Photos from the field: capturing the grandeur and heartbreak of Tasmania’s giant trees



Steve Pearce/The Tree Projects, Author provided

Jennifer Sanger, University of Tasmania

Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this new series, we’ve invited them to share their unique photos from the field.


Tasmania’s native forests are home to some of the tallest, most beautiful trees in the world. They provide a habitat for many species, from black cockatoos and masked owls to the critically endangered swift parrot.

But these old, giant trees are being logged at alarming rates, despite their enormous ecological and heritage value (and untapped tourism potential). Many were also destroyed in Tasmania’s early 2019 fires.




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Former Greens leader Bob Brown recently launched a legal challenge to Tasmania’s native forest logging. And this year, Forestry Watch, a small group of citizen scientists, found five giant trees measuring more than five metres in diameter inside logging coupes. “Coupes” are areas of forest chopped down in one logging operation.

These trees are too important to be destroyed in the name of the forestry industry. This is why my husband Steve Pearce and I climb, explore and photograph these trees: to raise awareness and foster appreciation for the forests and their magnificent giants.

Climbing trees is not just for the young, but for the young at heart. Kevin is in his early 70’s and helps us with measuring giant trees.
Steve Pearce/The Tree Projects, Author provided

What makes these trees so special?

Eualypytus regnans, known more commonly as Mountain Ash or Swamp Gum, can grow to 100 metres tall and live for more than 500 years. For a long time this species held the record as the tallest flowering tree. But last year, a 100.8 m tall Yellow Meranti (Shorea faguetiana) in Borneo, claimed the title — surpassing our tallest Eucalypt, named Centrioun, by a mere 30 centimetres.

Centrioun still holds the record as the tallest tree in the southern hemisphere. But five species of Eucalypt also grow above 85 m tall, with many ranking among some of the tallest trees in the world.

It’s not only their height that make these trees special, they’re also the most carbon dense forests in the world, with a single hectare storing more than 1,867 tonnes of carbon.




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Our giant trees and old growth forests provide a myriad of ecological services such as water supply, climate abatement and habitat for threatened species. A 2017 study from the Central Highlands forests in Victoria has shown they’re worth A$310 million for water supply, A$260 million for tourism and A$49 million for carbon storage.

This significantly dwarfs the A$12 million comparison for native forest timber production in the region.

Chopped wood in a logging coupe.
Chopping down old growth trees doesn’t make economic sense.
Steve Pearce/The Tree Projects, Author provided

Tasmania’s Big Tree Register

Logging organisation Sustainable Timber Tasmania’s giant tree policy recognises the national and international significance of giant trees. To qualify for protection, trees must be at least 85 m tall or at least an estimated 280 cubic metres in stem volume.




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While it’s a good place to start, this policy fails to consider the next generation of big, or truly exceptional trees that don’t quite reach these lofty heights.

That’s why we’ve created Tasmania’s Big Tree Register, an open-source public record of the location and measurements of more than 200 trees to help adventurers and tree-admirers locate and experience these giants for themselves. And, we hope, to protect them.

Last month, three giant trees measuring more than 5 m in diameter were added to the register. But these newly discovered trees are located in coupe TN034G, which is scheduled to be logged this year.

Logging is a very poor economic use for our forests. Native forest logging in Tasmania has struggled to make a profit due to declining demand for non-Forest Stewardship Council certified timber, which Sustainable Timber Tasmania recently failed. In fact, Sustainable Timber Tasmania sustained an eye watering cash loss of A$454 million over 20 years from 1997 to 2017.




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The following photos can help show why these trees, as one of the great wonders of the world, should be embraced as an important part of our environmental heritage, not turned to wood chips.

A portrait of an entire tree captured. Its canopy breaches the clouds.

Steve Pearce/The Tree Projects, Author provided

It’s not often you get to see the entirety of a tree in a single photo. This tree above is named Gandalf’s Staff and is a Eucalyptus regnans, measuring 84 m tall.

While Mountain Ash is the tallest species, others in Tasmania’s forests are also breathtakingly huge, such as the Tasmanian blue gum (Eucalyptus globulus) at 92 m, Manna gum (Eucalyptus viminalis) at 91 m, Alpine ash (Eucalyptus delegatensis) at 88 m and the Messmate Stringybark (Eucalyptus obliqua) at 86 m.

A woman appears tiny standing against an enormous felled tree.

Steve Pearce/The Tree Projects, Author provided

This giant tree, pictured above, was a Messmate Stringybark that was felled in coupe, but was left behind for unknown reasons. Its diameter is 4.4 metres. Other giant trees like this were cut down in this coupe, many of which provided excellent nesting habitat for the critically endangered swift parrot.

Nine people sit across the trunk of an enormous tree.
The citizen science group Forestry Watch helps search for and measure giant trees in Tasmania.
Steve Pearce/The Tree Projects, Author provided

Old-growth forests dominated by giant trees are excellent at storing large amounts of carbon. Large trees continue to grow over their lifetime and absorb more carbon than younger trees.

A man wraps a measuring tape around a huge tree trunk, covered in moss.

Steve Pearce/The Tree Projects, Author provided

The tree in the photo above is called Obolus, from Greek mythology, with a diameter of 5.1 m. Names are generally given to trees by the person who first records them, and usually reflect the characteristics of the tree or tie in with certain themes.

For example, several trees in a valley are all named after Lord of the Rings characters, such as Gandalf’s Staff (pictured above), Fangorn and Morannon.

The tops of the giant tree canopies are higher than the clouds.

Steve Pearce/The Tree Projects, Author provided

Giant trees are typically associated with Californian Redwoods or the Giant Sequoias in the US, where tall tree tourism is huge industry. The estimated revenue in 2012 from just four Coastal Redwood reserves is A$58 million dollars per year, providing more than 500 jobs to the local communities.

