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


Australian cities could lose some of their most common trees to climate change.
Jamen Percy/Shutterstock

Alessandro Ossola, Macquarie University; Hugh Munro Burley, Macquarie University; Leigh Staas, Macquarie University; Linda Beaumont, Macquarie University; Michelle Leishman, Macquarie University, and Rachael Gallagher, Macquarie University

We need trees in our lives. This past summer, Adelaide experienced the hottest temperature ever recorded in an Australian state capital, hitting 46.6 degrees on January 24. Trees beautify otherwise grey cities and cool our suburbs during heatwaves. But different species have different levels of tolerance of heat, lack of water and other threats posed by climate change.

In a newly published study, we investigated likely climate change impacts on 176 of the most common tree species planted across Australian cities. Our analysis showed more than 70% of these species will experience harsher climatic conditions across Australian cities by 2070. Some of the most commonly planted trees are unlikely to survive these conditions.

The golden wattle might struggle in our northern cities if they get hotter and drier.
Dryas/Wikimedia Commons, CC BY-SA

So which tree species are best suited to particular places? Which species are more likely to thrive, rather than just survive, under a changing climate? Which of our beloved tree species won’t make it?

Tree species growing in warmer cities are more likely to be affected than those in cooler cities. Some species, such as the golden wattle (Acacia longifolia) or the prickly paperbark (Melaleuca styphelioides), might not make it in northern cities, unless we invest precious resources – such as water – to maintain these civic assets. Other species, such as the native frangipani (Hymenosporum flavum) or the tuckeroo (Cupaniopsis anacardioides), will likely become more suitable for planting in southern cities.




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Why do cities need trees?

Trees are wonderfully effective at improving the microclimate of our cities, which makes tree plantings an effective and efficient way to adapt to climate change. The leaves of trees absorb and dissipate much of the sun’s radiation.

Trees cool air and land by several degrees compared to areas of concrete and asphalt. Swipe the heat map below to see how effectively trees cool down our cities. (Red indicates hotter areas, blue cooler areas.)

Swipe the map to see how much trees cool urban areas. Red indicates hotter areas, blue cooler areas. This temperature map was collected during a heatwave in Adelaide, South Australia, on February 9 2017 by AdaptWest over the cities of West Torrens, Charles Sturt and Port Adelaide-Enfield.
Used with permission of AdaptWest Adelaide (https://www.adaptwest.com.au/mapping/heat-maps)



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Governments recognise the importance of trees and have developed vital initiatives, such as the national 20 Million Trees program and the 5 Million Trees program in New South Wales. These are important first steps to increase urban tree cover across Australia. But the question arises: are we planting the right tree species?

What does the science say?

Australian cities are blessed with a higher diversity of tree species compared to other cities globally. However, the 30 most commonly planted species make up more than half of Australia’s urban forests.

This poses a great risk for our cities. If we were to lose one or two of these common species, the impact on our urban tree cover would be immense. Consequently, our best insurance is to increase the diversity of our trees.

Species composition of Australia’s urban forests across 60 local government areas. The size of each word is proportional to the number of tree stems recorded for each species.
Alessandro Ossola

Our quest to find climate-ready tree species is only just beginning. Supported by Hort Innovation Australia, the NSW Department of Planning, Industry and Environment, and the Commonwealth government, our team embarked on a project called Which Plant Where in conjunction with researchers at Western Sydney University. Our mission is to find the best plant species for urban landscapes that will be resilient to climate change.

We work with the nursery industry to provide evidence on species’ resilience to extreme heat and drought by testing plants to their limits in research glasshouses. Our work with plant growers and nurseries will inform them on how to adapt their business, by identifying the new challenges posed by climate change, as well as selecting highly diverse palettes of climate-ready species. We advise landscape architects, designers and urban planners about not only the best planting choices, but also how to increase the biodiversity of our cities.




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You can help!

We are committed to do more science in coming years, but you can start making a difference today. Australia’s National Tree Day will be celebrated again this year on Sunday, July 28. It’s a great opportunity to teach our families, communities and businesses about the importance of tree planting and environmental stewardship as key elements of adapting to climate change.

An old Chinese adage says:

The best time to plant a tree was 20 years ago. The second best time is now.

This weekend is your time. The game is simple – head to your closest plant nursery. Ask your local grower about which tree species are suitable for the local growing conditions and pick one you like. Then, plant a tree in your yard, or join one of the many planting events across Australia.

