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



File 20190326 36273 5tp4r3.jpg?ixlib=rb 1.1
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.




Read more:
How the warming world could turn many plants and animals into climate refugees


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.

Advertisements

To predict droughts, don’t look at the skies. Look in the soil… from space


Siyuan Tian, Australian National University and Albert Van Dijk, Australian National University

Another summer, another drought. Sydney’s water storages are running on empty, and desalinisation plants are being dusted off. Elsewhere, shrunken rivers, lakes and dams are swollen with rotting fish. Governments, irrigators and environmentalists blame each other for the drought, or just blame it on nature.

To be sure, Australia is large enough to usually leave some part of our country waiting for rain. So what exactly is a drought, and how do we know when we are in it?

This question matters, because declaring drought has practical implications. For example, it may entitle those affected to government assistance or insurance pay-outs.

But it is also a surprisingly difficult question. Droughts are not like other natural hazards. They are not a single extreme weather event, but the persistent lack of a quite common event: rain. What’s more, it’s not the lack of rain per se that ultimately affects us. The desert is a dry place but it cannot always be called in drought.

Ultimately, what matters are the impacts of drought: the damage to crops, pastures and environment; the uncontrollable fires that can take hold in dried-up forests and grasslands; the lack of water in dams and rivers that stops them from functioning. Each of these impacts is affected by more than just the amount of rain over an arbitrary number of months, and that makes defining drought difficult.




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


Scientists and governments alike have been looking for ways to measure drought in a way that relates more closely to its impacts. Any farmer or gardener can tell you that you don’t need much rain, but you do need it at the right time. This is where the soil becomes really important, because it is where plants get their water.

Too much rain at once, and most of it is lost to runoff or disappears deep into the soil. That does not mean it is lost. Runoff helps fill our rivers and waterways. Water sinking deep into the soil can still be available to some plants. While our lawn withers, trees carry on as if there is nothing wrong. That’s because their roots dig further, reaching soil moisture that is buried deep.

A good start in defining and measuring drought would be to know how much soil moisture the vegetation can still get out of the soil. That is a very hard thing to do, because each crop, grass and tree has a different root system and grows in a different soil type, and the distribution of moisture below the surface is not easy to predict. Many dryland and irrigation farmers use soil sensors to measure how well their crops are doing, but this does not tell us much about the rest of the landscape, about the flammability of forests, or the condition of pastures.

Not knowing how drought conditions will develop, graziers face a difficult choice: sell their livestock or buy in feed?
Shutterstock

Soils and satellites

As it turns out, you need to move further away to get closer to this problem – into space, to be precise. In our new research, published in Nature Communications, we show just how much satellite instruments can tell us about drought.

The satellite instruments have prosaic names such as SMOS and GRACE, but the way they measure water is mind-boggling. For example, the SMOS satellite unfurled a huge radio antenna in space to measure very specific radio waves emitted by the ground, and from it scientists can determine how much moisture is available in the topsoil.

Even more amazingly, GRACE (now replaced by GRACE Follow-On) was a pair of laser-guided satellites in a continuous high-speed chase around the Earth. By measuring the distance between each other with barely imaginable accuracy, they could measure miniscule changes in the Earth’s gravitational field caused by local increases or decreases in the amount of water below the surface.

By combining these data with a computer model that simulates the water cycle and plant growth, we created a detailed picture of the distribution of water below the surface.

It is a great example showing that space science is not just about galaxies and astronauts, but offers real insights and solutions by looking down at Earth. It also shows why having a strong Australian Space Agency is so important.




Read more:
The lessons we need to learn to deal with the ‘creeping disaster’ of drought


Taking it a step further, we discovered that the satellite measurements even allowed us to predict how much longer the vegetation in a given region could continue growing before the soils run dry. In this way, we can predict drought impacts before they happen, sometimes more than four months in advance.

Map showing how many months ahead, on average, drought impacts can be predicted with good accuracy.
author provided

This offers us a new way to look at drought prediction. Traditionally, we have looked up at the sky to predict droughts, but the weather has a short memory. Thanks to the influence of ocean currents, the Bureau of Meteorology can sometimes give us better-than-evens odds for the months ahead (for example, the next three months are not looking promising), but these predictions are often very uncertain.

Our results show there is at least as much value in knowing how much water is left for plants to use as there is in guessing how much rain is on the way. By combining the two information sources we should be able to improve our predictions still further.

