Destroying vegetation along fences and roads could worsen our extinction crisis — yet the NSW government just allowed it

Euan Ritchie, Deakin University; Ben Moore, Western Sydney University; Jen Martin, The University of Melbourne; Mark Hall, Western Sydney University; Megan C Evans, UNSW, and Ross Crates, Australian National UniversityWhat do koalas, barking owls, greater gliders, southern rainbow skinks, native bees, and regent honeyeaters all have in common? Like many native species, they can all be found in vegetation along fences and roadsides outside formal conservation areas.

They may be relatively small, but these patches and strips conserve critical remnant habitat and have disproportionate conservation value worldwide. They represent the last vestiges of once-expansive tracts of woodland and forests, long lost to the chainsaw or plough.

And yet, the NSW government last week made it legal for rural landholders to clear vegetation on their properties, up to 25 metres from their property boundaries, without approval. This radical measure is proposed to protect people and properties from fires, despite the lack of such an explicit recommendation from federal and state-based inquiries into the devastating 2019-20 bushfires.

This is poor environmental policy that lacks apparent consideration or justification of its potentially substantial ecological costs. It also gravely undermines the NSW government’s recent announcement of a plan for “zero extinction” within the state’s national parks, as the success of protected reserves for conservation is greatly enhanced by connection with surrounding “off-reserve” habitat.

Small breaks in habitat can have big impacts

A 25m firebreak might sound innocuous, but when multiplied by the length of property boundaries in NSW, the scale of potential clearing and impacts is alarming, and could run into the hundreds of thousands of kilometres.

Some plants, animals and fungi live in these strips of vegetation permanently. Others use them to travel between larger habitat patches. And for migratory species, the vegetation provides crucial refuelling stops on long distance journeys.

For example, the roadside area in Victoria’s Strathbogie Ranges shown below is home to nine species of tree-dwelling native mammals: two species of brushtail possums, three species of gliders (including threatened greater gliders), common ringtail possums, koalas, brush-tailed phascogales, and agile antenchinus (small marsupials).

Roadside and fenceline vegetation is often the only substantial remnant vegetation remaining in agricultural landscapes. This section, in northeast Victoria’s Strathbogie Ranges, running north to south from the intersection, is home to high arboreal mammal diversity, including the threatened greater glider.
Google Earth

Many of these species depend on tree hollows that can take a hundred years to form. If destroyed, they are effectively irreplaceable.

Creating breaks in largely continuous vegetation, or further fragmenting already disjointed vegetation, will not only directly destroy habitat, but can severely lower the quality of adjoining habitat.

This is because firebreaks of 25m (or 50m where neighbouring landholders both clear) could prevent the movement and dispersal of many plant and animal species, including critical pollinators such as native bees.

An entire suite of woodland birds, including the critically endangered regent honeyeater, are threatened because they depend on thin strips of vegetation communities that often occur inside fence-lines on private land.

Ecologically-sensitive fence replacement in regent honeyeater breeding habitat.
Ross Crates

For instance, scientific monitoring has shown five pairs of regent honeyeaters (50% of all birds located so far this season) are nesting or foraging within 25m of a single fence-line in the upper Hunter Valley. This highlights just how big an impact the loss of one small, private location could have on a species already on the brink of extinction.

But it’s not just regent honeyeaters. The management plan for the vulnerable glossy black cockatoo makes specific recommendation that vegetation corridors be maintained, as they’re essential for the cockatoos to travel between suitable large patches.

Native bee conservation also relies on the protection of remnant habitat adjoining fields. Continued removal of habitat on private land will hinder chances of conserving these species.

Glossy black cockatoos rely on remnant patches of vegetation.
Shutterstock

Disastrous clearing laws

The new clearing code does have some regulations in place, albeit meagre. For example, on the Rural Fire Service website, it says the code allows “clearing only in identified areas, such as areas which are zoned as Rural, and which are considered bush fire prone”. And according to the RFS boundary clearing tool landowners aren’t allowed to clear vegetation near watercourses (riparian vegetation).

Even before introducing this new code, NSW’s clearing laws were an environmental disaster. In 2019, The NSW Audit Office found:

clearing of native vegetation on rural land is not effectively regulated [and] action is rarely taken against landholders who unlawfully clear native vegetation.

The data back this up. In 2019, over 54,500 hectares were cleared in NSW. Of this, 74% was “unexplained”, which means the clearing was either lawful (but didn’t require state government approval), unlawful or not fully compliant with approvals.

Landholders need to show they’ve complied with clearing laws only after they’ve already cleared the land. But this is too late for wildlife, including plant species, many of which are threatened.

Landholders follow self-assessable codes, but problems with these policies have been identified time and time again — they cumulatively allow a huge amount of clearing, and compliance and enforcement are ineffective.

Vegetation along roadsides and close to fences can be critical habitat for greater gliders.

We also know, thanks to various case studies, the policy of “offsetting” environmental damage by improving biodiversity elsewhere doesn’t work.

So, could the federal environment and biodiversity protection law step in if habitat clearing gets out of hand? Probably not. The problem is these 25m strips are unlikely to be referred in the first place, or be considered a “significant impact” to trigger the federal law.

The code should be amended

Nobody disputes the need to keep people and their assets safe against the risks of fire. The code should be amended to ensure clearing is only permitted where a genuinely clear and measurable fire risk reduction is demonstrated.

Many native bees, like this blue-banded bee (*Amegilla* sp.), will use the nesting and foraging resources available in remnant vegetation patches.
Michael Duncan

Granting permission to clear considerable amounts of native vegetation, hundreds if not thousands of metres away from homes and key infrastructure in large properties is hard to reconcile, and it seems that no attempt has been made to properly justify this legislation.

We should expect that a comprehensive assessment of the likely impacts of a significant change like this would inform public debate prior to decisions being made. But to our knowledge, no one has analysed, or at least revealed, how much land this rule change will affect, nor exactly what vegetation types and wildlife will likely be most affected.

A potentially devastating environmental precedent is being set, if other regions of Australia were to follow suit. The environment and Australians deserve better.

