Category Archives: Environment

6 truths about chemtrails

Recently a listener wrote to us in response to a story we aired dismissing chemtrail conspiracy theories—our listener asked us to consider both sides of the argument.

‘Chemtrails’ are a type of aircraft contrails—which is short for ‘condensation trails’, long clouds formed by water vapour in aircraft exhaust or due to pressure changes from wings.

The difference is that chemtrails are supposedly deliberately created, either to change the climate as a form of geoengineering, or some other form of weather control, or maybe mind control, or some other mass-poisoning depending on what’s being sprayed.

This is, of course, generally considered to be nonsense.

In saying that, I have considered both sides of the argument, albeit correctly weighted. As always, Lost in Science gives greater weight to peer-reviewed scientific evidence. And there is in fact a surprising amount of published research relevant to this topic.

Contrails from USAAF B-17F Flying Fortress bombers over Europe, circa 1943. That is, propellor aircraft, 72 years ago. Scientists have attempted to analyse their effect on English climate at the time. (Photo: United States Air Force)

Now, I did try to respond to our listener, but unfortunately the email bounced, so I’m writing this blog post instead in the hope they see it. Hi! Please keep listening!

And since this a largely internet-based controversy, I’ve decided to go all out for clickbait and write this in the form of a listicle. Here we go…

1. Geoengineering is a thing

Geoengineering, a popular term for deliberately manipulating the climate, is becoming a hot topic as our inadvertent climate manipulation becomes more dire. But it comes with many moral, ethical and practical risks, so it’s currently much further down the list of preferred responses than stop burning fossil fuels.

We have in fact discussed it before on Lost in Science: in March 2013 we aired a discussion on the ethics of geoengineering between Peter Singer and Clive Hamilton (author of the book Earthmasters: Playing God with the climate).

And in 2011 we looked at a range of proposed mechanisms (Geoengineering as climate change plan B), largely collated from an excellent 2009 review from the UK’s Royal Society.

2. It includes solar radiation management

This is a fancy name for reducing the amount of sunlight reaching the Earth. This is not a new idea: apart from Mr Burns, volcanoes have been doing this forever by spewing ash into the atmosphere. The eruption of Mt Pinatubo in 1991 reduced global temperatures by about 0.1 °C for a couple of years.

In fact, one of the first people to push for injecting particles—or aerosols—into the atmosphere to counteract climate change was the father of the hydrogen bomb, Edward Teller. You can listen to me talking about him at the Laborastory.

3. Aerosols emitted by humans do affect climate

For instance, sulphur pollution from China’s coal-fired power stations are believed to have contributed to the slowing of global surface temperature rise.

4. There’s no evidence anyone’s doing it on purpose

Yes, it’s hard to prove a negative. However I can direct you to the physical science working group of the 5th Assessment Report of the United Nations’ Intergovernmental Panel on Climate Change (IPCC), who said, in their Summary for Policymakers (PDF 2.3 MB):

Limited evidence precludes a comprehensive quantitative assessment of both Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR) and their impact on the climate system… Modelling indicates that SRM methods, if realizable, have the potential to substantially offset a global temperature rise, but they would also modify the global water cycle, and would not reduce ocean acidification. If SRM were terminated for any reason, there is high confidence that global surface temperatures would rise very rapidly to values consistent with the greenhouse gas forcing. CDR and SRM methods carry side effects and long-term consequences on a global scale.

It doesn’t sound to me like they’re actually doing it, or that they think it’s a good idea. And surely if it was a global conspiracy, they’d be in on it?

5. The effect of contrails has been measured, and it’s small

This is the kicker: scientists have actually studied the impact of contrails. That same IPCC report has a whole section on it (section, Contrails and Contrail-Induced Cirrus).

They find that, unlike in solar radiation management proposals, contrails actually increase the temperature, because they block the outgoing infrared (heat) radiation from the ground more than they block the incoming sunlight.

You can read the whole thing yourself (Chapter 7, PDF 19.2 MB), but I’ll save you the the trouble by quoting their conclusion:

Persistent contrails from aviation contribute a RF of +0.01 (+0.005 to +0.03) W m–2 for year 2011, and the combined contrail and contrail-cirrus ERF from aviation is assessed to be +0.05 (+0.02 to +0.15) W m–2. This forcing can be much larger regionally but there is now medium confidence that it does not produce observable regional effects on either the mean or diurnal range of surface temperature.