Many practical decisions hinge on an accurate assessment of drought risk. How many firefighters should be on call? Should I sow a crop in this paddock? Should we prepare for water restrictions? Should we budget for drought assistance? In future years, satellites keeping an eye on Earth will help us make these decisions with much more confidence.The Conversation

Siyuan Tian, Postdoctoral fellow, Australian National University and Albert Van Dijk, Professor, Water and Landscape Dynamics, Fenner School of Environment & Society, Australian National University

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

The Darling River is simply not supposed to dry out, even in drought



File 20190115 180516 1t15oz7.jpg?ixlib=rb 1.1
Puddles in the bed of the Darling River are a sign of an ecosystem in crisis.
Jeremy Buckingham/Flickr, CC BY-SA

Fran Sheldon, Griffith University

The deaths of a million of fish in the lower Darling River system over the past few weeks should come as no surprise. Quite apart from specific warnings given to the NSW government by their own specialists in 2013, scientists have been warning of devastation since the 1990s.

Put simply, ecological evidence shows the Barwon-Darling River is not meant to dry out to disconnected pools – even during drought conditions. Water diversions have disrupted the natural balance of wetlands that support massive ecosystems.

Unless we allow flows to resume, we’re in danger of seeing one of the worst environmental catastrophes in Australia.




Read more:
Explainer: what causes algal blooms, and how we can stop them


Dryland river

The Barwon-Darling River is a “dryland river”, which means it is naturally prone to periods of extensive low flow punctuated by periods of flooding.

However, the presence of certain iconic river animals within its channels tell us that a dry river bed is not normal for this system. The murray cod, dead versions of which have recently bought graziers to tears and politicians to retch, are the sentinels of permanent deep waterholes and river channels – you just don’t find them in rivers that dry out regularly.

Less conspicuous is the large river mussel, Alathyria jacksoni, an inhabitant of this system for thousands of years. Its shells are abundant in aboriginal middens along the banks. These invertebrates are unable to tolerate low flows and low oxygen, and while dead fish will float (for a while), shoals of river mussels are probably dead on the river bed.

This extensive drying event will cause regional extinction of a whole raft of riverine species and impact others, such as the rakali. We are witnessing an ecosystem in collapse.

Catastrophic drying

We can see the effects of permanent drying around the world. The most famous example is the drying of the Aral Sea in Central Asia. Once the world’s fourth largest inland lake, it was reduced to less than 10% of its original volume after years of water extraction for irrigation.

The visual results of this exploitation still shock: images of large fishing boats stranded in a sea of sand, abandoned fishing villages, and a vastly changed microclimate for the regions surrounding the now-dry seabed. Its draining has been described as “the world’s worst environmental disaster”.




Read more:
Humans drained the Aral Sea once before – but there are no free refills this time round


So, what does the Aral Sea and its major tributaries and the Darling River system with its tributary rivers have in common? Quite a lot, actually. They both have limited access to the outside world: the Aral Sea basin has no outflow to the sea, and while the Darling River system connects to the River Murray at times of high flow, most of its water is held within a vast network of wetlands and floodplain channels. Both are semi-arid. More worryingly, both have more the 50% of their average inflows extracted for irrigation.

There is one striking difference between them. The Aral Sea was a permanent inland lake and its disappearance was visually obvious. The wetlands and floodplains of the Barwon-Darling are mostly ephemeral, and the extent of their drying is therefore hard to visualise.




Read more:
It’s time to restore public trust in the governing of the Murray Darling Basin


An orphaned ship in former Aral Sea, near Aral, Kazakhstan.
Wikipedia

All the main tributaries of the Darling River have floodplain wetland complexes in their lower reaches (such as the Gwydir Wetlands, Macquarie Marshes and Narran Lakes). When the rivers flow they absorb the water from upstream, filling before releasing water downstream to the next wetland complex; the wetlands acting like a series of tipping buckets. Regular river flows are essential for these sponge-like wetlands.

So, how has this hydrological harmony of regular flows and fill-and-spill wetlands changed? And how does this relate to the massive fish kills we are seeing in the lower Darling system?




Read more:
How is oxygen ‘sucked out’ of our waterways?


