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.
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.
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.
It’s tempting to think that our forests would be fine if we could simply stop trees being felled or burnt. But forests – particularly tropical ones – are more than just trees. They’re also the animals that skulk and swoop among them.
Worryingly, these furry and feathered companions are rapidly disappearing – and our new research indicates that this will have grave repercussions for the role forests play in combating climate breakdown.
Healthy tropical forests swarm with life. Beyond myriad invertebrates there are seed-eating rodents, a range of leaf eaters, birds of all kinds, and often primates. However, many forests have already lost most of their largest animals, mainly as a result of hunting to supply a growing bushmeat trade.
Hunting isn’t the only reason. Thanks to deforestation for farmland and logging, many forests today are highly fragmented. The small, unconnected patches that remain aren’t big enough to support populations of the largest species, which tend to need more space.
The disappearance of animals from otherwise intact habitats is known as defaunation, and it is leading to a growing number of empty forests not just in tropical countries, but around the world. The UK has already lost most of its largest species (think lynx, wolf, and wisent), while woodland bird numbers have declined by a quarter since 1970.
The impacts of this defaunation have attracted the attention of the world’s conservation scientists, but studies to date have usually been carried out at single locations. Consequently, we lack a worldwide picture that takes into account different types of forest and the diversity of animals that are disappearing.
To fill this gap, we worked with William Baldwin-Cantello, chief adviser on forests at the World Wide Fund for Nature UK, to gather together all the existing research and perform a meta-analysis – an analysis of analyses – on the available data.
Forest flora need flourishing fauna
Our findings reveal a worrying trend. The loss of animals compromises the ability of forests to reproduce. This effect is particularly severe when primates and birds disappear, because of the key role they play in seed dispersal. Trees make fruit to entice animals to transport their seeds, because they are more likely to germinate and grow successfully if they fall further from their parent tree. So when fruit-eating animals disappear, fewer seeds are dispersed and the trees struggle to reproduce.
This animal absence will slowly change how forests look. Most tropical forests today are dominated by trees whose seeds are dispersed by animals. Over time, they are likely to be gradually replaced by trees that use the wind to reproduce. Naturally, these usually have small seeds, and therefore produce smaller trees that store less carbon for the same area of forest. As a result, forests will store less and less carbon, even if we completely halt deforestation.
This is particularly concerning because roughly 20% of the carbon dioxide we emit is absorbed by the world’s vegetation and soils, and half of this is due to tropical forests alone.
Rethinking forest health
Conserving forests is essential for the fight against climate breakdown – and, we do have a global tool at our disposal to help. Known as Reducing Emissions from Deforestation and forest Degradation, or REDD+ for short, it allows wealthy countries with large carbon footprints to pay poorer, tropical countries to protect their forests.
Of course, REDD+ is only an effective tool if the forests countries pay to protect continue to store the same amount of carbon. We usually monitor this by taking satellite images of the quantity of forest canopy remaining. But what satellite imagery can’t do is measure aspects of forest quality beneath the canopy.
Our research strongly suggests that one aspect of forest quality – defaunation – is a vital early warning sign of future losses in the carbon storing capacity of forests. In light of this, policies for managing forest carbon around the world may need a rethink.
We need to pay more attention to what’s going on beneath global forest canopies through research on the ground, though this will be difficult in remote areas. More importantly, we must make sure we’re doing all we can to conserve the full complement of animal species that live in our forests. For example, we need to heavily invest in conservation actions that help communities accustomed to hunting bushmeat to meet their dietary protein needs without harming wildlife. We must also enforce existing rules better, such as those that outlaw hunting within parks and reserves.
Preventing defaunation in forests won’t be easy. But given what we know about the critical role forest animals play, doing so will be essential if we hope to retain diverse and carbon-rich forests in the tropics and around the world. If the beauty and wonder of the forest’s animals wasn’t enough reason to protect them, we now have another: by conserving wildlife, we will be helping to save ourselves from the catastrophic effects of climate breakdown.