Few Australians are aware of our own impressive trees. We could easily boost tourism to regional communities in Tasmania if the money was invested into tall tree infrastructure.The Conversation

Jennifer Sanger, Research Associate, University of Tasmania

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Gabon’s large trees store huge amounts of carbon. What must be done to protect them



Ivanov Gleb/Shutterstock

John Poulsen, Duke University

Large trees are the living, breathing giants that tower over tropical forests, providing habitat and food for countless animals, insects and other plants. Could these giants also be the key to slowing climate change?

The Earth’s climate is changing rapidly due to the buildup of greenhouse gases, like carbon dioxide, in the atmosphere as a result of human activities. Trees absorb carbon from the air and store it in their trunks, branches, and roots. In general, the larger the tree, the more carbon it stores.

Globally, tropical forests remove a staggering 15% of carbon dioxide emissions that humans produce. Africa’s tropical forests – the second largest block of rainforest in the world – have a large role to play in slowing climate change.

But large trees are in trouble everywhere. I carried out research to examine the distribution, drivers and threats to large trees in Gabon. Gabon has 87% forest cover and is the second most forested country in the world.

By carrying out this project, I was able to identify areas with a wealth of large trees (and therefore key carbon stores and sinks), what needed to be done to better protect them and eventually recommend those areas as a priority for conservation.

National inventory

In 2012, the government of Gabon began a national inventory of its forests to measure the amount of carbon stored in its trees – one of the first nationwide efforts in the tropics.

An inventory of this scale isn’t easy, especially in a heavily forested country. Technicians from Gabon’s National Parks Agency travelled to every corner of the country, sometimes hiking more than two days crossing swamps and traversing rivers, to measure the diameter and height of trees in plots a bit larger in size than a soccer field.

Using Gabon’s new inventory of 104 plots, we calculated the amount of carbon in 67,466 trees, representing at least 578 different species. We did this by applying equations to the tree measurements.

The results indicated that the density of carbon stored in Gabon’s trees is among the highest in the world. On average, Gabon’s old growth forests harbour more carbon per area than old growth forests in Amazonia and Asia.

Most of this carbon is stored in the largest trees – those with diameters bigger than 70cm at 1.3 meters from the ground. Just the largest 5% of trees stored 50% of the forest carbon. In other words, 3,373 trees out of the 67,466 measured trees contained half of the carbon.

Drivers of forest carbon stocks

Next, we examined the drivers of carbon stocks. What determines whether an area of forest holds many large trees and lots of carbon? Do environmental conditions or human activities have the largest impact on forest carbon stocks?

Environmental factors – such as soil fertility and depth, temperature, precipitation, slope and elevation – often influence the amount of carbon in a forest. During photosynthesis, trees harness energy from the sun to convert water, carbon dioxide, and minerals into carbohydrates for growth. Therefore, forests with low levels of soil minerals or that receive little rainfall should store less carbon than areas with abundant minerals and water.

Human activities – like agriculture and logging – also influence carbon stocks. Cutting down trees for timber, to clear land for farming, or for construction reduces the amount of carbon stored in forests.

We examined the amount of carbon in each tree plot in relation to the environmental factors and human activities associated with the plot. Surprisingly, we found that human activities, not environmental factors, overwhelmingly affect carbon stocks.

The impact of human activities on forest carbon was largely unexpected because of Gabon’s high forest cover (the second highest of any country) and low population density (9 people per square kilometer), 87% of which is located in urban areas. If human impacts are this strong in Gabon, what must their effects be in other tropical nations?

Although we don’t know for sure, we believe past and present swidden (slash-and-burn) agriculture is the principle cause for low carbon stocks in some areas. Forests close to villages had lower levels of carbon, probably because forest clearing for farming converts old growth forest to secondary forest.

Interestingly, forests in logging concessions held similar amounts of carbon as old growth forests. It is too early to conclude that timber harvest doesn’t reduce carbon levels by cutting large trees, but this finding gives hope that logging concessions can be managed sustainably to conserve carbon stocks.

Importantly, forests in national parks stored roughly 25% more carbon than forests outside of parks. Thus, protecting mostly undisturbed forests can effectively conserve carbon and biodiversity.

Saving Gabon’s giants

The critical role of humans in diminishing carbon stocks is both a blessing and a curse. One one hand, the future of forests are in our hands, giving us the power to choose our fate. On the other hand, we cannot ignore the responsibility to act collectively to secure these resources while considering the interests of the countries that host them.

Gabon is taking laudable actions to conserve its forests, including a protected area network of 13 parks. In addition, Gabon is reforming its logging sector and developing a nationwide land use plan. These actions are a great start, yet continued action is necessary to curb the effects of swidden agriculture and ensure that growing industrial agriculture does not reverse Gabon’s achievements.

Intact forests can pay returns. Norway recently committed to paying Gabon $150 million for stewardship of its forests. Conservation of forests requires sacrifice by the Gabonese people. Yet, this payment demonstrates that Gabon’s large trees are a national asset that can contribute to its development as well as an international resource requiring collective action to conserve.The Conversation

John Poulsen, Associate Professor of Tropical Ecology, Duke University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Are young trees or old forests more important for slowing climate change?



Jeremy Kieran/Unsplash, CC BY-SA

Tom Pugh, University of Birmingham

Forests are thought to be crucial in the fight against climate change – and with good reason. We’ve known for a long time that the extra CO₂ humans are putting in the atmosphere makes trees grow faster, taking a large portion of that CO₂ back out of the atmosphere and storing it in wood and soils.

But a recent finding that the world’s forests are on average getting “shorter and younger” could imply that the opposite is happening. Adding further confusion, another study recently found that young forests take up more CO₂ globally than older forests, perhaps suggesting that new trees planted today could offset our carbon sins more effectively than ancient woodland.