Clarification: some text has been added to clarify the land cleared is on the landowner’s property, not outside their property boundary

Euan Ritchie, Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University; Ben Moore, Senior Lecturer in Ecology, Hawkesbury Institute for the Environment, Western Sydney University; Jen Martin, Leader, Science Communication Teaching Program, The University of Melbourne; Mark Hall, Postdoctoral research fellow, Hawkesbury Institute for the Environment, Western Sydney University; Megan C Evans, Lecturer and ARC DECRA Fellow, UNSW, and Ross Crates, Postdoctoral fellow, Australian National University

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

Climate change is testing the resilience of native plants to fire, from ash forests to gymea lilies

One year following the 2019/20 fires, this forest has been slow to recover.
Rachael Nolan, CC BY-NC-ND

Rachael Helene Nolan, Western Sydney University; Andrea Leigh, University of Technology Sydney; Mark Ooi, UNSW; Ross Bradstock, University of Wollongong; Tim Curran, Lincoln University, New Zealand; Tom Fairman, The University of Melbourne, and Víctor Resco de Dios, Universitat de LleidaGreen shoots emerging from black tree trunks is an iconic image in the days following bushfires, thanks to the remarkable ability of many native plants to survive even the most intense flames.

But in recent years, the length, frequency and intensity of Australian bushfire seasons have increased, and will worsen further under climate change. Droughts and heatwaves are also projected to increase, and climate change may also affect the incidence of pest insect outbreaks, although this is difficult to predict.

How will our ecosystems cope with this combination of threats? In our recently published paper, we looked to answer this exact question — and the news isn’t good.

We found while many plants are really good at withstanding certain types of fire, the combination of drought, heatwaves and pest insects may push many fire-adapted plants to the brink in the future. The devastating Black Summer fires gave us a taste of this future.

Examples of fire-adapted plants: prolific flowering of pink flannel flowers (upper left), new foliage resprouting on geebung (upper right), seed release from a banksia cone (lower left), and an old man banksia seedling (lower right).
Rachael Nolan

What happens when fires become more frequent?

Ash forests are one of the most iconic in Australia, home to some of the tallest flowering plants on Earth. When severe fire occurs in these forests, the mature trees are killed and the forest regenerates entirely from the seed that falls from the dead canopy.

These regrowing trees, however, do not produce seed reliably until they’re 15 years old. This means if fire occurs again during this period, the trees will not regenerate, and the ash forest will collapse.

This would have serious consequences for the carbon stored in these trees, and the habitat these forests provide for animals.

Southeast Australia has experienced multiple fires since 2003, which means there’s a large area of regrowing ash forests across the landscape, especially in Victoria.

The Black Summer bushfires burned parts of these young forests, and nearly 10,000 football fields of ash forest was at risk of collapse. Thankfully, approximately half of this area was recovered through an artificial seeding program.

Ash to ashes: On the left, unburned ash forest in the Central Highlands of Victoria; on the right, ash forest which has been burned by a number of high severity bushfires in Alpine National Park. Without intervention, this area will no longer be dominated by ash and will transition to shrub or grassland.
T Fairman

What happens when fire seasons get longer?

Longer fire seasons means there’s a greater chance species will burn at a time of year that’s outside the historical norm. This can have devastating consequences for plant populations.

For example, out-of-season fires, such as in winter, can delay maturation of the Woronora beard-heath compared to summer fires, because of their seasonal requirements for releasing and germinating seeds. This means the species needs longer fire-free intervals when fires occur out of season.

The iconic gymea lily, a post-fire flowering species, is another plant under similar threat. New research showed when fires occur outside summer, the gymea lily didn’t flower as much and changed its seed chemistry.

While this resprouting species might persist in the short term, consistent out-of-season fires could have long-term impacts by reducing its reproduction and, therefore, population size.

Out-of-season fires could have long-term impacts on gymea lilies.
Shutterstock

When drought and heatwaves get more severe

In the lead up to the Black Summer fires, eastern Australia experienced the hottest and driest year on record. The drought and associated heatwaves triggered widespread canopy die-off.

Extremes of drought and heat can directly kill plants. And this increase in dead vegetation may increase the intensity of fires.

Another problem is that by coping with drought and heat stress, plants may deplete their stored energy reserves, which are vital for resprouting new leaves following fire. Depletion of energy reserves may result in a phenomenon called “resprouting exhaustion syndrome”, where fire-adapted plants no longer have the reserves to regenerate new leaves after fire.

Therefore, fire can deliver the final blow to resprouting plants already suffering from drought and heat stress.

Drought stressed eucalypt forest in 2019.
Rachael Nolan

Drought and heatwaves could also be a big problem for seeds. Many species rely on fire-triggered seed germination to survive following fire, such as many species of wattles, banksias and some eucalypts.

But drought and heat stress may reduce the number of seeds that get released, because they limit flowering and seed development in the lead up to bushfires, or trigger plants to release seeds prematurely.

For example, in Australian fire-prone ecosystems, temperatures between 40℃ and 100℃ are required to break the dormancy of seeds stored in soil and trigger germination. But during heatwaves, soil temperatures can be high enough to break these temperature thresholds. This means seeds could be released before the fire, and they won’t be available to germinate after the fire hits.

Heatwaves can also reduce the quality of seeds by deforming their DNA. This could reduce the success of seed germination after fire.

Burnt banksia — Many native plants, such as banksia, rely on fire to germinate their seeds.
Shutterstock

What about insects? The growth of new foliage following fire or drought is tasty to insects. If pest insect outbreaks occur after fire, they may remove all the leaves of recovering plants. This additional stress may push plants over their limit, resulting in their death.

This phenomenon has more typically been obverved in eucalypts following drought, where repeated defoliation (leaf loss) by pest insects triggered dieback in recovering trees.

When threats pile up

We expect many vegetation communities will remain resilient in the short-term, including most eucalpyt species.

But even in these resilient forests, we expect to see some changes in the types of species present in certain areas and changes to the structure of vegetation (such as the size of trees).