RF here is radiative forcing, the net thermal energy reaching the Earth. For comparison, the IPCC puts the total anthropogenic, or human-caused contribution at about 1.5 W m–2.

This is based on numerous published scientific papers. I’m not going to bore you with them here—instead you can click my Read more link and see the list. You’re welcome.

6. But aircraft emissions do have an impact overall

One of those references, Lee et al. (2009) added up the combined effect from aircraft carbon emissions and cirrus clouds caused by contrails. They found:

Total aviation RF (excluding induced cirrus) in 2005 was ~55 mW m–2, which was 3.5% of total anthropogenic forcing. Including estimates for aviation-induced cirrus RF increases the total aviation RF in 2005–78 mW m–2, which represents 4.9% of total anthropogenic forcing.

(Emphasis mine. And for readability I’ve taken out the uncertainties.)

According to the International Civil Aviation Organisation (ICAO), this 4.9% means that:

If global aviation was a country its emissions would be ranked 7th between Germany and South Korea on CO2 alone.

That’s quite a bit. So although the contribution of contrails alone is small, when you add in their carbon emissions then yes, flying planes does affect global temperature.

But even so, all this science suggests that, whatever you call them, contrails or ‘chemtrails’ are not being used as a deliberate global conspiracy.

However, we should still be concerned about the impact of air travel on the climate.

Continue reading 6 truths about chemtrails

Fish still radioactive near Fukushima, but mostly safe elsewhere

Recent catches of fish with record levels of radiation show there is still contamination in the waters around Fukushima following the nuclear disaster in March 2011, but fears of dangerous levels reaching the West Coast of the United States seem to be mostly exaggerated.

In January 2013, a bottom-dwelling Murasoi fish was caught with 2,540 times the legal limit for radioactivity of 100 becquerels per kilogram (about the same level as a banana). And then in February 2013, a greenling with 7,400 times the limit was caught in a cage next to the Fukushima Dai-ichi plant.

Fat greenling, Hexagrammos otakii, seen on some oyster shells
Fat greenling, Hexagrammos otakii, the fish (not the actual fish) found near Fukushima with radioactive caesium at a record level of 740,000 becquerels per kilogram (photo from OpenCage, via Wikimedia Commons)

Although most fish caught in the area are actually below the safe level, a paper published by Ken Buessler of the Woods Hole Oceanographic Institute in the United States found that the number above the limit is not decreasing with time as you’d expect. This indicates that radioactive caesium is still entering the food chain, either from sediments—these were bottom-feeding fish, remember—or from ongoing leaks (Buessler Ken O 2012, “Fishing for answers off Fukushima”, Science, vol. 338, pp. 480–482, DOI: 10.1126/science.1228250 [PDF 3.7 MB]).

This has since been admitted by the Japanese government, with radioactive water leaking from containment tanks into groundwater, which then flows into the Pacific Ocean at a rate of about 300 tons per day. This could mean that fish from Fukushima will be inedible for at least a decade, which could paradoxically mean that they benefit from the lack of fishing—although the long-term effects of radiation on the fish themselves is rarely discussed.

This may be because many of the fish don’t live long enough for it to have an impact, and conversely could be why radioactive isotopes have been detected in long-lived, migratory species like Pacific bluefin tuna (Thunnus orientalis), although even then at levels comparable to natural sources (Fisher NS, Beaugelin-Seiller K, Hinton TG, Baumann Z, Madigan DJ and Garnier-Laplace J 2013, “Evaluation of radiation doses and associated risk from the Fukushima nuclear accident to marine biota and human consumers of seafood”, Proceedings of the National Academy of Sciences, vol. 110, no. 26, pp. 10670–10675, doi: 10.1073/pnas.1221834110).

(Of course, there are other reasons to avoid tuna, such as overfishing or build-up of mercury and other toxic chemicals.)

As for fears of radiation directly reaching the United States, it was expected to take about 3 years to travel across the Pacific, so should be arriving right about now. The Woods Hole Oceanographic Institute is keeping an eye on that too, with a citizen science project asking people to send in samples of seawater for testing. As of yet though, their results are showing no detectible caesium from Fukushima.

