An unexpected consequence of climate change: heatwaves kill plant pests and save our favourite giant trees



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Gregory Moore, University of Melbourne

Australia is sweltering through another heatwave, and there will be more in the near future as climate change brings hotter, drier weather. In some parts of Australia, the number of days above 40℃ will double by 2090, and with it the tragedy of more heat-related deaths.

In the complex world of plant ecology, however, heatwaves aren’t always a bad thing. Rolling days of scorching temperatures can kill off plant pests, such as elm beetles and mistletoe, and even keep their numbers down for years.

This is what we saw after the 2009 heatwave that reached a record 46.4℃ in Melbourne and culminated in the catastrophic Black Saturday bushfires. Years later, the trees under threat from the pest species were thriving. Here are a few of our observations.

Saving red gums from mistletoe

In the days following Black Saturday, botanists, horticulturists and arborists noticed a curious heatwave side-effect: the foliage of native Australian mistletoes (Amyema miquelii and A. pendula species) growing on river red gums lost their green colour and turned grey.

The two species of mistletoe are important in the ecology of plant communities and to native bird and insect species. But infestation on older trees can lead to their deaths, particularly in drought years.

Australian mistletoe is not related to the northern hemisphere mistletoes of Christmas kissing fame. They are water and nutrient parasites on their host tree and can kill host tissues through excessive water loss.

A eucalyptus tree trunk covered in leaves on a dried brown grass
The native mistletoe, Amyema miquelii, strangles this eucalyptus coolabah in the Burke River floodplain.
John Robert McPherson/Wikimedia, CC BY-SA

Often mistletoes go largely unnoticed, only becoming obvious when they flower. This is because many have evolved foliage with a superficial resemblance to the host species, a phenomenon known as host mimicry or “crypsis”.

During the Black Saturday heatwave, many mistletoes growing on river red gums died. The gums not only survived, but when record rains came in 2010, they thrived. A decade on, the mistletoe numbers are gradually increasing, but they’re still not high enough to threaten the survival of older, significant red gums.




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We want both mistletoes and red gums to persist. But often the old red gums are last survivors of larger populations that have been cleared — a seed source for future regeneration.

Under-appreciated elms

In many parts of Australia, the exotic English and Dutch elms are important parts of the landscapes of cities and regional towns. Elms provide great shade, are resilient and often low-maintenance. They also provide important environmental services, such as nesting sites for native mammals and birds.

Indeed, as Dutch elm disease decimates elm populations across North America and Europe, Australia can claim to have many of the largest elms and the grandest elm avenues and boulevards in the world, which we often under-appreciate.

A street lined by tall elms
Australia is home to some of the most beautiful elm avenues in the world.
denisbin/Flickr, CC BY-ND

But sadly, over the past 30 years the grazing of the elm leaf beetle, Xanthogaleruca luteola, has threatened the grandeur of our elms. These beetles can strip leaves to mere skeletons, and while the damage doesn’t usually kill the tree, it can make them look unsightly.

On Black Saturday, tens of thousands of elm leaf beetles fell from trees after prolonged exposure to high temperature. So many died, they formed what looked like a shadow under the tree canopies. Beetle numbers remained low for at least five years after that.




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Control programs, which often involve spraying chemical pesticides, were not required in that five year period. This was good for the environment as the chemicals can affect non-target sites and species. And we calculated that this saved well over A$2 million for Melbourne alone, money that could be better spent on parks and gardens (and of course, the elms looked splendid!).

Our iconic Moreton Bay figs

Then there are our magnificent, iconic Moreton Bay figs (Ficus macrophylla). Their large, glossy leaves, huge trunks, veils of aerial roots and massive canopies spread for more than 40 metres, and make them an Australian favourite.

Moreton Bay figs are prone to insect infestations of the psyllid, Mycopsylla fici, which can seriously defoliate trees under certain conditions. The fallen leaves can also stick to the shoes of pedestrians, causing a slipping hazard.

In Melbourne, psyllid numbers that were high before Black Saturday fell to undetectable levels in the following month.

Once again, a heatwave and hot windy weather had done an unexpected service. The incidence of psyllids has remained low for a decade or more now and, as with elm leaf beetles, control measures proved unnecessary and money was saved.

An enromous Moreton Bay fig trunk in a park
Moreton Bay figs are prone to insect infestations.
Shutterstock

Winners and losers

Many urban trees are renowned for their resilience to stress, both natural and human-caused. Climate change is proving a significant stress to be overcome, but we’ve observed how the stress can affect pests and disease species more than their hosts.