Resprouting eucalypts, one year on following the 2019-2020 bushfires.
Rachael Nolan

As climate change progresses, many fire-prone ecosystems will be pushed beyond their historical limits. Our new research is only the beginning — how plants will respond is still highly uncertain, and more research is needed to untangle the interacting effects of fire, drought, heatwaves and pest insects.

We need to rapidly reduce carbon emissions before testing the limits of our ecosystems to recover from fire.

Rachael Helene Nolan, Postdoctoral research fellow, Western Sydney University; Andrea Leigh, Associate Professor, Faculty of Science, University of Technology Sydney; Mark Ooi, Senior Research Fellow, UNSW; Ross Bradstock, Emeritus professor, University of Wollongong; Tim Curran, Associate Professor of Ecology, Lincoln University, New Zealand; Tom Fairman, Future Fire Risk Analyst, The University of Melbourne, and Víctor Resco de Dios, Profesor de Incendios y Cambio Global en PVCF-Agrotecnio, Universitat de Lleida

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

The daily dance of flowers tracking the sun is more fascinating than most of us realise

Gregory Moore, The University of MelbourneWhen I was a child, I was intrigued by the Queensland box (Lophostemon confertus) growing in our backyard. I noticed its leaves hung vertical after lunch in summer, and were more or less horizontal by the next morning.

This an example of heliotropism, which literally means moving in relation to the sun. We can see it most clearly as spring arrives and various species burst into flower — you might even get the feeling that some flowers are watching you as they move.

Many of us probably first got to know of heliotropism at home, kindergarten or primary school by watching the enormous yellow and black flowering heads of aptly name sunflowers, which moved as they grew.

These flowers track the course of the sun spectacularly on warm and sunny, spring or summer days. Sometimes they move through an arc of almost 180⁰ from morning to evening.

So with the return of sunny days and flowers in full bloom this season, let’s look at why this phenomenon is so interesting.

The mechanics of tracking the sun

A number flowering species display heliotropism, including alpine buttercups, arctic poppies, alfalfa, soybean and many of the daisy-type species. So why do they do it?

This is *Heliotropium arborescens*, named for its heliotropism. They were very popular in gardens a century or more ago, but have fallen from favour as they can be poisonous and weedy.
Shutterstock

Flowers are really in the advertising game and will do anything they can to attract a suitable pollinator, as effectively and as efficiently as they can. There are several possible reasons why tracking the sun might have evolved to achieve more successful pollination.

By tracking the sun, flowers absorb more solar radiation and so remain warmer. The warmer temperature suits or even rewards insect pollinators that are more active when they have a higher body temperature.

Optimum flower warmth may also boost pollen development and germination, leading to a higher fertilisation rate and more seeds.

So, the flowers are clearly moving. But how?

For many heliotropic flowering species, there’s a special layer of cells called the pulvinus just under the flower heads. These cells pump water across their cell membranes in a controlled way, so that cells can be fully pumped up like a balloon or become empty and flaccid. Changes in these cells allow the flower head to move.

Venus fly trap — Fly traps have somewhat similar mechanics to heliotropism.
Shutterstock

When potassium from neighbouring plant cells is moved into the cells of the pulvinus, water follows and the cells inflate. When they move potassium out of the cells, they become flaccid.

These potassium pumps are involved in many other aspects of plant movement, too. This includes the opening and closing of stomata (tiny regulated leaf apertures), the rapid movement of mimosa leaves, or the closing of a fly trap.

But sunflowers dance differently

In 2016, scientists discovered that the pin-up example of heliotropism — the sunflower — had a different way of moving.

They found sunflower movement is due to significantly different growth rates on opposite sides of the flowering stem.

A sunflower facing a setting sun — Sunflowers move differently to other heliotropic flowers.
Aaron Burden/Unsplash

On the east-facing side, the cells grow and elongate quickly during the day, which slowly pushes the flower to face west as the daylight hours go by — following the sun. At night the west-side cells grow and elongate more rapidly, which pushes the flower back toward the east over night.

Everything is then set for the whole process to begin again at dawn next day, which is repeated daily until the flower stops growing and movement ceases.

While many people are aware of heliotropism in flowers, heliotropic movement of leaves is less commonly noticed or known. Plants with heliotropic flowers don’t necessarily have heliotropic leaves, and vice versa.

Heliotropism evolves in response to highly specific environmental conditions, and factors affecting flowers can be different from those impacting leaves.

The leaves of Queensland box, *Lophostemon confertus*, which track the sun.
Krzysztof Ziarnek, Kenraiz/Wikimedia Commons, CC BY-SA

For example, flowers are all about pollination and seed production. For leaves, it’s for maximising photosynthesis, avoiding over-heating on a hot day or even reducing water loss in harsh and arid conditions.

Some species, such as the Queensland box, arrange their leaves so they’re somewhat horizontal in the morning, capturing the full value of the available sunlight. But there are also instances where leaves align vertically to the sun in the middle of the day to minimise the risks of heat damage.

Plants are dynamic

It’s easy to think of plants as static organisms. But of course, they are forever changing, responding to their environments and growing. They are dynamic in their own way, and we tend to assume that when they do change, it will be at a very slow and steady pace.

Heliotropism shows us this is not necessarily the case. Plants changing daily can be a little unsettling in that we sense a change but may not be aware of what is causing our unease.

As for me, I still keep a watchful eye on those Queensland boxes!

Gregory Moore, Doctor of Botany, The University of Melbourne

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

Flies like yellow, bees like blue: how flower colours cater to the taste of pollinating insects

Hoverfly (*Eristalis tenax*) feeding on marigold.
Fir0002/Flagstaffotos, CC BY-NC

Jair Garcia, RMIT University; Adrian Dyer, RMIT University, and Mani Shrestha, Bayreuth UniversityWe all know the birds and the bees are important for pollination, and we often notice them in gardens and parks. But what about flies?

Flies are the second most common type of pollinator, so perhaps we should all be taught about the bees, the flies and then the birds. While we know animals may see colour differently, little was known about how fly pollination shapes the types of flowers we can find in nature.

In our new study we address this gap in our knowledge by evaluating how important fly pollinators sense and use colour, and how fly pollinated flowers have evolved colour signals.

