Everyone wants to ensure the long-term sustainability of forests, but how do we achieve it? In the face of global warming, changing fire regimes, agricultural expansion, timber harvesting, and conservation pressures, how do we know what is best for our forests?

Professor Barry Brook and his research group might have found the answer. The clues lie within the forest. He is working with PhD candidate Jessie Buettel to develop a model that can predict the impact of activity and global changes on forests.

He describes it like reading the signs on a person’s face. Wrinkles suggest age, sun spots suggest time outdoors, yellowing teeth might suggest smoking. They are looking at forests in the same way and making inferences. 

You can get clues and find patterns that are imprinted in the forests, he said.

One significant problem with studying impacts on forests is the timescale of change. It takes 30-300 years for forest systems to change. 

We don’t want to wait around for 20 or 50 years to see what the impacts of pressures on forests are – we want to know now so that we can manage forests appropriately.

Jessie’s project is particularly focused on where trees and other elements of the forest are found – their spread across the landscape and why trees are in certain locations and not others.

It looks at patterns of standing trees, the distribution of tree ages, where large trees have fallen and created gaps or displaced other trees, and how they essentially create a ‘potting mix’ for new trees to grow out of, or habitat for animals.

Jessie and Barry also measure other physical features like topography of the landscape and water-forms, and model how they have shaped the forest structure.

This is combined with pieces of historical information such as when fires or logging occurred.

From there they will reconstruct why today's forests look the way they do – how these ecosystems change over time, what might keep them in a stable condition, and how they respond to disturbance. 

Professor Barry Brook and his research group are taking an innovative and in-depth look at forests.

These are big-picture questions looking at how forests change over time, how responsive they are, how sensitive they are and so on.

The researchers will do this over lots of different sites across Australia, to get an idea of how different forests have responded to different drivers.

They are collaborating widely and observing a range of sites including forest reserves and long term ecological research sites like WARRA, which is operated by Forestry Tasmania. 

And from all that information taken today as a snapshot, we can actually infer deep time processes about how the forests function. That is fundamentally important to build models to say what is going to happen in the future, said Jessie.

Forest managers can then go and use the methods recommended by the model and report back on the outcomes.  There will be a feedback loop between practical management and real-world experiments. This will further improve the accuracy of the model over time. 

As the model improves, people will be able to manage forests with even more confidence about the long-term sustainability of their actions.

Forest use is inevitable

Professor Brook said that forests conserve a “really unique” suite of plants and animals, but that it is inevitable that people are going to want to use them.

“We need to move away from the debate about whether people are going to use forests and instead focus on what forests we use, how we use them and how we ensure that that usage is sustainable and an appropriate balance of conservation and economic use.” 

“The model will help determine how to manage these forest sustainably, to preserve their unique biota, so they can continue to fulfil their ecological function, which allows them to provide ecosystem services like carbon sequestration, managing flood waters and other things that are important for society as a whole.”

The model can predict, based on the information that we have today, what the impact of a particular activity might mean.

“This information can then inform management and policy decisions, like how much timber can be safely harvested for furniture and building houses, what methods of harvest are ideal, whether there should be a cool or a hot fire used for reserve management, and so on. 

The model will be useful for everyone from people trying to conserve forests who want to keep them in tact in say national parks, to foresters who want to understand the impact of say selective logging versus clear felling. You need these types of fundamental ecological models to make decisions like that, Jessie said.

Professor Brook said that while there has been a lot of focus on managing forestry and tourism pressures on forests, locking forests up in reserves is not always the answer. 

“Some management of forests is essential. Forests have essentially been managed for 40,000 years or more, it’s just that the indigenous populations were managing them with fire and other agents of change.

“Other than a few relics in remote areas, Australia’s forests are generally not pristine, pre-human systems. We can’t put a fence around them and not touch them and expect that they will look the same as they do today. They won’t. They will change in dramatic ways.

Professor Brook gives the example of excluding fires from forests, which canbe detrimental for forest sustainability.

“Throughout history a ‘stand replacing event’ would happen every 400 or 500 years. A lightning strike would burn forests to the ground leaving nothing but an ash bed. There would be other forests left intact, creating a patchwork effect, a mosaic of old, medium age, young forest, and some with multiple ages of regeneration as well.

Jessie notes, “We could be stopping this from happening by excluding fires. Wildfire has always killed old trees. By protecting them from it, we may be killing the trees.”

This is a conundrum that the researchers don’t expect to be able to solve, but they do hope to provide the type of data and models that help people answer questions. What if you do this, what if you do that… how will the forest respond?

Professor Brook doesn’t shirk from the controversy that their results might inspire, or what type of debate it sparks: they just want accurate science. Data that can be useful for decision making and future planning. 

Where can the model be used?

“We’re interested in how global changes are impacting on the tall forests of Tasmania and other places around Australia like Victoria and Western Australia.”

The researchers will be testing the model in forests across Australia and New Zealand to determine whether it works in other locations as well. 

Generality of a model is often sought. We hope to create a model that can be used in forests anywhere in the world, which we think will be the case as long as some local information is included. We focus on Tasmania but we look outwards as well.

About the researchers

Professor Barry Brook: Barry Brook started his career with a focus on threatened species and the impacts of people on the environment. One of the things that piqued his interest during his PhD was our ability, or lack thereof, to predict extinction risk in the face of things like deforestation, harvest of wildlife populations, and so on. He then began to research how fire impacts on plants and animals and the effects of deforestation from agricultural expansion in the tropical forests of south-east Asia and the Australian environment. He joined the School of Biological Sciences at the University of Tasmania in 2014.

“Tasmania is an incredible place to do forest research. It is a natural laboratory where you can get traction on the ecology. You can have a relationship with industry and conservationists. It is a microcosm that has all the pressures that forests might experience (world heritage areas, tourism, pulp mills, forestry).”

Ms Jessie Buettel: Jessie Buettel is a PhD student working with Professor Brook. He refers to her as a “forest ecologist extraordinaire.” She researches the ecological and human processes that shape Australia’s tall eucalypt forests. 

“On the forest floor—where most people might notice only sticks, logs and woody debris—for my PhD I am doing fieldwork and using models to discover how the now-fallen corpses of once-magnificent trees continue to exert a powerful influence on the living forest.”

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