James Rainey reads trees like most people read signposts.

The senior ecologist with the rewilding charity Trees for Life is using a small hand lens to identify a particular lichen that is wreathing the base of an aspen tree in a secluded glen on the west coast of Scotland. He is looking for “ecological clues” of species associated with the ancient Caledonian forest that once covered most of the Highlands, like this aspen, certain wildflowers, such as serrated wintergreen, and some lichens, such as black-eyed Susan and Norwegian specklebelly.

Wild pines have been growing in Scotland since the last ice age. This is a globally unique ecosystem that supports rare wildlife, including red squirrels, capercaillie and crossbills. Now less than 2% of the original growth survives, with just 84 individual Caledonian pinewoods officially recognised, having last been documented more than a quarter of a century ago.

But now Trees for Life and Woodland Trust Scotland have become aware of up to 50 other hitherto uncharted wild pinewoods, both from historical documents and anecdotal contemporary reports. The charities have turned tree detectives as they embark on the painstaking process of mapping – and hopefully reviving – these remote pockets of forgotten forest before they vanish for ever.

Rainey says the ecological investigators use three strands of evidence to pinpoint where these pinewoods first stood.

“First there’s the historical evidence, like old maps and texts,” he says. “Rev Timothy Pont, a Church of Scotland minister and cartographer, made incredible sketch maps of the Highlands in the late 1500s, which mention ‘fir woods’ in some areas, the old word for pine woods.”

There are cultural clues too, such as Gaelic place names referring to pine or woodlands.

The first ordnance surveys of the 1800s were remarkably accurate, and often used conifer symbols to represent pine woods. Trees for Life digitised these maps and superimposed the present-day landscape, making it easier to identify where they suggest unplanted or wild pine sites once were.

Rainey says: “Then we look at the landscape context of the site: is the pine associated with planting around a big house for example, or is the setting more natural?

“And finally, we use the ecological evidence: wild pine usually grows alongside old birch trees, while planted pine is often mixed with larch. Many ancient pinewoods also have lots of stumps scattered through them, and certain kinds of plants and lichens that indicate ecological continuity.”

After the last ice age, the pine was one of the first trees to return to Scotland, and there are microfossils in Glen Affric that date from 9,900 years ago. Mainly a tree of the Highlands and uplands, most of its decline has been caused by human deforestation.

“The emphasis after the second world war was on creating strategic resources for Britain, resulting in many areas of the Highlands being ploughed and planted in rows for commercial forestry,” says Rainey. “This was often done with cheap land that included ancient woodlands and it was really devastating to the last remaining trees.”

Restoration is possible, however, especially since some old trees survive along with the ancient woodland soil and seed bank: seeds stored in the soil, which can germinate once the heavy shade of commercial conifers is removed.

On the site we are currently exploring, which ranges along a river gorge, through woodland and commercial forestry then up to a high mountain dam across nearly 10 miles (16km), Trees for Life estimates there are about 85,000 seedlings unable to grow taller because of grazing by sheep and deer. Commercial trees – such as Sitka spruce – are not as tasty to the herbivores, so are usually left alone.

As the gorge deepens, Rainey points out the first indications of ancient woodland: a huge stool with thickly twisted trunks of regrowth, like a petrified octopus clinging to the rocky bank and aged between 400 and 500 years old.

Rainey has identified 23 pines in this area, 17 in the gorge and six on the crags higher up the mountain, all rooted in places least accessible to grazing deer. The needles have been taken for genetic testing to confirm their heritage.

Further along the gorge, we find a clump of pines beside the river, each of them in a uniquely gnarled and complicated shape, unlike the uniform rows of bushy soldiers standing to attention in the commercial plantations.

A few more kilometres in we find a young wild pine, a fresh blue-green in colour, probably a sapling from one of the ancient river trees, and aged about 12 years, according to the nodes that grow annually. It has already been eaten down by deer.

Much further up the mountain, buffeted by an icy wind, a handful of ancient pines are huddled in inaccessible spots across the otherwise bare shoulder.

Rainey says: “This would have been filled with trees but is now empty – these are the most critical areas in need of regeneration and we want the whole of the old growth woodlands to recover, not just the pines, but oak, rowan, birch, alder, hazel.

“In 100 years’ time people could be looking at quite a full woodland on this side of the hill and not believe that it was in such a state of degradation – the capercaillie and wildcat could live in a place like this – so if you want them back too then you have to restore these woods.”

They look a little like cockroaches and have bulging orange eyes, and trillions of them are about to erupt from the earth in much of the midwestern and eastern United States. The emergence of two groups of cicadas will assemble a chorus of the insects not seen in several hundred years, experts say.

The simultaneous appearance of the two cicada broods – known as Brood XIX and Brood XII – is a rare event, not having occurred since 1803, a year when Thomas Jefferson was US president. “It’s really exciting. I’ve been looking forward to this for many years,” said Catherine Dana, an entomologist who specializes in cicadas at the University of Illinois at Urbana-Champaign. “For the public, it’s going to be a really special experience.”

