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By itself, concrete is a very durable construction material. The magnificent Pantheon in Rome, the world’s largest unreinforced concrete dome, is in excellent condition after nearly 1,900 years. And yet many concrete structures from last century – bridges, highways and buildings – are crumbling. Many concrete structures built this century will be obsolete before its end.

Given the survival of ancient structures, this may seem curious. The critical difference is the modern use of steel reinforcement, known as rebar, concealed within the concrete. Steel is made mainly of iron, and one of iron’s unalterable properties is that it rusts. This ruins the durability of concrete structures in ways that are difficult to detect and costly to repair.

While repair may be justified to preserve the architectural legacy of iconic 20th-century buildings, such as those designed by reinforced concrete users like Frank Lloyd Wright, it is questionable whether this will be affordable or desirable for the vast majority of structures. The writer Robert Courland, in his book Concrete Planet, estimates that repair and rebuilding costs of concrete infrastructure, just in the United States, will be in the trillions of dollars – to be paid by future generations.

Old bridges need new money to replace. Phil's 1stPix/Flickr.com, CC BY-NC

Steel reinforcement was a dramatic innovation of the 19th century. The steel bars add strength, allowing the creation of long, cantilevered structures and thinner, less-supported slabs. It speeds up construction times, because less concrete is required to pour such slabs.

These qualities, pushed by assertive and sometimes duplicitous promotion by the concrete industry in the early 20th century, led to its massive popularity.

Reinforced concrete competes against more durable building technologies, like steel frame or traditional bricks and mortar. Around the world, it has replaced environmentally sensitive, low-carbon options like mud brick and rammed earth – historical practices that may also be more durable.

Early 20th-century engineers thought reinforced concrete structures would last a very long time – perhaps 1,000 years. In reality, their life span is more like 50-100 years, and sometimes less. Building codes and policies generally require buildings to survive for several decades, but deterioration can begin in as little as 10 years.

Many engineers and architects point to the natural affinities between steel and concrete: they have similar thermal expansion characteristics, and concrete’s alkalinity can help to inhibit rust. But there is still a lack of knowledge about their composite qualities – for example, in regard to sun-exposure-related changes in temperature.

The many alternative materials for concrete reinforcement – such as stainless steel, aluminium bronze and fibre-polymer composites – are not yet widely used. The affordability of plain steel reinforcement is attractive to developers. But many planners and developers fail to consider the extended costs of maintenance, repair or replacement.

Cheap and effective, in the short term at least. Luigi Chiesa/Wikimedia Commons, CC BY-SA

There are technologies that can address the problem of steel corrosion, such as cathodic protection, in which the entire structure is connected to a rust-inhibiting electric current. There are also interesting new methods to monitor corrosion, by electrical or acoustic means.

Another option is to treat the concrete with a rust-inhibiting compound, although these can be toxic and inappropriate for buildings. There are several new non-toxic inhibitors, including compounds extracted from bamboo and bacterially derived “biomolecules”.

Fundamentally, however, none of these developments can resolve the inherent problem that putting steel inside concrete ruins its potentially great durability.

The environmental costs of rebuilding

This has serious repercussions for the planet. Concrete is the third-largest contributor to carbon dioxide emissions, after automobiles and coal-fuelled power plants. Cement manufacturing alone is responsible for roughly 5% of global CO₂ emissions. Concrete also makes up the largest proportion of construction and demolition waste, and represents about a third of all landfill waste.

Recycling concrete is difficult and expensive, reduces its strength and may catalyse chemical reactions that speed up decay. The world needs to reduce its concrete production, but this will not be possible without building longer-lasting structures.

Rebar reclamation: an expensive job. Anna Frodesiak/Wikimedia Commons

In a recent paper, I suggest that the widespread acceptance of reinforced concrete may be the expression of a traditional, dominant and ultimately destructive view of matter as inert. But reinforced concrete is not really inert.

Concrete is commonly perceived as a stone-like, monolithic and homogeneous material. In fact, it is a complex mix of cooked limestone, clay-like materials and a wide variety of rock or sandy aggregates. Limestone itself is a sedimentary rock composed of shells and coral, whose formation is influenced by many biological, geological and climatological factors.

This means that concrete structures, for all their stone-like superficial qualities, are actually made of the skeletons of sea creatures ground up with rock. It takes millions upon millions of years for these sea creatures to live, die and form into limestone. This timescale contrasts starkly with the life spans of contemporary buildings.