This gives the species growing in very tough urban conditions, where they lack space and are often deprived of water and good soils, a slight advantage, which may be the difference between living and dying under climate change.




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Climate change is bringing far more losses than gains. But, occasionally, there will be wins, and those managing pests in our urban forests must take advantage when they present.

If insect pest numbers fall we can direct resources to establishing more trees and ensuring our trees are healthier. The best way to avoid pests and diseases attacking trees is by providing the best possible growing conditions. That way we avoid problems before they arise rather than treating symptoms.

So as you swelter during this heatwave, remember it may not be all bad news for our urban and natural environments. Sometimes, positive outcomes arise when and where we least expect them.




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The Conversation


Gregory Moore, Doctor of Botany, University of Melbourne

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

Bushfires threaten drinking water safety. The consequences could last for decades



Warnings about poor drinking water quality are in place in some areas affected by the bushfires.
From shutterstock.com

Stuart Khan, UNSW

Bushfires pose serious short- and long-term impacts to public drinking water quality. They can damage water supply infrastructure and water catchments, impeding the treatment processes that normally make our water safe to drink.

Several areas in New South Wales and Victoria have already been issued with warnings about the quality of their drinking water.

Here’s what we know about the short- and long-term risks.




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Short-term risks

Bushfires can damage or disrupt water supply infrastructure as they burn. And the risks can persist after the fires are out.

A loss of power, for example, disables important water treatment processes such as chlorine disinfection, needed to kill microorganisms and make our water safe to drink.

Drinking water for the towns of Eden and Boydtown on the NSW south coast has been affected in this way over recent days. Residents have been advised to boil their water before drinking it and using it for cooking, teeth brushing, and so on.

Other towns including Cobargo and Bermagui received similar warnings on New Year’s Eve.




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In some cases, untreated water, straight from a river supply, may be fed directly into drinking water systems. Water treatment plants are bypassed completely, due to damage, power loss, or an inability to keep pace with high volumes of water required for firefighting.

We’ve seen this in a number of southern NSW towns this week including Batlow, Adelong, Tumbarumba, and the southern region of Eurobodalla Council, stretching from Moruya to Tilba. Residents of these areas have also been urged to boil their drinking water.

Untreated river water, or river water which has not been properly disinfected with chlorine, is usually not safe for drinking in Australia. Various types of bacteria, as well as the parasites giardia and cryptosporidium, could be in such water.

Animals including cattle, birds and kangaroos can excrete these microorganisms into river water. Septic tanks and sewage treatment plants may also discharge effluents into waterways, adding harmful microorganisms.

Human infection with these microorganisms can cause a range of illnesses, including gastrointestinal diseases with symptoms of diarrhoea and vomiting.




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Long-term risks

Bushfires can damage drinking water catchments, which can lead to longer term threats to drinking water. Drinking water catchments are typically forested areas, and so are vulnerable to bushfire damage.

Severe impacts to waterways may not occur until after intense rainfall. Heavy rain can wash ash and eroded soil from the fires into waterways, affecting drinking water supplies downstream.

For example, bushfire ash contains nutrients, such as nitrogen and phosphorous. Increased nutrient concentrations can stimulate the growth of cyanobacteria, commonly known as “blue-green algae”.

Cyanobacteria produce chemicals which may cause a range of water quality problems, including poor taste and odour. Some cyanobacteria can produce toxic chemicals, requiring very careful management to protect treated drinking water.

Boiling water will kill microorganisms, but not chemical substances.
From shutterstock.com

Many water treatment plants include filtration processes to filter small suspended particles from the water. But an increase in suspended particles, like that which we see after bushfires, would challenge most filtration plants. The suspended particles would be removed, but they would clog the filters, requiring them to be more frequently pulled from normal operation and cleaned.

This cleaning, or backwashing, is a normal part of the treatment process. But if more time must be spent backwashing, that’s less time the filters are working to produce drinking water. And if the rate of drinking water filtration is slowed and fails to keep pace with demand, authorities may place limitations on water use.




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Boiling water isn’t always enough

In order to reduce the risk of gastrointestinal and other illnesses, water suppliers and health departments may issue a boil water alert, as we’ve seen in the past week. Bringing water to a “rolling boil” can reliably kill most of the microorganisms of concern.

In cases where water may be contaminated with chemical substances rather than microorganisms, boiling is usually not effective. So where there’s a risk of chemical contamination, public health messages are usually “do not drink tap water”. This means bottled water only.

Such “do not drink” alerts were issued this week following bushfire impacts to water treatment plants supplying the Victorian towns of Buchan and Omeo.