But what about Australia, you may ask? Well, because we’re in the southern hemisphere, it will take even longer to reach here—about 5 years, according to a report from the Australian Radiation Protection and Nuclear Safety Agency [PDF 1.7 MB] (although a small amount of atmospheric fallout was detected here in April 2011).  By then though, it will be diluted even more than it is in the United States, so is unlikely to be of concern.

Bushfires starting earlier as the climate changes

The new federal environment minister, Greg Hunt, “looked up what Wikipedia says” and concluded that Australia has always had bushfires in hotter months – but if he looked a bit harder, he might find that we’re getting more of those hot months and earlier.

To be sure, Wikipedia is quite reliable; they even say so themselves. But a government minister can probably find more detailed information, as can anyone else if they dig a bit.

One good, independent site is Romsey Australia, which lists major historical bushfires for each Australian state and territory. If you look at the starting date for all the NSW fires listed (from 1926 to 2006) you see the following:

Plot of starting dates of NSW bushfires from 1926 to 2006, with an average for each decade moving earlier in the year

The spread of bushfires throughout the year definitely appears to be increasing, and there’s a clear trend of them starting earlier. Now, it’s likely that the increased availability of data is a factor here, but I reckon this is at least as good as perfunctory ministerial Wikipedia research.

But is this climate change? After all, we also have the prime minister Tony Abbott claiming that “these fires are certainly not a function of climate change,” and that the United Nations climate chief Christiana Figueres was “talking through her hat” when she linked them.

Well, the Intergovernmental Panel on Climate Change (IPCC), in their 2007 Fourth Assessment Report, Working Group II on Impacts, Adaptation and Vulnerability, said that:

Fire frequency is expected to increase with human-induced climate change, especially where precipitation remains the same or is reduced (Stocks et al., 1998).

So far this year in their Fifth Assessment Report, the IPCC has only released the section on the physical science basis, with discussion of impacts yet to come. But they definitely predict that temperatures will continue to increase, and dry areas in the sub-tropics and mid-latitudes are likely to get drier – both factors that contribute to bushfires.

Now, I tend to agree that you can’t attribute a single event (or events, considering there were over 70 burning at the same time) to climate change, but if you look at the trend you see what the scientists were forecasting all along.

Climate change and droughts and flooding rains

The crazy weather of the 2012-13 Australian summer – which apparently isn’t over yet – prompts the question of whether climate change means this is what we should expect from now on. The answer is yes, that’s the trend, but the details are a bit more complicated, and definitely worth knowing.

First though, the simple answer is that, as the Australian Government’s Climate Commission pointed out in their report, The Angry Summer:

Extreme heatwaves and catastrophic bushfire conditions during the Angry Summer were made worse by climate change… All extreme weather events are now occurring in a climate system that is warmer and moister than it was 50 years ago. This influences the nature, impact and intensity of extreme weather events.

Having said that, it doesn’t mean that it’s always-always going to be like this. People tend to think that any weird weather is completely unprecedented and at the same time a permanent change, when in fact variation is a normal part of the system.

To take an example: Melbourne weather is famously variable, so you’d think Melburnians would be used that. But every year when the first hot days arrive in September or October everyone says “summer’s come early! Time to put away the warm clothes.” Then it gets cold again, and everyone says “where did that come from? Oh well, guess there’s not going to be much of a summer this year.” And so on. Every year. Even this past summer.

However, under climate change, the odds are skewed towards hotter weather, even as this variation continues. If there was no global warming, you’d still expect occasional records broken for extreme hot and cold weather. But with the 0.8°C warming we’ve seen under the past 100 years, that same variation around the average will produce slightly more hot records than cold ones.

Graph showing how a shift in average temperature changes the proportion of extreme events (click to embiggen)
Image from the Climate Commission’s Angry Summer report, showing the connection between a shifting average and the proportion of extreme events (adapted from IPCC report, 2007)

It’s important to remember this, so you don’t get fooled into thinking that global warming has stopped when it gets cold again in a few months time. After all, 0.8°C isn’t a very noticeable change when considered on a daily basis.