Teach your kids, family and friends about the difference they can start making today – for their future and our common good – one tree at a time. The Conversation

A plant nursery growing a diverse range of tree species for the upcoming planting season.
Alessandro Ossola

Alessandro Ossola, Research Coordinator Centre for Smart Green Cities, Macquarie University; Hugh Munro Burley, Spatial analyst, Macquarie University; Leigh Staas, Associate Director for Engagement & Research Partnerships | Smart Green Cities, Macquarie University; Linda Beaumont, Senior Lecturer, Macquarie University; Michelle Leishman, Distinguished Professor, Head of Department, Macquarie University, and Rachael Gallagher, , Macquarie University

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

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I’ve always wondered: are water crystals bad for the environment?



Gardeners use water crystals to drought-proof their plants.
Shutterstock

Michelle Ryan, Western Sydney University

This is an article from I’ve Always Wondered, a series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au


Are water crystals bad for the environment? –Terry Gilmour

This is an excellent question, and something an environmentally conscious gardener might wonder. With changing rainfall patterns, drought and an increasing average temperature in Australia many people are looking for ways to save water in their garden, and adding water crystals to your soil appears to be a good solution. But what do we really know about water crystals and are they bad for the environment?

Well, you can put your mind at ease: water crystals are not bad for the environment. In fact, in other forms they are actually used to help protect the environment.

What are water crystals?

Water crystals are tiny super-absorbent polymers (a long chain that’s made up of identical repeating molecules), about the size of a sugar crystal. They are added to potting mix or added to soil in a garden bed to increase the water holding capacity of the soil.

Water crystals act like a sponge, binding water molecules with the molecule chains in the crystals (with what’s technically known as cross-link bonding). This makes the crystal swell, creating a three-dimensional gel network up to 300 times its original size, absorbing water and nutrients.




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Over 5-6 years water crystals slowly degrade, releasing the absorbed water into the root zone of the plant and wetting the soil.

While many water crystals are marketed as water-saving, and many people use them to drought-proof their plants, it’s really important to know that these water crystals don’t actually conserve water. The plants still use the same amount of water, but instead of the water flowing through to the bottom of the pot and into the saucer and evaporating, or through to the bottom of the garden bed, the water crystals hold onto the water in the root zone of the plant. It makes for a more efficient use of the water in the soil.

Gardeners are not always able to frequently water their plants on hot summer days.
Shutterstock

Cross-linked vs linear polymers

To understand where the environmental concerns come from, we have to get a little technical.

The most common type of water crystal on the market is a cross-linked polyacrylamide. Cross-linked polyacrylamides are water absorbent but not water soluble. One of their best-known uses is in disposable nappies.

The environmental concern regarding water crystals comes from people confusing these cross-linked polyacrylamides with non-cross-linked polyacrylamide used by industry. While they are commonly described in the same way, they have a different chemical bonding and properties.




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Non-cross-linked (linear) polyacrylamide is water-soluble. It is currently used in Australian agriculture for improving soil and to help control erosion. It also plays an integral role in aiding flocculation as part of the sewage treatment process.

A 1997 study found when non-cross linked polyacrylamide degrades it creates acrylamide, a suspected carcinogen and neurotoxin.

Obviously this would be very concerning if it also affected water crystals! Acrylamide could leach into the soil and water and be taken up by plants, entering the human food chain. However there’s no proof cross-linked polyacrylamides – which are the water crystals you’d find in a gardening store – behave like this.

It is not clear if water crystals have a negative impact on Australia’s rivers and streams.
Shutterstock

It is also worth noting that further studies, including one published in 2008, found a very small amount (less than 0.5 parts per billion) of acrylamide was released into the environment, which does not cause any environmental concern.

You may also worry water crystals could impact aquatic life if they found their way into rivers and streams. The good news is there’s no reported toxicity or impact on aquatic life from commercially available water crystals (results are more mixed for the water soluble non-cross-linked polyacrylamide, with some studies finding little impact and others showing no toxicity.




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Are common garden chemicals a health risk?


The other good news is water crystals do not accumulate in the soil or water over the long term. The use of water crystals has no adverse impact on soil microbe populations, which we need for a good healthy soil. If used as directed there is no risk to human health (however, it is always good practice to wear gloves while handling any chemical product).