How does a world in which forests are getting younger and shorter fit with one where they are also growing faster and taking up more CO₂? Are old or young forests more important for slowing climate change? We can answer these questions by thinking about the lifecycle of forest patches, the proportion of them of different ages and how they all respond to a changing environment.




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The forest carbon budget

Let’s start by imagining the world before humans began clearing forests and burning fossil fuels.

In this world, trees that begin growing on open patches of ground grow relatively rapidly for their first several decades. The less successful trees are crowded out and die, but there’s much more growth than death overall, so there is a net removal of CO₂ from the atmosphere, locked away in new wood.

As trees get large two things generally happen. One, they become more vulnerable to other causes of death, such as storms, drought or lightning. Two, they may start to run out of nutrients or get too tall to transport water efficiently. As a result, their net uptake of CO₂ slows down and can approach zero.

Eventually, our patch of trees is disturbed by some big event, like a landslide or fire, killing the trees and opening space for the whole process to start again. The carbon in the dead trees is gradually returned to the atmosphere as they decompose.

The vast majority of the carbon is held in the patches of big, old trees. But in this pre-industrial world, the ability of these patches to continue taking up more carbon is weak. Most of the ongoing uptake is concentrated in the younger patches and is balanced by CO₂ losses from disturbed patches. The forest is carbon neutral.

A misty forest scene.
New trees absorb lots of carbon, old trees store more overall and dead trees shed their carbon to the atmosphere.
Greg Rosenke/Unsplash, CC BY-SA

Now enter humans. The world today has a greater area of young patches of forest than we would naturally expect because historically, we have harvested forests for wood, or converted them to farmland, before allowing them to revert back to forest. Those clearances and harvests of old forests released a lot of CO₂, but when they are allowed to regrow, the resulting young and relatively short forest will continue to remove CO₂ from the atmosphere until it regains its neutral state. In effect, we forced the forest to lend some CO₂ to the atmosphere and the atmosphere will eventually repay that debt, but not a molecule more.

But adding extra CO₂ into the atmosphere, as humans have done so recklessly since the dawn of the industrial revolution, changes the total amount of capital in the system.

And the forest has been taking its share of that capital. We know from controlled experiments that higher atmospheric CO₂ levels enable trees to grow faster. The extent to which the full effect is realised in real forests varies. But computer models and observations agree that faster tree growth due to elevated CO₂ in the atmosphere is currently causing a large carbon uptake. So, more CO₂ in the atmosphere is causing both young and old patches of forest to take up CO₂, and this uptake is larger than that caused by previously felled forests regrowing.

The effect of climate change

But the implications of climate change are quite different. All else being equal, warming tends to increase the likelihood of death among trees, from drought, wildfire or insect outbreaks. This will lower the average age of trees as we move into the future. But, in this case, that younger age does not have a loan-like effect on CO₂. Those young patches of trees may take up CO₂ more strongly than the older patches they replace, but this is more than countered by the increased rate of death. The capacity of the forest to store carbon has been reduced. Rather than the forest loaning CO₂ to the atmosphere, it’s been forced to make a donation.

So increased tree growth from CO₂ and increased death from warming are in competition. In the tropics at least, increased growth is still outstripping increased mortality, meaning that these forests continue to take up huge amounts of carbon. But the gap is narrowing. If that uptake continues to slow, it would mean more of our CO₂ emissions stay in the atmosphere, accelerating climate change.

Overall, both young and old forests play important roles in slowing climate change. Both are taking up CO₂, primarily because there is more CO₂ about. Young forests take up a bit more, but this is largely an accident of history. The extra carbon uptake we get from having a relatively youthful forest will diminish as that forest ages. We can plant new forests to try to generate further uptake, but space is limited.

But it’s important to separate the question of uptake from that of storage. The world’s big, old forests store an enormous amount of carbon, keeping it out of the atmosphere, and will continue to do so, even if their net CO₂ uptake decreases. So long as they are not cut down or burned to ashes, that is.The Conversation

Tom Pugh, Reader in Biosphere-Atmosphere Exchange, University of Birmingham

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Planting non-native trees accelerates the release of carbon back into the atmosphere



native forest.

Lauren Waller and Warwick Allen, University of Canterbury

Large-scale reforestation projects such as New Zealand’s One Billion Trees programme are underway in many countries to help sequester carbon from the atmosphere.

But there is ongoing debate about whether to prioritise native or non-native plants to fight climate change. As our recent research shows, non-native plants often grow faster compared to native plants, but they also decompose faster and this helps to accelerate the release of 150% more carbon dioxide from the soil.

Our results highlight a challenging gap in our understanding of carbon cycling in newly planted or regenerating forests.

It is relatively easy to measure plant biomass (how quickly a plant grows) and to estimate how much carbon dioxide it has removed from the atmosphere. But measuring carbon release is more difficult because it involves complex interactions between the plant, plant-eating insects and soil microorganisms.

This lack of an integrated carbon cycling model that includes species interactions makes predictions for carbon budgeting exceedingly difficult.




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How non-native plants change the carbon cycle

There is uncertainty in our climate forecasting because we don’t fully understand how the factors that influence carbon cycling – the process in which carbon is both accumulated and lost by plants and soils – differ across ecosystems.

Carbon sequestration projects typically use fast-growing plant species that accumulate carbon in their tissues rapidly. Few projects focus on what goes on in the soil.

Non-native plants often accelerate carbon cycling. They usually have less dense tissues and can grow and incorporate carbon into their tissues faster than native plants. But they also decompose more readily, increasing carbon release back to the atmosphere.

Our research, recently published in the journal Science, shows that when non-native plants arrive in a new place, they establish new interactions with soil organisms. So far, research has mostly focused on how this resetting of interactions with soil microorganisms, herbivorous insects and other organisms helps exotic plants to invade a new place quickly, often overwhelming native species.

Invasive non-native plants have already become a major problem worldwide, and are changing the composition and function of entire ecosystems. But it is less clear how the interactions of invasive non-native plants with other organisms affect carbon cycling.