Steel is often perceived to be inert and resilient too. Terms such as “Iron Age” suggest an ancient durability, although Iron Age artefacts are comparatively rare precisely because they rust. If construction steel is visible, it can be maintained – for instance, when the Sydney Harbour Bridge is repeatedly painted and repainted.

However, when embedded in concrete, steel is hidden but secretly active. Moisture entering through thousands of tiny cracks creates an electrochemical reaction. One end of the rebar becomes an anode and the other a cathode, forming a “battery” that powers the transformation of iron into rust. Rust can expand the rebar up to four times its size, enlarging cracks and forcing the concrete to fracture apart in a process called spalling, more widely known as “concrete cancer”.

Concrete cancer: not pretty. Sarang/Wikimedia Commons

I suggest that we need to change our thinking, to recognise concrete and steel as vibrant and active materials. This is not a case of changing any facts, but rather of re-orientating how we understand and act on those facts. Avoiding waste, pollution and needless rebuilding will require thinking well beyond disciplinary conceptions of time, and this is especially true for the building and construction industries.

The collapsed civilisations of the past show us the consequences of short-term thinking. We should focus on building structures that stand the test of time – lest we end up with hulking, derelict artefacts that are no more fit for their original purpose than the statues of Easter Island.

Guy Keulemans does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

Flatworms of the genus Temnosewellia liivng on the Orbost spiny crayfish (Euastacus diversus). Andrew Murray

I am so proud of our recent publication, mostly because it has been a long time coming. We received an Australian Research Council grant in the year 2000 to work on this so it has taken us some time to achieve our goal.

The characters in this story are the Australian freshwater spiny crayfish and their flatworm friends, which are called temnocephalans. These worms spend their entire lives living on the bodies of the crayfish, and in many cases, one species of flatworm is found on only one species of crayfish.

Their partnership has endured for 100 million years. To put that in perspective, our own species Homo sapiens has occupied the earth for 0.2 million years, so we are a blink compared to these ancient creatures. There are three genera discussed in our paper: one genus of crayfish and two types of temnocephalans. I will introduce them in turns.

Spiny crayfish (genus Euastacus)

The genus Euastacus are cool-climate specialists who live in leafy upland rivers, where they hide under rocks and burrow into the banks. The genus originated on the ancient continent of Gondwana and persists only in eastern Australia.

Unlike their more familiar relatives such as yabbies, spiny crayfish grow slowly and live for a long time. The larger species, such as the Murray Cray, take up to 7 years to become sexually mature and can live for 50 years or more. Nobody knows exactly how long, and really large specimens (which could be very old indeed) are increasingly difficult to find.

Fishing pressure and habitat alteration has caused serious declines in many species, while climate change puts all of them at risk. No less than 75% of the Euastacus species are endangered. Those most at risk reside on isolated mountains in northern Queensland.

We collected 37 different species of Euastacus for our study. Each one lives in a different river system or National Park, and some were collected by hand, others using nets. Patience and persistence were required in every case.

I remember one trip in particular, when David, Kim, my husband and I were in the Grampians National Park on New Year’s Eve 2003 – after a day of collecting we set up our microscopes on a picnic table in the campsite to pick worms from our crayfish and label our specimens. Members of the public were intrigued and after looking down our microscope, one young camper presented us with a drawing of a crayfish (probably Euastacus bispinosus) that has hung on my office wall ever since.

Drawing of a spiny crayfish by Daniel Artus, age 5. Original artwork, Daniel Artus

Temnocephalans – ectosymbiotic flatworms

I have written about temnocephalans before, and it is worth looking at the video in my article here to see how they move.

Basically, they look like little hands with eyeballs and they stay attached to the crayfish using large suction discs. The “fingers” are tentacles that they use to catch prey from the water.

We have no evidence that they harm the crayfish, so we say that they are symbiotic (meaning the relationship is probably of mutual benefit). It may be that temnocephalans keep the crayfish clear of other parasites and that crayfish stir up sediment providing sources of food for the worms.

There are two genera of temnocephalans in our study: Temnohaswellia have six tentacles and are usually white, while the genus Temnosewellia are brown and have five tentacles. The former genus was named after William Haswell, a director of the Queensland Museum, while the latter was named after our own co-author Kim Sewell.