Specialed flower visiting flies: a hoverfly (*Eristalis tenax*) (left panel), and a bee-fly (*Poecilanthrax apache*) (right panel)
Michael Becker, Pdeley

The way we see influences what we choose

We know that different humans often have preferences for certain colours, and in a similar way bees prefer blue hues.

Our colleague Lea Hannah has observed that hoverflies (Eristalis tenax) are much better at distinguishing between different shades of yellow than between different blues. Other research has also reported hoverflies have innate responses to yellow colours.

Many flowering plants depend on attracting pollinators to reproduce, so the appearance of their flowers has evolved to cater to the preferences of the pollinators. We wanted to find out what this might mean for how different insects like bees or flies shape flower colours in a complex natural environment where both types of insect are present.

The Australian case study

Australia is a natural laboratory for understanding flower evolution due to its geological isolation. On the mainland Australian continent, flowers have predominately evolved colours to suit animal pollination.

Around Australia there are plant communities with different pollinators. For example, Macquarie Island has no bees, and flies are the only animal pollinator.

We assembled data from different locations, including a native habitat in mainland Australia where both bees and flies forage, to model how different insects influence flower colour signal evolution.

Measuring flower colours

Since we know different animals sense colour in different ways, we recorded the spectrum of different wavelengths of light reflected from the flowers with a spectrometer. We subsequently modelled these spectral signatures of plant flowers considering animal perception, allowing us to objectively quantify how signals have evolved. These analyses included mapping the evolutionary ancestry of the plants.

Generalisation or specialisation?

According to one school of thought, flower evolution is driven by competition between flowering plants. In this scenario, different species might have very different colours from one another, to increase their chances of being reliably identified and pollinated. This is a bit like how exclusive brands seek customers by having readily identifiable branding.

An alternative hypothesis to competition is facilitation. Plants may share preferred colour signals to attract a higher number of specific insects. This explanation is like how some competing businesses can do better by being physically close together to attract many customers.

Our results demonstrate how flower colour signalling has dynamically evolved depending on the availability of insect pollinators, as happens in marketplaces.

In Victoria, flowers have converged to evolve colour signals preferred by their pollinators. The flowers of fly-pollinated orchids are typically yellowish-green, while closely related orchids pollinated by bees have more bluish and purple colours. The flowers appeared to share the preferred colours of their main pollinator, consistent with a facilitation hypothesis.

Typical flowers preferred by bees (*Lobelia rhombifolia*, left panel) and flies (*Pterostylis melagramma*, right panel) encountered in our study sites. Inserts show the spectral profile for each species as measured by a spectrometer.
Mani Shrestha

Our research showed flies can see differences between flowers of different species in response to the pollinator local “market”.

On Macquarie Island, where flies are the only pollinators, flower colours diverge from each other – but still stay within the range of the flies’ preferred colours. This is consistent with a competition strategy, where differences between plant species allow flies to more easily identify the colour of recently visited flowers.

When both fly and bee pollinators are present, flowers pollinated by flies appear to “filter out” bees to reduce the number of ineffective and opportunistic visitors. For example, in the Himalayas specialised plants require flies with long tongues to access floral rewards. This is similar to when a store wants to exclusively attract customers specifically interested in their product range.

Our findings on fly colour vision, along with novel precision agriculture techniques, can help using flies as alternative pollinators of crops. It also allows us to understand that if we want to see a full range of pollinating insects including beautiful hoverflies in our parks and gardens, we need to plant a range of flower types and colours.

Jair Garcia, Research fellow, RMIT University; Adrian Dyer, Associate Professor, RMIT University, and Mani Shrestha, Postdoc & International Fellow, Disturbance Ecology, Bayreuth University

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

How would planting 8 billion trees every year for 20 years affect Earth’s climate?

Planting 8 billion trees a year would replace about half of the 15 billion cut down annually.
Michael Tewelde/AFP via Getty Images

Karen D. Holl, University of California, Santa Cruz

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

If we planted 8 billion trees a year for 20 years, what would happen on Earth? – Shivam K., age 14, Nawada, Bihar, India

Politicians, business leaders, YouTubers and celebrities are calling for the planting of millions, billions or even trillions of trees to slow climate change.

There are currently almost 8 billion people on Earth. If every single person planted a tree each year for the next 20 years, that would mean roughly 160 billion new trees.

Could massive tree planting actually slow climate change?

Trees and carbon

Carbon dioxide is the main gas that causes global warming. Through photosynthesis, trees and other plants transform carbon dioxide from the atmosphere into carbohydrates, which they use to make stems, leaves and roots.

The amount of carbon a tree can store varies a great deal. It depends on the tree species, where it is growing and how old it is.

Let’s say the average tree takes up 50 pounds of carbon dioxide a year. If a person planted a tree every year for 20 years – and each one survived, which is highly unlikely – those 20 trees would take up about 1,000 pounds, or half a ton, of carbon dioxide per year.

The average person in the United States produces a whopping 15.5 tons of carbon dioxide a year compared with 1.9 tons for an average person in India. This means that if each person in the U.S. planted one tree per year it would offset only about 3% of the carbon dioxide they produce each year, after all 20 trees had matured. But, it would offset 26% for somebody in India.

Planting trees is certainly part of the solution to climate change, but there are more important ones.

Aerial view of patchwork deforestation of rainforest. — Clearing the Amazon rainforest for livestock farms in Brazil in 2017.
Brazil Photos/LightRocket via Getty Images

Protecting the trees we have

There are about 3 trillion trees on Earth, which is only half as many as 12,000 years ago, at the start of human civilization.

People cut down an estimated 15 billion trees each year. A lot of those trees are in tropical forests, but deforestation is happening all over the planet.

Protecting existing forests makes sense. Not only do they absorb carbon dioxide in the trees and the soil, but they provide habitat for animals. Trees can provide firewood and fruit for people. In cities, they can offer shade and recreational spaces.

But trees should not be planted where they didn’t grow before, such as in native grasslands or savannas. These ecosystems provide important habitat for their own animals and plants – and already store carbon if they are left undisturbed.