So that’s the big picture, but to find out exactly what it means for weather in your area you have to turn to the climate scientists and their computer models. You can look them up yourself: for an overview, see For more technical and detailed report from the CSIRO and the Bureau of Meteorology, see

When you go to these sites, you’ll see patterns that are largely a continuation of what we’ve experienced so far. Temperatures will rise on average, with the greatest warming in the middle of Australia and the north-west.

But there will also be more hot days and warm nights, including an increase in the number of days per year over 35°C. For instance, Melbourne currently has 9 days above 35°C per year (that’s average: in 2013 we’ve already had 14), but by 2070 it could be as high as 26. Brisbane will go from an average of 1 to up to 21. Darwin could be up to 308 days above 35°C every year.

Rainfall is a little more complicated. On average, warmer weather puts more moisture into the atmosphere, but changing temperatures also change wind patterns. The top end is not going to have much of a drop in average rainfall, but the rest of the continent will – especially the southwest. Perth is already experiencing much drier conditions.

Rainfall trend map showing the changes in annual totals across Australia from 1910 to 2012, with the biggest drops in the southwest and the biggest increases in the northwest (click to embiggen)
Rainfall trend map showing the changes in annual totals across Australia from 1910 to 2012 (Image from the Bureau of Meteorology)

But not only will rainfall reduce, it will also vary much more. We’re likely to have more very wet days and more very dry days. So yes, more droughts: again, the south-west will be worst hit, with an 80% increase in drought by 2070.

What’s that you say, Mr Andrew Bolt? Doesn’t the recent flooding in Queensland and NSW prove these predictions wrong? No, because I said there’d be more variation.

Continue reading Climate change and droughts and flooding rains

Bottom of the food chain at the bottom of the world

Australian scientists recently completed a mission studying algae and krill that live under Antarctic sea ice, in an effort to understand the workings of their ecosystem and how it may be affected by climate change.

The 2 month investigation was part of the international Sea Ice Physics and Ecosystem eXperiment-II, or SIPEX-II, and it took place onboard the icebreaker Aurora Australis – currently back in Antarctica on its never-ending mission to transport supplies and personnel to and from Australia’s Antarctic stations.

One part of the mission used an underwater robot called ROV – short for ‘Remotely Operated Vehicle’ – equipped with a light sensor to measure reductions in blue and green light beneath the ice, and hence estimate the amount of algae.

The other part involved capturing larval and juvenile krill and examining their metabolism, growth rate and diet. These tiny crustaceans go through 12 larval stages, about which not much is known as previous research has mostly focused on adults, and even then usually in the Antarctic summer rather than winter as experienced by SIPEX-II.

Krill feed on the sea ice algae, and are themselves food for larger animals like penguins, seals and whales. So together the krill and algae form the foundations of the Southern Ocean ecosystem.

Other members of SIPEX-II looked at different physical and biological aspects, such as ice and snow cover measured with laser and radar-equipped helicopters, algae physiology, sea ice biogeochemistry, and water temperature, oxygen content and salinity.

With climate change predicted to reduce sea ice by 35% by the end of this century, we need to know how the Antarctic ecosystem works so that we can understand the impact of losing its cover.

Find out more about this project on the website of the Australian Antarctic Division.

(This story aired on 13 December 2012 – you can listen to the podcast.)

Great Barrier Reef coral loss is probably our fault

The Great Barrier Reef is the largest coral reef system in the world, stretching over 2,600 kilometres along the coast of Queensland and covering an area of 344,400 square kilometres. But over the past 27 years it’s lost half its coral, apparently thanks to human activity.

Researchers from the Australian Institute of Marine Science in Townsville have been monitoring the amount of coral since 1985. Back then, the reefs they studied had 28% coral cover, but in 2012 they only had 13.8%. That’s a reduction of 50.7% (De’ath G, Fabricius KE, Sweatman H & Puotinen M 2012, “The 27–year decline of coral cover on the Great Barrier Reef and its causes”, Proceedings of the National Academy of Sciences, vol. 109, no. 44, pp. 17995-17999, doi:10.1073/pnas.1208909109).

This reduction wasn’t uniform across the whole system, as the far northern reefs have remained fairly stable at about 24% coral cover. But there’s been a decline in the central region – which they classify as between Cooktown and Mackay – and in the southern region below Mackay, where there’s been a steep drop of over 75% in the past decade alone.