While high flows will still make it through the Barwon-Darling, filling the floodplains and wetlands, and connecting to the River Murray, the low and medium flow events have disappeared. Instead, these are captured in the upper sections of the basin in artificial water storages and used in irrigation.

This has essentially dried the wetlands and floodplains at the ends of the tributaries. Any water not diverted for irrigation is now absorbed by the continually parched upstream wetlands, leaving the lower reaches vulnerable when drought hits.

By continually keeping the Barwon-Darling in a state of low (or no) flow, with its natural wetlands dry, we have reduced its ability to cope with extended drought.




Read more:
Why a wetland might not be wet


While droughts are a natural part of this system and its river animals have adapted, they can’t adjust to continual high water caused in some areas by water diversions – and they certainly can’t survive long-term drying.

The Basin Plan has come some way in restoring some flows to the Barwon-Darling, but unless we find a way to restore more of the low and medium flows to this system we are likely witnessing Australia’s worst environmental disaster.




Read more:
It will take decades, but the Murray Darling Basin Plan is delivering environmental improvements


The Conversation


Fran Sheldon, Professor, Australian Rivers Institute, Griffith University, Griffith University

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

Australia’s 2018 in weather: drought, heat and fire


File 20190109 32145 fgmsp9.jpg?ixlib=rb 1.1
Queensland’s ‘unprecedented’ bushfires were part of a year of extremes.
RACQ CQ/AAP

Karl Braganza, Australian Bureau of Meteorology

Last year was a time of exceptional weather and record-breaking heat according to the Bureau of Meteorology’s annual climate statement, which was released last night.

The Bureau issued four Special Climate Statements relating to “extreme” and “abnormal” heat, and reported a number of broken climate records.

One of the headline stories for the year was drought across eastern Australia — centred on New South Wales, but also affecting Victoria, eastern South Australia and southern Queensland.


Bureau of Meteorology

With the whole of NSW declared in drought during the latter half of 2018, this drought will be recorded as one of the more significant in Australia’s history, ranking alongside the Millennium, 1960s, World War Two and Federation Droughts. Of those historic droughts, only the Millennium Drought saw similar, accompanying high temperatures.

The below-average rainfall has persisted for around two years across much of NSW and adjacent regions. The drought conditions were particularly severe in the recent spring period, with low rainfall, persistently high temperatures, and record high evaporation.

This exceptionally dry period was influenced by sea surface temperatures to the west of the continent. Perhaps fortuitously, a developing El Niño in the Pacific Ocean failed to mature in the second half of the year. An El Niño would have typically exerted a further drying influence on eastern Australia.




Read more:
Australia moves to El Niño alert and the drought is likely to continue


The dry conditions in eastern states were severe enough to see Australia record its lowest September rainfall on record, and the second-lowest on record for any month — behind April 1902, during the prolonged Federation Drought. Over 2018, Australia’s annual rainfall was 11% below average, and the lowest recorded since 2005, during the Millennium Drought.

In contrast, above-average rainfall was recorded across parts of the tropical north, and most significantly in the Kimberley, consistent with recent trends of increasing rainfall in that region.

The drought conditions were exacerbated by record or near-record temperatures across many parts of the country. It was Australia’s third warmest year on record, behind 2013 and 2005. Daytime maximum temperatures were the warmest on record for NSW and Victoria, and second-warmest for South Australia, the Northern Territory and Australia as a whole.


Bureau of Meteorology

Persistent dry conditions through winter are typically associated with low soil moisture and heatwaves in the following spring and summer, and 2018 followed this pattern — with the added contribution of a warming climate.

The year ended with some record-breaking heat events. Perhaps the most significant of these was the extreme heat along the central and northern Queensland coast in late November and early December, which saw maximum daytime temperatures of 42.6 °C in Cairns and 44.9 °C in Proserpine on the 26th of November.

These temperatures, combined with persistent dry conditions in the preceding months, saw catastrophic fire weather and bushfires along 600km of the Queensland coast, an event that fire agencies have called unprecedented for the state.




Read more:
Sydney storms could be making the Queensland fires worse


The year ended with a burst of heat over the Christmas-New Year period, with temperatures at least 10 degrees warmer than average across southern South Australia, most of Victoria and southern NSW, leading to Australia’s warmest December on record.


Subscribe to receive Bureau Climate Information emails.The Conversation

Karl Braganza, Climate Scientist, Australian Bureau of Meteorology

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

Why is everyone talking about natural sequence farming?