Some temnocephalan species live on more than one crayfish species, a pattern common among the Temnohaswellia. Others are found exclusively on one species of crayfish, a pattern common among the Temnosewellia. This is true especially among the far northern populations, which are most at risk of extinction.

In order to complete this study, we dissected individual worms so we could send samples to London for DNA analysis and keep enough of the animal in Australian so we could identify each species.

In some cases, the temnocephalans we found did not even have names. Kim, Lester and David had to complete careful microscopic and taxonomic work and publish species descriptions before we could continue.

Co-evolution

By analysing DNA sequences from 37 crayfish species and 33 species of temnocephalans, we were able to describe the ancient association between them.

The evolutionary history was reconstructed in matched evolutionary trees (called a co-phylogeny) allowing us to see patterns of divergence over a period of time that included extensive climate change as continents separated and drifted north.

Host-shifts are evident in the patterns revealed, meaning when one group diverged (as in when a new crayfish species formed) the other followed (a new temnocephalan species was born). There are few datasets available of this type and they are of great interest to evolutionary biologists.

Co-extinction

Unfortunately, the close association between crayfish and flatworm species means that if one goes extinct the other is likely to follow. Our analysis suggests that if all the endangered Euastacus species go extinct, then 60% of temnocephalan species will follow suit.

Both types of organisms are so unique and special they deserve protection, but climate change will make this challenging due to their reliance on clear cold water and shady habitats.

It is our hope that by highlighting these issues, more people will care about the future of freshwater crayfish and the tiny animals (there are others) that live on them or in their burrows. In any case, we are delighted to be able to offer this unique insight into the phenomenon of co-evolution.

Disclosure

Susan Lawler and co-authors received funding from the Australian Research Council.

Biggest ever deep Atlantic exploration mission launched by UK scientists.

The Mexican government is planning a marine reserve extending 200 miles out from the Caribbean coast on the Yucatán peninsula. However a network of caves connecting the sea to the jungle will remain outside of the reserve. Environmentalists are calling for this unique ecosystem to be protected too to safeguard its future and that of the wider reserve

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Chee Dale, Derbyshire Every so often, looming out of the mist, I’d encounter the massive arch of a viaduct, like Inca ruins lost in the jungle

Grike is a northern English word, probably of Norse origin, used most commonly for the solution fissures that characterise limestone pavements, and therefore not often heard in upland Derbyshire, which has almost none. But I can’t help thinking of Chee Dale as a colossal grike. The familiar version offers protection to juicy plants from the ever-voracious sheep and Chee Dale does something similar.

Above Litton, early in the morning, a mower had already cut a field for silage, leaving it shorn and lemony. Down in the valley, just beyond the line of pretty terraced cottages at Blackwell Mill, I entered a different world, a canyon thrumming with vegetation, primeval and unkempt. It had rained overnight, and the surface of the Wye was steaming, mist billowing off the river and soaking the leaves of the overhanging ash and elm. At first I walked through drifts of ramsons, still flowering, still pungent, but as the tight walls of the valley closed in, I found myself waist deep in butterburs, my trousers soaked in seconds as I pushed through, vast black slugs reclining on their rhubarb-like leaves.

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British astronaut Tim Peake is preparing to return to Earth after an historic six-month stay aboard the International Space Station.

Government-funded ice breaker criticised for guiding luxury cruise in the Arctic as worries grow over the environmental impact of tourists.

VOCAL MAGIC: How exactly do our vocal cords produce the wide range of notes we need for singing?

The Dead Sea is one of the great ecological treasures of the world but it is shrinking at an alarming rate, as Kevin Connolly reports.

Official figures released today by the Forestry Commission show that the government is falling far short of its own tree-planting targets

Coal is the biggest source of electricity. Coal image from www.shutterstock.com

As the world moves to combat climate change, it’s increasingly doubtful that coal will continue to be a viable energy source, because of its high greenhouse gas emissions. But coal played a vital role in the Industrial Revolution and continues to fuel some of the world’s largest economies. This series looks at coal’s past, present and uncertain future.

CC BY-ND

China's coal future is up in the air. Coal image from www.shutterstock.com

As the world moves to combat climate change, it’s increasingly doubtful that coal will continue to be a viable energy source, because of its high greenhouse gas emissions. But coal played a vital role in the Industrial Revolution and continues to fuel some of the world’s largest economies. This series looks at coal’s past, present and uncertain future.