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Planting non-native trees releases more carbon

We established 160 experimental plant communities, with different combinations of native and non-native plants. We collected and reared herbivorous insects and created identical mixtures which we added to half of the plots.

We also cultured soil microorganisms to create two different soils that we split across the plant communities. One soil contained microorganisms familiar to the plants and another was unfamiliar.

Herbivorous insects and soil microorganisms feed on live and decaying plant tissue. Their ability to grow depends on the nutritional quality of that food. We found that non-native plants provided a better food source for herbivores compared with native plants – and that resulted in more plant-eating insects in communities dominated by non-native plants.

Similarly, exotic plants also raised the abundance of soil microorganisms involved in the rapid decomposition of plant material. This synergy of multiple organisms and interactions (fast-growing plants with less dense tissues, high herbivore abundance, and increased decomposition by soil microorganisms) means that more of the plant carbon is released back into the atmosphere.

In a practical sense, these soil treatments (soils with microorganisms familiar vs. unfamiliar to the plants) mimic the difference between reforestation (replanting an area) and afforestation (planting trees to create a new forest).

Reforested areas are typically replanted with native species that occurred there before, whereas afforested areas are planted with new species. Our results suggest planting non-native trees into soils with microorganisms they have never encountered (in other words, afforestation with non-native plants) may lead to more rapid release of carbon and undermine the effort to mitigate climate change.The Conversation

Lauren Waller, Postdoctoral Fellow and Warwick Allen, Postdoctoral fellow, University of Canterbury

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Lemurs are the world’s most endangered mammals, but planting trees can help save them



Black-and-white ruffed lemurs are important indicators of rainforest health.
Franck Rabenahy, CC BY-ND

Andrea L. Baden, Hunter College

Madagascar, the world’s fourth-largest island, is a global biodiversity hotspot.
Andrea Baden

The island of Madagascar off the southeastern coast of Africa hosts at least 12,000 plant species and 700 vertebrate species, 80% to 90% of which are found nowhere else on Earth.

Isolated for the last 88 million years and covering an area approximately the size of the northeastern United States, Madagascar is one of the world’s hottest biodiversity hotspots. Its island-wide species diversity is striking, but its tropical forest biodiversity is truly exceptional.

Sadly, human activities are ravaging tropical forests worldwide. Habitat fragmentation, over-harvesting of wood and other forest products, over-hunting, invasive species, pollution and climate change are depleting many of these forests’ native species.

Among these threats, climate change receives special attention because of its global reach. But in my research, I have found that in Madagascar it is not the dominant reason for species decline, although of course it’s an important long-term factor.

As a primatologist and lemur specialist, I study how human pressures affect Madagascar’s highly diverse and endemic signature species. In two recent studies, colleagues and I have found that in particular, the ruffed lemur – an important seed disperser and indicator of rainforest health – is being disproportionately impacted by human activities. Importantly, habitat loss is driving ruffed lemurs’ distributions and genetic health. These findings will be key to helping save them.

Deforestation from slash-and-burn agriculture in the peripheral zones of Ranomafana National Park, Madagascar.
Nina Beeby/Ranomafana Ruffed Lemur Project, CC BY-ND

The forest is disappearing

Madagascar has lost nearly half (44%) of its forests within the last 60 years, largely due to slash-and-burn agriculture – known locally as “tavy” – and charcoal production. Habitat loss and fragmentation runs throughout Madagascar’s history, and the rates of change are staggering.

This destruction threatens Madagascar’s biodiversity and its human population. Nearly 50% of the country’s remaining forest is now located within 300 feet (100 meters) of an unforested area. Deforestation, illegal hunting and collection for the pet trade are pushing many species toward the brink of extinction.

In fact, the International Union for Conservation of Nature estimates that 95% of Madagascar’s lemurs are now threatened, making them the world’s most endangered mammals. Pressure on Madagascar’s biodiversity has significantly increased over the last decade.

A red ruffed lemur, one of two Varecia species endemic to Madagascar.
Varecia Garbutt, CC BY-ND

Deforestation threatens ruffed lemur survival

In a newly published study, climate scientist Toni Lyn Morelli, species distribution expert Adam Smith and I worked with 19 other researchers to study how deforestation and climate change will affect two critically endangered ruffed lemur species over the next century. Using combinations of different deforestation and climate change scenarios, we estimate that suitable rainforest habitat could be reduced by as much as 93%.

If left unchecked, deforestation alone could effectively eliminate ruffed lemurs’ entire eastern rainforest habitat and with it, the animals themselves. In sum, for these lemurs the effects of forest loss will outpace climate change.

But we also found that if current protected areas lose no more forest, climate change and deforestation outside of parks will reduce suitable habitat by only 62%. This means that maintaining and enhancing the integrity of protected areas will be essential for saving Madagascar’s rainforest habitats.

Warm colors indicate areas where lemurs can move about readily, which promotes genetic diversity; cool colors indicate areas where they are more constrained and less able to mate with members of other population groups.
Baden et al. (2019), Nature Scientific Reports, CC BY-ND

In a study published in November 2019, my colleagues and I showed that ruffed lemurs depend on habitat cover to survive. We investigated natural and human-caused impediments that prevent the lemurs from spreading across their range, and tracked the movement of their genes as they ranged between habitats and reproduced. This movement, known as gene flow, is important for maintaining genetic variability within populations, allowing lemurs to adapt to their ever-changing environments.

Based on this analysis, we parsed out which landscape variables – including rivers, elevation, roads, habitat quality and human population density – best explained gene flow in ruffed lemurs. We found that human activity was the best predictor of ruffed lemurs’ population structure and gene flow. Deforestation alongside human communities was the most significant barrier.

Taken together, these and other lines of evidence show that deforestation poses an imminent threat to conservation on Madagascar. Based on our projections, habitat loss is a more immediate threat to lemurs than climate change, at least in the immediate future.