Charlie Gardner, Lecturer in Conservation Biology, University of Kent; Jake Bicknell, Lecturer in Conservation Biology, University of Kent; Matthew Struebig, Senior Lecturer in Biological Conservation, University of Kent, and Zoe Davies, Professor of Biodiversity Conservation, University of Kent
Reducing emissions from deforestation and farming is an urgent global priority if we want to control climate change. However, like many climate change problems, the solution is complicated. Cutting down forests to plant edible crops feeds some of the world’s hungriest people.
More than 820 million people suffer from hunger, and about 2 billion people face moderate food insecurity – meaning they do not always know when their next meal will come.
But villagers in the Himalayas are turning to a traditional practice that can slow land clearing and feed people: growing and collecting food from the forests.
Food in the forest
My research in the Himalayan region, where high population density means farmland is very scarce, investigated how people used their forests as a food source.
An “edible forest” is one in which people have planted trees and crops that can produce food in the forest, as well as harvesting what naturally grows. In fact, this is a traditional practice in the Himalayan region. A farmer I interviewed in Siding village, at the base of Mardi Himal – one of the peaks in Annapurna Himalayan range – told me:
I go to [the] forest when food is scarce at home. I collect vegetables, fruits, nuts, medicinal herbs, spices, roots and tubers. Sometimes I also collect wild honey, bamboo shoots and mushroom, which is consumed at home and also sold in the market. Occasionally, we also get wild meat.
Traditionally, these villagers see forest and farms as an extension of each other rather than distinct categories, and manage them so they support each other.
Generally, people plant trees useful for households – for their wood, for example, or fruit – in the forest close to the villages, and preserve those grown naturally.
The community itself protects the forest, in the past even pooling grains and cash to hire a guard if needed.
This forest food is supplementary, becoming more important in scarce times and as a buffer during famine. Taking wood for fuel or timber is strictly regulated, but there are no restrictions on gathering food, to the great benefit of the poorest.
Collecting food is mainly the work of women, who gather a few things whenever they go into the forest for firewood or animal fodder. They have a great deal of knowledge about edible plants. Men take part by hunting for honey and wild animals. Children, too, go to the forest in their free time to gather berries and tubers.
Sometimes villagers collect these foods to sell in nearby markets as a seasonal source of cash.
The centralised forest management and curtailment of traditional rights of the communities that came with modern forest bureaucracy in the Himalayan region distanced people from the forest. This also led to rapid deforestation between the mid-1960s to 1980s.
This trend was reversed in the early 1990s, when community rights came to the forefront and communally managed forestry gained a strong foothold. This helped reduce poverty. Yet it is still hard for locals to grow food in the forests as they once did. One farmer told me,
We do not destroy forest when collecting these things, but conservation regulation is making this collection difficult.
We need power to move from centralised governments to local stewardship and local knowledge. Government oversight would still be required to protect the local interests, but any new mechanism needs to be developed in consultation with local communities. Research institutions could play a role in finding better ways to meet the interest of local communities when they manage their forest.
A new category of land use
Edible forests are a departure from standard schemes to reduce emissions from deforestation and land degradation, in which developed countries pay less developed countries to preserve or replant their forests.
If people are actively planting and harvesting in a forest, it may not qualify as protected or conserved land. Conversely, if a local community depends on their forest for food, they may hesitate to register for a formal scheme, for fear they will lose a valuable resource.
If reforestation schemes can be expanded to take into account planting that doesn’t compromise tree coverage, we can encourage rapid growth of edible forests and speed up our response to climate change. It will help meet goals like food security, mitigation and adaptation to climate change, and reducing desertification and land degradation that the United Nations’ Intergovernmental Panel on Climate Change has recommended for sustainable land management in the light of climate change.
Climate change and food insecurity are the main drivers of migration away from rural areas in developing countries, which brings its own challenges for sustainable land management.
Wages sent home by those who move away is a huge part of food security and reducing poverty for many people. In 2018 about US$530 billion was transferred to low- and middle-income countries between family members, compared with US$162 billion in development aid.
This flow of money means families with marginal land – like farmland on hill slopes in Nepal’s case – can afford to slowly convert it to plantations or forests. Migration and remittances – which contribute some 28% of Nepal’s gross domestic product – helps increase forest coverage, especially in marginal lands vulnerable to erosion and landslides.