Ian Rutherfurd, University of Melbourne

On the eve of the recent National Drought Summit, prime minister Scott Morrison and deputy prime minister Michael McCormack visited Mulloon Creek near Canberra, shown recently on the ABC’s Australian Story. They were there to see a creek that was still flowing, and green with vegetation, despite seven months of drought.

Mulloon Creek was the legacy of a long collaboration between prominent agriculturalist Peter Andrews, and Tony Coote, the owner of the property who died in August. For decades they have implemented Andrews’ “natural sequence farming” system at Mulloon Creek.




Read more:
Government to set up new multi-billion Future Drought Fund


Central to the system is slowing flow in the creek with “leaky weirs”. These force water back into the bed and banks of the creek, which rehydrates the floodplain. This rehydrated floodplain is then said to be more productive and sustainable.

McCormack, who is also the minister for infrastructure, transport and regional development, was impressed and declared the success of Mulloon as a “model for everyone … this needs to be replicated right around our nation”. The ABC program suggested this form of farming could reduce the impact of drought across Australia. So, what is the evidence?

The promise of natural sequence farming

There are plenty of anecdotes but little published science around the effectiveness of natural sequence farming. What there is describes some modest floodplain rehydration, little change to stream flows, some trapping of sediment and some improvements in soil condition. These results are encouraging but not miraculous.

How much each of the different components of natural sequence farming contributes is not always clear, and the economic arguments for widespread adoption are modest. At present, there is not the standard of evidence to support this farming method as a panacea for drought relief, as proposed by the deputy prime minister.




Read more:
Helping farmers in distress doesn’t help them be the best: the drought relief dilemma


But if the evidence does emerge, why wouldn’t farmers simply adopt the methods as part of a sensible business model? Don’t all farmers want to do better in drought?

In the ABC show, and elsewhere, supporters of natural sequence farming argue that it is hard for farmers to adopt the methods because government regulations restrict use of willows, blackberries and other weeds, that they claim, are particularly effective in restoring streams.

Governments are correct to be wary of this call to use weeds, and some research suggests that native plants can do a similar job. This restriction on use of weeds might be galling for proponents of natural sequence farming but it should not be a fundamental impediment to adoption.

A more important frustration for natural sequence farming practitioners is how widely the approach can be applied. In Australian Story, John Ryan, a rural journalist, says:

I am sick of politicians, farmers groups, and government departments telling me that Peter Andrews only works where you’ve got little creeks in a mountain valley … I’ve seen it work on flat-lands, steep lands, anywhere.

Natural sequence farming arose in the attempt to restore upland valleys and creeks in southern NSW that were once environmentally valuable chains of ponds or swampy meadows. But these waterways have become deeply incised, degraded, and disconnected from their floodplains. Not only does this incision produce a great deal of sediment pollution, but it produces many agricultural problems.




Read more:
Spring is coming, and there’s little drought relief in sight


In reality, small and medium-sized stream systems across much of Australia have deepened after European settlement. If the leaky weirs of natural sequence farming are effective, then they could be applied across many gullied and incised streams across the country.

We’ve already been doing it

The good news is that landholders and governments have already been using aspects of natural sequence farming in those very gullies for decades to control erosion.

Since the 1970s, across the world, one useful method for controlling erosion has been grade-control structures. They were once made of concrete but are now usually made of dumped rock (called rock-chutes), and also logs.

Rock chutes in Barwidgee Creek, 1992, Ovens River catchment, Victoria. Source: T McCormack NE Catchment Management Authority.
T McCormack NE Catchment Management Authority
The same creek in 2002. It is now heavily vegetated and has pools of water, just like Mulloon Park.
T McCormack NE Catchment Management Authority

These structures reduce the speed of water flow, trap sediment, encourage vegetation, and stop gullies from deepening. These are all goals of natural sequence farming using leaky weirs.

There are thousands of such structures, supported by government initiatives, across the Australian landscape acting as an unrecognised experiment in rehydration and drought protection.




Read more:
We must strengthen, not weaken, environmental protections during drought – or face irreversible loss


Perhaps governments should already have evaluated these structures, but the rehydration potential of these works has not been recognised in the past. It is time that this public investment was scientifically evaluated.

We may find that natural sequence farming and the routine government construction of grade-control structures have similar effects on farmland and the environment.