So environmentally conscious gardeners don’t need to worry about water crystals. They’re great for people who don’t have time to water their pot plants every day in summer. Remember, these crystals do not save water but increase the water holding capacity of the soil, so you still need to water your plants regularly – especially on hot days!The Conversation

Michelle Ryan, Lecturer – Environmental Health and Management, Western Sydney University

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

The small patch of bush over your back fence might be key to a species’ survival


File 20181212 76965 x1w7xf.jpg?ixlib=rb 1.1
A kangaroo finds refuge in a small patch of vegetation surrounded by a new housing estate.
Georgia Garrard, Author provided

Brendan Wintle, University of Melbourne and Sarah Bekessy, RMIT University

It may not look like a pristine expanse of Amazon rainforest or an African savannah, but the patch of bush at the end of the street could be one of the only places on the planet that harbour a particular species of endangered animal or plant.

Our newly published global study of the conservation value of landscapes in 27 countries across four continents has found these small patches of habitat are critical to the long-term survival of many rare and endangered species.

In Australia, our cities are home to, on average, three times as many threatened species per unit area as rural environments. This means urbanisation is one of the most destructive processes for biodiversity.

It tends to be the smaller patches of vegetation that go first, making way for a housing development, a freeway extension, or power lines. Despite government commitments to enhance the vegetation cover of urban areas and halt species extinctions, the loss of vegetation in Australian cities continues.




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This story plays out all over the world day after day. Of course, it’s not just an urban story. Patches of rural vegetation are continually making way for, say, a new pivot irrigation system or a new mine to provide local jobs.

Remnant salmon gum woodland surrounded by cropland near Bencubbin in Western Australia’s northeast wheatbelt.
Mike Griffiths, Author provided

Mostly, policymakers and scientists do not consider these losses to be, on their own, a fatal blow to the biodiversity of a region or country. Small, often isolated patches of vegetation are considered expendable, tradeable, of limited ecological value due to their small size and relatively large amount of “edgy” habitat. Wrong.

Research forces a rethink

Our study analysed the relationship between conservation value of vegetation patches and their size and isolation in landscapes across Europe, Australia, North America and Africa. The findings prompt a rethink of long-held views about the relative importance of small, isolated habitat patches for biodiversity conservation. We show that these patches often have unique ecological and environmental characteristics.

The critically endangered Western Ringtail Possum lives mainly in small habitat patches in or around urban areas near Perth and is under intense pressure from housing development, foxes, cats and dogs.
Yokochi K., Bencini R./Wikimedia Commons, CC BY

That’s because they are the last patches left over from extensive clearing of flat, fertile land for agriculture or urban growth close to rivers and bays. They often contain habitats for rare or endangered species that have disappeared from the rest of the landscape. This makes these small, isolated patches of habitat disproportionately important for the survival of many species.

Our study calls for a rethink of urban planning and vegetation management regulations and policies that allow small patches of vegetation to be destroyed with lower (and often zero) scrutiny. We argue that the environment is suffering a death by a thousand cuts. The existence of large conservation reserves doesn’t compensate for the small patches of habitat being destroyed or degraded because those reserves tend to contain different species to the ones being lost.

The combined impact of the loss of many small patches is massive. It’s a significant contributor to our current extinction crisis.




Read more:
Let’s get this straight, habitat loss is the number-one threat to Australia’s species


Why are small patches seen as dispensable?

A key variable used in decisions on vegetation-clearing applications is the size of patch being destroyed. Authorities that regulate vegetation management and approve applications are more permissive of destruction of small patches of vegetation.

This is partly due to a large body of ecological theory known as island biogeography theory and subordinate theories from metapopulation ecology and landscape ecology. These theories suggest that species richness and individual species’ population sizes depend on the degree of isolation of the patch, its size and the quality of the habitat it contains.

While it is crucial that we conserve large, intact landscapes and wilderness, the problem with conserving only large and well-connected patches of high-quality vegetation is that not all species will be conserved. This is because some species exist only in small, isolated and partially degraded habitats, such as those characteristic of urban bushlands or remnant bush in agricultural areas.

A remnant wetland is still valuable habitat for species like the Pacific Heron.
Wayne Butterworth/Wikimedia Commons, CC BY

For this reason, we highlight the importance of protecting and restoring habitats in these small isolated patches. And these areas do tend to be more vulnerable to invasion by weeds or feral animals. If the impacts of invasive species are not managed, they will eventually lead to the destruction of the habitat values and the loss of the species those habitats support.