There is an opportunity to increase planting in these lands, which have been abandoned for farming. If official reforestation policies can acknowledge and support edible forests, we could see the Himalayan region lead the pack on a new way of thinking about forests and food.
Tomorrow a special report on how land use affects climate change will be released by the Intergovernmental Panel on Climate Change.
Land degradation, deforestation, and the expansion of our deserts, along with agriculture and the other ways people shape land, are all major contributors to global climate change.
Conversely, trees remove carbon dioxide and store it safely in their trunks, roots and branches. Research published in July estimated that planting a trillion trees could be a powerful tool against climate change.
However, planting new trees as a climate action pales in comparison to protecting existing forests. Restoring degraded forests and expanding them by 350 million hectares will store a comparable amount of carbon as 900 million hectares of new trees.
Natural climate solutions
Using ecological mechanisms for reducing and storing carbon is a growing field of study. Broadly known as “natural climate solutions”, carbon can be stored in wetlands, grasslands, natural forests and agriculture.
This is called “sequestration”, and the more diverse and longer-lived the ecosystem, the more it helps mitigate the effect of climate change.
Research has estimated these natural carbon sinks can provide 37% of the CO₂ reduction needed to keep the rise in global temperatures below 2℃.
But this research can be wrongly interpreted to imply that the priority is to plant young trees. In fact, the major climate solution is the protection and recovery of carbon-rich and long-lived ecosystems, especially natural forests.
With the imminent release of the new IPCC report, now is a good time to prioritise the protection and recovery of existing ecosystems over planting trees.
Forest ecosystems (including the soil) store more carbon than the atmosphere. Their loss would trigger emissions that would exceed the remaining carbon budget for limiting global warming to less than the 2℃ above pre-industrial levels, let alone 1.5℃, threshold.
Natural forest systems, with their rich and complex biodiversity, the product of ecological and evolutionary processes, are stable, resilient, far better at adapting to changing conditions and store more carbon than young, degraded or plantation forests.
Protect existing trees
Forest degradation is caused by selective logging, temporary clearing, and other human land use. In some areas, emissions from degradation can exceed those of deforestation. Once damaged, natural ecosystems are more vulnerable to drought, fires and climate change.
Recently published research found helping natural forest regrow can have a globally significant effect on carbon dioxide levels. This approach – called proforestation – is a more effective, immediate and low-cost method for removing and storing atmospheric carbon in the long-term than tree planting. And it can be used across many different kinds of forests around the world.
Avoiding further loss and degradation of primary forests and intact forest landscapes, and allowing degraded forests to naturally regrow, would reduce global carbon emissions annually by about 1 gigatonnes (Gt), and reduce another 2-4 Gt of carbon emissions just through natural regrowth.
Research has predicted that protecting primary forests while allowing degraded forests to recover, along with limited expansion of natural forests, would remove 153 billion tonnes of carbon from the atmosphere between now and 2150.
By the numbers
Tree planting carries more limited climate benefits. The recent Science paper focused on mapping and quantifying increases in tree canopy cover in areas that naturally support trees. However, increasing canopy cover through natural forest regeneration can sequester 40 times more carbon over the course of the century than establishing new plantations.
We need to think very carefully about how we use land that has already been cleared: land is a finite resource, and we need to grow food and resources for a global population set to hit 9 billion by 2050.
Any expansion of natural forest area is best achieved through allowing degraded forests to naturally recover. Allowing trees to regenerate naturally, using nearby remnants of primary forests and seed banks in the soil of recently cleared forests, is more likely to result in a resilient and diverse forest than planting massive numbers of seedlings.
Instead of planting entirely new areas, we should prioritise reconnecting forested areas and restoring the edges of forest, to protect their mature core. This means our carbon-storing forests will be more resilient and longer-lasting.
For forests to effectively help avert dangerous climate change, global and regional policies are needed to protect, restore and regenerate natural forests, alongside a carbon-zero energy economy.
A version of this article was co-published with Pursuit.
Victoria has some of the most carbon-dense native forests in the world. Advocates for logging these forests often argue that wood products in buildings and furniture become long-term storage for carbon.