The researchers also looked at what caused these reductions, by modelling possible causes against the observed fluctuations in coral cover. What they found was that 48% of the coral reduction could be attributed to tropical cyclones, 42% to outbreaks of crown-of-thorns starfish, and 10% to mass coral bleaching (primarily two events, in 1998 and 2003).

Climate change would seem to be a factor here, as it’s been linked to the increasing intensity of tropical cyclones (see Knutson TR, et al. 2010, “Tropical cyclones and climate change”, Nature Geoscience, no. 3, pp.  157–163, doi: 10.1038/ngeo779 [PDF 641 KB]).

Temperature also seems to be a major cause of coral bleaching, which is when the coral loses its symbiotic zooxanthellae. These single-celled organisms photosynthesise and provide energy for the coral polyps – as well as the vibrant colours of the coral. In turn, they get nutrients and a home. However, the zooxanthellae seem to be sensitive to temperature, as a rise of only 1°C  can cause mass deaths of them and subsequently their host coral.

But even though climate change is the biggest culprit, the researchers admit it’s unlikely that in the near future we’re going to make a big impact or reduce temperatures. So instead, they suggest concentrating on the crown-of-thorns starfish. If we could cut out just the starfish, but cyclones and bleaching continued, the coral cover would still increase by 0.89% per year.

And we have a chance of doing this, because the crown-of-thorns starfish itself is influenced by human activity.

Crown-of-thorns starfish competing to eat the last remaining piece of coral (click to embiggen)
Crown-of-thorns starfish, Acanthaster planci, competing to eat the last remaining piece of Acropora coral (Photo by JSLUCAS75, via Wikimedia Commons)
As the name suggests, the crown-of-thorns, or Acanthaster planci, is a spiny starfish, or sea star. It’s the second-largest species of sea star in the world, with adults reaching 25-35 cm in diameter and having up to 21 arms. It feeds by latching onto coral with its multiple tube feet and then extruding its stomach out through its mouth to digest coral polyps.

It sounds like a nasty, introduced species, but actually it’s been in the Great Barrier Reef for at least 8000 years. In fact, it’s found in coral reefs across the Indian and Pacific Oceans, from the coast of Africa to the coast of America.

And at normal population numbers, it seems to be a natural part of the reef ecosystem. It prefers to eat the faster-growing coral species, giving the slower-growing species a chance to compete. But occasionally the numbers increase to plague proportions, and the starfish have to eat everything.

Now it’s not 100% certain what causes these outbreaks, but the leading theory is that it’s due to water quality. The starfish larvae feed on phytoplankton, and phytoplankton numbers increase with inorganic nutrients in the water. And these inorganic nutrients increase greatly when fertiliser is washed off farmland, particularly after floods.

So the researchers recommend more effort to improve water quality in order to reduce the numbers of crown-of-thorns starfish. This is in preference to hunting them down one-by-one – which is favoured by MP Bob Katter – because in the past that’s proven to be rather expensive and labour-intensive, but overall ineffective across the whole reef (although hunting does work for protecting a small area, so it’s good for tourist operators).

In the end, it all comes down to pollution, whether greenhouse gases or fertiliser run-off. And until we can cut the former, we need to concentrate on the latter. The crown-of-thorns starfish may in fact be a natural feature of the Great Barrier Reef, but it’s our activities that turn it into a threat.

(This story aired on 22 November 2012 – you can listen to the podcast.)

Pot plants fight pollution

Indoor plants make homes or offices more pleasant to be in, but they can also make them healthier by removing pollutants from the air.

The air you breathe when inside is actually more polluted than that outside. It contains all the fossil fuel emissions you get on the street, but in addition it has extra CO2 from people breathing out, as well as things called volatile organic compounds.

Volatile organic compounds, or VOCs, are chemicals that evaporate from plastic or synthetic furniture, fabrics, fittings, paints, varnishes, solvents, and so on. They include substances like benzene – a known carcinogen – as well as toluene, ethylbenzene and xylene.

