News

Scientists need your help to track dying trees

By Geoff Adams

By Belinda Medlyn, professor, Western Sydney University; Brendan Choat, associate professor, Western Sydney University; and Martin De Kauwe, senior research fellow, Univerity of NSW

Most citizen science initiatives ask people to record living things, like frogs, wombats or feral animals.

But dead things can also be hugely informative for science.

We have just launched a new citizen science project, The Dead Tree Detective, which aims to record where and when trees have died in Australia.

The current drought across south-eastern Australia has been so severe that native trees have begun to perish, and we need people to send in photographs tracking what has died.

These records will be valuable for scientists trying to understand and predict how native forests and woodlands are vulnerable to climate extremes.

Understanding where trees are most at risk is becoming urgent because it’s increasingly clear that climate change is already under way.

On average, temperatures across Australia have risen more than one degree Celsius since 1910, and winter rainfall in southern Australia has declined. Further increases in temperature, and increasing time spent in drought, are forecast.

How our native plants cope with these changes will affect (among other things) biodiversity, water supplies, fire risk and carbon storage.

Unfortunately, how climate change is likely to affect Australian vegetation is a complex problem, and one we don’t yet have a good handle on.

It’s been estimated an increase of two degrees Celsius would see 40 per cent of eucalypt species stranded in climate conditions to which they are not adapted.

But what happens if species move out of their climatic niche? It’s possible there will be a gradual migration across the landscape as plants move to keep up with the climate.

It’s also possible that plants will generally grow better, if carbon dioxide rises and frosts become less common (although this is a complicated and disputed claim).

However, a third possibility is that increasing climate extremes will lead to mass tree deaths, with severe consequences.

There are examples of all three possibilities in the scientific literature, but reports of widespread tree death are becoming increasingly commonplace.

Many scientists, including ourselves, are now trying to identify the circumstances under which we may see trees die from climate stress.

Quantifying these thresholds is going to be key for working out where vegetation may be headed.

There is no system in place to record tree death from drought in Australia.

For example, during the millennium drought, the most severe and extended drought for a century in southern Australia, there are almost no records of native tree death other than along the rivers, where over-extraction of water was also an issue.

Were there no deaths? Or were they simply not recorded?

We’re hearing anecdotal reports of tree death in the news and on Twitter.

We’re aiming to capture these anecdotal reports, and back them up with information including photographs, locations, numbers and species of trees affected, on the Dead Tree Detective.

We encourage anyone who sees dead trees around them to hop online and contribute.

The Dead Tree Detective also allows people to record tree deaths from other causes — and trees that have come back to life again (sometimes dead isn’t dead).

It can be depressing to see trees die — but recording their deaths for science helps to ensure they won’t have died in vain.

To participate, go to the study's website.