Small and isolated patches of vegetation on the urban fringe are under enormous pressure from human use, pets, escaped seed of Agapanthus and the many other invasive species we plant in our gardens. These plants spread into local bushland, where they outcompete the native plants.

Communities can make a difference

As well as these perils, being on the urban fringe also brings opportunity. If a remnant patch of vegetation at the end of the street is seen to be of national environmental importance, that presents a great opportunity to channel the energies of community groups into conserving and restoring these patches.

A patch that is actively cared for by the community will provide better habitat for species. It’s also less likely to fall foul of development aspirations or infrastructure projects. The vicious cycle of degradation and neglect of small patches of habitat can be converted into a virtuous cycle when their value is communicated and local communities get behind preserving and managing them.

Volunteer community groups can play a vital role in preserving and enhancing small habitat patches.
Robin Clarey, Friends of Edithvale Seaford Wetlands, Author provided

Urban planners and developers can get on board too. Rather than policies that enable the loss of vegetation in urban areas, we should be looking at restoring habitats in places that have lost or are losing them. This is key to designing healthy, liveable cities as well as protecting threatened species.

Biodiversity-sensitive urban design makes more of local vegetation by complementing the natural remnant patches with similar habitat features in the built environment, while delivering health and well-being benefits to residents. Urban development should be seen as an opportunity to enhance biodiversity through restoration, instead of an inevitable driver of species loss.




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The Conversation


Brendan Wintle, Professor Conservation Ecology, University of Melbourne and Sarah Bekessy, Professor, RMIT University

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

Gardening improves the health of social housing residents and provides a sense of purpose



File 20180721 142411 mjf8l8.jpg?ixlib=rb 1.1
Gardens bring people together.
Elaine Casap/Unsplash

Tonia Gray, Western Sydney University; Danielle Tracey, Western Sydney University; Kumara Ward, Western Sydney University, and Son Truong, Western Sydney University

Studies indicate spending time in nature brings physical, mental and social benefits. These include stress reduction, improved mood, accelerated healing, attention restoration, productivity and heightened imagination and creativity.

Increased urbanisation has made it more difficult to connect with nature. And members of lower socioeconomic and minority ethnic groups, people over 65 and those living with disability are less likely to visit green spaces. This could be due to inaccessible facilities and safety fears.

A gardening program for disadvantaged groups, running in New South Wales since 1999, has aimed to overcome the inequity in access to green spaces. Called Community Greening, the program has reached almost 100,000 participants and established 627 community and youth-led gardens across the state.




Read more:
The science is in: gardening is good for you


Our independent evaluation explored the program’s impact on new participants and communities in social housing by tracking six new garden sites in 2017. Around 85% of participants told us the program had a positive effect on their health and 91% said it benefited their community. And 73% said they were exercising more and 61% were eating better. One participant said engaging in the program even helped them quit smoking.

These insights have advanced our understanding of how community gardening improves the mental and physical health of Australians living in social housing communities in our cities.

Our study

Trends towards urbanisation and loss of green space have sparked concerns about population health and well-being. This has led to a growing body of research on the impact of community gardens on children and adults.

The Community Greening program is supported by the Royal Botanic Garden Sydney in partnership with Housing New South Wales. Anecdotal feedback gathered by the botanic garden over the past two decades has shown gardening improves well-being and cohesion, fosters a sense of belonging, reduces stress and enhances life skills.

Community Greening provides gardens for people in social housing.

Based on this understanding, Community Greening aims to:

  • improve physical and mental health
  • reduce anti-social behaviour
  • build community cohesion
  • tackle economic disadvantage
  • promote understanding of native food plants
  • conserve the environment
  • provide skills training to enable future employment opportunities
  • share expert knowledge of the garden.

Our research investigated these outcomes in participants, and whether they changed during the course of the program. We collected data using questionnaires over seven months (before and after participation). We also conducted focus group interviews with participants and open-ended questionnaires with staff working at the community sites.




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Of the 23 people who completed both questionnaires before and afterwards, 14 were female and nine were male. They had an average age of 59, ranging from 29-83. Fifteen participants were born in Australia while the rest came from Fiji, Iran, Poland, New Zealand, Philippines, Chile, Afghanistan and Mauritius. One participant identified as an Aboriginal and/or Torres Strait Islander and five people (22%) reported English was not their first language.

Initially, 27% reported they had never gardened prior to the program. At the post-test questionnaire, the frequency of attendance improved for many of them. Over 40% gardened once a week and 22% every day.