Research by a team at the University of Technology, Sydney, has studied the ability for potted plants to remove these volatile chemicals. They used both laboratory settings with closed containers and real-world office settings, with a number of different plants, including Spathiphyllum wallisii ‘Sweet Chico’ (Peace Lily), Dracaena deremensis ‘Janet Craig’, Zamioculcas zamiifolia (Aroid Palm), Monstera deliciosa and Sansevieria trifasciata (Mother-in-law’s Tongue or Snake Plant).

Potted plant Dracaena deremensis 'Janet Craig' flowering (click to embiggen)
One of the species used in the study, Dracaena deremensis ‘Janet Craig’ (photo by Nick J. Howe, via Wikimedia Commons)

In the offices they found that for high concentrations of VOCs (greater than 100 parts per billion), the pot plants could reduce them by 50-75%.

Interestingly though, the species of plant didn’t matter – instead, it’s what they call the ‘plant microcosm’, as bacteria in the soil or potting mix digest the VOCs. This means that generally the bigger the pot, the more pollution will be removed – although, there appears to be a limit after which adding more soil with more bacteria won’t remove more VOCs.

Only about two standard-sized pot plants were needed to service an average 12 square metre office – an indoor jungle with dozens of plants was not required.

The plants have another benefits too, like removing CO2 (although that requires them to be placed in sunshine to photosynthesise), reducing dust levels, stabilising temperature and humidity, and reducing noise.

With all that and the ability to remove toxic chemicals, how can you go wrong?


Wood RA, Burchett MD, Alquezar R, Orwell RL, Tarran J & Torpy F 2006, “The potted-plant microcosm substantially reduces indoor air VOC pollution: I. office field-study”, Water, Air, and Soil Pollution, vol. 175, no. 1-4, pp. 163-180, DOI: 10.1007/s11270-006-9124-z

Orwell RL, Wood RA, Burchett MD, Tarran J & Torpy F 2006, “The potted-plant microcosm substantially reduces indoor air VOC pollution: II. laboratory study”, Water, Air, and Soil Pollution, vol. 177, no. 1-4, pp. 59-80, DOI: 10.1007/s11270-006-9092-3

Burchett MD, Torpy F, Brennan, J & Craig A 2010, Greening the great indoors for human
health and wellbeing, Final report to Horticulture Australia Ltd

Glacial pace

In 2007 the Intergovernmental Panel on Climate Change cautioned that “glaciers in the Himalaya are receding faster than in any other part of the world … and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high” (IPCC Fourth Assessment Report: Climate Change 2007, Working Group II: Impacts, Adaptation and Vulnerability, section 10.6.2).

But they retracted that claim quickly, because nobody could actually demonstrate they had any data to back it up. Few Himalayan glaciers were actually measured in the 20th century, and none were measured in the seven years prior to the statement being issued.

But a flurry of scientific research since then has shown a far more unpredictable situation than the generalisation that the Himalayan glaciers are melting.

Map of anomalies in the Earth's gravitational field, centred on south-east Asia, produced by the Gravity Recovery and Climate Experiment as a way of determining mass densities such as thickness of glacial ice (click to embiggen)
Map of anomalies in the Earth’s gravitational field, used to determine mass densities such as thickness of glacial ice. These maps are produced by the Gravity Recovery and Climate Experiment (GRACE), using two satellites nicknamed Tom and Jerry because they chase each other around the Earth. The satellites constantly track their separation distance, which changes when they pass over a gravitational anomaly (image by The University of Texas Center for Space Research and NASA)

The Himalaya mountain range is a vast geological formation stretching thousands of kilometres through Asia, from Bhutan in the east to Afghanistan in the west, and contains glaciers in multiple climates which are responding differently to rising air temperatures.

Those in the east are melting, but in recent years more than half of the glaciers further west near Pakistan have defied predictions by gaining mass. This is based not only on observations of the contraction or expansion of the leading edge of glaciers, but on satellite monitoring of glaciers measuring thickness of the ice.

Glacial ice is fed by annual precipitation from rain and snow and lost through melting in the warmer parts of the year. Current understanding is that increased rainfall in these areas has produced the increase in size of the glaciers, combined with low summer temperatures reducing the annual melt.

At the other end of the mountain range around Mt Everest, glaciers are thinning in Tibet and Nepal due to more ice melting from the glaciers each year than is being replaced. Many of these are fed by annual rainfall events like monsoons, rather than the year-round snow of some of the western glaciers, and reduced rainfall patterns could explain the continued weight loss.