In 1961 naturalist David Attenborough filmed ruffed lemurs for the BBC.

This matters not only for lemurs, but also for other plants and animals in the areas where lemurs are found. The same is true at the global level: More than one-third (about 36.5%) of Earth’s plant species are exceedingly rare and disproportionately affected by human use of land. Regions where the most rare species live are experiencing higher levels of human impact.

Crisis can drive conservation

Scientists have warned that the fate of Madagascar’s rich natural heritage hangs in the balance. Results from our work suggest that strengthening protected areas and reforestation efforts will help to mitigate this devastation while environmentalists work toward long-term solutions for curbing the runaway greenhouse gas emissions that drive climate change.

A young woman participates in reforestation efforts in Kianjavato, Madagascar.
Brittani Robertson/Madagascar Biodiversity Partnership, CC BY-ND

Already, nonprofits are working hard toward these goals. A partnership between Dr. Edward E. Louis Jr., founder of Madagascar Biodiversity Partnership and director of Conservation Genetics at Omaha’s Henry Doorly Zoo, and the Arbor Day Foundation’s Plant Madagascar project has replanted nearly 3 million trees throughout Kianjavato, one region identified by our study. Members of Centre ValBio’s reforestation team – a nonprofit based just outside of Ranomafana National Park that facilitates our ruffed lemur research – are following suit.

At an international conference in Nairobi earlier this year, Madagascar’s president, Andry Rajoelina, promised to reforest 40,000 hectares (99,000 acres) every year for the next five years – the equivalent of 75,000 football fields. This commitment, while encouraging, unfortunately lacks a coherent implementation plan.

Our projections highlight areas of habitat persistence, as well as areas where ruffed lemurs could experience near-complete habitat loss or genetic isolation in the not-so-distant future. Lemurs are an effective indicator of total non-primate community richness in Madagascar, which is another way of saying that protecting lemurs will protect biodiversity. Our results can help pinpoint where to start.

[ Like what you’ve read? Want more? Sign up for The Conversation’s daily newsletter. ]The Conversation

Andrea L. Baden, Assistant Professor of Anthropology, Hunter College

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Entire hillsides of trees turned brown this summer. Is it the start of ecosystem collapse?



Rachael Nolan, CC BY-NC

Rachael Helene Nolan, Western Sydney University; Belinda Medlyn, Western Sydney University; Brendan Choat, Western Sydney University, and Rhiannon Smith, University of New England

The drought in eastern Australia was a significant driver of this season’s unprecedented bushfires. But it also caused another, less well known environmental calamity this summer: entire hillsides of trees turned from green to brown.

We’ve observed extensive canopy dieback from southeast Queensland down to Canberra. Reports of more dead and dying trees from other regions across Australia are flowing in through the citizen science project, the Dead Tree Detective.




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A few dead trees are not an unusual sight during a drought. But in some places, it is the first time in living memory so much canopy has died off.

Ecologists are now pondering the implications. There are warnings that some Australian tree species could disappear from large parts of their ranges as the climate changes. Could we be witnessing the start of ecosystem collapse?

Extensive canopy dieback in Kains Flat, NSW, January 2020.
Matt Herbert

Why are canopies dying now?

Much of eastern Australia has been in drought since the start of 2017. While this drought is not yet as long as the Millennium Drought, it appears to be more intense. Many areas have received the lowest rainfall on record, including long periods of time with no rainfall. This has been coupled with above-average temperatures and extreme heatwaves.

The higher the temperature, the greater the moisture loss from leaves. This is usually good for a tree because it cools the canopy. But if there is not enough water in the soil, the increased water loss can push trees over a threshold, causing extensive leaf “scorching”, or browning. The extensive canopy dieback we have observed this summer suggests that the soil had finally become too dry for many trees.

Widespread rainfall deciciencies and higher temperatures across many parts of Australia.
Bureau of Meteorology

Are the trees dead?

Brown or bare trees are not necessarily dead. Many eucalypts can lose all their leaves but resprout after rain.

Many parts of eastern Australia are now flushed with green after rain. In these areas, it will be important to assess the extent of tree recovery. If trees are not showing signs of recovery after significant rainfall, they’re unlikely to survive. In some cases carbohydrate reserves – which trees need to resprout new leaves – may be too depleted for trees to recover.

Snowgums in the New England area resprouting in March 2020, following heavy rain. The trees lost most of their canopy during drought in 2019.
Trevor Stace, University of New England

The drought may also hinder post-fire recovery. Most eucalypt forests eventually recover from bushfires by resprouting new leaves. Some forests also recover when fire triggers seedlings to germinate.

But it’s likely that some forests now recovering from fire were already struggling with canopy dieback. So these two disturbances will test how resilient our forests are to back-to-back drought and bushfire.

Trees recovering from drought and/or fire may also enter the “dieback spiral”. The new flush of leaves following rain can make a particularly tasty meal for insects. Trees will then attempt to grow more foliage in response, but their ability to keep producing new leaves gradually declines as they deplete their carbohydrate reserves, and they can die.

Dieback spiral has led to extensive tree loss in the past, including in the New England area of NSW.

Should we be worried?

The capacity of eucalypts to resprout makes them naturally resilient to extended drought. There are some records of canopy dieback from severe droughts in the past, such as the Federation Drought. We assume (although we don’t know for sure) the forests recovered after these events. So they may bounce back after the current drought.

However, it’s hard not to be concerned. Climate change will bring increased drought, heatwaves and fires that could, over time, see extensive losses of trees across the landscape – as happened on the Monaro High Plain after the Millennium Drought.




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Australian research in 2016 warned that due to climate change, the habitat of 90% of eucalypt species could decline and 16 species were expected to lose their home environments within 60 years.