However, these claims are misleading. Most native trees cut down in Victoria become woodchips, pulp and pallets, which have short lifespans before going to landfill. In landfill, the wood breaks down and releases carbon back into the atmosphere.
On the other hand, our evolving carbon market means Australia’s native forests are extremely valuable as long-term carbon stores. It’s time to recognise logging for short-lived wood products is a poor use of native forests.
The problem with logging native forests
These forests can store up to 1,140 tonnes of carbon per hectare for centuries.
But around 1.82 million hectares of Victorian native forests are allocated to the government’s logging business, VicForests.
VicForests claims logging is the only market for the large area of native forest allocated to it. In other words, its forests are exclusively valued as timber asset, in the same way a wheat crop would be exclusively valued for wheat grain production.
In Victorian native forests, industrial scale clearfell logging removes around 40% of the forest biomass for logs fit for sale.
The remaining 60% is debris, which is either burned off or decomposes – becoming a major source of greenhouse gas emission.
Myth one: storing carbon in wood products
The first myth we want to address is logging native forests is beneficial because the carbon is stored in wood products. This argument depends on the proportion of forest biomass ending up in wood products, and how long they last before ending up in landfill.
On average, logs suitable to be sawn into timber make up only an average 35% of total logs cut from Victorian native forests.
Of this 35%, sawmills convert less than 40% into sawn timber for building and furniture. Offcuts are woodchipped and pulped for paper manufacturing, along with sawdust sold to chicken broiler sheds for bedding.
Sawn timber equates to 14% of log volume cut from the forest. The remaining 84% of logs cut are used in short-lived and often disposable products like copy paper and pallets.
The maximum lifespan of a timber pallet is seven years. At the end of their service, timber pallets are sent to landfill, chipped for particleboard, reused for landscape mulch or burnt for energy generation.
Longer-lived wood products, such as the small proportion of native timber used in building and furniture, have a lifespan of around 90 years. These wood products are used to justify logging native forests.
But at the end of their service life, the majority of these wood products also end up in landfill.
In fact, for the 500,000 tonnes of wood waste generated annually from building, demolition and other related commercial processes in Victoria, over two thirds end up in landfill, according to a Sustainability Victoria report.
Myth two: the need to log South East Asian rainforests
A second myth is using logs from Victorian native forests will prevent logging and degradation of rainforests across South East Asia, particularly for paper production.
This is patently absurd. The wood from the Victorian plantation sector – essentially timber farms, rather than trees growing “wild” in native forests – could replace native forest logs used for paper manufacturing in Victoria several times over.
In fact, in 2016-17 89% of logs used to make wood pulp (pulplogs) for paper production in Victoria came from plantation trees, with the majority of hardwood logs exported.
And Australia is a net exporter by volume of lower-value unprocessed logs and woodchips.
Processing pulplogs from well managed plantations in Victoria instead of exporting them would give a much needed jobs boost for local economies.
With most of these plantations established on previously cleared farmland, they offer one of the most robust ways for the land use sector to off-set greenhouse gas emissions.
The time is right for Australian governments to develop a long-term carbon storage plan that includes intact native forests.
Logging results in at least 94% of a forest’s stored carbon ending up in the atmosphere. A maximum of 6% of its carbon remains in sawn timber, for up to 90 years (but typically much shorter). This is patently counterproductive from a carbon-storage point of view.
State-owned forest management companies, such as VicForests, can transition away from the timber business and begin managing forests for carbon storage. Such a concept is not new – the federal government has already approved a way to value the carbon storage of plantations.
The same must now be developed to better protect native forests and the large amounts of carbon they can store.
Chris Taylor, Research Fellow, Fenner School of Environment and Society, Australian National University and David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University
The 2009 Black Saturday fires burned 437,000 hectares of Victoria, including tens of thousands of hectares of Mountain Ash forest.
As we approach the tenth anniversary of these fires, we are reminded of their legacy by the thousands of tall Mountain ash “skeletons” still standing across the landscape. Most of them are scattered amid a mosaic of regenerating forest, including areas regrowing after logging.
