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The hands of the Doomsday Clock currently stand at two-and-a-half-minutes to midnight. Professor Ray Pierrehumbert of Oxford University and the Bulletin of Atomic Scientists explains why support for science and the global March for Science on 22 April is crucial

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Good management of mega-constellations of spacecraft can avoid polluting the orbital environment.

March for Science on 22 April will see scientists and supporters at more than 500 locations stand up for evidence-based thinking

Scientists and science supporters will take to the streets in a global March for Science on 22 April . What began as a small Facebook group in the US capital, Washington DC has spiralled into a global phenomenon that will now see marches and other events in more than 500 locations around the world, from Seattle to Seoul.

It is great news that so many people are prepared to stand up and defend the need for evidence-based thinking and the scientific method. But it is also a sad comment on our times that a March for Science is needed at all. Post-truth populism has infected democracies around the world, scientific objectivity is under threat from multiple sources and there seems a real danger of falling into a modern dystopian dark age.

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Scientists are ditching their labs for the streets in a mass protest against the Trump administration’s war on facts, but will the effort resonate with skeptics?

On Saturday, thousands of scientists are set to abandon the cloistered neutrality of their laboratories to plunge into the the political fray against Donald Trump in what will likely be the largest ever protest by science advocates.

The March for Science, a demonstration modeled in part on January’s huge Women’s March, will inundate Washington DC’s national mall with a jumble of marine biologists, birdwatchers, climate researchers and others enraged by what they see as an assault by Trump’s administration upon evidence-based thinking and scientists themselves.

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The two brown bears were found by Ukrainian charity Four Paws.

Based on reports, an infrastructure fund of Australia-based Macquarie Group has acquired a large solar portfolio from India’s Hindustan Power.

Nuvation Energy announces that their new 11-60 VDC battery management system.

A year ago, NSW was considered the worst place to invest in wind and solar energy in the country. Now the Coalition state government has a plan that could rival Labor states in its ambition.

Claxton, Norfolk At Thorpe Hall near Haddiscoe, 340 pairs of rooks once nested, but this spring there is not one

Assessing the rook population in the Yare valley has long been a favourite ritual of my springs. Since the nests are coarse bundles of sticks in the bare treetops it is easy to combine the serious census work with the season’s wider pleasures: the sounds of first chiffchaffs or blackcaps, the lemon wings of male brimstone butterflies, and the year’s first glamorous colour from primroses, marsh marigolds and walls of blackthorn blossom.

However, by the time I reached the third of my 30 rookeries, I sensed that this year would be different. A site that had once held 100 nests was completely empty. Thereafter, each old place revealed the new story of absence.

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Scientists find live specimens of the giant shipworm, described as "rare and enigmatic".

Nano-Nouvelle says lithium-ion battery boosting technology is ready for use on commercial battery production lines.

Renewable energy made up just over 41% of Germany’s power supply last month, the most ever at around 19.5 TWh, as nuclear continues its decline.

The Australian Petroleum Statistics provide statistics on petroleum production, refinery inputs and outputs, sales and stocks of petroleum products, and prices.

Wollemia pine pollen cone. Wollemia pines (found in the wild only in Australia) are one of the most ancient tree species in the world, dating back 200 million years. Velela/Wikipedia

They say that trees live for thousands of years. Like many things that “they” say, there is a germ of truth in the saying (even though it is mostly false).

The vast majority of trees that burst forth from seeds dropped on the Australian continent die before reaching maturity, and in fact most die within a few years of germination.

But depending on how you define a tree, a very select few trees can live for an astoundingly long time.

What are the oldest trees?

If we define a “tree” as a single stemmed woody plant at least 2 metres tall, which is what most people would identify as a tree, then the oldest in Australia could be a Huon Pine (Lagarostrobos franklinii) in Tasmania, the oldest stem of which is up to 2,000 years old.

However, the Huon Pine is also a clonal life form – the above-ground stems share a common root stock. If that common root stock is considered to be the base of multi-trunked tree, then that tree could be as old as 11,000 years.

But if you accept a clonal life form as a tree, even that ancient Huon age pales into insignificance against the 43,000-year-old king’s holly (Lomatia tasmanica), also found in Tasmania.