Such a change would have huge consequences for how ecosystems function – reducing the capacity for ecosystem services such as carbon storage, altering catchment water resources and reducing habitat for native animals.

Some trees resprouted new leaves after losing their canopy. But in some cases these leaves are now dying, like on these scribbly gums in the NSW Pilliga in August 2019.
Rachael Nolan

Where to from here?

Records of dead and dying trees on the Dead Tree Detective map.
Dead Tree Detective

Landholders can help bush on their property recover after drought, by protecting germinating seedlings from livestock and collecting local seed for later revegetation. Trees that appear dead should not be cut down as they may recover, and even if dead can provide valuable animal habitat.

Most importantly, however, we need to monitor trees carefully to see where they’ve died, and where they are recovering. A citizen science project, the Dead Tree Detective, is helping map the extent of tree die-off across Australia.

People send in photos of dead and dying trees – to date, over 267 records have been uploaded. These records can be used to target where to monitor forests during drought, including on-ground assessments of tree health and quantifying the physiological responses of trees to drought stress.

There is no ongoing forest health monitoring program in Australia, so this dataset is invaluable in helping us determine exactly how vulnerable Australia’s forests are to the double whammy of severe drought and bushfires.The Conversation

Rachael Helene Nolan, Postdoctoral research fellow, Western Sydney University; Belinda Medlyn, Professor, Western Sydney University; Brendan Choat, Associate Professor, Western Sydney University, and Rhiannon Smith, Research Fellow, University of New England

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Thousands of city trees have been lost to development, when we need them more than ever


Thami Croeser, RMIT University; Camilo Ordóñez, University of Melbourne, and Rodney van der Ree, University of Melbourne

Climate change is on everyone’s lips this summer. We’ve had bushfires, smoke haze, heatwaves, flooding, mass protests and a National Climate Emergency Summit, all within a few months. The search is on for solutions. Trees often feature prominently when talking about solutions, but our research shows trees are being lost to big developments – about 2,000 within a decade in inner Melbourne.

Big development isn’t the only challenge for urban tree cover. During the period covered by our newly published study, the inner city lost a further 8,000 street trees to a variety of causes – vandals, establishment failures of young trees, drought, smaller developments and vehicle damage.

Still, thanks to a program that plants 3,000 trees a year, canopy growth has kept just ahead of losses in the City of Melbourne.




Read more:
Our cities need more trees, but some commonly planted ones won’t survive climate change


Canopy cover is crucial for keeping urban areas liveable, shading our streets to help us cope with hot weather and to counter the powerful urban heat island effect. Trees can also be a flood-proofing tool.

Trees add beauty and character to our streets, and (so far) they’re not a political wedge issue in the ongoing culture war that is Australian climate policy. In short, they’re a very good idea, at just the right time.

Counting the trees lost to development

The thing is, this good idea happens in the midst of a construction boom. In Melbourne alone, this includes thousands of new dwellings and billions of dollars of new infrastructure. Many of the new buildings are very large – there’s a handy open database that shows these developments.

This map shows the scale of development under way in the inner city.
City of Melbourne

Next time you’re walking past a large construction site, look for empty tree pits – the square holes in footpaths where trees have been removed. Maybe you’ve already seen these and wondered what all the construction means for our trees. Well, now we know.

Our study puts a number on the impact of major development on city trees. In the City of Melbourne – that’s just the innermost suburbs and the CBD – major developments cost our streets about 2,000 trees from 2008-2017.

Using council databases and a mapping tool, we tracked removals of trees within ten metres of hundreds of major developments. We found much higher rates of tree removal around major development sites than in control sites that weren’t developed.

An example of our analysis, comparing tree losses around sites with major development (orange) to control sites (blue). Trees within 10m of major developments were much more likely to be removed.
https://doi.org/10.1016/j.scs.2020.102096

Even with the City of Melbourne’s robust tree-protection rules, trees can be removed or damaged due to site access needs, scaffolding, compacted soil, root conflicts with services access, and even the occasional poisoning.

The City of Melbourne invited artist Louise Lavarack to create a roadside memorial to a poisoned plane tree, which was then shrouded in gauze bandages.
Tony & Wayne/Flickr, CC BY-NC



Read more:
We’re investing heavily in urban greening, so how are our cities doing?


Tree protection limits losses

The silver lining in this story is that the city council’s tree-protection policy seems to be quite effective at saving our bigger trees. The vast majority of removals we saw were of trees with trunks less than 30cm thick. Only one in 20 of the trees lost was a large mature tree over 60cm thick.

This may partly reflect the fact that the council charges developers for not only tree replacement but also the dollar equivalent of lost amenity and ecological values. It gets very expensive to remove a large tree once you factor in all the valuable services it provides. When a tree is a metre thick, costs can exceed $100,000 – and that’s if there are no alternatives to removal.

The protection of bigger trees means Melbourne retained canopy fairly well, despite losing over 2,000 trees. Only 8% of city-wide canopy losses during our study period happened near major development sites. This modest loss is still serious, as removals are having more of an impact on future canopy growth than current cover.




Read more:
How tree bonds can help preserve the urban forest


Lessons for our cities

While Melbourne-centric, there are lessons in this study for cities everywhere. Robust policies to protect and retain trees backed up by clear financial incentives are valuable, as even well-resourced councils with strong policy face an uphill battle when development gets intense.

Our findings highlight that retaining and establishing young trees is especially difficult. This is troubling given these are the trees that must deliver the canopy that will in future shelter the streets in which we live and work.




Read more:
Keeping the city cool isn’t just about tree cover – it calls for a commons-based climate response


Improved investments in how young trees are planted and how long we look after them can help. For example, in a promising local study, researchers showed that trees planted in a way that catches rainwater run-off from roads grow twice as fast, provided planting design avoids waterlogging.

Finally, in the context of rapid development, buildings themselves can play a positive role. Green roofs, green walls and rain gardens are just a few of the ways developments can help our cities deal with both heat and flooding.