Something remarkable happened in China in 2014. China’s coal consumption - the highest in the world - appeared to stabilise for the first time in 16 years. Many commentators proclaimed a new era for China’s energy mix and perhaps even the beginning of the demise of coal in China.

As China is the world’s largest greenhouse gas emitter, this was heralded as good news for the climate.

But the future is rather more uncertain. China is a major regional power with a major energy economy. Its primary energy consumption has grown by more than 500% over the past 30 years. China overtook the United States as the world’s largest primary energy consumer in 2010.

Not surprisingly, the world has been watching the role of coal in China’s energy development with considerable interest over the past few decades.

Twin threats: pollution and climate change

In 2010, China released its 12th Five-Year Plan (FYP), the country’s defining economic plan for 2011-15. It fundamentally changed China’s approach to energy and climate policies.

Instead of broad goals and statements, the plan shifted to specific policy instruments aimed at reducing emissions. It was driven in no small part by domestic environmental concerns centred on smog, air and water pollution.

The 12th FYP established binding targets to reduce energy intensity by 16%, reduce carbon dioxide (CO₂) emissions intensity (emissions per unit of GDP) by 17%, and increase the proportion of non-fossil fuels in the primary energy mix to 11.4% – all by 2015.

These targets were reinforced by the historic US-China Joint Announcement on Climate Change in 2014.

Through the announcement, and its pledge ahead of the Paris climate summit in December 2015, China promised to peak in CO₂ emissions around 2030 (and try to peak earlier), cut emissions intensity by 60-65% of the 2005 level, and source around 20% of its primary energy consumption from non-fossil fuels by 2030. Provided that economic growth is limited to 5.5% (China’s economy grew by 6.9% in 2015), China’s emissions in 2030 would return to close to 2005 levels.

After the Paris Agreement, China announced its 13th Five-Year Plan, covering 2016-20. With a focus on capping energy consumption to within 5 billion tonnes of coal equivalent (capping overall energy use, not only coal use) by 2020 and addressing air pollution, energy intensity will be reduced by 15%, CO₂ emissions intensity will fall by 18%, and the proportion of non-fossil fuels will increase to 15%.

What does this mean for coal?

BP’s 2016 Energy Outlook shows China’s fuel mix is changing. The share of coal in primary energy is projected to fall from 66% in 2014 to 47% by 2035. Demand for coal is likely to peak in 2027 and then fall by 0.3% each year over the next seven years.

To compensate for China’s reduced reliance on coal, the share of natural gas is expected to more than double, with the share of non-fossil fuels also increasing rapidly to bridge the gap.

One interesting question is what does this mean for coal-fired power infrastructure in China?

Two main drivers influence the building of new power plants.

The first is growth in future electricity demand. This is influenced by population growth and the intensification of energy use in developing economies, such as China.

The second is “business-as-usual retirement” of infrastructure. This is driven largely by regulatory compliance and competitiveness in the electricity market, as well as a preference to shift to low-carbon sources to assist in meeting emissions reduction targets.

Most power plants approaching retirement age are located mainly in the USA and Europe, as you can see in the chart below. China, on the other hand, has a remarkably young fleet with a median age of 10 years.

And this is where the dilemma emerges. Very few plants are approaching the age of natural retirement in China, even by 2030 when emissions are scheduled to peak.

Global Data/Author provided, CC BY-ND

Given the age of coal-fired infrastructure in China, it doesn’t appear as though business-as-usual retirements will drive a dramatic reduction in China’s coal use.

Increasing climate action

Of course the pledges announced prior to Paris are only part of the story. The Paris Agreement aims to hold warming to well below 2℃ and attempt to limit warming to 1.5℃.

Estimates suggest the Paris pledges would result in warming of 2.7-3.6℃. Accordingly, much greater emissions-reduction efforts are likely to be required to hold global average temperature increase to less than 2℃.

A recent study looked at the implications for global coal-fired power investments (operating, committed and planned) for a 2℃ average temperature rise scenario (in line with the International Energy Agency’s global mitigation scenario).

The investments in recent and new coal-fired power plant capacity are dominated by expansion in Asia, in particular China and India. A global reduction in coal-fired power infrastructure to shift from the business-as-usual scenario to the 2℃ mitigation scenario unsurprisingly would require China to make a significant contribution to this reduction.