Doing more

To slow climate change, people need to do much more than plant trees. Humans need to reduce their carbon dioxide and other greenhouse gas emissions quickly by transitioning to renewable energy sources, like solar and wind. People should also reduce the amount they drive and fly – and eat less meat, as meat has a much larger carbon footprint per calorie than grains and vegetables.

It is important that everybody – businesses, politicians, governments, adults and even kids – do what they can to reduce fossil fuel emissions. I know it can seem pretty overwhelming to think about what you as one person can do to help the planet. Fortunately, there are many options.

Volunteer with a local conservation organization, where you can help protect and restore local habitats. Discuss with your family new lifestyle choices, like biking, walking or taking public transit rather than driving.

Two Girl Scouts take a stand against deforestation.

And don’t be afraid to lead an effort to protect trees, locally or globally. Two 11-year-old Girl Scouts, concerned about the destruction of rainforests for palm oil plantations, led an effort to eliminate palm oil in Girl Scout cookies.

Sometimes change is slow, but together people can make it happen.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Karen D. Holl, Professor of Restoration Ecology, University of California, Santa Cruz

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

Planning to plant an Australian native like wattle? Read this first — you might be spreading a weed

Coastal wattle.
Dr David Chael, Author provided

Singarayer Florentine, Federation University AustraliaAustralian native plants are having a moment in the sun, with more of us seeking out and planting native species than in the past. Our gardens — and our social media feeds — are brimming with beautiful Australian native blooms.

But not all Australian native species belong in all Australian environments. In fact, many have become pests in places far from their original homes.

They can crowd out other native endemic species, affect the local balance of insects and other animals, wreck soils and even increase fire risk.

Here are three Australian native plants that have become invasive species after ending up in places they don’t belong.

Sydney golden wattle (Acacia longifolia subspecies longifolia)

Originally extending from East Gippsland in Victoria up about as far as Brisbane in Queensland, this species is undoubtedly photogenic. It’s also an invasive weed in parts of Victoria, South Australia and Western Australia.

It was spread across the nation by well-meaning gardeners who saw it as a charming ornamental plant. However, its seeds made their way into the wild and took off — it’s what’s known in my field as “a garden escapee”.

Like many weeds, this species can capitalise on a natural disaster; after fire it can send out shoots from its base. Acacias are often one of the first species to sprout following a bushfire. They’re now completely dominant and spreading in many areas.

Sydney golden wattle is an invasive weed in other parts of Victoria, South Australia and Western Australia.
Gill Armstrong, Author provided

Seeds of Sydney golden wattle can last in the soil for many decades, long after the parent plants have died. The heat from a fire cracks the hard seed coat, allowing water to enter and germination to take off.

In the Grampians, in Victoria, Sydney golden wattle is causing terrible soil problems. Many native plants endemic to this area don’t like high levels of soil nitrogen, but Acacia longifolia subsp. longifolia is a nitrogen-fixing plant.

Acacia longifolia subsp. longifolia has quite long, thin seed pods.
Gill Armstrong, Author provided

In other words, it increases the nitrogen in the soil and changes the soil nutrient status and even physical aspects of the soil. It can grow tall and produce a lot of foliage, which reduces the amount of light coming to the ground. That makes it harder for native species lower to the ground to survive.

This is a major challenge, especially in biodiversity-rich places like the Grampians.

Coast wattle (Acacia longifolia subspecies sophorae)

The blooms on Acacia longifolia subspecies sophorae (Coast wattle) look more or less the same as many other wattles, but the leaves are a bit shorter and stubbier.

Originally, Coast wattle occurred along the east coast from western Victoria — up about as far as Brisbane and down south as far as Tasmania (where Sydney golden wattle did not occur naturally).

_Acacia longifolia subsp. sophorae_, also known as 'Coastal Wattle', has shorter, stubby leaves. — Acacia longifolia subsp. sophorae, also known as ‘Coastal Wattle’, has shorter, stubby leaves.
Tatters ✾/Flickr, CC BY

It was originally restricted to sandy sites at the top of beaches but has been deliberately planted as a “sand-binder” in other sites. It’s also naturally spread into heathlands inland of the beaches and is now causing huge problems around our coasts.

Like the earlier example, it dominates local ecosystems and displaces native species endemic to the area (particularly in our species-rich heathlands), which affects local insect habitats. It is also now modifying natural sand dune patterns.

It is increasing fire risk by changing heathland plant profiles from mostly short shrubs of limited bulk to tall, dense shrublands with much higher fuel levels.

Coast teatree (Leptospermum laevigatum)

As with Coast wattle, Coast teatree was formerly restricted to a narrow strip on sandy soils just above the beaches of south-eastern Australia. But it has now spread into nearby heathlands and woodlands. It’s even reached as far as Western Australia.

This teatree plant is now considered an invasive species in parts of Victoria and South Australia.

Although the mature plants are usually killed by fire, the seeds are abundant and very good at surviving; they pop out of their capsules after fires.

Coast teatree produces a lot of seeds.
Dr David Chael, Author provided

They are high-density plants that burn quickly in a fire. They are very quick to take over and push out endemic species.

For example, parts of the Wilson’s Prom National Park in Victoria, which was originally a Banksia woodland, have now been converted almost to a teatree monoculture. It is very sad.

A call to action

Authorities are trying their best to keep these and other native invasive species under control, but in some cases things may never go back to the way they were. Sometimes, the best you can hope for is just to strike a balance between native and invasive species.

When you do landcare restoration work or home gardening, I urge you to look up the plant history and see if the species you’re thinking of planting is listed as one that might cause problems in future.

When you go to purchase from a nursery or plant centre, be cautious. Think twice before you bring something into your garden. Too many species have “jumped the garden fence” and now cost us a great deal in control efforts and in native species loss.

Lots of apps, such as PlantNet, can help you identify plants and see what is native to your area.

Australia has spent billions trying to control invasive species and environmental weeds. Anything you can do to help is a bonus.