There are plenty of precedents overseas. In Berlin, laws requiring building greening have resulted in 4 million square metres of green roof area – three times the area of Melbourne’s Hoddle Grid. In Singapore, developments must include vegetation with leaf area up to four times the development’s site area, using green roofs and walls. Tokyo has required green roofs on new buildings for nearly 20 years.

The solutions are out there, and urban greening is rising in profile. Recent commitments in Melbourne, Canberra and Adelaide are promising. Our study findings are a reminder that, even for the willing, we’ll have to take two steps forward, because there’s inevitably going to be one step back.




Read more:
For green cities to become mainstream, we need to learn from local success stories and scale up


The Conversation


Thami Croeser, Research Officer, Centre for Urban Research, RMIT University; Camilo Ordóñez, Research Fellow, School of Ecosystem and Forest Sciences, University of Melbourne, and Rodney van der Ree, Adjunct Associate Professor, School of BioSciences. National Technical Executive – Ecology, WSP Pty Ltd, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Here are 5 practical ways trees can help us survive climate change



Shutterstock

Gregory Moore, University of Melbourne

As the brutal reality of climate change dawned this summer, you may have asked yourself a hard question: am I well-prepared to live in a warmer world?

There are many ways we can ready ourselves for climate change. I’m an urban forestry scientist, and since the 1980s I’ve been preparing students to work with trees as the planet warms.

In Australia, trees and urban ecosystems must be at the heart of our climate change response.

Governments have a big role to play – but here are five actions everyday Australians can take as well.




Read more:
Go native: why we need ‘wildlife allotments’ to bring species back to the ‘burbs


1. Plant trees to cool your home

At the current rate of warming, the number of days above 40℃ in cities including Melbourne and Brisbane, will double by 2050 – even if we manage to limit future temperature rises to 2℃.

Trees can help cool your home. Two medium-sized trees (8-10m tall) to the north or northwest of a house can lower the temperature inside by several degrees, saving you hundreds of dollars in power costs each year.

Trees can cool your home by several degrees.
Shutterstock

Green roofs and walls can reduce urban temperatures, but are costly to install and maintain. Climbing plants, such as vines on a pergola, can provide great shade, too.

Trees also suck up carbon dioxide and extend the life of the paint on your external walls.

2. Keep your street trees alive

Climate change poses a real threat to many street trees. But it’s in everyone’s interests to keep trees on your nature strip alive.

Adequate tree canopy cover is the least costly, most sustainable way of cooling our cities. Trees cool the surrounding air when their leaves transpire and the water evaporates. Shade from trees can also triple the lifespan of bitumen, which can save governments millions each year in road resurfacing.

Tree roots also soak up water after storms, which will become more extreme in a warming climate. In fact, estimates suggest trees can hold up to 40% of the rainwater that hits them.

But tree canopy cover is declining in Australia. In Melbourne, for instance, it falls by 1-1.5% annually, mainly due to tree removals on private land.

Governments are removing trees from public and private land at the time we need them most.
Shutterstock

This shows state laws fail to recognise the value of trees, and we’re losing them when we need them most.

Infrastructure works such as level crossing removals have removed trees in places such as the Gandolfo Gardens in Melbourne’s inner north, despite community and political opposition. Some of these trees were more than a century old.

So what can you do to help? Ask your local council if they keep a register of important trees of your suburb, and whether those trees are protected by local planning schemes. Depending on the council, you can even nominate a tree for protection and significant status.

But once a development has been approved, it’s usually too late to save even special trees.

3. Green our rural areas

Outside cities, we must preserve remnant vegetation and revegetate less productive agricultural land. This will provide shade and moderate increasingly strong winds, caused by climate change.

Planting along creeks can lower water temperatures, which keeps sensitive native fish healthy and reduces riverbank erosion.

Strategically planting windbreaks and preserving roadside vegetation are good ways to improve rural canopy cover. This can also increase farm production, reduce stock losses and prevent erosion.

To help, work with groups like Landcare and Greening Australia to vegetate roadsides and river banks.

4. Make plants part of your bushfire plan

Climate change is bringing earlier fire seasons and more intense, frequent fires. Fires will occur where they hadn’t in the past, such as suburban areas. We saw this in the Melbourne suburbs of Bundoora, Mill Park, Plenty and Greensborough in December last year.

It’s important to have a fire-smart garden. It might seem counter-intuitive to plant trees around the house to fortify your fire defences, but some plants actually help reduce the spread of fire – through their less flammable leaves and summer green foliage – and screen your house from embers.




Read more:
Low flammability plants could help our homes survive bushfires


Depending on where you live, suitable trees to plant include crepe myrtle, the hybrid flame tree, Persian ironwood, some fruit trees and even some native eucalypts.

Gardens play a role in mitigating fire risk to your home.
Shutterstock

If you’re in a bushfire-prone area, landscape your garden by strategically planting trees, making sure their canopies don’t overhang the house. Also ensure shrubs do not grow under trees, as they might feed fire up into the canopy.

And in bad fire conditions, rake your garden to put distance between fuel and your home.




Read more:
Keeping the city cool isn’t just about tree cover – it calls for a commons-based climate response


5. What if my trees fall during storms?

The fear of a whole tree falling over during storms, or shedding large limbs, is understandable. Human injury or death from trees is extremely rare, but tragedies do occur.

Make sure your trees are healthy, and their root systems are not disturbed when utility services such as plumbing, gas supplies and communication cables are installed.

Coping with a warming world

Urban trees are not just ornaments, but vital infrastructure. They make cities liveable and sustainable and they allow citizens to live healthier and longer lives.

