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Lennon Bartlett uses a boat to row to his parents’ house next door in central Lismore after the Wilsons river breached its banks early on Friday morning, flooding the northern New South Wales city. Flood waters caused by the remnants of Cyclone Debbie are still rising and are expected to peak in the early afternoon

• Ex-cyclone Debbie: deaths feared in Lismore – live updates

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CEFC appoints head of Impact Investing team at Social Ventures Australia as its new chief executive officer.

China begins closing down its legal ivory trade, but will consumer attitudes to prized artwork change?

SpaceX flies and lands a Falcon 9 rocket that had already been used on a previous mission.

LOST IN SPACE: A large portion of Mars' atmospheric gases have been literally lost in space, according to a new study.

New WA Premier Mark McGowan is pressing ahead with his election promise to scrap the Roe 8 highway extension—but it will come at a cost.

Astronauts Peggy Whitson and Shane Kimbrough were meant to be installing debris shields on the ISS.

The Hazelwood mine will fill with water once it's closed. AAP/Country Fire Authority

The Hazelwood coal mine and power plant has employed generations of families in Victoria’s Latrobe Valley since the end of the second world war. With the mine to close at the end of March 2017, hundreds of local residents face unemployment. When the mining stops, the pit at Hazelwood will eventually become a “pit lake” as it fills with groundwater.

Several options are on the table for the Hazelwood lake, and questions have been raised about the cost of rehabilitating the mine.

There are thousands of pit lakes on every inhabited continent, but few have been designed for people to use for recreation. Although Australians are increasingly embracing these lakes for swimming and boating, most pit lakes are unsafe and are on private property.

Germany’s brown coal mines

Depending often on the local geology, pit lakes can have poor water quality and unstable banks, which pose risks to nearby communities and the environment. However, pit lakes can also be sources of income through recreation or industry, particularly for local communities after the mining stops.

The challenge for the residents of the Latrobe Valley (and other mining regions) is to decide how new pit lakes can benefit the local economy. The challenge for scientists is how to rehabilitate these lakes for community benefit.

The coal mines of former East Germany have developed into pit lakes and can provide a vision of what Australian pit lakes might become.

Lusatia pit lake in the former East Germany is now an economic asset for the community. Melanie Blanchette, Author provided

Lignite (brown coal) mines were closed in East Germany after reunification in 1990, causing regional economic collapse and emigration. In an attempt to boost the local economy, the German government tasked a state-owned company with rapidly rehabilitating the landscape and filling the pits with river and groundwater for recreational use.

In 2009 the annual economic benefit of the lake district was between €10.4 million and €16.2 million. Current lake activities include swimming, boating and scuba diving. Businesses use the steep slopes of slowly filling pit lakes as vineyards, while spa hotels with lakeside boulevards cater to upmarket clientele.

Germany’s experience shows that pit lakes can lead to public benefit. However, many of these lakes require expensive ongoing active treatment, such as liming and pumping water through treatment facilities.

Due (in part) to the remoteness and low population density of Australia, this level of active treatment is unlikely to be economically feasible.

Natural rehabilitation

But active ongoing treatment isn’t the only option for improving pit lakes. Pit lakes have the capacity to change over time and become similar to natural lakes.

Pit lakes can naturally improve over decades (as seen in the coal-strip lakes of the US Midwest), if they are exposed to “passive” treatments that increase the amount of nutrients, beneficial microbes, seeds and insect larvae.

Every pit lake has a unique suite of biological and physical characteristics that make it easier or more difficult to rehabilitate. The US coal-strip pit lakes would be considered “easy” to rehabilitate because they were shallow, had large catchments and significant amounts of organic matter. However, the lakes still took decades to recover.

It’s hard to say exactly how Hazelwood will stack up on this scale without seeing modelling, but we can assume that its large size will create difficulties, as will any potential water quality issues. On the other hand, because the pit is still dry there’s an opportunity for pre-filling treatments that improve biodiversity and water quality.

For example, using heavy earthmoving equipment to “sculpt” the edge of the pit creates more natural habitats that encourage aquatic life to take hold. Careful introduction of appropriate wetland plants can enhance the system. Working with hydrologists and engineers, drainage lines connecting the pit lake to the wider catchment can provide the lake with sources of terrestrial nutrients to kickstart ecosystem development.