Gardening benefits

Overall, we found participants felt a sense of agency, community pride and achievement. The gardening program helped encourage change and community development. Some were happy to learn a new hobby.

Community Greening participants found a lot of benefits to gardening.
Research infographic/Screenshot, Author provided

Gardening also served as an opportunity to socialise with neighbours. In previous years within some social housing communities, it was commonplace for residents to simply stay inside their units without interacting with anyone.

Many participants said they saw a marked improvement in their health and well-being. One participant remarked:

I suffer with a lot of health problems, and a lot of times I’ve been sitting at home, been depressed and not been happy about my illness, and since I’ve become more involved with the garden it helped me to not worry about my health so much like I used to and it actually improved my eating habits. It has changed my life positively. I don’t have time to feel sorry for myself anymore…

Some described the gardening experience as calming and cathartic – especially those who suffered from depression and anxiety. Some spoke of the positive aspect of having something to do each day and their feelings of achievement.

Another participant said:

Going outside gives me not only physical exercise, but it provides a certain amount of joy in that you’re seeing the benefit of your hard work coming through in healthy plants. Whether it’s vegetables or a conifer, you’re seeing it grow and you’re seeing the benefit…

Additional improvements in social health included a genuine enthusiasm for working in a team, with increased co-operation and social cohesion between staff and tenants. The housing managers and social workers work alongside tenants helping to foster trust, co-operation, social collaboration and healthy relationships.

The ConversationMore importantly, this research has provided validation that Community Greening has aligned with contemporary social-housing priorities. These include supporting health and well-being, nurturing a sense of community, enhancing safety and developing a sense of place.

Tonia Gray, Associate Professor, Centre for Educational Research, Western Sydney University; Danielle Tracey, Associate Professor, Adult and Postgraduate Education, Western Sydney University; Kumara Ward, Lecturer, Early Childhood Education, Western Sydney University, and Son Truong, Senior Lecturer, Secondary Education, Western Sydney University

This article was originally published on The Conversation. Read the original article.

How the Wardian case revolutionised the plant trade – and Australian gardens



File 20180724 194158 1g4vkjn.jpg?ixlib=rb 1.1
Melburnians admire the first primrose to arrive in the colony, transported by a Wardian case, in Edward Hopley’s A Primrose from England, circa 1855.
Bendigo Art Gallery, Gift of Mr and Mrs Leonard Lansell 1964.

Luke Keogh, Deakin University

The first journey of a Wardian case was an experiment. In 1829, the surgeon and amateur naturalist Nathanial Bagshaw Ward accidentally discovered that plants enclosed in airtight glass cases can survive for long periods without watering. Four years later he decided to test his invention by transporting two of his cases filled with a selection of ferns, mosses and grasses from London to Sydney, the longest sea journey then known.

On November 23 1833, Ward received a letter from Charles Mallard, the ship captain responsible for the two cases, telling him: “your experiment for the preservation of plants alive … has fully succeeded”.

Gleichenia microphylla.
Krzysztof Ziarnek, Kenraiz/Wikimedia Commons, CC BY

The next challenge was the return journey. In February 1834, the cases were replanted with specimens from Australia. Eight months later, when Ward and friend George Loddiges, a well-known nurseryman, went aboard the ship in London they inspected the healthy fronds of a delicate coral fern (Gleichenia microphylla), an Australian plant never before seen in Britain. The experiment was a success.

The Wardian case, as it would become known, revolutionised the movement of live plants around the globe. They were shaped like a miniature greenhouse, made of timber and had glass inserts in the roof. In the cases, plants had a greater chance of survival when in transit.

Wardian cases full of cycads from Rockhampton, Queensland, arrive at the Missouri Botanic Gardens after a long journey via London and New York, c.1920.
Missouri Botanic Gardens.

Often thought of as only a product of the gardening crazes of the Victorian era, the Wardian case was actually a notorious prime mover of plants. Some of the key uses of the case include moving tea from China to India to lay the foundations of the Assam and Darjeeling tea districts; helping move rubber from Brazil and transporting it via London to Asia, which is now the leading producer of the crop; and repeatedly moving bananas over many decades to the Pacific Islands, Central America and the Caribbean.

A tea plantation in India: the cases moved tea from China to India to lay the foundations of the Assam and Darjeeling tea districts.
Wikimedia Commons

The Wardian case resolved a major bottleneck in the transport of live plant species, but it also had major consequences for environmental relationships in the 19th and 20th centuries.