For centuries these silent witnesses to urban development have been helping our environment. Urban ecosystems depend on a healthy urban forest for their survival, and so do we.The Conversation

Gregory Moore, Doctor of Botany, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Trees can add $50,000 value to a Sydney house, so you might want to put down that chainsaw



Allowing residents to remove trees within three metres of buildings or ‘ancillary structures’ could dramatically alter the green infrastructure of dense inner Sydney suburbs like Rozelle.
Tom Casey/Shutterstock

Sara Wilkinson, University of Technology Sydney; Agnieszka Zalejska-Jonsson, KTH Royal Institute of Technology, and Sumita Ghosh, University of Technology Sydney

Sydney’s Inner West Council has a new policy that it is reported means “residents will no longer need to seek council approval to prune or remove trees within three metres of an existing home or structure”. Hold on, don’t reach for that chainsaw yet, because research shows good green infrastructure – trees, green roofs and walls – can add value to your home.

Green infrastructure offers significant, economic, social and environmental benefits. Urban greening is particularly important in dense urban areas like Sydney’s Inner West. Among its benefits, green infrastructure:

Some of these benefits accrue to owners/occupiers, whereas others provide wider societal benefits.




Read more:
Higher-density cities need greening to stay healthy and liveable


A 2017 study focusing on three Sydney suburbs found a 10% increase in street tree canopy could increase property values by A$50,000 on average. And the shading effect of trees can reduce energy bills by up to A$800 a year in Sydney. So retaining your green infrastructure – your trees, that is – can deliver direct financial gains.

On a larger scale, a collaborative project with Horticulture Innovation Australia Limited compared carbon and economic benefits from urban trees considering different landuses along sections of two roads in Sydney. Higher benefits were recorded for the Pacific Highway, with 106 trees per hectare and 58.6% residential land use, compared to Parramatta Road, with 70 trees per hectare and 15.8% residential.

For the Pacific Highway section, total carbon storage and the structural value of trees (the cost of replacing a tree with a similar tree) were estimated at A$1.64 million and A$640 million respectively. Trees were also valuable for carbon sequestration and removing air pollution.

Tree species, age, health and density, as well as land use, are key indicators for financial and wider ecosystem benefits. Specifically, urban trees in private yards in residential areas are vital in providing individual landowner and collective government/non-government benefits.

Take away the trees close to these houses in Marrickville, in Sydney’s Inner West, and how much would be left?
Graeme Bartlett/Wikipedia, CC BY-SA

Challenges of growth

As populations grow, cities increase density, with less green infrastructure. The loss of greenery affects the natural environment and both human and non-human well-being.




Read more:
We’re investing heavily in urban greening, so how are our cities doing?


Tree canopy cover across Greater Sydney plummets closer to the city centre.
© State of New South Wales through the Greater Sydney Commission. Data: SPOT5 Woody Extent and Foliage Projective Cover (FPH) 5-10m, 2011, NSW Office of Environment and Heritage

Trees and other green infrastructure reduce some impacts of urban density. However, policies, government incentives and national priorities can produce progress in urban greening or lead to setbacks. In the case of the Inner West Council, for instance, the inability to fund monitoring of changes in tree cover could lead to reductions at the very time when we need more canopy cover.

Key concerns include installation and maintenance costs of green infrastructure (trees, green roofs and walls) in property development, and tree root damage. Knowledge and skills are needed to maintain green infrastructure. As a result, developers often consider other options more feasible.

In the short and long term, multiple performance benefits and economic and environmental values are needed to establish the viability of green infrastructure.




Read more:
Australian cities are lagging behind in greening up their buildings


Learning from Stockholm

Stockholm shares many issues found in Australian cities. Stockholm houses over 20% of Sweden’s inhabitants, is increasing in density and redeveloping land to house a growing population. Aiming to be fossil-free by 2050, Stockholm acknowledges the built environment’s role in limiting climate change and its impacts.

In a research project we intend to use virtual reality (VR) and electroencephalogram (EEG) technology to assess perceptions of green infrastructure and reactions to it in various spaces.

Our project combines VR with EEG hardware, which measures human reactions to stimuli, to learn how people perceive and value green infrastructure in residential development.

Identifying all the value of green infrastructure

The many benefits of green infrastructure are both tangible and non-tangible. Economic benefits include:

  • those that directly benefit owners, occupants or investors – stormwater, increased property values and energy savings
  • other financial impacts – greenhouse gas savings, market-based savings and community benefits.



Read more:
If planners understand it’s cool to green cities, what’s stopping them?


The various approaches to evaluating net value present a challenge in quantifying the value of green infrastructure. The most common – cost-benefit analysis, triple bottom line, life cycle assessment and life cycle costing – are all inadequate for evaluating trade-offs between economic and environmental performance. Conventional cost-benefit analysis is insufficient for investment analysis, as it doesn’t include environmental costs and benefits.

This is salient for green infrastructure, as owners/investors incur substantial direct costs, whereas various shareholders share the value. Perhaps, in recognition of the shared value, a range of subsidies could be adopted to compensate investors. Discounted rates anyone?

Recent efforts to evaluate the business case for green infrastructure include attempts to identify and quantify the creation of economic, environment and community/social value. However, an approach that includes a more comprehensive set of value drivers is needed to do this. This is the gap we aim to fill.

The results of experiments using VR and EEG technology and semi-structured interviews will provide a comprehensive understanding of green infrastructure. This will be correlated with capital and rental values to determine various degrees of willingness to pay.

With this knowledge, property developers in Sweden and Australia will be able to make a more informed and holistic business case for increasing green infrastructure for more liveable, healthy cities.

Maybe we can then persuade more people, including those in the Inner West, to hang onto their trees and leave the chainsaws in the garage.The Conversation

Sara Wilkinson, Professor, School of the Built Environment, University of Technology Sydney; Agnieszka Zalejska-Jonsson, Researcher, Division of Building and Real Estate Economics, KTH Royal Institute of Technology, and Sumita Ghosh, Associate Professor in Planning, School of the Built Environment, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.