There are thousands of species of cicadas around the world but only 10 are considered periodical – having a life cycle that involves the juvenile cicadas living underground and feeding on plant sap for years before emerging en masse to the surface.

This year will see Brood XIX, the largest of all periodical cicada groups, emerge after a 13-year dormancy underground at the same time as Brood XII, a smaller group that appears every 17 years. The emergence will occur in spring, as early as this month in some places, and will see trillions of cicadas pop up in as many as 16 states, from Maryland to Oklahoma and from Illinois to Alabama.

This phenomenon, which has been dubbed “cicada-geddon” or “cicada-palooza”, will see huge clumps of cicadas across urban and rural areas, where the insects will make quite a noise – their songs collectively can be louder than a revving motorbike. After a frenzy of calling and mating and being devoured by predators, the cicadas will begin the cycle all over again in July.

The two broods may only overlap slightly in a small area of central Illinois, meaning there mostly won’t be a larger-than-normal boom in numbers in any one place, but researchers have said the emergence of all seven periodical species found in the US will be noticeable in many places and provide a rare glimpse of a grand ecological spectacle.

“I like to remind people that this is a natural wonder of the world. You just don’t see this biomass of terrestrial life anywhere else,” said Dana. There are several theories as to why cicadas do this, among the most popular being that an overwhelming surge of the creatures ensures that a good number will survive predators to spawn the next generation.

Some Americans are planning trips in order to see hotspots of cicadas, with other, more insect-phobic people wondering whether they should flee the onslaught. Cicadas aren’t harmful to people or pets in any way, though, with the insects having a straw-like mouth rather than any sort of biting parts. Some cicadas have been found to expel jets of urine when threatened, however.

As with most interactions between humans and the natural world, humans pose the bigger threat. Cicadas choose to burst aboveground when the soil temperature hits a certain point – usually around 64F (17C) – and global heating, caused by the burning of fossil fuels, is potentially scrambling this natural process.

“This could mess with their phenology. If they come out earlier than usual, that can be problematic for them,” said Dana.

For now, onlookers can still enjoy this rare burst of nature in their gardens and public spaces. “Sit back and be in awe at the spectacle,” advised John Cooley, a cicada expert at the University of Connecticut who tracks the emergences. “It will be over soon enough. Then think about where you will be in 13 or 17 years. It’s a time for introspection.”

When I am asked to choose my favourite insect, I have no hesitation in choosing the common wasp (Vespula vulgaris). I have been stung many times, having first fallen into a wasp nest at 5 years old though spared many of the stings by wasps entangled in the thick sweater my great-aunt had knitted.

But the wasp gets your attention and causes a reaction. It is perhaps the marmite of the insect world, you love it or hate it but you’re never indifferent and that gives me something to work on.

Wasps are in fact extremely valuable to people. They carry out pollination; an adult wasp’s main diet is nectar, which means it also carries pollen from plant to plant. And wasp nests provide a safe nursery ground for the larvae of some of our most spectacular pollinating hoverflies including the impressive Hornet Hoverfly (Volucella zonaria).

Wasps are also one of nature’s chief pest controllers. They go out hunting for their larvae, and bring back flies, aphids, caterpillars and many other invertebrates. And they are incredible architects, building paper nests from chewed up wood.

A wasp queen will begin by building a cylindrical column known as a petiole which she covers in a chemical she produces to repels ants. When she has finished, she produces a single cell and surrounds it with a further six cells, giving the cells their characteristic hexagonal shape. She continues building cells in a layer until she has 20-30 then lays an egg in each. Once the eggs have hatched she divides her time between feeding the larvae and nest building.

At full size, larvae spin a cover over their cell until they emerge into adult workers. The workers gather proteins to feed further larvae and sugars to feed themselves while they continue with nest building. When a worker wasp brings food to the developing larvae, the larvae return the favour by excreting a sweet honey-like gift for the worker. With enough adults fully grown the queen can focus on reproduction and is in turn fed by the workers. Each nest may contain 5,000-10,000 individuals and is spherical in shape.

Towards late summer the nests are at maximum capacity, with lots of adults and few larvae. New queens and male drones emerge from the nest; after mating the new queens overwinter in sheltered locations and the drones die (just as with their close cousins the ants and the bees).

A worker wasp measures about 12-17mm in length. The queens are larger, measuring around 20mm in length. Most worker wasps will only live as adults for a few weeks but the queen will hibernate underground to lay her eggs in summer so may survive for up to a year. The colonies last just one year and once the new queens depart, the other wasps in the colony die as the winter frosts come.

Wasps have a sting to allow them to capture and immobilise their prey. They may also sting to defend their nest. Wasps navigate via geo-location of large objects, this is the reason they will often circle people as they are mapping where we are which must be frustrating if we are moving.

So the worker wasp is born into a job for life, and paid in a sweet currency that is not available elsewhere. In late summer, when the new queens have flown the nest, the worker wasps are faced with the loss of job and purpose, as well as the loss of the sweet substances to which they have become addicted.

