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Published: 17 January 2013

Wetlands are being wedged


Australia’s coastal wetlands will be increasingly trapped between urban development on land and an ocean rising as a result of climate change, imperilling the survival of unique plants, birds and fish, leading ecologists have warned.

Botany Bay: sea level rise not only threatens Sydney’s main airport and other infrastructure, but it also threatens to engulf wetlands. If towns, cities, roads, etc lie on the landward side, wetlands will have no room to move.
Botany Bay: sea level rise not only threatens Sydney’s main airport and other infrastructure, but it also threatens to engulf wetlands. If towns, cities, roads, etc lie on the landward side, wetlands will have no room to move.
Credit: Jesse Allen via NASA

Researchers at the ARC Centre of Excellence for Environmental Decisions (CEED) say Australia’s planners and coastal communities need to think up to 100 years ahead to ensure the survival of mangroves, salt marshes, sedge lands and melaleuca swamps and their wildlife.

‘Sea levels are currently predicted to rise by up to 1 metre during this century – and there are indications they may be rising even faster than this,’ says Dr Jonathan Rhodes of CEED and The University of Queensland.

‘In past periods of rising sea levels, coastal wetlands have coped by migrating inland as the salt waters rose – but today, especially along the east coast of Australia, they are likely to run into urban development on and behind the coast.

‘Unless we can make room for them to move, there is a risk they may go locally extinct – along with the bird, fish and other wildlife they support, and the services they provide to humans.’

Dr Rhodes and colleagues Ms Rebecca Runting and Dr Morena Mills have been using a computer model called SLAMM (Sea Level Affecting Marshes Model) to identify areas where coastal wetlands would naturally retreat to as the ocean comes up – and where existing or future urban development may intrude.

‘It isn’t just about looking at the land contours – you also have to factor in changes in erosion and sediment deposition, in salinity levels and the effects of man-made structures, if you want to work out where mangroves and salt marshes could move to in the future,’ Ms Runting says.

‘These models give you a much better idea of what is going to happen than the so-called “bath-tub” models that only account for water level.’

Dr Rhodes says while many Australian coastal cities and towns now take steps to conserve existing mangroves and salt marshes, these may prove in vain if they don’t look and plan a century or more ahead to account for rising sea levels, which will bring dramatic change to coastal landscapes.

‘It’s true you can build a one kilometre long sea wall at a cost of about $7-8 million per metre in height and put urban development in behind it – but the reality is that we’re not going to be able to defend the entire Australian coastline with such measures, as sea levels will keep on rising as long as the climate is warming and the polar ice melting.’

Ice-cap melting may last for centuries and could eventually raise sea levels by tens of metres, scientists fear.

The CEED team’s research indicates that as sea-levels begin to rise, mangroves may be initial winners and salt marshes losers in the struggle for new places to survive. But if sea-level rise accelerates, even mangroves may fail to keep up, and may need to be translocated.

The same applies to threatened native animals such as the false water rat, which suffers from cat predation as its mangrove habitat becomes increasingly impacted by urbanisation.

‘Sea-level rise means that anyone and anything that lives along the coast has to be ready and willing to move – and our research is helping provide the answers about where they might move to, in plenty of time to do something about it,’ says Dr Rhodes.

Source: CEED







Published: 17 January 2013

Crunch time for metals recycling?

Alex Serpo

With the world facing a rare-earth metals crisis, a paper published in the leading journal Science last year examined how far we are from cradle-to-cradle metal recycling, and identified future constraints and opportunities.

End-of-life recycling rates for commonly used metals such as iron, copper, zinc and lead are above 50 per cent. However, rare earths and other lesser known metals are seldom, if ever, recycled.
End-of-life recycling rates for commonly used metals such as iron, copper, zinc and lead are above 50 per cent. However, rare earths and other lesser known metals are seldom, if ever, recycled.
Credit: © rihardzz/istockphoto

In the paper, ‘Challenges in metal recycling’ written by US researcher, Barbara Reck, the author identifies a modern paradigm shift in metals use – today, humans exploit virtually every stable element in the periodic table.

In other words, we are now capitalising on every element’s unique physical and chemical properties, whereas for most of human history, we utilised only a handful of metals.