King’s Holly, or Lomatia tasmanica, can form clones nearly 50,000 years old. Natalie Tapson/Flickr, CC BY-NC-SA

Once you accept that a common, genetically identical stock can define a tree, then the absolute “winner” for oldest tree (or the oldest clonal material belonging to a tree) must go to the Wollemi Pine (Wollemia nobilis). It may be more than 60 million years old.

The Wollemi pine clones itself, forming exact genetic copies. It was thought to be extinct until a tiny remnant population was discovered in Wollemi National Park in 1994. The trunk of the oldest above-ground component, known as the Bill Tree, is about 400-450 years old. But the pine sprouts multiple trunks, so the Bill Tree’s roots may be more than 1,000 years old.

There is also substantial evidence that the tree has been cloning itself and its unique genes ever since it disappeared from the fossil record more than 60 million years ago.

How do you date a tree?

If no humans were around to record the planting or germination of a tree, how can its age be determined? The trees themselves can help tell us their age, but not just by looking at their size. Big trees are not necessarily old trees - they might just be very healthy or fast-growing individuals.

A much more reliable way to determine age of a tree is through their wood and the science of dendrochronology (tree-ring dating).

Dendrochronology involves counting tree rings to date a tree. The wider the ring, the more water the tree absorbed in a given year. sheila miguez/flickr, CC BY-SA

Many trees lay down different types of cell wall material in response to seasonal patterns of light, temperature or moisture. Where the cell walls laid down at the beginning of the growth season look different to those laid down at the end of the season, rings of annual growth can be seen in cross-sections of the tree.

This map of growth patterns can also be cross-dated or correlated with major events like multi-year droughts or volcanic eruptions that spewed material into the atmosphere to be incorporated into the wood of the tree. But the cell walls are more than just calendars.

Why so old?

Individual tree stems can live for so long because of the structure of the wood and the tree’s defence mechanisms. The woody cell walls are very strong and resist breakage.

In fact, scientists have recently discovered that these walls contain a structure – nanocrystaline cellulose – that is currently the strongest known substance for its weight.

Wood can, however, be broken down by insects and fungi. Even though there is little nutrition or energy in wood, there is some – and there are plenty of organisms that will try and use it.

But trees are not defenceless, and can fight back with physical barriers or even chemical warfare. When one tree is attacked by these destructive forces, individuals may even signal to other trees to be aware and prepare their own defences to fight off death and decay.

The death of trees

So why don’t all trees live for centuries or millennia, and why do so many die before even reaching maturity?

Adult Wollemi pines in the wild. J.Plaza/Van Berkel Distributors

Seedlings and young trees may die because they have germinated in an area where there’s not enough water, nutrients or light to keep them alive as adults. Young trees also haven’t had much time to develop barriers or defences against other organisms and may be browsed or eaten to death.

Some trees simply fall prey to accidents: wind storms, fires or droughts. This is just as well, because there is a vast number of plants and animals – including humans – which rely on the wood and other components of these dead trees for their food and shelter.

But increasingly we may see trees dying because the environment is changing around them and they may not be able to cope. This is not just due to climate change; urban development and agricultural expansion, pollution and even too much fertiliser acting as a poison – even our most remote environments are subject to these changes.

But that doesn’t necessarily mean we will have no more very old trees. The Wollemi Pine’s genes have already survived over millions of years, multiple ice ages and warming periods and even the fall of the dinosaurs and rise of humans. And now, people have deliberately spread Wollemi Pine trees all around the world so they are living in a wide range of countries and climates, meaning that the risk of them all dying out is substantially reduced.

Maybe we can do the same for other trees, ensuring that trees will outlive us all.

Cris Brack is a member of the Institute of Foresters of Australia and Director National Arboretum, Canberra Foundation.

Matthew Brookhouse 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.

Rick Perry's request for the DOE to investigate how federal subsidies boost one form of energy at the expense of baseload generation was clearly meant as a swipe at wind and solar energy resources.

Solar already achieved that milestone in more than 30 countries, according to the World Economic Forum. So what happened?

Germany’s first competitive auction for offshore wind projects included what is likely one of the world’s first subsidy-free offshore wind projects.

TrinaBESS have announced that the company will introduce its large-scale Battery Energy Storage System called TrinaMega for the US Market

Poaching, illegal logging and fishing are threatening some of the world's most iconic natural heritage sites.

As the cost of solar, storage and wind continue to fall, the pressure on utility business models and their so-called "parenting advantage" will increase significantly.