Perhaps that is why they’re drawn to humans, who often surround ourselves with the sweet supplements such as jam and beer to which they are attracted. But humans are big and threatening and we wave our arms at the wasps, who feel threatened, and then sting. If only there was a wasp welfare state we would all learn to love them.

• Paul Hetherington is Director of Fundraising and Communications at the charity Buglife

• Welcome to the Guardian’s invertebrate of the year competition! Every day for the next two weeks we’ll be profiling one of the incredible invertebrates that live in and around the UK. Let us know which invertebrates you think we should be including here. And at midnight on Friday 12 April, voting will open to decide which is our favourite invertebrate – for now – with the winner to be announced on Monday 15 April.

St Piran was a young Irish priest, it is said, who preached against King Aengus of Munster for planning to ditch his wife for a younger lady of the court. Piran was tied to a millstone and thrown off the highest cliffs into the sea.

But the stone floated and Piran was blown over to Cornwall, where he made another new home, enjoying feasting and fine wines and bringing Christianity to the druidic masses. His spells as a hermit attracted particular admiration and, when he rediscovered tin, his popularity among the locals became legendary.

Fifteen centuries later, a competition on BBC Springwatch led to (one of) Cornwall’s patron saints lending his name to an equally charismatic opportunist and hermit.

St Piran’s hermit crab only grows to 15mm and, like its saintly namesake, has a similar aptitude to making himself a new home. The crab takes up residence in empty periwinkles, dog whelks and other gastropod shells.

Historically, it has been a creature of warmer Mediterranean and eastern Atlantic waters. The coast of Cornwall became its new northern-most outpost when it colonised them in the 1960s. But it vanished not long after it arrived: populations entered a death spiral in the years after the Torrey Canyon oil spill in 1967. The detergents used to clean up the oil-wrecked rock pools and shoreline of the west coast didn’t help it either.

In 2016, it was discovered having returned to the South Devon coast – probably swept by currents from its nearest colonies in Brittany and the Channel Islands. Now warming seas appear to be assisting its spread around the south-west coast. It was recently found on Newquay beaches.

This crab is a good looker, with striking black-and-white-spotted eyes mounted on red eye stalks, bright red antennae and vivid blobs of red and electric blue on its legs and claws.

Unsurprisingly, given its size, it is shyer than the common hermit crab, and likes to curl up inside its shell and wait out all dangers.

So why not vote for an invertebrate that shows the resilience of the natural world, and cheer on the return of St Piran’s hermit crab – and our own capacity to appreciate such small miracles of life.

• Welcome to the Guardian’s UK invertebrate of the year competition. Every day between 2 April and 12 April we’ll be profiling one of the incredible invertebrates that live in and around the UK. Let us know which invertebrates you think we should be including here. And at midnight on Friday 12 April, voting will open to decide which is our favourite invertebrate – for now – with the winner to be announced on Monday 15 April.

Dotted along the length of Britain’s rivers are various obstacles – some as large as dams, others as small as weirs (which bisect a river like steps) – stopping creatures, sediment and plants from moving along the watercourse. Only 1% of the UK’s rivers are free of artificial barriers.

Moves are under way in many countries to remove such obstacles and let rivers “re-naturalise” and follow their own paths. But while many scientists agree that river barriers need to go in the UK too, other people are hesitant – concerned about creating unpredictable water flows in already flood-prone regions.

“Our rivers and our lakes are the most damaged of all ecosystems,” says Paul Kemp, a professor of ecological engineering at the University of Southampton. Globally, freshwater ecosystems are home to about a third of the planet’s vertebrate species, and these have been declining at twice the rate of marine and land-based animals. The situation in England is dire, with about 15% of rivers achieving good ecological status, according to the Rivers Trust.

Removing barriers “results in the greatest impact the most rapidly and for the least amount of money,” says Kemp.

In England, there are more than 50,000 barriers disrupting the passage of the country’s beleaguered rivers, according to the Environment Agency database. Scientists within the organisation suspect that there are many more. The overwhelming majority of these are relatively small: about 27,500 culverts, usually round concrete pipes, and around 16,300 weirs, which adjust the water level and effectively create a small dam.

These barriers are not only costly to maintain – they also cause avoidable environmental damage.

“A few decades ago, we thought only migratory species needed to move,” says Dr Perikles Karageorgopoulos, a senior technical specialist at the Environment Agency. “But we increasingly understand that all species need to move, from the tiniest ones that will have local migrations through to the others that migrate for many kilometres to overwinter or reach their spawning grounds.” Having so many barriers effectively creates a network of small dams or lakes, which offer plants and animals very different habitats from those found in free-flowing rivers, and are often not appropriate for river species.

Sediments also need to move. Barriers trap soil and geomorphological materials upstream, depriving downstream areas of sand and gravel, which are crucial for spawning creatures and many plants.

“Removing weirs is the most effective way of restoring a river,” says Karageorgopoulos. This is what happened in 2010, when a disused mill weir on the River Ouse in East Sussex failed and had to be removed. That stretch of the river had become a “ponded river with lilies”, he says. Now “there is a huge physical diversity that supports a large variety of species” – which also makes the river and its creatures more resilient to climate change.

