental stress, Professor Medlyn said her team had subjected full-sized trees to artificial droughts and heatwaves.

"We actually enclose trees that are up to 10 metres tall inside a chamber, and that chamber is temperature-controlled and humidity-controlled.

"Hopefully that's going to help us to predict where and when different trees start hitting their thresholds at which they might start to die."

Professor Belinda Medlyn's team encloses whole trees inside climate-controlled chambers to study the effects of droughts and heatwaves on trees. ( Supplied: Western Sydney University )

A sanctuary in decline

David Paull's property near Coonabarabran in NSW has experienced drought since 2004, but lately he has started noticing large native trees dying and it has got him worried.

"I've been seeing widespread tree deaths and forest decline in the last couple of years — it's extremely noticeable," he said.

Mr Paull lives on a 323-hectare block surrounded by the dense Pilliga Forest. A part-time grazier and a consulting ecologist, he said his home was his sanctuary and it distressed him to see it in decline.

"All the different birds, ants, and wildlife activity I see here reminds me this is a living system and it's in relatively good health.

"But I can't say that now because I've noticed a big decline in the bird types and insect types here in particular."

A short drive from Mr Paull's property is a ridge line that provides a view to his expansive backyard.

Home to 200 bird species, the Pilliga Forest is now scattered with patches of dead eucalypts.

"Look closely," he said, "and you can see most trees have dry foliage and aren't flowering or seeding as they should be."

Ecologist David Paull takes a photo of a dead tree for the Dead Tree Detective citizen science project. ( ABC Western Plains: Jessie Davies )

Mr Paull's consulting work takes him to some of the most drought-affected parts of the state.

"I travel out to far western NSW often and out west the trees are suffering really badly," he said.

"In particular I've noticed this along the main water courses where you would expect trees to be thriving but today they are dying. That is an extremely bad sign."

He is enthusiastic about the launch of the Dead Tree Detective project and welcomes the rise of citizen science.

"Local people see these things and it just goes unrecorded but it is so important because I don't think the Government is monitoring the gradual decline of the environment's health."

The next generation

Farmer Gordon Williams knows the importance of trees on his property.

"They're part of your landscape," he said.

"They give shelter to pastures, they give shelter to livestock. If you lose too many trees, you end up on that downward slippery slope."

Gordon Williams is planting his next generation of trees now. ( ABC New England: Matt Bedford )

Looking forward 30 years, he is actively succession planning for his trees.

"I'm looking to manage my old trees as best I can — you're always going to have dead ones," he said.

"I manage the trees that are naturally regenerating by … stocking out lower grade areas.

"We're also looking at planting new trees where it's unlikely that any amount of regeneration is going to happen."