An untold story

Botanists and horticulturalists used this simple box for over a century to carry hundreds of thousands of plants around the globe, whether they were in England or the United States, France or India, Russia or Japan. The Australian story of the Wardian case is an important and untold one.

Wardian cases line the paths at the Adelaide Botanic Gardens.
Adelaide Botanic Gardens.

Each state has an important connection to it. New South Wales received the first plants from Ward himself. The Royal Botanic Gardens, Kew, sent its first Wardian cases, full of fruit trees and ornamental plants, to Western Australia. The Adelaide Botanic Gardens even had a path lined with Wardian cases. Tasmania was vital in the 19th-century fern trade. And Queensland used the Wardian case to transport the cactoblastis moth to help solve the prickly pear infestation.

Victoria’s connection to the case is unsurprisingly one of gardeners and ornamental plants. Today, Victoria is home to Australia’s largest nursery industry, by some reports worth more than $1.6 billion annually and employing more than 11,000 people. The industry today cannot be separated from the long global history of moving beautiful and useful plants to Australia more than a century ago. Two examples illuminate the thriving early trade in Victoria.

Preparing to send live plants in Wardian cases at the Jardin d’Agronomie Tropicale, Paris, c.1910.
Image courtesy Bibliothèque historique du CIRAD.

Published in 1855, Charles Mackay’s widely circulated poem The Primrose was about the landing in Melbourne of a beautiful rare flower and the procession from the docks to an exhibition location in the city. It read, in part:
“She has cross’d the stormy ocean/A pilgrim, to our shore/As fresh as Youth and Beauty/And dear as days of yore.”

By some reports, more than 3,000 people turned out to see the floral traveller. Police were called in to restore order to Melbourne’s streets during the procession. News of the fanfare was carried in major international newspapers including Harper’s Weekly and the Illustrated London News.

The British artist Edward Hopley painted the scene, A Primrose from England (1855), to memorialise both the moment of the plant arriving in Melbourne and, in typical Hopley style, the social milieu of the period.

The technology for moving the plant was not lost on either artist. The primrose that Mackay so eloquently lyricised and Hopley so captivatingly brought to life arrived in Melbourne in a specially designed Wardian case. It would not have arrived without this technology for moving plants. It was not just the primrose. In the decades following 1858, the Wardian case played a major role in shaping the aesthetics and species available in the Victorian landscape.

Melbourne, the Garden Capital of Victoria, Australia, by James Northfield.
State Library Victoria.

In early April 1862, three decades after Ward’s invention, the well-known Victorian nurseryman Thomas Lang delivered a lecture to the Ballarat Horticultural society titled “On Wardian, or Plant Cases”. Lang began by describing his first encounter with the cases in Edinburgh. He went on to detail the many useful plants, such as the giant Californian redwood, that he had introduced with the help of the case. By his own estimate, Lang transported nearly a million plants to Victoria in just one decade in the late 19th century, a staggering number by just one nurseryman.

Californian redwoods in Victoria’s Great Otway National Park.
Shutterstock

Now living in regional Victoria, after many years of travel researching a book on the Wardian case, I often think about Lang and the enthusiasm colonists had for bringing over beautiful plants. Lang proclaimed in his lecture of 1862: “The comfort, the pleasures, the commercial interests, the happiness of mankind are promoted by the use of Wardian cases.”

To move beautiful ornamental plants here was very much part of the home-making process for colonists.

But it was always a trade. While beautiful plants came into Australia, many useful ones went out. Often we forget that the beauty of our gardens is as much about moving plants, as it is about the hard work of tilling the soil.

Next time your hands are covered in soil, it might be good to wonder where that camellia or fuchsia or rose or apple or kiwi fruit or lemon originated – chances are it travelled in a Wardian case.


The ConversationLuke Keogh’s book The Wardian Case will be published next year by the University of Chicago Press. He delivers the Redmond Barry Fellowship Presentation at the University of Melbourne on July 25 2018.

Luke Keogh, Visiting Scholar, Deakin University

This article was originally published on The Conversation. Read the original article.

The secret agents protecting our crops and gardens


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Lacewings are fantastic predators and are easy to rear and release.
Dan Papacek & Tony Meredith (Bugs for Bugs), Author provided

Lizzy Lowe, Macquarie University and Manu Saunders, University of New England

Insect pests cause a huge amount of damage to crops globally. In Australia alone, pests are responsible for around A$360 million of crop losses a year. Controlling pest outbreaks is crucial for food security and human health. Since the 1940s, our primary defence against crop pests has been synthetic pesticides. But using pesticides comes at a huge cost.