Singarayer Florentine, Professor (Restoration Ecologist), Federation University Australia

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

Super Roots

Friday essay: trees have many stories to tell. Is this our last chance to read them?

Gregory Moore, The University of MelbourneAs tree scientist, I am fascinated by the magnificent biology of trees. I also find it enthralling and encouraging that trees are being appreciated by writers around the world right now.

Three fresh books (chosen from a wider field of titles on the topic) exemplify how trees can be written about as more than just background or an incidental part of a landscape, but as integral to meaning.

My Forests: Travel with Trees by Janine Burke, The Heartbeat of Trees by Peter Wohlleben, and Tree Story, a collection curated by Charlotte Day and Brian Martin — are mixed in style and content. But all make clear the close relationships between people and trees and the vital importance of those connections.

It is not surprising that at a time of significant climate change, where natural ecosystems around the world are being devastated and after 18 months of a global pandemic, books on trees are proving popular.

There is an air of desperation in these three titles. Things are changing fast, trees and forests grow slowly, we are wasting time.

Hardy annuals

Books about trees are published every year. Some are beautifully illustrated with photos or hand-drawn images of special trees in large coffee table formats. Some, like J. R. R. Tolkien’s Lord of the Rings, have trees and forests as characters. Tolkien told a fan that his magnificent Ents were “either souls sent to inhabit trees, or else were folk who slowly took the likeness of trees owing to their inborn love of trees”.

Tolkien’s writing, including a story collection called Tree and Leaf, reminds us of the differences between tree time and human time — we humans are hasty folk. This is something I dwell upon often.

The Magic Faraway Tree by Enid Blyton was one of the first books I can recall reading where a tree played a major role and it helped set me on a path of lifelong reading and interest in botany.

That childhood favourite connects to Richard Powers’ The Overstory, which draws together a disparate fictional band of tree protectors. After his book became a hit, Powers recommended 26 other titles for tree-loving readers.

This library of tree books has served a wide and varied readership well and sustained those of us who despair at the wholesale clearing of forests and trees in our cities and suburbs.

Legacies lost

In most Australian cities we are losing trees and canopy cover at a rate of about 1-1.5% per year. I’m still saddened by the loss of a lemon scented gum (Corymbia citriodora) that grew at the city end of the Tullamarine Freeway in Melbourne. I miss its shade in summer but also the delicious scent that wafted through the car window at certain times of the year.

In October last year, protesters mourned a sacred 350-year-old Djab Wurrung Directions Tree, cut down along Victoria’s Western Highway.

There has been a growing disconnect between people and trees and vegetated spaces, particularly for those living in cities. Many people have become so focused on urban survival they have become distanced from the essential and intimate dependence that human beings have on plant life.

Earth as we know it, and the lifeforms it sustains, depend upon and have been shaped by plants and their evolution. Human beings can only survive on our planet because of the ecosystems made possible by plants and trees. If these systems are put in jeopardy because people fail to appreciate the importance of plants, then entire ecosystems are put in peril with profound consequences for humankind.

Climate change is giving us a glimpse of how these important relationships are affected by bushfires, stronger winds from unusual directions and more frequent storms with heavy rainfall that can lead of the loss of grand old trees that have stood as silent sentinels for decades and centuries.

All plants in an ecosystem are important to its function, but the large size and long lives of trees explain why they are often focused upon as representatives of their communities. Their size makes them obvious and contributes to the ambience of any landscape, but can also inspire a sense of awe and in some urban-dwellers, fear.

Their long life spans provide a sense of certainly and continuity in uncertain times of rapid change — their presence can link several human generations, when other connections have been lost. They also provide a tangible prospect, if they are left alone or are properly managed, for links to future generations. All of this can be very reassuring for people who feel vulnerable and oppressed by rapid change.

A fresh crop

All three of the new books selected tend to anthropomorphise trees and aspects of their biology, attributing to them distinctly human qualities. Sometimes they are described by a mood, such as an upbeat growth in spring or by a willingness to share resources with other species. While this may be annoying to some scientists, it allows many people to relate or even identify more closely with trees, especially when there is complex biology and ecology involved.

Peter Wohlleben’s bestselling 2016 book The Hidden life of Trees, took readers on a voyage of discovery with a blend of science, philosophy and spiritualism.

Like that first book, his latest — The Heartbeat of Trees — can be enthralling and annoying almost in equal measure. But the author clearly relates the importance of using our senses when we are in forests to explore the complexity of tree biology. By doing so not only will we achieve a better understanding of trees, but also of ourselves and the importance of trees and vegetated places for human development, our physical and mental health and the sustainability of our societies. It will surely resonate strongly with readers after the pandemic lockdowns of the past year, which saw people flocking to parks, gardens and forests.

A personal and professional travelogue woven together by trees is the framework of My Forests: Travel with Trees, by Janine Burke. As an art historian Burke weaves her own experiences with trees with those depicted in paintings, ancient mythology and historic and literary texts.

It is a set of idiosyncratic connections that may not resonate with all readers, but the strong cultural links between trees and ancient human history are undeniable. The reader can learn a great deal about people but relatively little about trees themselves — they remain illusory, almost furtive.

Tree Story, curated by Charlotte Day and Brian Martin catalogues a recent exhibition at Monash University Museum of Art. It is an eclectic mix of style, content, form and media. Some of the images and text do not do justice to the works, but the book does provide a permanent and curated record of what was offered.

The book makes it clear that people see and connect with trees in different, varied and curious ways. While the works may look at the past, there are clear implications, messages and lessons for the present and importantly for the future. Indigenous voices and perspectives speak loudly, longingly and desperately. The works plead that we cannot go on treating trees in this way: for our own health and sustainable futures we must recognise that ultimately all earthly life is essentially one.

Strengthening the bond

The three books, in their own and different ways, challenge how we think about and interact with trees. They broaden the relationship that exists between trees and people and encourage an active and positive interaction. There is a unifying theme that healthy relationships will benefit both people and trees.

Authors and artists recount their personal stories of trees benefiting their own physical and mental well-being. Research shows that trees along streets and roadways have a traffic calming effect that results in slower speeds and more courteous driver behaviour. In a huge study of women’s health in the United States it was shown that green spaces (parks, gardens and trees) significantly correlated with many aspects of improved health.