But while we can track the obvious visible destruction of fire and logging, we know very little about what’s happening beneath the ground.
In a new study published in Nature Geoscience, we investigated how forest soils were impacted by fire and logging. To our surprise, we found it can take up to 80 years for soils to recover.
Decades of damage
Soils have crucial roles in forests. They are the basis for almost all terrestrial life and influence plant growth and survival, communities of beneficial fungi and bacteria, and cycles of key nutrients (including storing massive amounts of carbon).
To test the influence of severe and intensive disturbances like fire and logging, we compared key soil measures (such as the nutrients that plants need for growth) in forests with different histories. This included old forests that have been undisturbed since the 1850s, forests burned by major fires in 1939, 1983 and 2009, forests that were clearfell-logged in the 1980s or 2009-10, or salvage-logged in 2009-10 after being burned in the Black Saturday fires.
We found major impacts on forest soils, with pronounced reductions of key soil nutrients like available phosphorus and nitrate.
A shock finding was how long these impacts lasted: at least 80 years after fire, and at least 30 years after clearfell logging (which removes all vegetation in an area using heavy machinery).
However, the effects of disturbance on soils may persist for much longer than 80 years. During a fire, soil temperatures can exceed 500℃, which can result in soil nutrient loss and long-lasting structural changes to the soil.
We found the frequency of fires was also a key factor. For instance, forests that have burned twice since 1850 had significantly lower measures of organic carbon, available phosphorus, sulfur and nitrate, relative to forests that had been burned once.
Sites subject to clearfell logging also had significantly lower levels of organic carbon, nitrate and available phosphorus, relative to unlogged areas. Clearfell logging involves removing all commercially valuable trees from a site – most of which are used to make paper. The debris remaining after logging (tree heads, lateral branches, understorey trees) is then burned and the cut site is aerially sewn with Mountain Ash seed to start the process of regeneration.
Logging compounds the damage
The impacts of logging on forest soils differs from that of fire because of the high-intensity combination of clearing the forest with machinery and post-logging “slash” burning of debris left on the ground. This can expose the forest floor, compact the soil, deplete soil nutrients, and release large amounts of carbon dioxide into the atmosphere.
Predicted future increases in the number, frequency, intensity and extent of fires in Mountain Ash forests, coupled with ongoing logging, will likely result in further declines in soil nutrients in the long term. These kinds of effects on soils matter in Mountain Ash forests because 98.8% of the forest have already been burned or logged and are 80 years old or younger.
To maintain the vital roles that soils play in ecosystems, such as carbon storage and supporting plant growth, land managers must consider the repercussions of current and future disturbances on forest soils when planning how to use or protect land. Indeed, a critical part of long-term sustainable forest management must be to create more undisturbed areas, to conserve soil conditions.
Specifically, clearfell logging should be limited wherever possible, especially in areas that have been subject to previous fire and logging.
Ecologically vital, large old trees in Mountain Ash forests may take over a century to recover from fire or logging. Our new findings indicate that forest soils may take a similar amount of time to recover.
Giant eucalypts play an irreplaceable part in many of Australia’s ecosystems. These towering elders develop hollows, which make them nature’s high-rises, housing everything from endangered squirrel-gliders to lace monitors. Over 300 species of vertebrates in Australia depend on hollows in large old trees.
These “skyscraper trees” can take more than 190 years to grow big enough to play this nesting and denning role, yet developers are cutting them down at an astounding speed. In other places, such as Victoria’s Central Highlands Mountain Ash forests, the history of logging and fire mean that less than 1.2% of the original old-growth forest remains (that supports the highest density of large old hollow trees). And it’s not much better in other parts of our country.
David Lindenmayer explains how these trees form, the role they play – and how very hard they are to replace.
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The 1800s was a time of colonial expansion across the globe. During this time the great and the good of Britain filled their grand gardens with exotic novelties from all corners of the world.
Amongst these were many species of Asian rhododendron, a diverse and colourful genus of shrubs and small trees, whose high altitude origins made them well suited to the cool temperate climate of England and Scotland.