Another modern shift is that of recycling, a ubiquitous aspect of modern life. ‘The generation between 20 and 30 are now the first generation to have grown up with recycling bins as part of normal life,’ writes Reck from Yale University's Center for Industrial Ecology.

Reck adds, however, that the extent of modern metals recycling is well below potential.

'Metals are infinitely recyclable in principle. But in practice, recycling is often inefficient or essentially nonexistent because of limits imposed by social behaviour, product design, recycling technologies, and the thermodynamics of separation.'

She identifies two metrics that provide the most accurate measures of the rate of metals recycling – 'recycled content' and 'end-of-life recycling rate'.

Recycled content describes the share of scrap in metal production, which is important to get a sense of the magnitude of secondary supply. End-of-life recycling rate, on the other hand, is defined as the fraction of metal in discarded products that is reused in such a way as to retain its functional properties.

The paper makes reference to a United Nations’ panel that recently defined and quantified recycling rates for 60 elements. Two key trends are clear from this research.

The first is that end-of-life recycling rates for the commonly used base metals such as iron, copper, zinc and lead are above 50 per cent.

The second trend is that many trace elements are seldom, if ever, recycled. Most of these trace elements are increasingly used in small amounts for very precise technological purposes, such as red phosphors, high-strength magnets, thin-film solar cells, and computer chips.

In those applications, often involving highly comingled 'specialty metals', recovery can be so technologically and economically challenging that the attempt to recycle is seldom made.

'After millennia of products made almost entirely of a handful of metals, modern technology is today using almost every possible metal, but often only once. Few approaches could be more unsustainable,’ comments Reck.

Greater opportunities for collecting used metals have improved recycling rates over recent decades.
Greater opportunities for collecting used metals have improved recycling rates over recent decades.
Credit: Bidgee under CC-BY-SA-3.0 via Wikimedia Commons

In her paper, Recki identifies lead as a notable exception : '...80 per cent of today’s lead use is for batteries in automobiles and for backup power supplies, and collection and pre-processing rates from these uses are estimated to be within 90–95 per cent as a result of stringent regulation worldwide. The result is a nearly closed-loop system for lead use in batteries.'

While improved product design and enhanced deployment of modern recycling methodology will both improve recycling rates, Reck identifies one activity that stands out as the key to increasing recovery.

'It seems mundane at first telling, but the activity with the greatest potential to improve metal recycling is collection,' she writes. 'Much improvement is possible, but limitations of many kinds – not all of them technological – will preclude complete closure of the materials cycle.'

Reck also identifies a perverse incentive when it comes to product design for recycling: the more advanced and highly engineered the product, the more difficult it is to recycle. This is particularly true for electronics products, but also applies to other goods like cars, aeroplanes and whitegoods.

Collectively, today’s high-tech products make use of almost every metal, in contrast to earlier products that used only a handful of the more common metals.
Collectively, today’s high-tech products make use of almost every metal, in contrast to earlier products that used only a handful of the more common metals.
Credit: © Yutaka Tsutano under CC BY 2.0 licence via flickr

The paper identifies another paradox of modern materials recovery. 'It is not much of an exaggeration to say that we manufacture modern products with the best possible technologies we can devise, but generally recycle them with relatively basic approaches.

'It is unfortunate from a materials perspective that, for reasons of scale and economics, often only the more basic technologies (shredding, crushing, magnetic sorting) are routinely applied, whereas more advanced technologies (such as laser, near-infrared, or x-ray sorting) are limited to selected recyclate streams.'

The paper dismisses the common notions of infinite recyclability for bulk recycling of common metals.

'Markov chain modelling shows that a unit of the common metals iron, copper, or nickel is only reused two or three times before being lost, gainsaying the notion of metals being repeatedly recyclable.'

Reck’s concluding comments identify how materials substitution could help improve the sustainability of metals supplies.

'Sometimes, scarce metals can be replaced by more common metals with only modest loss of product performance. Examples are aluminum-doped zinc oxides substituting for indium tin oxides in liquid crystal.’

This is a lightly edited version of an article that first appeared in Business Environment Network (BEN) and is reproduced with permission.






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