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Impacts to catchments from bushfires and subsequent erosion can have long-lasting effects, potentially worsening untreated drinking water quality for many years, even decades.

Following these bushfires, many water treatment plant operators and catchment managers will need to adapt to changed conditions and brace for more extreme weather events in the future.The Conversation

Stuart Khan, Professor of Civil & Environmental Engineering, UNSW

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

Animals are disappearing from forests, with grave consequences for the fight against climate breakdown – new research



A toucan eating a fruit in the tropical wetlands of the Pantanal, Brazil.
Uwe Bergwitz/Shutterstock

Charlie Gardner, University of Kent; Jake Bicknell, University of Kent; Matthew Struebig, University of Kent, and Zoe Davies, University of Kent

It’s tempting to think that our forests would be fine if we could simply stop trees being felled or burnt. But forests – particularly tropical ones – are more than just trees. They’re also the animals that skulk and swoop among them.

Worryingly, these furry and feathered companions are rapidly disappearing – and our new research indicates that this will have grave repercussions for the role forests play in combating climate breakdown.

Healthy tropical forests swarm with life. Beyond myriad invertebrates there are seed-eating rodents, a range of leaf eaters, birds of all kinds, and often primates. However, many forests have already lost most of their largest animals, mainly as a result of hunting to supply a growing bushmeat trade.

Hunting isn’t the only reason. Thanks to deforestation for farmland and logging, many forests today are highly fragmented. The small, unconnected patches that remain aren’t big enough to support populations of the largest species, which tend to need more space.

The disappearance of animals from otherwise intact habitats is known as defaunation, and it is leading to a growing number of empty forests not just in tropical countries, but around the world. The UK has already lost most of its largest species (think lynx, wolf, and wisent), while woodland bird numbers have declined by a quarter since 1970.




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The impacts of this defaunation have attracted the attention of the world’s conservation scientists, but studies to date have usually been carried out at single locations. Consequently, we lack a worldwide picture that takes into account different types of forest and the diversity of animals that are disappearing.

To fill this gap, we worked with William Baldwin-Cantello, chief adviser on forests at the World Wide Fund for Nature UK, to gather together all the existing research and perform a meta-analysis – an analysis of analyses – on the available data.

Forest flora need flourishing fauna

Our findings reveal a worrying trend. The loss of animals compromises the ability of forests to reproduce. This effect is particularly severe when primates and birds disappear, because of the key role they play in seed dispersal. Trees make fruit to entice animals to transport their seeds, because they are more likely to germinate and grow successfully if they fall further from their parent tree. So when fruit-eating animals disappear, fewer seeds are dispersed and the trees struggle to reproduce.

A black howler monkey eating a juicy cashew fruit.
akramer/Shutterstock

This animal absence will slowly change how forests look. Most tropical forests today are dominated by trees whose seeds are dispersed by animals. Over time, they are likely to be gradually replaced by trees that use the wind to reproduce. Naturally, these usually have small seeds, and therefore produce smaller trees that store less carbon for the same area of forest. As a result, forests will store less and less carbon, even if we completely halt deforestation.

This is particularly concerning because roughly 20% of the carbon dioxide we emit is absorbed by the world’s vegetation and soils, and half of this is due to tropical forests alone.

Rethinking forest health

Conserving forests is essential for the fight against climate breakdown – and, we do have a global tool at our disposal to help. Known as Reducing Emissions from Deforestation and forest Degradation, or REDD+ for short, it allows wealthy countries with large carbon footprints to pay poorer, tropical countries to protect their forests.

Of course, REDD+ is only an effective tool if the forests countries pay to protect continue to store the same amount of carbon. We usually monitor this by taking satellite images of the quantity of forest canopy remaining. But what satellite imagery can’t do is measure aspects of forest quality beneath the canopy.

Our research strongly suggests that one aspect of forest quality – defaunation – is a vital early warning sign of future losses in the carbon storing capacity of forests. In light of this, policies for managing forest carbon around the world may need a rethink.

We need to pay more attention to what’s going on beneath global forest canopies through research on the ground, though this will be difficult in remote areas. More importantly, we must make sure we’re doing all we can to conserve the full complement of animal species that live in our forests. For example, we need to heavily invest in conservation actions that help communities accustomed to hunting bushmeat to meet their dietary protein needs without harming wildlife. We must also enforce existing rules better, such as those that outlaw hunting within parks and reserves.