Throughout the 19th century, commercial collectors and field naturalists discovered rhododendron species in southern China, the Himalayas, on the high peaks of Borneo, Java and especially New Guinea.
These finds lead Victoria’s government botanist of the time, Ferdinand von Mueller, to speculate about finding rhododendrons on the high tropical mountains on the northeast coast of Queensland. He wrote:
When in 1855 [I] saw… the bold outlines of Mount Bellenden-Ker, the highest mount of tropical Australia, towering to 5,000 feet, [I] was led to think, that the upper region might prove to be the home of species of Rhododendron… forms of plants characteristic of cool Malayan sylvan regions.
But the lofty heights of Mt Bellenden Ker were unknown to European Australians. It would be another 32 years before an expedition led by naturalist W.A. Sayer reached its central peak.
Sayer’s expedition, accompanied by two indigenous assistants, reached the mountain’s high ridge after several mishap-filled attempts. It was here they confirmed Mueller’s suspicions. Sayer’s account of its discovery is interesting:
The top of the range is razor-backed, and on travelling along the range beyond the spur by which we ascended, I could not see the sides, they being, if anything, hanging over. We tumbled rocks over, but could not hear them fall.
It was here that I observed the Rhodendron Lochae growing, and asked the Kanaka to get it; but he remarked, ‘S’pose I fall, I no see daylight any more; I go bung altogether;’ so I had to get it myself.
Mueller received the hard-won specimens and named the species Rhododendron lochae (later corrected to R. lochiae) after Lady Loch, the wife of the Victorian Governor.
Since then, rhododendron plants have been found on nine peaks and tablelands in the Wet Tropics region of north Queensland. Populations on peaks south of Cairns are called Rhododendron lochiae, whilst plants growing on mountains to the north of Cairns are considered by some to be a distinct species: Rhododendron viriosum.
Both northern and southern plants are straggly shrubs that grow in thin soils or rock cracks, sometimes in open cloud-swept boulder fields, sometimes in deep shade along creeks, or rarely as epiphytes on moss-covered trees. They produce bunches of gloriously red, bell-shaped flowers, followed by dry brown capsules filled with small winged seeds that are apparently spread by wind.
They grow slowly but with relative ease from cuttings, and are often cultivated in gardens and nurseries in temperate Australia. However, over time knowledge of the precise origin of these cultivated plants has been lost, which means they are unsuitable for detailed scientific investigations.
All of Australia’s rhododendron populations are located at altitudes above 950m in National Parks within the Wet Tropics World Heritage Area. Most are difficult to access, requiring arduous climbs on rough foot tracks through leech-infested rainforest. And yet, although isolated in protected areas, they are threatened by human activities: loss of habitat due to climate change.
Recent climate modelling research published by scientists from James Cook University and the CSIRO predicts significant reductions in suitable habitat for a suite of mountaintop flora species in Australia’s tropics (our rhododendrons were not included in the analysis, but occupy the habitats assessed).
The habitat of many of these species is predicted to disappear altogether well before the end of the century.
Using rhododendron as a model, the Australian Tropical Herbarium at James Cook University is working to save these threatened species through “ex situ” conservation – cultivation in temperate zone public gardens, well outside their natural range. Because the threatening process – climate change – is not readily mitigated, establishing precautionary ex situ collections is the only viable conservation intervention for these plants.
With funding from the Australian Rhododendron Society Victoria Branch and the Ian Potter Foundation, and the support of traditional owners, Queensland National Parks and the Wet Tropics Management Authority, we have mounted expeditions to collect samples from most of the known populations.
These expeditions have put expert naturalists into rarely visited and challenging environments. Beyond gathering rhododendron samples, new moss species have been discovered and are being named, a fern previously thought extinct was rediscovered, and beautiful little epiphytic orchids have been found on a mountain where they’d not previously been recorded. Golden bower-bird bowers have been mapped in remote mountain rainforests, and a likely new species of snail has been discovered.
Australia now has a well-documented and genetically diverse collection of native rhododendron plants thriving in the Dandenong Ranges Botanic Garden.
We plan to expand this work, ensuring the preservation and public display of rhododendron and many other mountain species threatened by climate change.