Not all bugs are bad!

Bees, flies and butterflies help to pollinate our plants. Decomposers like beetles and worms help break down wastes and return nutrients to the soil. Meanwhile, predators and parasites help control the species that are pests. One of the biggest environmental problems with pesticides is that they can affect these beneficial species as well as the pests they’re targeting.

Predatory insects and spiders control pests with none of the health and environmental risks of chemicals. So when we kill these species with insecticides, we are shooting ourselves in the foot.




Read more:
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Losing insects also has flow-on effects for larger animals that rely on them for food. Because invertebrates have such important roles to play in our environment, losing them to insecticides can completely change how ecosystems function.

An alternative to insecticides

Biological control (or biocontrol) relies on “secret agents” – the natural enemies (predators and parasitoids) of pests that live freely in the ecosystems around us.

There is a huge range of predatory invertebrates that eat pests. They include dragonflies, preying mantids, beetles (including ladybugs), lacewings, spiders, mites, wasps, and even some flies.

Parasitoids, meanwhile, are insects that lay their eggs in the bodies of other invertebrates. Their larvae extract nutrients from the host during their development, which ultimately kills the host. Wasps are best known for this strategy but there are also parasitoid flies and beetles.

Lady birds are voracious predators ready to eat pests in crops and gardens.
Manu Saunders

Predators and parasitoids are useful because they use pest insects, like caterpillars and aphids, as food to reproduce and grow their populations. We walk past many of these hard working agents every day without knowing it.

One biocontrol method that gardeners and land managers use is called augmentation. This simply means raising lots of live individuals of particular natural enemies, like ladybirds or wasps, and releasing them into an area to control pests.

Alternatively, gardeners might change the local environment to encourage these natural enemies to move in on their own. They might include natural insectariums or planting different types of vegetation to encourage diverse invertebrate communities. There is increasing evidence of the success of these strategies in organic farming so we should be thinking about using them more broadly.

Selecting your insects

If you want to release biocontrol agents, you need to choose them carefully, just like human special agents. Like any introduced plant or animal, there is a risk that good bugs could become pests (if they feed on the wrong insects, for example).

Selecting biological control agents requires close collaboration between managers, skilled entomologists and other scientists. For each new species, they identify the pest and some potential predators. They look at the predator’s life cycle and resource needs, and consider how it interacts not just with pests, but with other insects too. If agents are coming in from overseas, they also need to be cleared by government biosecurity.

Parasiotid wasps, lacewings, predatory mites, ladybird beetles, and nematodes are all common biocontrol agents. These species are relatively easy to raise in large numbers and work well when released into the field. Spiders are also a really important predator of many pest insects, but they’re often overlooked in the biocontrol game because they are harder to breed – and for some reason people don’t always like releasing large numbers of spiders.

Many biocontrol agents are enemies of pests in general, preying on aphids, caterpillars and fruit flies alike. It’s important to have generalists around for every day pest control, but sometimes a more targeted approach is needed. This is when specialised predators or parasitoids come in. These are species that only target specific pests like leaf miners, beetles, scale insects or spider mites. This way the target pest can be managed with no risk of the parasitoids accidentally attacking other beneficial invertebrates.

Raising good bugs

It’s very exciting to get live insects in the mail!
Lizzy Lowe

Once a biocontrol agent has been selected, greenhouses or lab facilities start raising a large population. This is an emerging market in Australia, but there are already a number of companies in Australia who specialise in rearing biological control agents.

This is a tricky job because demand for the product is variable and is not easy to predict. Warmer seasons are the peak time for most pests, but problems can arise at any time of the year. In most cases the biocontrol company will maintain breeding colonies throughout the year and will be ready to ramp up production at a moment’s notice when a farmer identifies a pest problem. Each company usually provides 10-20 different biocontrol agents and are always looking for new species that might be useful.




Read more:
Birds, bees and bugs: your garden is an ecosystem, and it needs looking after


When it comes to getting the agents to the farmers, the bugs can be shipped as eggs (ready to hatch on arrival), or as live adults ready to disperse and lay their own eggs. The packages are express posted in boxes designed to keep the insects cool and safe.