“A diverse habitat is much more resilient to high or low [water] flows and extreme temperatures, and can provide a refuge for many species,” he explains. “In the past, the same river reach would have warmed up and become deoxygenated during low flows and warm weather. The warm water flowing downstream would have affected the ecology downstream too.”

In addition to that particular section, the weir removal had a positive impact on the river more than a kilometre upstream, Karageorgopoulos says. Within two years, the stretch of river was reclassified, moving from poor to good.

“It’s a good technique for focusing your efforts around restoration,” says Jesse O’Hanley, an environmental systems specialist and current associate dean of research and innovation at the University of Kent. “A lot of restoration efforts happen at a very small scale like planting some trees, bending the river in a little way or putting in some rocks. It’s a very hyper-localised solution that doesn’t really scale up and it’s expensive. It’s usually easier to let the river take care of it on its own.” This is what removing river barriers does: it lets rivers re-naturalise.

But letting a river choose its own path is a risky business, especially in flood-ravaged parts of England.

The Environment Agency estimates that about 3.4m properties in England are in areas at risk from surface flooding. Would removing river barriers make the situation worse, or improve it?

“Flooding is a natural process,” says Karageorgopoulos. “When you get really big floods, there just physically isn’t space in the river to contain the water.”

Rivers run in three dimensions: there is the flow we usually see in which water follows the channel of the river; but rivers also run laterally, breaching their banks and dispersing sideways on to flood plains, as well as vertically, linking the riverbed to the water table below. Obstacles and barriers have several consequences for a river’s passage in all three of those directions, both up- and downstream from the impediment.

The risk of flooding is always context specific, says Carlos Garcia de Leaniz, a professor of aquatic biosciences at Swansea University. Weirs and culverts can make flooding worse upstream, because they slow the water in the river, collecting it in mini-ponds and stopping it from flowing downstream. It is also quite easy for culverts to be blocked by trees and debris.

Additionally, the barriers stop sediment from moving down the river, causing it to collect in specific places. This substrate acts as a blanket on the riverbed, cutting off the link between the river and the water table, as the water cannot filter through. “That means less water is able to reach the water table and more water needs to be carried by the river channel,” says Garcia de Leaniz. “That means the risk of flooding may actually increase.”

The reality is that flooding is necessary and will happen – it’s about deciding where that water will go.

All the scientists the Observer contacted agreed that it is possible to predict the outcomes of taking away a culvert or weir. “There will be localised changes in flooding, and that is one of the consequences [of barrier removal],” says Hannah Cloke, a professor of hydrology and co-director of Water@Reading at the University of Reading. “But you can predict where those will be, and those are the kinds of things we should be doing anyway – making space for water on the flood plain.”

In a 2019 report, the Environment Agency warned that if current development continues on flood plains, the number of properties at risk of flooding could double in the next 50 years.

“We can only engineer our way out of some level of flooding… We can’t keep building giant concrete walls and structures in our rivers to control the water – that’s impossible. Working with the landscape is a much more sensible way of managing our rivers, and also has benefits for ecosystems and water quality,” says Cloke.

Europe and the US are leading the global charge on barrier removal, particularly when it comes to dam removal. (Britain has about 2,800 dams.)

The European Union has decided that by 2030 it wants 25,000 kilometres of rivers in Europe to be free-flowing, says Garcia de Leaniz. He headed the EU-funded Amber (Adaptive Management of Barriers in European Rivers) project, which found that there are more than 1m barriers fragmenting rivers in Europe and the UK. “Europe is making great headway; the UK, not so much,” he says.

A significant reason for this is that the UK, particularly England, is much more densely populated. “It is much easier to restore rivers when few people live around,” says Garcia de Leaniz. He also has a pragmatic approach to barrier removal. “We have so many obstacles to choose from; let’s start with those that are obsolete and those that pose a flood risk or hazard,” he says. “And in the bigger scheme of things, some people would argue that for the cost of removing one big dam, you can remove 100 or more barriers, which is going to be much more beneficial.”

In England, the Environment Agency tends to work on a more ad hoc basis, says Karageorgopoulos. While it has a list of priority barriers to remove – such as those that are costing money to maintain and which serve no function – it has to move when opportunities present themselves. Although the Environment Agency owns or maintains the vast majority of these barriers, many of them are on private land or affect private land.

A major challenge, says Kemp, is land and river ownership. “You can’t just go and do a strategy on a river because you’ve got multiple owners of that land and you have to work with them collegiately, and try to find a solution,” he says.

Often, the Environment Agency “will be able to do things when they find a landowner who is receptive to the idea, so it is very opportunistic,” says Kemp.

Even if the owner is on board, the process still takes time. Many years of planning and stakeholder consultation are required, says Karageorgopoulos. “Money is the obvious [obstacle],” to barrier removals, but communities and anglers are often vocal opponents. “We are human – we like routine. We’ve even had opposition from people who like to feed the swans and ducks in a specific location,” says Karageorgopoulos. But when there are no land restrictions and “everyone is onboard, it is the easiest way” to improve river health.