Preventing defaunation in forests won’t be easy. But given what we know about the critical role forest animals play, doing so will be essential if we hope to retain diverse and carbon-rich forests in the tropics and around the world. If the beauty and wonder of the forest’s animals wasn’t enough reason to protect them, we now have another: by conserving wildlife, we will be helping to save ourselves from the catastrophic effects of climate breakdown.


Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.The Conversation

Charlie Gardner, Lecturer in Conservation Biology, University of Kent; Jake Bicknell, Lecturer in Conservation Biology, University of Kent; Matthew Struebig, Senior Lecturer in Biological Conservation, University of Kent, and Zoe Davies, Professor of Biodiversity Conservation, University of Kent

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

Mass slaughter of wedge-tailed eagles could have Australia-wide consequences


Simon Cherriman, Murdoch University

Last week it was revealed that at least 136 wedge-tailed eagles have been intentionally poisoned in East Gippsland, with concerns that more are yet to be found.

In the past five years I have used satellite tracking devices to research wedge-tailed eagles’ movements across Australia, and I’ve never encountered raptor deaths on this scale.




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It’s been suggested that the birds were killed to protect lambs. Tragically, not only was this illegal cull unnecessary – evidence suggests that eagles do not often kill livestock – but it could also have ecological consequences right across Australia.

Juvenile birds

There are two main categories of wedge-tailed eagles, based on their age class: sedentary breeding adults, which stay in a home range with nest sites; and highly nomadic juvenile birds that can cover huge distances. There are usually fewer adult birds in one place, because they are territorial.

The very high number of birds affected make it likely that they were largely juveniles. There is currently no accurate data on how many wedge-tailed eagles are in Australia, but this single culling event could have serious effects on future generations’ breeding capacity.




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Sites of persecution can have impacts to eagle populations if they become “ecological sinks”. These are places that draw birds in from a wide area, perhaps because of an unnaturally abundant food source, and then result in birds dying. If these ongoing “mortality black holes” cause hundreds of birds to die in relatively short periods of time, this can start impacting the population.

Do eagles kill lambs?

The wedge-tailed eagle is a powerful predator that kills a variety of mammals. Anecdotal observations by landowners describe birds attacking live lambs and even half-grown sheep. There are also cases in the literature of them working in tandem to hunt larger prey such as kangaroos – behaviour that has been widely documented for large eagle species.

However, evidence gathered during extensive research in Australia has shown that in most cases, eagles seen feeding on lamb or sheep carcasses are “cleaning up” after other predators like foxes and crows, which were actually the direct cause of death.

There are no documented cases of wedge-tailed eagles causing significant economic impacts to the sheep industry. But even if they did, there are other options besides culling. Carcasses placed near livestock would provide easier alternative food sources, for example. Shepherds can effectively guard flocks and protect lambs. Finally, given that wedge-tailed eagles are protected, it may be appropriate for the government to pay compensation for livestock losses.




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It must also be emphasised that eagles prey on a range of other species that are considered to be agricultural pests, such as overabundant native kangaroos, cockatoos, and feral species like rabbits and foxes.

The ConversationSome eagles live, and some die. Such is life on this amazing, arid continent. Death itself is a normal ecological phenomenon, but unnatural deaths on such a large scale can have disastrous consequences for long-lived raptors like the wedge-tailed eagle. We must as a community respect the critical role that predators play in the landscape.

Simon Cherriman, Ornithology, Murdoch University

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

Antarctica and the US Government Shutdown


The link below is to an article that reports on the consequences of the US shutdown in Antarctica.

For more visit:
http://www.treehugger.com/natural-sciences/unprecedented-antarctic-disaster-unfolding-darkness.html

Polar Bears and Climate Change


The link below is to an article that looks at Polar Bears and the consequences of climate change.

For more visit:
http://inhabitat.com/climate-change-is-forcing-polar-bears-to-consume-more-contaminants/

Tasmania: Ocean Warming is Happening


According to a recent report ocean warming is happening off the east coast of Tasmania. The consequences of such warming includes the decline of important kelp forests, fish distribution and changes in fish habitats, and a growing population of destructive sea urchins.

For more visit:
http://www2.utas.edu.au/tools/recent-news/news/cascade-of-climate-change

 

Birds: Feeding Birds not a Good Thing?


Many people love to have native birds visit their gardens. To achieve this we feed birds in a variety of ways. Feeding wild birds does have consequences for the long term survival of the birds being fed. The following link is to an article with more on this subject.

For more visit:
http://www.nwf.org/News-and-Magazines/National-Wildlife/Birds/Archives/2011/Effects-of-Bird-Feeding.aspx