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Seagrass, protector of shipwrecks and buried treasure



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Nature’s bank vault.
Author provided

Oscar Serrano, Edith Cowan University; Carlos Duarte, King Abdullah University of Science and Technology; David John Gregory, National Museum of Denmark; Dorte Krause-Jensen, Aarhus University, and Eugenia Apostolaki, Hellenic Centre for Marine Research

For more than 6,000 years, seagrass meadows in Australia’s coastal waters have been acting as security vaults for priceless cultural heritage.

They’ve locked away thousands of shipwrecks in conditions perfect for preserving the fragile, centuries-old timbers of early European and Asian explorers, and could even hold secrets of seafaring by Aboriginal Australians.

Seagrass meadows accumulate marine sediments beneath their leaves, slowly burying and safeguarding wrecks in conditions that museum curators can only dream of. It’s a process that takes centuries, as mats of seagrass and sediments cover the wrecks and all their buried treasure.

Seagrass sedimentary deposits also hold archives of wider environmental change over millennia and are important sinks for atmospheric carbon dioxide, known as Blue Carbon.

But human development, climate change and storms are threatening fragile seagrass meadows around the world, and that risks the loss of the important cultural heritage they protect as well as some of the world’s most productive marine ecosystems.




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Our research, carried out by an international team of scientists in Australia, Denmark, Saudi Arabia and Greece, shows that seagrass meadows, hidden beneath our oceans, gradually build up the seafloor over millennia by trapping sediments and particles and depositing those materials as they grow.

The organic and chemical structure of seagrass sedimentary deposits is key to its ability to protect shipwrecks and submerged prehistoric landscapes. These structures are extraordinarily resistant to decay, creating thick sediment deposits that seal oxygen away from archaeological sites, preventing ships’ timbers and other materials from rotting away.

Seagrass meadows are under environmental stress due to climate change, storms and human activity. Recent disturbances and losses have exposed shipwrecks and archaeological artefacts that were previously preserved beneath the sediment. Once the protective cover of seagrass is gone, the ships and other sites begin to break down. If you lose seagrass, you lose cultural heritage.

Seagrass meadow losses in the Mediterranean have exposed Phoenician, Greek and Roman ships and cargo, many of which are thousands of years old. Unless these effects can be stemmed, the frequency of exposures is likely to increase. This has already put European archaeologists and marine scientists in a race against the clock.

Roman amphorae from a late Roman shipwreck in South Prasonisi islet, Greece, surrounded by seagrass meadows.
T. Theodoulou., Author provided

Around 7,000 shipwrecks are thought to lie in Australia’s coastal waters. Seagrass disturbance led to the unearthing in 1973 of the James Matthews, a former slave ship that sank in 1841 in Cockburn Sound, Western Australia, and the Sydney Cove, which ran aground off Tasmania’s Preservation Island in 1797, forcing survivors to walk 700km to Sydney.

Artefacts and pieces of the James Matthews’ hull have been recovered and studied at the WA Museum. Meanwhile, the recovery of beer bottles from the Sydney Cove has led, remarkably, to 220-year-old brewing yeast being cultivated and used to create a new beer – fittingly enough called The Wreck.

Revealing wrecks

We and our colleagues are aiming to match shipwreck data with seagrass meadow maps. From there, we hope new acoustic techniques for below-seabed imaging will allow exploration of underwater sites without disturbing the overlying seagrass meadows. Controlled archaeological excavation could then be undertaken to excavate, document and preserve sites and artefacts.

We also believe there’s significant potential to find archaeological heritage of early Indigenous Australians buried and preserved in seagrass meadows. Sea level around Australia rose around 6,000 years ago, potentialy submerging ancient indigenous settlements located in coastal areas, which may now be covered by seagrass.

The danger of not putting these protections in place is evidenced by treasure-hunters off the Florida coast, who have adopted a destructive technique called “mailboxing” to search for gold in Spanish galleons. This involves punching holes into sediment to find and then pillage wrecks, an action that damages seagrass meadows and archaeological remains.




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We desperately need to store more carbon – seagrass could be the answer


The accumulated sediments in seagrass meadows could also help build a record of environmental conditions, including fingerprints of human culture. These archives can be used to reconstruct prehistoric changes in land use and agriculture, mining and metallurgical activities, impacts of human activities on coastal ecosystems, and changes associated with colonisation events by different cultures. Think of it as a coastal equivalent to polar ice cores. Seagrass records could even help us understand, predict and manage the effects of current environmental changes.