Research has also found, probably not surprisingly, that dirty ice melts more slowly than clean ice, because rocks and other material on the surface provides a level of insulation against the warmer air.

Some of this analysis was only made possible by using recently declassified spy satellite photos shot in stereovision of the Russian and Chinese Himalayan borders dating back to 1959.

An estimate from 2010 predicted the Asian glaciers lost about 55 billion metric tonnes of ice annually. However, a pair of gravity measuring satellites nicknamed Tom and Jerry – from the Gravity Recovery and Climate Experiment – have indicated only a fraction of that figure at about 5 billion metric tonnes. That’s about the volume of 5,700 Empire state buildings.

One of the reasons such research is important is concern for freshwater supplies of countries fed by rivers originating in the mountains, such as the Ganges in India and the Yangtze in China. But calculations of the annual amount of water that flows into these rivers is that very little of the water comes from glacial sources, and the majority of flow in these epic rivers comes from more localised seasonal rainfall further downstream in the catchment.

The interaction of glaciers with climate and weather patterns are obviously dynamic, but the difficulties in measuring them can leave predictions about their future on thin ice.

Mistletoe missed when it’s gone

Mistletoe is a parasitic plant that most people think is only useful for triggering Christmas kisses and as an ingredient in magic strength potion from Ancient Gaul. But recently published research suggests that it plays a crucial role in its ecosystem.

Professor David Watson gathering mistletoe (click to read more)
Professor David Watson gathering mistletoe – golden sickle not pictured (Photo Charles Sturt University)

Professor David Watson and Matthew Herring of Charles Sturt University set out to test whether mistletoe is a keystone species – that’s an organism that appears insignificant but actually has a large effect on other species. The best way to test whether a species is a keystone is to remove it from an ecosystem and see what happens. However, that’s usually not only extremely difficult, but risks causing irreparable damage.

In this case though, it’s possible to remove mistletoe without damaging their host trees. After obtaining the necessary permissions, the researchers and teams of volunteers spent two years removing 46 tonnes of mistletoe – predominantly Amyema miquellii, known as either Box, Stalked or Drooping Mistletoe – from 17 woodland sites in the southern Riverina region of New South Wales. They then waited another three years before returning to compare the changes with 11 control sites and 12 where mistletoe was naturally missing.

As predicted, the absence of mistletoe affected the local bird population, with a third of species missing after only 3 years. But what was surprising was that the birds affected weren’t those that nested or fed in mistletoe, but instead it was the insect-eaters. Watson believes that this is because mistletoe drops more leaf litter than its host tree, so its removal takes away the habitat for the insects on which the birds feed.

This study is believed to be the first test of a keystone plant, and the most rigorous ever test of any keystone. Its unexpected outcome demonstrates the subtle dependencies that can exist in ecosystems, and how a single species may do more than you think.

Reference: Watson DM & Herring M 2012, “Mistletoe as a keystone resource: an experimental test”, Proceedings of the Royal Society B: Biological Sciences, vol. 279, no. 1743, pp. 3853-3860 (doi: 10.1098/rspb.2012.0856)

Myna inconvenience

The Common Myna (Acridotheres tristis) is hated so much that on ABC’s Wildwatch it was voted Australia’s number one pest or problem, above cane toads and rabbits. So much, that even when research shows it might not be worth trying to eradicate, newspapers report the exact opposite. In fact, their only redeeming feature seems to as an easy source of headline puns.

Common Mynas are also known as Indian Mynas, and as the name suggests they originally came from India. But, perhaps because they thrive in human habitats, they’ve since spread throughout the world, and are found on every continent except Antarctica.

So they’re an invasive species, but how damaging are they really? Well, it’s actually hard to tell. They lay their eggs in tree or wall cavities, and compete with native species that do the same. And they mate for life, forming a formidable pair that aggressively defends a 1-3 hectare territory from other birds.

This tendency to attack smaller birds is probably one of the reasons people hate them. Although, I should point out that many of these incidents are mistaken identification of the even more aggressive native species, the Noisy Miner (Manorina melanocephala). They both look fairly similar, with black heads and yellow beaks and eyeliner.

