Are more Aussie trees dying of drought? Scientists need your help spotting dead trees



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As climate change threatens Australian trees, it’s important to identify which are at risk.
Nicolás Boullosa/flickr, CC BY-SA

Belinda Medlyn, Western Sydney University; Brendan Choat, Western Sydney University, and Martin De Kauwe, UNSW

Most citizen science initiatives ask people to record living things, like frogs, wombats, or feral animals. But dead things can also be hugely informative for science. We have just launched a new citizen science project, The Dead Tree Detective, which aims to record where and when trees have died in Australia.

The current drought across southeastern Australia has been so severe that native trees have begun to perish, and we need people to send in photographs tracking what has died. These records will be valuable for scientists trying to understand and predict how native forests and woodlands are vulnerable to climate extremes.




Read more:
Recent Australian droughts may be the worst in 800 years


Understanding where trees are most at risk is becoming urgent because it’s increasingly clear that climate change is already underway. On average, temperatures across Australia have risen more than 1℃ since 1910, and winter rainfall in southern Australia has declined. Further increases in temperature, and increasing time spent in drought, are forecast.

How our native plants cope with these changes will affect (among other things) biodiversity, water supplies, fire risk, and carbon storage. Unfortunately, how climate change is likely to affect Australian vegetation is a complex problem, and one we don’t yet have a good handle on.

Phil Spark of Woolomin, NSW submitted this photo to The Dead Tree Detective project online.
Author provided

Climate niche

All plants have a preferred average climate where they grow best (their “climatic niche”). Many Australian tree species have small climatic niches.

It’s been estimated an increase of 2℃ would see 40% of eucalypt species stranded in climate conditions to which they are not adapted.

But what happens if species move out of their climatic niche? It’s possible there will be a gradual migration across the landscape as plants move to keep up with the climate.




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It’s also possible that plants will generally grow better, if carbon dioxide rises and frosts become less common (although this is a complicated and disputed claim.

Farmers have reported anecdotal evidence of tree deaths on social media.
Author provided

However, a third possibility is that increasing climate extremes will lead to mass tree deaths, with severe consequences.

There are examples of all three possibilities in the scientific literature, but reports of widespread tree death are becoming increasingly commonplace.

Many scientists, including ourselves, are now trying to identify the circumstances under which we may see trees die from climate stress. Quantifying these thresholds is going to be key for working out where vegetation may be headed.

The water transport system

Australian plants must deal with the most variable rainfall in the world. Only trees adapted to prolonged drought can survive. However, drought severity is forecast to increase, and rising heat extremes will exacerbate drought stress past their tolerance.

To explain why droughts overwhelm trees, we need to look at the water transport system that keeps them alive. Essentially, trees draw water from the soil through their roots and up to their leaves. Plants do not have a pump (like our hearts) to move water – instead, water is pulled up under tension using energy from sunlight. Our research illustrates how this transport system breaks down during droughts.

Lyn Lacey submitted these photos of dead trees at Ashford, NSW to The Dead Tree Detective.
Author provided

In hot weather, more moisture evaporates from trees’ leaves, putting more pressure on their water transport system. This evaporation can actually be useful, because it keeps the trees’ leaves cool during heatwaves. However if there is not enough water available, leaf temperatures can become lethally high, scorching the tree canopy.

We’ve also identified how drought tolerance varies among native tree species. Species growing in low-rainfall areas are better equipped to handle drought, showing they are finely tuned to their climate niche and suggesting many species will be vulnerable if climate change increases drought severity.

Based on all of these data, we hope to be able to predict where and when trees will be vulnerable to death from drought and heat stress. The problem lies in testing our predictions – and that’s where citizen science comes in. Satellite remote sensing can help us track overall greenness of ecosystems, but it can’t detect individual tree death. Observation on the ground is needed.

These images show a failure of the water transport system in Eucalyptus saligna. Left: well-watered plant. Right: severely droughted plant. On the right, air bubbles blocking the transport system can be seen.
Brendan Choat, Author provided

However, there is no system in place to record tree death from drought in Australia. For example, during the Millennium Drought, the most severe and extended drought for a century in southern Australia, there are almost no records of native tree death (other than along the rivers, where over-extraction of water was also an issue). Were there no deaths? Or were they simply not recorded?

The current drought gripping the southeast has not been as long as the Millennium Drought, but it does appear to be more intense, with some places receiving almost no rain for two years. We’ve also had a summer of repeated heatwaves, which will have intensified the stress.




Read more:
Is Australia’s current drought caused by climate change? It’s complicated


We’re hearing anecdotal reports of tree death in the news and on twitter. We’re aiming to capture these anecdotal reports, and back them up with information including photographs, locations, numbers and species of trees affected, on the Dead Tree Detective.