Plants and trees are not passive participants in ecosystems. They actively contribute to the complexity, resilience and survival of these systems and while the environment affects and changes them, they also modify the environment. Shade from trees cools the understorey and soils, making it possible for a more diverse range of species to thrive. Shade on creeks and rivers helps native fish survive and breed.

Felled trees — Great Otways National Park.
Unsplash, CC BY

These books highlight the complexity of the relationships that many of us have with trees – relationships that can bring change to both us and the trees.

Wohlleben asks that we use all our senses when we interact with trees and forests. There is more going on than meets the eye. Burke reminds us that culture and tradition influence our perception of trees and forests. The works exhibited in Tree Story help us to explore these influences and their meaning.

Tree in forest — The stories trees tell …
Unsplash, CC BY

We are far from knowing all there is to know about plants, trees, forests and ecosystems. The scientific approach is but one method of questing for truth. The open-minded approaches explored in these books could stimulate new discoveries.

The books remind us of the pace of change being wrought on trees and forests by climate change and that the stakes, if we don’t reverse this decline, are very high.

Scientists should never dismiss what they don’t understand. Neither should readers. As climates change, the presence of trees and green space will be recognised as a priority. Trees will be a part of our futures no matter where we live because we cannot have economically viable, environmentally sustainable or liveable places without them.

woman reading under a tree — Books can remind us what we have, and what’s at stake.
Shutterstock

Gregory Moore, Doctor of Botany, The University of Melbourne

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

A lone tree makes it easier for birds and bees to navigate farmland, like a stepping stone between habitats

Carla Archibald, Deakin University; Eduardo van den Berg, Federal University of Lavras, and Jonathan Rhodes, The University of QueenslandVast, treeless paddocks and fields can be dangerous for wildlife, who encounter them as “roadblocks” between natural areas nearby. But our new research found even one lone tree in an otherwise empty paddock can make a huge difference to an animal’s movement.

We focused on the Atlantic Forest in Brazil, a biodiversity hotspot with 1,361 different known species of wildlife, such as jaguars, sloths, tamarins and toucans. Habitat loss from expanding and intensifying farmland, however, increasingly threatens the forest’s rich diversity of species and ecosystems.

We researched the value of paddock trees and hedges for birds and bees, and found small habitat features like these can double how easily they find their way through farmland.

This is important because enabling wildlife to journey across farmlands not only benefits the conservation of species, but also people. It means bees can improve crop pollination, and seed-dispersing birds can help restore ecosystems.

Connecting habitats

Lone trees in paddocks, hedges and tree-lined fences are common features of farmlands across the world, from Brazil to Australia.

They may be few and far between, but this scattered vegetation makes important areas of refuge for birds and bees, acting like roads or stepping stones to larger natural habitats nearby.

Scattered paddock trees, for instance, offer shelter, food, and places to land. They’ve also been found to create cooler areas within their canopy and right beneath it, providing some relief on scorching summer days.

Hedges and tree-lined fences are also important, as they provide a safe pathway by providing hiding places from predators.

White-browed meadowlark perched on a bush in a farm paddock within the Atlantic Forest.
Milton Andrade Jr, CC BY

For our research, we used satellite images of the Atlantic Forest and randomly selected 20 landscapes containing different amounts of forest cover.

We then used mathematical models to calculate the habitat connectivity of these landscapes for three groups of species — bees, small birds such as the rufous-bellied thrush, and large birds such as toucans — based on how far they can travel.

And we found in areas with low forest cover, wildlife is twice as likely to move from one natural habitat to another if paddock trees and hedges can be used as stepping stones.

We also found vegetation around creeks and waterways are the most prevalent and important type of on-farm habitat for wildlife movement. In Brazil, there are legal protections for these areas preventing them from being cleared, which means vegetation along waterways has become relatively common compared to lone trees and hedges, in places with lower forest cover.

Insights for Australia

While the contribution of lone trees, hedges and tree-lined fences towards conservation targets is relatively low, our research shows they’re still important. And we can apply this knowledge more widely.

Two koalas sitting on a branch — Koalas use roadside vegetation for feeding and resting.
Shutterstock

For example, in Australia, many koala populations depend on scattered trees for movement and habitat. In 2018, CSIRO researchers in Queensland tracked koalas using GPS, and found koalas used roadside vegetation and scattered trees for feeding and resting significantly more than they expected.

Likewise, lone trees, hedges and tree-lined fences can also facilitate the movement of Australian fruit-eating birds such as the olive-backed oriole and the rose-crowned fruit dove. Improving habitat connectivity can help these birds travel across landscapes, feeding and dispersing seeds as they go.

In fragmented landscapes, where larger patches of vegetation are hard to find, dispersing the seeds of native plants encourages natural regeneration of ecosystems. This is a key strategy to help achieve environmental restoration and conservation targets.

Policies overlook lone trees

In Brazil, there’s a strong initiative to restore natural areas, known as the Brazilian Pact for Restoration. This pact is a commitment from non-government organisations, government, companies and research centres to restore 15 million hectares of native vegetation by 2050.

However, the pact doesn’t recognise the value of lone trees, hedges and tree-lined fences.

Likewise, the Brazilian Forest Code has historically provided strong legal protection for forests since it was introduced. While this policy does value vegetation along waterways, it overlooks the value of lone trees, hedges or tree-lined fences.

These oversights could result in poor connectivity between natural areas, seriously hampering conservation efforts.

Australia doesn’t fare much better. For example, in Queensland, the native vegetation management laws protect only intact native vegetation or vegetation of a certain age. This means scattered, but vital, vegetation isn’t protected from land clearing.

Small habitat features scattered across a farm paddock in the Atlantic Forest.
Flávia Freire Siqueira, CC BY., Author provided

Helping your local wildlife

But farmers and other landowners in Australia can make a big difference through land stewardship grant schemes (such as from Landcare) and private land conservation programs (such as Land for Wildlife or conservation covenants).