It will not “fix” England’s rivers, though, warns Cloke. “Naturalising rivers is always a good idea because natural flows are what rivers are designed to do,” she says. “In the long term, it’s probably helpful and is one of the lowest hanging fruits.”

However, none of this will address the major threats to British rivers – namely huge quantities of pollution in the form of sewage and agricultural and industrial waste, and development. “Should we be building on floodplains? No. Should we be polluting our rivers? No. Those are the giant questions that need careful thinking from government,” she says.

Do you pay with crypto, dig the blockchain and drive a Tesla? You’re an early adopter, a future-chaser, right? So, naturally, you’ll vote jelly.

These animals are taking over the ocean. They are the great survivors of evolution – and of the Anthropocene. They are thriving in an era of warming oceans and algal blooms, and when humans have wiped out larger marine predators. Jellyfish can survive when human pollution reduces oxygen levels in the ocean. And so we will embrace their future, our grandchildren tucking into jellyfish and chips.

British seas are mostly too cold to be swarming with jellyfish species but the barrel jellyfish is Britain’s largest jelly, and most frequently found in south-western seas.

Its hefty, translucent, mushroom-shaped bell can grow to the size of a dustbin lid. A pretty dustbin lid, sometimes shaded in yellow, pink or blue. The bottom edge of the bell is fringed with violet, and this contains the jelly’s sense organs. Below are eight frilly, stocky arms, which look a little like elongated cauliflowers. These contain small, stinging tentacles, which deliver food to surrounding tiny mouths, hundreds of them. The stings are designed to disable zooplankton – tiny sea creatures – and so don’t harm us.

Watch this gentle giant swim, pulsing in the blue depths, mesmerising us with its sensuous curves and extraterrestrial strangeness.

If you’re a traditionalist and lover of history, the barrel jellyfish deserves your vote too. Jellyfish have floated through Earth’s oceans for more than 500m years, miraculous beings with bodies made up of 90% water and living without brain, heart or blood.

Sadly, we tend to encounter them washed up, dead, on our beaches in early summer months. These jellies have underestimated their own size, following their tiny prey into shallow water and become stranded, washed in, washed up by the waves and tides.

In some parts of the world, people have eaten similar species from the Rhizostomae order for thousands of years. Its bland flesh is livened up with strong sesame oil and soy, and served in sushi, noodles and even ice-cream.

But this 35kg behemoth is the favourite food of the world’s largest sea turtle, the leatherback. It, of course, is struggling to survive in an ocean filled with plastic bags that can, fatally, resemble its favourite jellyfish prey.

So vote jelly. Vote for the great the survivor, food for the gods of the sea, and the real deal – definitely not a plastic bag.

• Welcome to the Guardian’s UK invertebrate of the year competition. Every day between 2 April and 12 April we’ll be profiling one of the incredible invertebrates that live in and around the UK. Let us know which invertebrates you think we should be including here. And at midnight on Friday 12 April, voting will open to decide which is our favourite invertebrate – for now – with the winner to be announced on Monday 15 April.

It sounds like a set-up for an ecological horror film – to save one species of owl, US wildlife officials want to shoot down half a million of its cousins.

The federal government’s latest proposal to save the endangered spotted owls has raised complicated questions about the ethics of killing one species to save another, and the role of humans to intervene in the cascading ecological conundrums that they have caused.

The spotted owl – an elusive icon of the American west – has lost most of its habitat in the old growth forests of the Pacific north-west and Canada due to logging and development. The species has also faced increasing competition from the barred owl – a slightly larger, more successful cousin which was lured west over the last century as settlers and homesteaders reshaped the North American landscape.

Now, to save the spotted owls, the US Fish and Wildlife Service has finalised a proposal to cull hundreds of thousands of barred owls across California, Washington and Oregon over the next 30 years.

The plan has pitted animal welfare and conservation groups against each other. The proposal was published in November, but it drew renewed attention last week after 82 animal welfare organisations based around the US signed a letter calling it “colossally reckless”. Researchers and wildlife officials who support the plan have said that if the barred owls are not culled, the northern spotted owl’s demise is ensured.

“This is a case that poses a genuine ethical dilemma,” said Michael Paul Nelson, a professor of environmental ethics and philosophy at Oregon State University. “You’re either going to kill a bunch of individual living beings, or you’re going to let a species disappear. No matter what, harm is done.”

An invasive species, or natural competition?

Spotted and barred owls look very similar to the untrained eye, and they can interbreed to birth offspring that are called “sparred owls”. But the barred owls are more adept survivors. They hunt a greater variety of prey, are slightly less discerning about where they nest, and tend to reproduce more quickly. And over the past few decades, biologists have noticed that the barred owls are edging the spotted owls out of their territory.