We encourage anyone who sees dead trees around them to hop online and contribute. The Detective also allows people to record tree deaths from other causes – and trees that have come back to life again (sometimes dead isn’t dead). It can be depressing to see trees die – but recording their deaths for science helps to ensure they won’t have died in vain.The Conversation

Belinda Medlyn, Professor, Western Sydney University; Brendan Choat, Associate Professor, Western Sydney University, and Martin De Kauwe, Senior Research Fellow, UNSW

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

Antarctica’s ‘moss forests’ are drying and dying



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Lush moss beds in East Antarctica’s Windmill Islands.
Sharon Robinson, Author provided

Melinda Waterman, University of Wollongong; Johanna Turnbull, University of Wollongong, and Sharon Robinson, University of Wollongong

The lush moss beds that grow near East Antarctica’s coast are among the only plants that can withstand life on the frozen continent. But our new research shows that these slow-growing plants are changing at a far faster rate than anticipated.

We began monitoring plant ecosystems 18 years ago, near Australia’s Casey Station in the Windmill Islands, East Antarctica.

Casey Station is on East Antarctica’s coast. Click map to zoom.
Australian Antarctic Data Centre

As we report in Nature Climate Change today, within just 13 years we observed significant changes in the composition and health of these moss beds, due to the drying effects of weather changes prompted by damage to the ozone layer.

Living on the edge

Visitors to Antarctica expect to see a stark landscape of white and blue: ice, water, and sky. But in some places summer brings a surprisingly verdant green, as lush mosses emerge from under their winter snow blanket.

Because it contains the best moss beds on continental Antarctica, Casey Station is dubbed the Daintree of the Antarctic. Individual plants have been growing here for at least 100 years; fertilised by ancient penguin poo.




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Antarctic mosses are extremophiles, the only plants that can survive the continent’s frigid winters. They live in a frozen desert where life-sustaining water is mostly locked up as ice, and they grow at a glacial pace – typically just 1 mm a year.

These mosses are home to tardigrades and other organisms, all of which survive harsh conditions by drying out and becoming dormant. When meltwater is available, mosses soak it up like a sponge and spring back to life.

The short summer growing season runs from December to March. Day temperatures finally rise above freezing, providing water from melting snow. Overnight temperatures drop below zero and mosses refreeze. Harsh, drying winds reach speeds of 200 km per hour. This is life on the edge.

Tough turf

When we first began monitoring the moss beds, they were dominated by Schistidium antarctici, a species found only in Antarctica. These areas were typically submerged through most of the summer, favouring the water-loving Schistidium. But as the area dries, two hardy, global species have encroached on Schistidium’s turf.

Like tree rings, mosses preserve a record of past climate in their shoots. From this we found nearly half of the mosses showed evidence of drying.

Healthy green moss has turned red or grey, indicating that plants are under stress and dying. This is due to the area drying because of colder summers and stronger winds. This increased desertification of East Antarctica is caused by both climate change and ozone depletion.

Moss beds, with moss in the foreground showing signs of stress.
Sharon Robinson, Author provided

Since the 1970s, man-made substances have thinned Earth’s protective sunscreen, the ozone layer, creating a hole that appears directly over Antarctica during the southern spring (September–November). This has dramatically affected the southern hemisphere’s climate. Westerly winds have moved closer to Antarctica and strengthened, shielding much of continental East Antarctica from global warming.

Our study shows that these effects are contributing to drying of East Antarctica, which is in turn altering plant communities and affecting the health of some native plant species. East Antarctica’s mosses can be viewed as sentinels for a rapidly drying coastal climate.

But there is good news. The ozone layer is slowly recovering as pollutants are phased out thanks to the 1987 Montreal Protocol. What is likely to happen to Antarctic coastal climates when ozone levels recover fully by the middle of this century?




Read more:
The ozone hole leaves a lasting impression on southern climate


Unlike other polar regions, East Antarctica has so far experienced little or no warming.

Antarctic ice-free areas are currently less than 1% of the continent but are predicted to expand over the coming century. Our research suggests that this may isolate moss beds from snow banks, which are their water reservoirs. Ironically, increased ice melt may be bad news for some Antarctic mosses.

East Antarctica is drying – first at the hands of ozone depletion, and then by climate change. How its native mosses fare in the future depends on how we control greenhouse gas emissions. But with decisive action and continued monitoring, we can hopefully preserve these fascinating ecosystems for the future.The Conversation

Melinda Waterman, Associate lecturer, University of Wollongong; Johanna Turnbull, Associate Lecturer in Biology, University of Wollongong, and Sharon Robinson, Professor, University of Wollongong

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

Don’t worry, the chance of dying from potting mix is very slim



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Potting mix is known to carry harmful bacteria and fungi.
Photo by Markus Spiske on Unsplash

Peter Collignon, Australian National University

Gardening is generally a healthy and pleasurable hobby or occupation. However, any activity carries some risk – and gardening is no exception.