Passive processes tend to be slow. The challenge for scientists is to speed them up. However, many of the ecological processes that underpin pit lake development (as described above) are well-studied in artificial and natural lakes.

Turning an abandoned pit lake into a resort is not a far-fetched idea. As Germany’s mine pit projects show, communities can embrace a changing economy, and the science indicates that passive treatment systems can improve pit lakes.

The legacy of past mines and our demand for resources will ensure that more pit lakes will be produced. Ultimately, we will have to decide how we want to co-exist with these new lakes.

Melanie Blanchette receives funding from the Australian Coal Association Research Program and is a member of the International Mine Water Association.

Mark Lund receives funding from the Australian Coal Association Research Program and the mining industry. He is a member of the International Mine Water Association.

Mass migration of species to cooler climes has profound implications for society, pushing disease-carrying insects, crop pests and crucial pollinators into new areas, says international team of scientists

Global warming is reshuffling the ranges of animals and plants around the world with profound consequences for humanity, according to a major new analysis.

Rising temperatures on land and sea are increasingly forcing species to migrate to cooler climes, pushing disease-carrying insects into new areas, moving the pests that attack crops and shifting the pollinators that fertilise many of them, an international team of scientists has said.

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The spectacular James Webb Space Telescope is bound next for the giant Apollo testing chamber.

Research will be carried out into the age and rarity of the tusk.

The word climate does not appear once in the letter triggering the UK’s departure from Europe. But it’s not just in London that the issue seems to be slipping from the political stage

The word climate does not appear once in the letter triggering the UK’s departure from Europe. Despite the world experiencing a second, successive, record annual rise in carbon dioxide concentrations, on one level the omission is hardly surprising.

When the environment minister, George Eustice, revealed that the government had commissioned no research at all on the likely impact of Brexit on environmental policy it reflected how low green issues had fallen on the political agenda. Just how far is revealed by the fact that more than 1,100 EU environmental safeguards will need translating into UK law.

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Elephant conservationists hopeful that demand for ivory in China is falling amid government clampdown on ivory sellers, but experts remain wary of poaching

The wholesale price of raw legal ivory has dropped by almost two thirds since China, the world’s largest ivory importer and trader, announced plans to close down its domestic market, according to new research.

Researchers working for the conservation organisation Save the Elephants visited Beijing and Shanghai, as well as six cities whose markets had never been surveyed before: Changzhou, Hangzhou, Nanjing, Shenyang, Suzhou and Tianjin. The researchers, Lucy Vigne and Esmond Martin, concluded that the legal trade in ivory is dying.

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Social change starts with individuals who decide to do things differently.

How life will change with the climate.

Who will protect climate change refugees?

Indigenous rangers are on the frontline of the battle to protect Australia's natural environment from noxious weeds, feral animals and dangerous wildfires.

System will include 3.4m solar panels and 1.1m batteries, with operations set to begin by end of 2017

A huge $1bn solar farm and battery project will be built and ready to operate in South Australia’s Riverland region by the end of the year.

Related: Elon Musk, meet Port Augusta: four renewable energy projects ready to go

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Free reusables, 25p charge on disposables and green slogans in cafes could cut some of 2.5bn cups thrown away each year, finds study

Incentives such as a tax on disposable coffee cups or free reuseable replacements could help cut the number thrown away in the UK every year by between 50m and 300m, according to new research.

An estimated 2.5bn throwaway coffee cups are used in the UK every year by consumers buying coffee from chains and cafes, creating approximately 25,000 tonnes of waste.

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Sherwood Forest, Nottinghamshire Spring hasn’t ignited its neighbours but this red-barked giant is vibrant in the sunlight

A banner of red falls amid ranks of anaemic grey: if sentient, this tree would have to be either mortified or cocksure, cutting such a bold dash in demure company. I shamble through ankle-snagging greenery and brownery as if through stubborn snow. My steps are crisp and disturb a sweet smell.

I get to the tree. It’s magnificent: 40 metres at least. It seems all trunk, until odd, brief branches pop from its bark, lichen-greened serpents from a mythical head. Higher, and finally, the serpent branches thicken and burst with evergreen.

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