Accordingly, China would need not only to reverse its growth trend in installed capacity by 2030, but also decommission some 400 gigawatts of coal-fired infrastructure, approximately equivalent to a third of its capacity, before the end of its useful life.

The implication is that non-OECD countries including China could be asked to carry more of the economic burden to transform the global energy system because these countries will need to prematurely retire cost-effective coal power assets. Questions about whether this is realistic and around compensation for the cost of such early retirements may influence the prospects of addressing the risk of climate change.

A second driver of China’s coal consumption trend is the push to reduce air pollution, in particular damaging pollution known as PM2.5. While BP’s Energy Outlook for 2016 suggests that this will drive the switch from coal to natural gas, in the absence of serious constraints on carbon emissions, energy security drivers may favour the use of coal-derived synthetic natural gas (syngas or SNG).

While this reduces air pollution, the production process is very carbon-intensive. China has made ambitious plans to develop this technology.

With the release of the 13th FYP earlier this year, the energy sector was expecting a limit on total coal consumption and cuts to coal production in order to peak emissions by 2030.

Yet while some production cuts have been announced, precisely how this will play out for coal-fired power infrastructure and actual coal consumption remains to be seen.

Caroline Stott, UQ Energy Initiative Research Officer, contributed to this article.

Chris Greig owns shares in Rio Tinto, BHP and Wesfarmers. He is chief investigator on a grant provided by ACALET (Australian Coal Association Lowe Emissions Technologies Ltd).

How UK astronaut Tim Peake will get back from the International Space Station (ISS).

The Paris climate conference set the ambitious goal of finding ways to limit global warming to 1.5C, rather than the previous threshold of 2C. But what would be the difference? And how realistic is such a target? Environment 360 reports

How ambitious is the world? The Paris climate conference last December astounded many by pledging not just to keep warming “well below two degrees celsius,” but also to “pursue efforts” to limit warming to 1.5C. That raised a hugely important question: What’s the difference between a two-degree world and a 1.5-degree world?

Given we are already at one degree above pre-industrial levels, halting at 1.5C would look to be at least twice as hard as the two-degree option.

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European Union launches infringement procedure against Poland over tree-clearing in the Białowieża forest, a protected Unesco World Heritage site

The European Union on Thursday launched an investigation into Polish logging in its ancient Białowieża forest, a protected Unesco World Heritage site which includes some of Europe’s last primeval woodland.

“The commission has launched an infringement procedure against Poland ... the commission is in contact with the Polish authorities to make sure that any measures are in line with EU law,” a spokesman said.

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Poll shows Brexiters are also more likely to think media exaggerates agreement on climate science, distrust scientists and oppose windfarms

British people backing a leave vote in the EU referendum are almost twice as likely to believe that climate change does not have a human cause, according to a new poll.

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The UK could play a great role in the creation of Europe’s integrated single energy market – and reap its share of the significant benefits

Energy is the lifeblood of society. It heats our homes, powers our industry and entertainment, and fuels our transport. It has become yet another punchbag in the UK referendum campaign, with claims and counterclaims about costs. But there is a simple and very positive story to be told.

Some 65 years ago, after the devastation of world war two, the European Coal and Steel Community provided the vision, the coordination, and the investment that fuelled an unparalleled period of growth and stability in Europe. It laid the foundations for what then became the European Communities, the EEC and then the European Union. But ironically the energy sector got left behind.

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The sea eagle, also known as the white-tailed eagle, was driven to extinction in Britain earlier this century. Now, thanks to a reintroduction programme by Scottish Natural Heritage and the RSPB, it has returned one of its former haunts, the Inner Hebrides island of Mull in Scotland

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Hundreds of fishermen and officials rescued 24 of the whales after their pod swam ashore in Probolinggo, East Java

Eight pilot whales have died after a mass stranding on the coast of Indonesia’s main island of Java that sparked a major rescue operation, an official said Thursday.

Thirty-two of the short-finned pilot whales came ashore during high tide early Wednesday in Probolinggo, East Java province.

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Climate Central: The last monitoring station in the world without a 400 parts per million reading has now reached it, NOAA confirms

We’re officially living in a new world.

Carbon dioxide has been steadily rising since the start of the Industrial Revolution, setting a new high year after year. There’s a notable new entry to the record books. The last station on Earth without a 400 parts per million (ppm) reading has reached it.

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