How weather radar can keep tabs on the elusive magpie goose

Magpie Geese taking off from a mango orchard in the Northern Territory.
Rebecca Rogers, Author provided

Rebecca Rogers, Charles Darwin University

You’re probably familiar with weather radar that shows bands of rain blowing in to ruin your plans for the day, or the ominous swirling pattern of a cyclone.

But rain isn’t the only thing that shows up on the radar screen. Anything moving through the sky will – like a large group of birds in flight.

Ecologists have begun to realise that weather radar data have huge potential to reveal the movements of flying animals all over the country.

At the forefront of this research is the magpie goose, an occasionally controversial waterbird prized by some and detested by others.

It’s a lovely day in northern Australia, and you are a magpie goose. These waterbirds are an ideal test case for weather-radar tracking.
Shutterstock

Chasing angels

To understand how we got to this point, first we need to go back 80 years. Prior to World War II, engineers were racing to improve radar systems to detect enemy aircraft when they noticed strange unexplained rings on their screens that they called angels.

Some of these angels, they realised later, were caused by groups of birds and bats taking off and flying through the radar beam. Since this discovery, there has been a steady increase in researchers using weather radar to understand how and why animals move through the air.

How weather radar works

Radar works by sending out a sweeping beam of radio waves and listening for echoes. It processes these echoes to map the positions of objects around it.

With weather radar, the radar beam won’t only bounce off raindrops – it will also reflect back from birds. Some weather radars send out these pulses at a precise frequency, which allows them to use the Doppler effect to determine how fast objects are moving towards or away from the radar.

Meteorologists have ways to filter out clutter caused by flying animals, so they can see where it is raining. Ecologists are doing the reverse, filtering out rain from the raw data collected by weather radars in order to track the movements of birds, bats and even insect swarms.

Weather radars cover a good part of the Australian continent, which makes them very useful for tracking birds.
Rogers et al. (2019) – Austral Ecology

Most weather radars can give us a three-dimensional picture of what is happening in the air every 5–10 minutes. In Australia the data is archived for years and even decades in some places, and it is all available free of charge for researchers. This means we can not only understand how animals are using the airspace now, but also how these movement patterns may have changed over time.

Is it a bird? Is it a plane?

So how do we actually tell whether those pixels on the screen are caused by rain, birds or something less common like bushfire smoke?

This is where things can get a bit more tricky. For some cases, like tracking bats coming out of a cave or roost tree, the job for the ecologist is fairly simple. For roosting species like these, we often observed very characteristic rings on the radar similar to the angels described by those early radar engineers. Examples of the rings can be found all over Australia caused by flying foxes.

Flying animals leave traces in weather radar images. The image at left shows an ‘angel echo’ caused by flying foxes coming out of a roost in NSW, while the one on the right reveals ‘blooms’ of activity on the Darwin radar, likely to be caused by magpie geese and other waterbirds taking off for their morning feeding flights.
Rogers et al. (2019) – Austral Ecology

For broadly distributed species, like the magpie geese found all across northern Australia, the picture is not so easy to interpret. These animals tend to produce patterns best described as blooms of activity: they appear across the radar image, spreading out and then blending together like a bunch of flowers blooming all at once.

These patterns can look similar to rain clouds to the untrained eye. However, with some understanding of how the radar works and the behaviour of the birds – like when they are active or how high they fly – we can quickly begin to narrow down what might be causing different patterns on radar images.

Why track magpie geese?

Magpie geese cross paths with humans in many different ways.

They are hunted by Indigenous people for food, they are considered a pest for mango farmers and a strike risk for planes, and they could be vectors for disease.

Tracking magpie geese can help us better understand this native species and ensure it thrives long into the future.

---

Read more:
Most native bird species are losing their homes, even the ones you see every day

---

Like many waterbirds, magpie geese have distinct daily patterns of movement, which makes them ideal candidates for trialling the use of weather radar to track Australian birds.

In Darwin, blooms of activity occur all over the radar in the morning and evening when magpie geese are taking off from wetlands and mango orchards for their daily feeding flights.

By using GPS tracking collars and annual survey data, we are starting to see how these patterns in the radar data correspond to real behaviour. These results are showing how weather radar could be repurposed to track the movement of magpie geese – and after that, many other kinds of birds in Australia.

Rebecca Rogers, PhD Candidate, Charles Darwin University

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

Advertisement

Fish kills and undrinkable water: here’s what to expect for the Murray Darling this summer

Dry conditions will make for a difficult summer in the Murray Darling Basin.
AAP/Dean Lewins

Jamie Pittock, Australian National University

A grim summer is likely for the rivers of the Murray-Darling Basin and the people, flora and fauna that rely on it. Having worked for sustainable management of these rivers for decades, I fear the coming months will be among the worst in history for Australia’s most important river system.

The 34 months from January 2017 to October 2019 were the driest on record in the basin. Low water inflows have led to dam levels lower than those seen in the devastating Millennium drought.