“Barred owl removal is not something the Service takes lightly,” said Jodie Delavan, a public affairs officer with USFWS in Oregon. “However, the Service has a legal and ethical responsibility to do all it can to recover northern spotted owl populations. Unless invasive barred owls are managed, the federally listed northern spotted owl will be extirpated in all or a significant portion of its range.”

The northern spotted owls were listed as threatened in 1990 after fierce campaigning by environmentalists who fought to protect the ancient forests where the birds nest from the logging. But the protections came too late – 70% of their habitat is already gone. The climate crisis and increasingly fierce megafires now threaten to destroy what little remains of their forest habitats.

The arrival of barred owls in the west appears to have hastened the spotted owl’s decline. It’s unclear why exactly the barred owls migrated westward, but researchers agree that it coincided with the arrival of European settlers in the east, and their reshaping of the owls’ native landscape. Previously, a scarcity of tree habitats in the Great Plains may have prevented the barred owls from venturing west until homesteaders planted trees for lumber, which provided new habitats. They also abandoned or outlawed Indigenous forest management practices, trapped beavers, over-hunted deer and elk, and drove away bison – all of which caused forests to overgrow.

That’s one of the reasons that the Fish and Wildlife Service, and biologists, consider the barred owls to be an invasive species – human intervention led to their arrival in the west. And that is why many believe it is humans’ responsibility to remove them.

“I grappled with it constantly. It’s not an easy thing,” said David Wiens, a wildlife biologist with the US Geological Survey who has spent his career studying interactions between spotted owls and barred owls. Several years ago, he and fellow researchers ran an experiment that involved shooting more than 2,400 barred owls across the north-west – and found that over five years, culling the barred owls helped spotted owl populations stabilise.

Even as the researchers culled barred owls, however, more of them moved in. In order to truly control their populations in the west, hunters would have to keep shooting them over a long period of time. “It’s a very tough decision,” he said. “Do you use lethal removal techniques? Or do you do nothing – just throw up your hands and let the cards fall where they will?”

Many conservationists have – squeamishly – agreed that the barred owls should be culled. But animal rights activists, some wildlife groups and the editorial board of the Los Angeles Times remains sceptical.

“The United States is targeting a native species not ever hunted for simply engaging in normal range expansions,” said Wayne Pacelle, president of the Center for a Human Economy and its lobbying arm, Animal Wellness Action, who co-authored the letter opposing the culling proposal. “If the US Fish and Wildlife Service is now going to start to manage social conflicts between animals, where does this end?”

Pacelle disputes the idea that the barred owl is invasive – as it is, after all, native to North America. And killing hundreds of thousands of them, over three decades, in an area where they are guaranteed to keep returning is “unworkable and inhumane”, he said.

The trouble is, he added, “we don’t have an easy fix for the spotted owl.”

Fraught questions for the Anthropocene

For Lisa Sideris, a professor of environmental studies at the University of California, Santa Barbara, who specialises in environmental ethics and the intersections of science and religion, the case of the two owls inspires introspection about the follies of anthropocentrism. “Some would argue that humans have altered ecosystems and the whole planet to such an extent that it becomes very hard to discern what it would mean to restore something back to natural conditions and whether that’s even possible.”

This isn’t the first time the coy spotted owls have pushed people to grapple with fraught philosophical ideas. “The spotted owl has been the poster animal for environmental conflicts for decades,” said Sideris.

The species found itself at the centre of what became known as the Timber Wars in the 1980s and 1990s. Loggers and environmentalists seeking to save old growth forests in California and the Pacific north-west clashed – in the courtroom and in the woods. In Oakland, California, Judi Bari and Darryl Cherney – two anti-logging activists campaigning to save the spotted owl – were critically injured by a pipe bomb that exploded under their car. In 1990, amid escalating conflict, the spotted owl was listed as threatened under the Endangered Species Act – and made the cover of Time magazine.

Still, tensions between timber industry leaders – who said that efforts to save the owl would cost tens of thousands of jobs – and environmentalists continued to build. In 2021, the Trump administration drastically slashed protections for the spotted owl. Joe Biden reversed the decision, but conceded 200,000 acres in owl habitat as part of the settlement of a timber industry lawsuit.

The spotted owl and the barred owl remain caught in the political crossfire. And all the while, wildlife officials and biologists are left with fraught questions about how best to save the species under strained circumstances.

Getting rid of the barred owls is ultimately a “triage” – a way to give the spotted owl some more time, and a fighting chance at survival, said Tom Wheeler, executive director of the conservation group Epic. “Does this just mean that there will always have to be somebody with a shotgun in our forest killing owls?” said Wheeler. “I think that we have to – as supporters of this – somewhat acknowledge that that is a possibility. And we have to be OK with that.”

Preventing extinction has become a sisyphean task, said Nelson, and despite government, scientists and conservationists’ best efforts, it remains impossible to predict or control exactly how nature will react.

“There is a hubris that underlies this idea that we’re just going to engineer our way out of these situations,” he said. “Because that is the same attitude that created these problems in the first place.”