Potting mix is known to carry harmful bacteria and fungi. And there have been reports of deaths from diseases, such as the Legionnaires’ disease (a lung infection), that have been attributed to bacteria in potting mix.

Many bacteria and fungi that can cause infections in people live in soil and water. So it’s not surprising that potting mix can also have in it bacteria and fungi that may on occasion cause harm to people, and in rare cases even kill them. But it’s important to note that, overall, the risk is very low.




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Fertilising more than plants

Potting mix is usually a mixture of inorganic and organic material. It’s also often at a higher temperature compared to soil because of where and how it’s stored, so it retains heat for longer. Bacteria and fungi generally grow better and reach higher numbers when they are in moist and warm environments.

Potting mix is usually warmer than soil, which makes it a better environment for bacteria and fungi to grow.
from shutterstock.com

If bacteria or fungi are already present in low numbers, they can quickly grow to very high numbers in optimal conditions. This includes many bacteria in soil that can cause problems in people – such as strains of nocardia (causes nocardiosis, an infection of the lungs or whole body), legionella (causes Legionnaires’ disease), and clostridium (causes tetanus).

Numerous fungi can also be present in soil and potting mix. In certain areas of the world, soil contains fungi that can invade if inhaled and cause disease. These include the lung infection histoplasmosis, which is caused by a fungus that lives mainly in parts of the United States, but also in some parts of Central and South America, Africa, Asia, and Australia.

Protecting ourselves

The risk to most people of becoming infected with any of these bacterial or fungal diseases is very low. Disease is more likely to be a risk when the micro-organisms are present in very high numbers.

Bacteria or fungi also need to be introduced into our bodies to cause disease. This usually happens through inhalation, where the organisms go into the lungs. It can also occur through the skin, such as with the chronic fungal infection sporotrichosis, also known as “rose gardener’s disease”. If, for any reason, micro-organisms are present in high numbers, then the exposure and risk will be higher.

A fungal infection known as rose gardener’s disease can happen with the organism entering the skin directly through an injury.
from shutterstock.com

There are many things we can do to protect ourselves from introducing bacteria or fungi into our bodies. The most essential is basic hygiene.

If people smoke, eat or drink without first washing their hands, they are at an increased risk of legionella infection from potting mix. This implies direct inhalation isn’t the only way for the bacteria to enter the body, but that oral intake of micro-organisms via contaminated hands is also a risk.

Another added protection measure is wearing gloves. This doesn’t mean you should then not wash your hands before eating. A physical barrier in addition to washing hands obviously provides better protection.




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(At least) five reasons you should wear gardening gloves


Masks can be worn in high-risk situations, such as when opening a bag of potting mix. Directing the bag away from the gardener when opened, and being in a well-ventilated area, will decrease any inhalation risk.

Signs of infection

People who have a lower immunity, such as those with diseases such as HIV or lymphoma, are more at risk of catching something from potting mix. So it’s even more important they use extra appropriate precautions, including wearing masks when in higher-risk situations.

Simple safety provisions can protect us from harmful bacteria and fungi.
Shutterstock

The symptoms or signs of infection acquired from soil or potting mix depend on where the infection is and what micro-organism is causing it. With potting mix, the main worry is legionella longbeachae. This generally causes a lung infection such as pneumonia.

Symptoms can initially be fever, aches and pains, which are fairly general of illness. But as the infection involves more of the respiratory tract, cough, shortness of breath and/or pain on breathing may develop.

Treatment

While potting-mix-linked legionella infections are uncommon, cases have occurred in countries including Australia, Japan and the US.

So, if people develop symptoms that are ongoing and have had recent exposure to potting mix within the incubation period (two to ten days after exposure), they need to seek medical help and make it clear to that person that they were worried about potting mix being involved.

It’s important to note the potting mix connection because antibiotics needed to kill legionella are different to standard penicillin-like antibiotics often used to treat pneumonia acquired in the community.




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The ConversationOverall, though, we need to keep these risks in perspective. Millions of people garden and all will be exposed to soil and/or potting mix. Very few of these infections occur in Australia and elsewhere. Fairly simple provisions such as washing hands, wearing gloves and – where necessary – wearing a mask will ensure rates of infection remain low.

Peter Collignon, Professor, infectious diseases and microbiology, Australian National University

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

Article: Extinction – Pinta Giant Tortoise


The link below is to an article that reports on the extinction of the Pinta Giant Tortoise, with the last representative of the species dying in the Galapagos National Park.

For more visit:
http://www.bbc.co.uk/news/world-18574279