No relief is in sight. The Bureau of Meteorology is forecasting drier-than-average conditions for the second half of November and December. Across the summer, rainfall is also projected to be below average.

So let’s take a look at what this summer will likely bring for the Murray Darling Basin – on which our economy, food security and well-being depend.

A farmer stands in the dry river bed of the Darling River in February this year.
Dean Lewins/AAP

Not a pretty picture

As the river system continues to dry up and tributaries stop flowing, the damaging effect on people and the environment will accelerate. Mass fish kills of the kind we saw last summer are again likely as water in rivers, waterholes and lakes declines in quality and evaporates.

Three million Australians depend on the basin’s rivers for their water and livelihoods. Adelaide can use its desalination plants and Canberra has enough stored water for now. But other towns and cities in the basin risk running out of water.

---

Read more:
Paddling blind: why we urgently need a water audit

---

Governments were warned well before the drought to better secure water supplies through infrastructure and other measures. But the response was inadequate.

Some towns such as Armidale in New South Wales have been preparing to truck water to homes, at great expense. Water costs will likely increase to pay for infrastructure such as pumps and pipelines. The shortages will particularly affect Indigenous communities, pastoralists who need water for domestic use and livestock, irrigation farmers and tourism business on the rivers.

Water in major storages as reported at 13 November 2019.
Murray Darling Basin Authority

As we saw during the Millennium drought, when wetland soils dry some sediments will oxidise to form sulfuric acid. This kills fauna and flora and can make water undrinkable.

Red gum floodplain forests and other wetland flora will continue to die. Most of these wetlands have not had a drink since 2011. The desiccation, due to mismanagement and drought, is likely to see the return of hypersalinity – a huge excess of salt in the water – with river flows too weak to flush the salt out to sea.

---

Read more:
Murray-Darling report shows public authorities must take climate change risk seriously

---

If drought-breaking rains do come, as they did in 2010-11, this would create a new threat. Floodwaters would inundate leaf litter on the floodplains, triggering a bacterial feast that depletes the water of oxygen. These so-called “blackwater” events kill fish, crayfish and other aquatic animals.

The risk of blackwater events has largely arisen because government authorities have failed to manage water as they had agreed. In particular, the NSW and Victorian governments have not worked with farmers to allow managed river flows to inundate floodplains.

The prospect of thousands of dead fish in the Murray Darling Basin looms large again this summer.
AAP/GRAEME MCCRABB

How did we get here?

The severity and impacts of this drought should not come as a surprise. In the 1980s, the CSIRO’s first projections of climate change impacts in the basin foreshadowed what is unfolding now.

Despite the decades-old warnings, water management authorities in some catchments favoured water extraction by irrigators over rural communities, pastoralists and the environment. For example, the NSW Natural Resources Commission in September found that state government changes to water regulations brought forward the drying up of the Darling River by three years.

---

Read more:
We can’t drought-proof Australia, and trying is a fool’s errand

---

Since the basin plan was adopted in 2012 our federal and state political leaders have reduced the volume of real water needed to keep the rivers healthy, supply water to people and flush salt out to sea. For example, in May 2018 the federal government and Labor opposition agreed to reduce water allocated to the environment by 70 billion litres a year on average, without a legitimate scientific basis.

The basin plan is based on historical river flow records, without explicitly allowing for diminished inflows resulting from climate change. Australian water management has followed what’s been termed a “hydro-illogical cycle” where drought triggers reform, but government leaders lose attention once it rains. This suggests meaningful reform must be implemented when drought is occurring and politicians are under pressure to respond.

Severe drought and mismanagement means a dire summer for the Murray-Darling river system.
Dean Lewins/AAP

How to fix this

Governments must assume that climate-induced drought conditions in the basin are the new normal, and plan for it.

Action should include:

• Revising water allocations consistent with climate change projections

• Investing in managed aquifer recharge to supply more towns with reliable and safe water

• Restoring rivers by reallocating enough water to sustain their health

• Increasing wetland resilience by reconnecting rivers to their floodplains in wetter years

• Improving river health, such as by fencing out livestock.

Investing in these adaptation actions now would provide jobs during the drought and prepare Australia for a much drier future in the Murray-Darling Basin.

Jamie Pittock, Professor, Fenner School of Environment & Society, Australian National University

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

Non-native species should count in conservation – even in Australia

Australia is home to many new species, including wild camels found nowhere else on Earth.
Author provided

Arian Wallach, University of Technology Sydney; Chelsea Batavia, Oregon State University; Danielle Celermajer, University of Sydney; Daniel Ramp, University of Technology Sydney; Erick Lundgren, University of Technology Sydney, and Esty Yanco, University of Technology Sydney

As the world struggles to keep tabs on biodiversity decline, conservation largely relies on a single international database to track life on Earth. It is a mammoth and impressive undertaking – but a glaring omission from the list may be frustrating conservation efforts.