On 18 March, 2022, scientists at the Concordia research station on the east Antarctic plateau documented a remarkable event. They recorded the largest jump in temperature ever measured at a meteorological centre on Earth. According to their instruments, the region that day experienced a rise of 38.5C above its seasonal average: a world record.

This startling leap – in the coldest place on the planet – left polar researchers struggling for words to describe it. “It is simply mind-boggling,” said Prof Michael Meredith, science leader at the British Antarctic Survey. “In sub-zero temperatures such a massive leap is tolerable but if we had a 40C rise in the UK now that would take temperatures for a spring day to over 50C – and that would be deadly for the population.”

This amazement was shared by glaciologist Prof Martin Siegert, of the University of Exeter. “No one in our community thought that anything like this could ever happen. It is extraordinary and a real concern,” he told the Observer. “We are now having to wrestle with something that is completely unprecedented.”

Poleward winds, which previously made few inroads into the atmosphere above Antarctica, are now carrying more and more warm, moist air from lower latitudes – including Australia – deep into the continent, say scientists, and these have been blamed for the dramatic polar “heatwave” that hit Concordia. Exactly why these currents are now able to plunge so deep into the continent’s air space is not yet clear, however.

Nor has this huge temperature hike turned out to be an isolated event, scientists have discovered. For the past two years they have been inundated with rising numbers of reports of disturbing meteorological anomalies on the continent. Glaciers bordering the west Antarctic ice-sheet are losing mass to the ocean at an increasing rate, while levels of sea ice, which float on the oceans around the continent, have plunged dramatically, having remained stable for more than a century.

These events have raised fears that the Antarctic, once thought to be too cold to experience the early impacts of global warming, is now succumbing dramatically and rapidly to the swelling levels of greenhouse gases that humans continue to pump into the atmosphere.

These dangers were highlighted by a team of scientists, led by Will Hobbs of the University of Tasmania, in a paper that was published last week in the Journal of Climate. After examining recent changes in sea ice coverage in Antarctica, the group concluded there had been an “abrupt critical transition” in the continent’s climate that could have repercussions for both local Antarctic ecosystems and the global climate system.

“The extreme lows in Antarctic sea ice have led researchers to suggest that a regime shift is under way in the Southern Ocean, and we found multiple lines of evidence that support such a shift to a new sea ice state,” said Hobbs.

The dramatic nature of this transformation was emphasised by Meredith. “Antarctic sea ice coverage actually increased slightly in the late 20th and early 21st century. However, in the middle of the last decade it fell off a cliff. It is a harbinger of the new ground with the Antarctic climate system, and that could be very troubling for the region and for the rest of the planet.”

The continent is now catching up with the Arctic, where the impacts of global warming have, until now, been the most intense experienced across the planet, added Siegert. “The Arctic is currently warming at four times the rate experienced by the rest of the planet. But the Antarctic has started to catch up, so that it is already warming twice as quickly as the planet overall.”

A key reason for the Arctic and Antarctic to be taking disproportionate hits from global warming is because the Earth’s oceans – warmed by fossil-fuel burning – are losing their sea ice at their polar extremities. The dark waters that used to lie below the ice are being exposed and solar radiation is no longer reflected back into space. Instead, it is being absorbed by the sea, further heating the oceans there.

“Essentially, it is a vicious circle of warming oceans and melting of sea ice, though the root cause is humanity and its continuing burning of fossil fuels and its production of greenhouse gases,” said Meredith. “This whole business has to be laid at our door.”

As to the consequences of this meteorological metamorphosis, these could be devastating, researchers warn. If all the ice on Antarctica were to melt, this would raise sea levels around the globe by more than 60 metres. Islands and coastal zones where much of the world’s population now have homes would be inundated.

Such an apocalypse is unlikely to occur for some time, however. Antarctica’s ice sheet covers 14m square kilometres (about 5.4m square miles), roughly the area of the United States and Mexico combined, and contains about 30m cubic kilometres (7.2m cubic miles) of ice – about 60% of the world’s fresh water. This vast covering hides a mountain range that is nearly as high as the Alps, so it will take a very long time for that to melt completely, say scientists.

Nevertheless, there is now a real danger that some significant sea level rises will occur in the next few decades as the ice sheets and glaciers of west Antarctica continue to shrink. These are being eroded at their bases by warming ocean water and could disintegrate in a few decades. If they disappear entirely, that would raise sea levels by 5m – sufficient to cause damage to coastal populations around the world. How quickly that will happen is difficult to assess. The Intergovernmental Panel on Climate Change has said that sea levels are likely to rise between 0.3m to 1.1m by the end of the century. Many experts now fear this is a dangerous underestimate. In the past, climate change deniers accused scientists of exaggerating the threat of global warming. However, the evidence that is now emerging from Antarctica and other parts of the world makes it very clear that scientists did not exaggerate. Indeed, they very probably underrated by a considerable degree the threat that now faces humanity.