But whatever the outcome, gully management is not likely to mark the end of drought in the Australian landscape.The Conversation

Ian Rutherfurd, Associate Professor in Geography, University of Melbourne

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

We need more carbon in our soil to help Australian farmers through the drought


File 20181011 72127 z4wp9y.jpg?ixlib=rb 1.1
Healthy soils can hold water even during droughts.
Evie Shaffer/Unsplash

Nanthi Bolan, University of Newcastle

Australia has never been a stranger to droughts, but climate change is now super-charging them.

Besides taking a toll on human health, droughts also bake the earth. This means the ground holds less water, creating a vicious cycle of dryness.

Our research has investigated ways to improve the health and structure of soil so it can hold more water, even during droughts. It’s vital to help farmers safeguard their soil as we adapt to an increasingly drought-prone climate.




Read more:
Australia moves to El Niño alert and the drought is likely to continue


Soil moisture is key

The immediate effect of drought is complete loss of soil water. Low moisture reduces soil health and productivity, and increases the loss of fertile top soil through wind and water erosion.

To describe how we can improve soil health, we first need to explain some technical aspects of soil moisture.

Soil with good structure tends to hold moisture, protecting soil health and agricultural productivity.
Author provided

Soil moisture is dictated by three factors: the ability of the soil to absorb water; its capacity to store that water; and the speed at which the water is lost through evaporation and runoff, or used by growing plants.

These three factors are primarily determined by the proportions of sand, silt and clay; together these create the “soil structure”. The right mixture means there are plenty of “pores” – small open spaces in the soil.




Read more:
How to fight desertification and drought at home and away


Soils dominated by very small “micropores” (30-75 micrometres), such as clay soil, tend to store more water than those dominated by macropores (more than 75 micrometers), such as sandy soil.

If the balance is skewed, soil can actually repel water, increasing runoff. This is a major concern in Australia, especially in some areas of Western Australia and South Australia.

Improving soil structure

Good soil structure essentially means it can hold more water for longer (other factors include compaction and surface crust).

Farmers can improve soil structure by using minimum tillage, crop rotation and return of crop residues after harvest.

Another important part of the puzzle is the amount of organic matter in the soil –it breaks down into carbon and nutrients, which is essential for absorbing and storing water.

There are three basic ways to increase the amount of organic matter a given area:

  • grow more plants in that spot, and leave the crop and root residue after harvest

  • slow down decomposition by tilling less and generally not disturbing the soil more than absolutely necessary

  • apply external organic matter through compost, mulch, biochar and biosolids (treated sewage sludge).

Typically, biosolids are used to give nutrients to the soil, but we researched its impact on carbon storage as well. When we visited a young farmer in Orange, NSW, he showed us two sites: one with biosolids, and one without. The site with biosolids grew a bumper crop of maize the farmer could use as fodder for his cattle; the field without it was stunted.

The farmer told us the extra carbon had captured more moisture, which meant strong seedling growth and a useful crop.




Read more:
On dangerous ground: land degradation is turning soils into deserts


This illustrates the value of biowastes including compost, manure, crop residues and biosolids in capturing and retaining moisture for crop growth, reducing the impact of drought on soil health and productivity.

Improving soil health cannot happen overnight, and it’s difficult to achieve while in midst of a drought. But how farmers manage their soil in the good times can help prepare them for managing the impacts of the next drought when it invariably comes.


The author would like to thank Dr Michael Crawford, CEO of Soil CRC, for his substantial contribution to this article.The Conversation

Nanthi Bolan, Professor of Enviornmental Science, University of Newcastle

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

We must strengthen, not weaken, environmental protections during drought – or face irreversible loss



File 20180924 129862 1fr9qma.jpg?ixlib=rb 1.1
The Flock Bronzewing is an inland species that is vulnerable to drought. Those vulnerabilities are heightened in an era of climate change and increased risks from feral predators.
Shutterstock

John Woinarski, Charles Darwin University; Chris Dickman, University of Sydney; Richard Kingsford, UNSW, and Sarah Legge, Australian National University

Australian rural communities face hardships during extended drought, and it is generally appropriate that governments then provide special support for affected landholders and communities.

However, some politicians and commentators have recently claimed that such circumstances should be addressed by circumventing environmental laws or management – by, for example, reallocating environmental water to grow fodder or opening up conservation reserves for livestock grazing.