These schemes and programs can help landowners finance revegetation and protect native vegetation. Grants and programs vary by state and territory, and local council.

Restoring natural areas is a key goal on the global conservation agenda for the next decade, and it’s clear that lone trees, hedges and tree-lined fences on farms may play a larger role than once thought.

So think twice before you remove a tree or a hedge. It might be a crucial stepping stone for your local birds and bees.

The authors gratefully acknowledge the contributions of Dr Flávia Freire Siqueira who led this research collaboration, and co-authours Dr Dulcineia de Carvalho and Dr Vanessa Leite Rezende from the Federal University of Lavras.

Carla Archibald, Research Fellow, Conservation Science, Deakin University; Eduardo van den Berg, , Federal University of Lavras, and Jonathan Rhodes, Associate Professor, The University of Queensland

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

An act of God, or just bad management? Why trees fall and how to prevent it

Gregory Moore, The University of MelbourneThe savage storms that swept Victoria last week sent trees crashing down, destroying homes and blocking roads. Under climate change, stronger winds and extreme storms will be more frequent. This will cause more trees to fall and, sadly, people may die.

These incidents are sometimes described as an act of God or Mother Nature’s fury. Such descriptions obscure the role of good management in minimising the chance a tree will fall. The fact is, much can be done to prevent these events.

Trees must be better managed for several reasons. The first, of course, is to prevent damage to life and property. The second is to avoid unnecessary tree removals. Following storms, councils typically see a spike in requests for tree removals – sometimes for perfectly healthy trees.

A better understanding of the science behind falling trees – followed by informed action – will help keep us safe and ensure trees continue to provide their many benefits.

tree lying on home — We must try to stop trees falling over to prevent damage to life and property.
James Ross/AAP

Why trees fall over

First, it’s important to note that fallen trees are the exception at any time, including storms. Most trees won’t topple over or shed major limbs. I estimate fewer than three trees in 100,000 fall during a storm.

Often, fallen trees near homes, suburbs and towns were mistreated or poorly managed in preceding years. In the rare event a tree does fall over, it’s usually due to one or more of these factors:

1. Soggy soil

In strong winds, tree roots are more likely to break free from wet soil than drier soil. In arboriculture, such events are called windthrow.

A root system may become waterlogged when landscaping alters drainage around trees, or when house foundations disrupt underground water movement. This can be overcome by improving soil drainage with pipes or surface contouring that redirects water away from trees.

You can also encourage a tree’s root growth by mulching around the tree under the “dripline” – the outer edge of the canopy from which water drips to the ground. Applying a mixed-particle-size organic mulch to a depth of 75-100 millimetres will help keep the soil friable, aerated and moist. But bear in mind, mulch can be a fire risk in some conditions.

Root systems can also become waterlogged after heavy rain. So when both heavy rain and strong winds are predicted, be alert to the possibility of falling trees.

People inspect trees fallen on cars — A combination of heavy rain and strong winds can cause trees to fall.
Shutterstock

2. Direct root damage

Human-caused damage to root systems is a common cause of tree failure. Such damage can include roots being:

cut when utility services are installed
restricted by a new road, footpath or driveway
compacted over time, such as when they extend under driveways.

Trees can take a long time to respond to disturbances. When a tree falls in a storm, it may be the result of damage inflicted 10-15 years ago.

tree uprroted — This elm, growing very close to a footpath, fell in Melbourne during a 2005 storm.
Author provided

3. Wind direction

Trees anchor themselves against prevailing winds by growing roots in a particular pattern. Most of the supporting root structure of large trees grows on the windward side of the trunk.

If winds come from an uncommon direction, and with a greater-than-usual speed, trees may be vulnerable to falling. Even if the winds come from the usual direction, if the roots on the windward side are damaged, the tree may topple over.

The risk of this happening is likely to worsen under climate change, when winds are more likely to come from new directions.

4. Dead limbs

Dead or dying tree limbs with little foliage are most at risk of falling during storms. The risk can be reduced by removing dead wood in the canopy.

Trees can also fall during strong winds when they have so-called “co-dominant” stems. These V-shaped stems are about the same diameter and emerge from the same place on the trunk.

If you think you might have such trees on your property, it’s well worth having them inspected. Arborists are trained to recognise these trees and assess their danger.

car bumper stopped at fallen tree trunk — Storms can trigger falling trees which block roads.
Shutterstock

Trees are worth the trouble

Even with the best tree management regime, there is no guarantee every tree will stay upright during a storm. Even a healthy, well managed tree can fall over in extremely high winds.

While falling trees are rare, there are steps we can take to minimise the damage they cause. For example, in densely populated areas, we should consider moving power and communications infrastructure underground.

By now, you may be thinking large trees are just too unsafe to grow in urban areas, and should be removed. But we need trees to help us cope with storms and other extreme weather.

Removing all trees around a building can cause wind speeds to double, which puts roofs, buildings and lives at greater risk. Removing trees from steep slopes can cause the land to become unstable and more prone to landslides. And of course, trees keep us cooler during summer heatwaves.

Victoria’s spate of fallen trees is a concern, but removing them is not the answer. Instead, we must learn how to better manage and live with them.

Gregory Moore, Doctor of Botany, The University of Melbourne

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

Small breaks in habitat can have big impacts

Disastrous clearing laws

The code should be amended

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What happens when fires become more frequent?

What happens when fire seasons get longer?

When drought and heatwaves get more severe

When threats pile up

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The mechanics of tracking the sun

But sunflowers dance differently

Plants are dynamic

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The way we see influences what we choose

The Australian case study

Measuring flower colours

Generalisation or specialisation?

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Trees and carbon

Protecting the trees we have

Doing more

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Sydney golden wattle (Acacia longifolia subspecies longifolia)

Coast wattle (Acacia longifolia subspecies sophorae)

Coast teatree (Leptospermum laevigatum)

A call to action

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Hardy annuals

Legacies lost

A fresh crop

Strengthening the bond

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Connecting habitats

Insights for Australia

Policies overlook lone trees

Helping your local wildlife

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Why trees fall over

Trees are worth the trouble

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