“The picture is further confused in Antarctica because, historically, we have had problems getting data,” added Meredith. “We have never had the information about weather and ecosystem, compared with the data we get from the rest of the world, because the continent is so remote and so hostile. Our records are comparatively short and that means that the climate models we have created, although very capable, are based on sparse data. They cannot capture all of the physics, chemistry and biology. They can make predictions that are coherent but they cannot capture the sort of extremes that we’re now beginning to observe.”

The woes facing Antarctica are not merely of human concern, however. “We are already seeing serious ecological impacts that threaten to spread through the food chain,” said Prof Kate Hendry, a chemical oceanographer based at the British Antarctic Survey.

A critical example is provided by the algae which grow under and around sea ice in west Antarctica. This is starting to disappear, with very serious implications, added Hendry. Algae is eaten by krill, the tiny marine crustaceans that are one of the most abundant animals on Earth and which provide food for predators that include fish, penguins, seals and whales. “If krill starts to disappear in the wake of algae, then all sorts of disruption to the food chain will occur,” said Hendry.

The threat posed by the disappearance of krill goes deeper, however. They play a key role in limiting global warming. Algae absorb carbon dioxide. Krill then eat them and excrete it, the faeces sinking to the seabed and staying there. Decreased levels of algae and krill would then mean less carbon from the atmosphere would be deposited on the ocean floor and would instead remain near the sea surface, where it would return to the atmosphere.

“They act like a conveyor belt that takes carbon out of the atmosphere and carries it down to the deep ocean floor where it can be locked away. So if we start messing with that system, there could be all sorts of other knock-on effects for our attempts to cope with the impact of global warming,” added Hendry. “It is a scary scenario. Nevertheless that, unfortunately, is what we are now facing.”

Another victim of the sudden, catastrophic warming that has gripped the continent is its most famous resident: the emperor penguin. Last year the species, which is found only in Antarctica, suffered a catastrophic breeding failure because the platforms of sea ice on which they are born started to break up long before the young penguins could grow waterproof feathers.

“We have never seen emperor penguins fail to breed, at this scale, in a single season,” said Peter Fretwell, of the British Antarctic Survey. “The loss of sea ice in this region during the Antarctic summer made it very unlikely that displaced chicks would survive.”

Researchers say that the discovery of the loss of emperor penguins suggests that more than 90% of colonies will be wiped out by the end of the century, if global warming trends continue at their current disastrous rate. “The chicks cannot live on sea ice until they have fledged,” said Meredith. “After that, they can look after themselves. But the sea ice is breaking up before they reach that stage and mass drowning events are now happening. Colonies of penguins are being wiped out. And that’s a tragedy. This is an iconic species, one that is emblematic of Antarctica and the new vulnerability of its ecosystems.”

The crisis facing the continent has widespread implications. More than 40 nations are signatories of the Antarctic Treaty’s environmental protocol, which is supposed to shield it from a host of different threats, with habitat degradation being one of the most important. The fact that the continent is now undergoing alarming shifts in its ice covering, eco-systems and climate is a clear sign that this protection is no longer being provided.

“The cause of this ecological and meteorological change lies outside the continent,” added Siegert. “It is being caused because the rest of the world is continuing to emit vast amounts carbon dioxide.

“Nevertheless, there is a good case for arguing that if countries are knowingly polluting the atmosphere with greenhouse gases, and Antarctica is being affected as a consequence, then the treaty protocol is being breached by its signatories and their behaviour could be challenged on legal and political grounds. It should certainly make for some challenging meetings at the UN in the coming years.”

Greta Thunberg was detained by police at a demonstration in The Hague, in the Netherlands.

The climate activist was put in a bus by local police along with other protesters who tried to block a major highway into the city on Saturday.

Thunberg had joined a protest by hundreds of activists and was detained when she joined a group of about 100 people who tried to block the A12 highway.

Before she was detained, Thunberg said: “We are in a planetary emergency and we are not going to stand by and let people lose their lives and livelihood and be forced to become climate refugees when we can do something.”

The road has been blocked for several hours dozens of times in recent months by activists demanding an end to all subsidies for the use of fossil fuels.

At previous protests, police drove detained protesters to another part of the city, where they were released without further consequences.

Thunberg was seen flashing a victory sign as she sat in the bus used by police to take detained demonstrators from the scene.

The Extinction Rebellion campaign group said before the demonstration that the activists would block a main highway into The Hague, but a heavy police presence, including officers on horseback, initially prevented the activists from getting on to the road.

A small group of people managed to sit down on another road and were detained after ignoring police orders to leave.

Extinction Rebellion activists have blocked the highway that runs past the temporary home of the Dutch parliament more than 30 times to protest against subsidies.

The demonstrators waved flags and chanted: “We are unstoppable, another world is possible.”

One held a banner reading: “This is a dead end street.”

In February, Thunberg, 21, was acquitted by a court in London of refusing to follow a police order to leave a protest blocking the entrance to an oil and gas industry conference last year.

Her activism has inspired a global youth movement demanding stronger efforts to fight the climate crisis since she began staging weekly protests outside the Swedish parliament in 2018.

She has repeatedly been fined in Sweden and the UK for civil disobedience in connection with protests.