But subverting or weakening existing protective conservation management practices and policies will exacerbate the impacts of drought on natural environments and biodiversity.




Read more:
Giving environmental water to drought-stricken farmers sounds straightforward, but it’s a bad idea


Drought-related decline in wildlife

Impacts of severe weather on some natural systems are obvious and well-recognised. For example, during periods of elevated sea temperature, coral bleaching may conspicuously signal extensive environmental degradation and biodiversity loss.

On land, however, the impacts of comparable extreme climatic events on natural systems may be less obvious, even if of comparable magnitude.

Nonetheless, the record is clear: drought leads to extensive and severe declines in many wildlife species.

Early observers in Australia reported the collapse of bird communities (“the bush fell silent”) and other wildlife across vast areas during the Federation Drought.

There were comparable responses during the Millennium Drought.

Unsurprisingly, wetland environments, and species dependent on them, may bear the brunt of impacts. That said, impacts are pervasive across all landscapes exposed to drought.

Drought contributed to the extinction of one of Australia’s most beautiful birds, the Paradise Parrot. For example, the pastoralist and zoologist Charles Barnard noted:

Previous to the terrible drought of 1902 it was not uncommon to see a pair of these birds when out mustering … but since that year not a single specimen has been seen … For three years… there had been no wet season, and very little grass grew, consequently there was little seed; then the worst year came on, in which no grass grew, so that the birds could not find a living, and … perished … they have not found their way back.

Drought contributed to the extinction of one of Australia’s most beautiful birds, the Paradise Parrot.
Wikimedia, CC BY

After the long droughts break, native plant and animal species may take many years to recover, and some never recover or return to their former range.

Threatened plant and animal species – with an already tenuous toe-hold on existence – are often the most affected.

Days of extremely hot temperatures also exceed the thermoregulatory tolerance of some species. That means mass mortality for some animals; and large numbers of even hardy native trees may be killed by heat and lack of rain across extensive areas.

Furthermore, water sources can disappear from much of the landscape. Organisms dependent on floods are now more vulnerable, given that overallocation of water from rivers has increased drying of wetlands.

Drought is not new in Australia, but the stresses are greater now

Of course, drought has long been a recurrent characteristic of Australia. Indeed, many Australian plants and animals are among the most drought-adapted and resilient in the world. But drought impacts on wildlife are now likely to be of unprecedented severity and duration, for several reasons:

  1. with global climate change, droughts will be more severe and frequent. There will be less opportunity for wildlife to recover in the reduced interval between drought periods

  2. feral cats and introduced foxes now occur across most of Australia. In drought periods, these hunt more effectively because drought reduces the ground-layer vegetation that many native prey species rely upon for shelter. Cats and foxes also congregate and hunt more efficiently as wildlife cluster around the few water sources that are left

  3. prior to European settlement, the reduction in vegetation during drought would have been accompanied by natural feedback loops, notably reduction in the density of native herbivores. Now, livestock are often maintained in drought-affected areas, with supplementary food provided, but they also graze on what little native vegetation remains. Now, wildlife must compete with feral goats, camels and rabbits for the last vestiges of vegetation

  4. clearing of native vegetation across much of the eastern rangelands means it will now be much harder for species lost from some areas during drought to recolonise their former haunts after drought. The habitat connectivity has been lost

  5. many wildlife species could previously endure drought by maintaining a residue of their population in small refuge areas, where nutrients or moisture persisted in an otherwise hostile landscape. Now, livestock, feral herbivores and predators also congregate at these areas, making them less effective as native wildlife refuges

  6. in at least woodland and forest habitats, droughts may interact with other factors. Notably, drought increases the likelihood of high intensity and extensive bushfires that can cause long-lasting damage to wildlife and environments.




Read more:
Australia burns while politicians fiddle with the leadership


Our intention here is not to downplay the needs or plight of rural communities affected by drought.

Rather, we seek to bring attention to the other life struggling in that landscape. Australia should bolster, not diminish, conservation efforts during drought times. If we don’t, we will suffer irretrievable losses to our nature.The Conversation

John Woinarski, Professor (conservation biology), Charles Darwin University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Richard Kingsford, Professor, School of Biological, Earth and Environmental Sciences, UNSW, and Sarah Legge, Associate Professor, Australian National University

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