The big difference, apart from the spelling, is that Common Mynas are mostly brown and the native Noisy Miners are grey. And instead of attacking in pairs, Noisy Miners tend to gang up on other birds in larger numbers.

Comparison photos of a Common Myna, Noisy Miner and Bell Miner (click to embiggen)
From left to right, Common Myna (Acridotheres tristis), Noisy Miner (Manorina melanocephala) and Bell Miner (Manorina melanophrys). Photos by Dick Daniels, Quartl and Brett Donald respectively, via Wikimedia Commons

But whether they’re mynas or miners, the impact of competition is relatively difficult to measure compared to something like predation. If one species is actively killing another, it’s pretty easy to see the effect just by counting the victims.

But competition is more subtle. So what Kate Grarock and colleagues from the Australian National University and the University of Canberra have done is to use data from a birdwatcher club, the Canberra Ornithologists Group, to track how populations of various species across Canberra were changing after the arrival of mynas (Grarock K, Tidemann CR, Wood J & Lindenmayer DB 2012, “Is it benign or is it a pariah? Empirical evidence for the impact of the Common Myna (Acridotheres tristis) on Australian birds”, PLOS One, vol. 7, no. 7: e40622, doi:10.1371/journal.pone.0040622).

They tracked bird populations according to the number of years since mynas arrived – they were first introduced to Melbourne in 1862 to control insects in market gardens, but didn’t reach Canberra until 1968 – together with a lot of sophisticated statistical analysis that corrected for factors like urban development and type of vegetation.

The bird species they analysed were split into three groups: there were other cavity-nesters, such as cockatoos, parrots and kookaburras; then there were birds smaller than about 25 cm, like Willy Wagtails and Magpie-Larks, which you might expect to be intimidated by Common Mynas; and finally there were large birds about 30 cm or bigger, like magpies and currawongs, that should be harder to push around and so are sort of a control group.

What they found was a definite negative correlation between myna numbers and three of the cavity-nesting species: the Sulphur-crested Cockatoo, the Crimson Rosella and the Laughing Kookaburra. And seven of the small bird species were affected as well.

As expected, there was no correlation with large species numbers. But interestingly, there was also no significant effect on four other cavity-nesting species, namely the Galah, Australian King-Parrot, Eastern Rosella and Common Starling. And one of the small bird species seemed to be OK, although that was
only the House Sparrow.

But an important point is that the majority of the species actually increased in number over the 29-year study period. It’s just that their increase seemed to be at a slower rate after the arrival of mynas than it would otherwise have been.

There are two interesting aspects to this. The first is the point made earlier, that the level of hatred directed towards mynas in the community has led to some slightly inaccurate, hysteria-inducing science reporting.

The Age newspaper on 13 August 2012 reported on the Canberra study but got the numbers wrong. For instance, Crimson Rosellas increased in number by 5.9 birds per km2 every year. But The Age mistakenly reported that rate of increase as the total population density. So because the rate of increase was slower in the presence of mynas – 3.5 birds per km2 per year slower – they interpreted that as a decline in overall numbers to 2.4 birds per km2. Which of course it wasn’t (actual Crimson Rosella numbers were around 50-150 birds per km2).

These numbers may sound tricky, but they’re easy to verify as the entire research paper is available for free online (look  under ‘Results’). However, that didn’t prevent the publishing of another article with exactly the same mistake in The Age on 23 September 2012.

This time, they even quoted Kate Grarock, saying ”I think it’s great that the community is involved with environmental management. However I do fear that the passion for hating the myna is way too extreme. Australians appear to be more worried about mynas than cane toads, foxes, feral cats and rabbits.”

Unfortunately, the newspaper had already decided its conclusion that Common Mynas are a major pest that’s reducing species abundance. Which of course is the story that everyone expected to read, even though the actual research found an increase in the abundance of most of the species.

Which brings me to my other point, which is that the biggest factor affecting species numbers was change in habitat. Many of these birds, including both Common Mynas and Noisy Miners, do best in urban or lightly-forested areas, and are not found in dense forests.

The researchers concluded that attempting to eradicate Common Mynas would be very difficult and probably nowhere near as cost-effective as improving habitat to encourage native species.

It seems though that you won’t read that in The Age. Instead, you can read Kate Grarock’s own commentary on The Conversation website,