But to do all this, we first need to realise what a truly valuable resource seagrass is. Granted, it doesn’t look spectacular, but it can do some pretty spectacular things – from sucking carbon out of the skies, to underpinning entire ecosystems, and even guarding buried treasure.The Conversation

Oscar Serrano, Doctor of Global Change, Edith Cowan University; Carlos Duarte, Adjunct professor, King Abdullah University of Science and Technology; David John Gregory, Senior Researcher, National Museum of Denmark; Dorte Krause-Jensen, Senior Researcher, Marine Ecology, Aarhus University, and Eugenia Apostolaki, Researcher, Institute of Oceanography, Hellenic Centre for Marine Research

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

It’s clear why coal struggles for finance – and the government can’t change that


Samantha Hepburn, Deakin University

The federal government has announced a raft of new measures ostensibly designed to secure energy pricing, boost investment in new “reliable” energy generation, and improve competitiveness in the retail energy market.

At a meeting of state and federal energy ministers last week, it also rejected the greenhouse emissions reductions outlined in the previous National Energy Guarantee, and proposed supporting new coal-fired power stations as part of a plan to boost investment in new electricity generation.




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One of the main reasons new coal projects do not proceed is because of the “unquantifiable” financial risk of carbon. Former Clean Energy Finance Corporation chief executive Oliver Yates has argued that coal-fired power generation would not be financially backable without the government providing indemnity against future carbon taxes.

He may have meant it as a reason not to proceed with coal at all, but federal energy minister Angus Taylor has signalled that he is seriously considering such a move.

In outlining his policy position, Taylor has also effectively expanded the definition of new electricity generation to include old facilities that would have been retired but may be revived with financial assistance.

Differing recommendations

The federal government says its new proposals are based on recommendations made in a July report by the Australian Competition and Consumer Commission (ACCC), aimed at ensuring affordable electricity. But there are some key differences between the report’s recommendations and the government’s plans.

The crucial one, at least as far as coal’s fortunes are concerned, is the proposal for the government to enter into contracts called “energy offtake agreements”. Under this approach, the government would agree to buy future electricity at a set price, from new generation projects that could include coal-fired electricity from either new coal plants or refitted coal plants. This, the government argues, would keep power prices in line while also providing greater investment certainty and make energy projects easier to finance.

The ACCC report did indeed recommend underwriting new power generation investments, but not with the obvious goal of propping up coal. Rather, it recommended that this support be directed to “appropriate new generation projects which meet certain criteria”, so as to reduce prices by boosting market competition.

It is hard to see how the government’s desire to artificially sustain the life of coal-fired electricity – in the face of ever-worsening economic prospects – is consistent with either the ACCC’s rationale of supporting sustainable, new generation energy projects in order to improve competition in the energy market.

Federal shadow climate change minister Mark Butler has indicated he would not support the inclusion of coal in any such agreements, and that the plan could cost taxpayers billions.

Is coal ‘new generation’ or not?

Taylor has argued that the backing and guarantees for new electricity generation could well include coal, because “it may well be that the best options we have available to us are expansions of existing coal facilities”.

But the reality, given our climate targets, is that coal can only be an option where it is supported by clean technology. And even the cleanest of “clean coal” is not on a par with renewable energy.

The latest generation of high-efficiency “ultra-supercritical” coal-fired plants are very expensive to build and run, particularly if they include carbon capture and storage – which they would certainly need to. If all of Australia’s existing coal plants were replaced with ultra-supercritical ones that did not include expensive carbon capture and storage technology, emissions would fall by between 26 million and 40 million tonnes by 2030. But Australia’s climate target calls for a reduction of 160 million tonnes by that deadline.

On the other hand, with carbon capture and storage, the emissions reductions would be much greater, but the electricity could cost up to three times the current wholesale price. This would mean the government would be effectively subsidising the production of electricity that is more expensive and more environmentally damaging than renewables.




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This raises the ultimate question of why – given Australia’s emissions targets and its responsibilities under the Paris Agreement – the government is prepared to subsidise coal-fired electricity at all.

There is no doubt that climate change is an important public concern. The attempt to characterise Taylor as “minister for getting power prices down” belies the fact that energy policy is not just about price and reliability, but about broader social and environmental welfare too. Electricity absolutely must be sustainable as well as affordable.

This is what energy security means today. Carbon-intensive energy production is neither environmentally sustainable nor financially viable. It is that simple. That is precisely why the financial risks of carbon are so high.The Conversation

Samantha Hepburn, Director of the Centre for Energy and Natural Resources Law, Deakin Law School, Deakin University

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