Once the farmer or natural resource manager receives the bugs, applying them is quite simple. The secret agents are released among the crops, usually by hand, but in some special cases they may be airlifted in via specialised drones!

Drones can be used to deploy biological control agents.
Nathan Roy (Aerobugs)

It’s important to monitor the pests and the biological control agents after release to check that the agents are working. Some farmers are happy to do this themselves but most biological control companies have experts to visit the farms and keep an eye on all parties.

Can I use good bugs in my garden?

The ConversationIf you have a problem with a pest like aphids it is possible to buy predators such as ladybirds or lacewings to quickly deal with the problem. But for long term pest control, there are probably already some natural enemies living in your garden! The easiest and cheapest way to help them is to put the insecticides away and ensure your garden is a friendly environment for secret agents.

Lizzy Lowe, Postdoctoral researcher, Macquarie University and Manu Saunders, Research fellow, University of New England

This article was originally published on The Conversation. Read the original article.

Going to ground: how used coffee beans can help your garden and your health



File 20180201 157495 1dbwul7.jpg?ixlib=rb 1.1
Coffee’s usefulness doesn’t have to end here.
Yanadhorn/Shutterstock.com

Tien Huynh, RMIT University

Did you know that your morning cup of coffee contributes to six million tonnes of spent coffee grounds going to landfill every year? This does not have to be the fate of your caffeine addiction and there are many opportunities to up-cycle spent coffee grounds into valuable commodities.

From fresh fruit, to roasted bean, to used up grounds, coffee’s chemical composition offers a range of uses beyond making your daily brew.




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Sustainable shopping: here’s how to find coffee that doesn’t cost the Earth


Potential applications range from biofuels, to health products, and fertiliser for farms or your garden. So why are we throwing this precious product away?

The answer is that processing and production can be more complex than you might imagine – even when we’re talking about simply using coffee grounds in your garden. What’s more, many recycling initiatives to turn waste coffee into valuable commodities are still in their early stages.

When composted properly, coffee can be an excellent fertiliser.
Author provided

You may have noticed that some cafes now offer free spent coffee grounds for customers to take home and use in the garden. In theory, this is a great initiative but the reality is that fresh coffee grounds are high in caffeine, chlorogenic acid and tannins that are beneficial to humans but toxic to plants.

The spent coffee must be detoxified by composting for a minimum of 98 days for plants to benefit from the potassium and nitrogen contained in the roasted beans. Without adequate composting, the benefits are scant (see below). So if you do take some coffee grounds home from your local cafe, make sure you compost them before sprinkling them on the veggie patch.

Parsley plants after 70 days in soil containing a) 21 days composted spent coffee; b) fresh spent coffee grounds; c) newspaper; d) soil only; and e) fertiliser.
Brendan Janissen, unpublished experimental results., Author provided

The good news is that properly composted coffee grounds offer a cheap alternative to agro-industrial fertilisers, potentially helping urban communities become greener and more sustainable. Savvy businesses have begun processing coffee grounds on a commercial scale, turning them into nutrient-rich fertilisers or soil conditioners in convenient pellets for use in the garden.

The coffee berries before harvest.
Author provided

But why stop there? A potentially even more valuable ingredient is the chlorogenic acid. Although toxic to plants, as mentioned above, chlorogenic acid has potential as a natural health supplement for humans, because of its antioxidant, anticancer and neuroprotective properties.




Read more:
Where’s that bean been? Coffee’s journey from crop to cafe


The whole coffee production process is abundant in chlorogenic acid, particularly in raw coffee beans. Chlorogenic acid conversion efficiency is even better from green coffee pulp, with a 50% recovery rate, compared with 19% for spent coffee grounds.

As undersized and imperfect beans are discarded at this raw stage, many businesses have seized the opportunity to market green coffee extracts as a weight loss product, although more research is needed to confirm this potential.

Roasted coffee beans ready for grinding.
Author provided

The list doesn’t end there. Coffee waste can be used to create a diverse list of chemicals, including enzymes and hormones for digestion of common biological compounds and to improve plant growth; and feedstocks for high-end crops such as mushrooms. Coffee oil has even been trialled as a fuel for London buses.

The ConversationWith abundant waste supplies due to the popularity of coffee consumption, by recycling the byproducts, perhaps we can enjoy one of our favourite beverages without too much guilt.

Tien Huynh, Senior Lecturer in the School of Sciences, RMIT University

This article was originally published on The Conversation. Read the original article.