---

Read more:
In defence of invasive alien species

---

The International Union for the Conservation of Nature’s Red List aims to be a “complete barometer of life”. But non-native wildlife is excluded from the list.

Our study, published today in the journal Conservation Biology, questions the wisdom of this omission. It means, for example, vulnerable species facing existential threats in their “home country” may be exterminated freely in another. Excluding these animals, such as wild camels in Australia, and rare Australian frogs living overseas, distorts conservation science.

What counts as ‘native’?

The concept of “native” draws a sharp line between species that count and those that don’t. It is essentially an ethical choice, and a disputed one at that. Regardless of whether one defends or disputes the concept, it is problematic to use a moral term to filter a critical source of scientific data.

Trash Animals: How We Live with Nature’s Filthy, Feral, Invasive, and Unwanted Species.

The invisible components of biodiversity – those populations excluded from conservation’s definition of life – can be found in trash lists, where they are described as invasive, aliens, pests, and feral.

So what does the world look like if we include all wildlife in biodiversity assessments? We rummaged around in the “trash piles” to find out.

When all life counts

By focusing on Australian non-native vertebrate species – amphibians, birds, fishes, mammals, and reptiles – we did something many conservationists would find unthinkable. We added unloved species such as feral cats, cane toads, the Indian myna, and carp to Australia’s biodiversity counts.

We created maps showing the range of 87 species whose ancestors were introduced into Australia, and 47 species native to Australia that were introduced elsewhere, since European colonisation.

Many of these so-called invasive species are at risk of extinction in their native ranges; 32% are assessed as threatened or decreasing in the Red List. For 15 of them, non-native ranges provide a lifeline.

Australia’s vertebrate species that are threatened or near threatened in their native ranges with significant populations overseas. From left-to-right: Indian hog deer, banteng, wild cattle, wild water buffalo, wild camel; wild goat, carp, wild donkey, brumby, Mozambique tilapia; European rabbit, Javan rusa, sambar deer, and (emigrants) green and golden bell frog, growling grass frog.
Arian Wallach et al

Not only does Australia contribute to the survival and flourishing of these species, but immigrant vertebrates have also added 52 species to the number of vertebrate species in Australia (after accounting for extinctions).

This number in no way indicates that non-native species replace or make up for those that have been lost. And it does not exonerate humans of their role in causing extinctions. But the current data do not even allow us to acknowledge that these species exist.

Because they are not counted in conservation, these non-native populations are subjected to mass eradication programs. Paradoxically, in assessing how such programs are justified, we found conservation is the most frequently cited reason for killing these wild animals.

Dromedary camels were extinct in the wild for some 5,000 years until they “went feral” in Australia, where they are now endemic. Rather than celebrating what is arguably the most extraordinary rewilding event in the world, wild camels were declared a pest. Between 2009 and 2013, Australia spent A$19 million to gun down 160,000 individuals of a species found nowhere else on Earth in the wild.

Likewise, 89% of the global distribution of Javan rusa, a deer species vulnerable to extinction, is in Australia. As pest, they are culled and hunted for sport.

Stated motivations for killing Australia’s immigrant vertebrate wildlife, shown as percentages of species targeted per taxonomic group. Numbers above bars indicate absolute number of species targeted.

Nativism not only renders countless species invisible, along with their unique and fascinating ecologies; it also exposes them to unfettered, unscientific, unmonitored, and unlamented mass killing programs.

---

Read more:
From feral camels to ‘cocaine hippos’, large animals are rewilding the world

---

Mass killing of non-native species, if questioned at all, is generally explained as protecting native species. But ecology is complex. One cannot simply assume that all non-native populations, in all contexts, do nothing but harm.

Where non-native species do contribute to the loss of native species, humans need to confront the ethical complexities and shoulder real responsibility, rather than simply reach for a gun as a first solution.

In many situations changing harmful human behaviours, like persecuting apex predators such as dingoes, can solve problems that appear to be caused solely by non-native species.

Irrespective of whether we value non-native species or not, there is no scientific justification for expunging large swaths of the living world from conservation data. Smuggling ethically dubious distinctions into data harms conservation science, and has grave repercussions.

---

Read more:
The toad we love to hate

---

Persisting with the assumption that we have the right to pick and choose which species “count” looks like playing God. By now, we should have learned we must not.

Arian Wallach, Lecturer, Centre for Compassionate Conservation, University of Technology Sydney; Chelsea Batavia, Postdoctoral research associate, Oregon State University; Danielle Celermajer, Professor of Sociology and Social Policy, University of Sydney; Daniel Ramp, Associate Professor and Director, Centre for Compassionate Conservation, University of Technology Sydney; Erick Lundgren, PhD Student, Centre for Compassionate Conservation, University of Technology Sydney, and Esty Yanco, PhD Candidate, Centre for Compassionate Conservation, University of Technology Sydney

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