On the east coast of Australia, in tropical North Queensland, lies the Daintree rainforest – a place where the density of trees forms an almost impenetrable mass of green.

Stepping into the forest can feel like stepping back in time. It contains many ancient plant families dating back to the ancient supercontinent of Gondwana. The air is warm and thick with humidity, carrying the earthy scent of wet leaves and soil. Sunlight filters through the dense canopy in scattered beams, while ferns and seedlings carpet the forest floor.

The Daintree and other tropical rainforests, including those in the Amazon, the Congo Basin and Southeast Asia, have been called the “lungs” of our Earth. They absorb carbon dioxide from the air while releasing water vapour and oxygen via photosynthesis – the process by which plants take in carbon dioxide and fix energy.

Because of this, their leafy canopies play a crucial role in regulating the global climate – and mitigating global warming.

But our recent research shows that rising temperatures will severely affect the ability of tropical forests to photosynthesise. This will hinder their capacity to absorb carbon dioxide from the atmosphere, reducing their role in mitigating global warming and exacerbating climate change.

Coping with a rapidly changing climate

The ability of plants to adjust to different environments (also known as acclimating) is an important strategy for them to cope with a changing world.

Plants can dynamically acclimate to their environment. When warmed, they can adjust their photosynthesis to perform more efficiently at moderately higher temperatures. This allows them to maintain or even increase their carbon uptake under these new conditions.

However, tropical trees may have a limited capacity to acclimate to warming, because they have evolved under relatively stable climatic conditions. As a result, they are already near the upper limit of temperatures they can tolerate without suffering damage.

Warming the leaves of tropical rainforest trees

To test this theory, we set up an experiment in the Daintree rainforest focusing on tropical trees between 15 and 30 metres tall.

Using a canopy crane to access the treetops, we installed custom-made leaf-heater boxes to warm leaves from four mature tree species by 4°C – a temperature rise predicted for tropical systems by 2100.

Boxes were made from plastic takeaway containers with fishing wire to hold the leaf in place and a heating wire to heat the leaves. Leaf temperatures were measured throughout the experiment and a feedback control algorithm was used to maintain consistent heating.

The experiment lasted eight months, making it one of the longest running in-situ leaf warming experiments in a mature tropical forest.

By comparing the physiological responses of warmed leaves to the responses of non-warmed leaves, we were able to capture a realistic picture of how tropical tree leaves might respond to future climate warming.

Warming reduces photosynthesis across all species

Our study found warming reduced photosynthesis across all species.

Photosynthetic rates dropped by an average of 35% in warmed leaves compared to non-warmed controls. This decline was driven by two key factors.

First, the leaf pores, called stomata, which allow carbon dioxide to enter and water to escape, became less open in response to the drier air around the warmed leaves.

Second, the warmer temperatures interfered with the enzymes essential for photosynthesis, reducing their ability to fix carbon.

Even after eight months of warming, the trees showed little ability to adjust to the higher temperatures. They did not improve their capacity to photosynthesise effectively at the elevated temperatures, nor did they shift the maximum temperature at which photosynthesis could be maintained.

This supports the idea that these trees may already be operating close to their thermal limits.

Significant implications for the global water cycle

Our findings of reduced carbon uptake and decreased water loss due to stomatal closure under warmer temperatures align with the concept of a “weakened pulse” of water exchange in tropical systems.

This has significant implications for the global water cycle.

While stomatal closure can limit water released to the atmosphere, a drier atmosphere simultaneously extracts more moisture from trees, creating a complex dynamic.

The response of tropical forests to warming will undoubtedly affect the water cycle, but the overall impact remains uncertain.

Little room to adapt

Other studies have also pointed to detrimental effects of climate change on tropical ecosystems, including a warmer and drier atmosphere.

Lowland tropical environments are already near the physiological limits for photosynthesis. This leaves little room for trees to adapt to rising temperatures and drier conditions.

Combined with predictions of warming and drying from climate models, these studies point to less resilient tropical forests under climate change, weakening their role as the lungs of the Earth.

Protecting rainforest biodiversity offers hope

However, the biodiversity of tropical rainforests offers some hope, as not all species are equally vulnerable.

Recent research shows fast-growing species are less affected by warming compared to slow-growing ones. While this is promising, it’s important to remember that species that live longer play the most significant role in long-term carbon storage.

These findings highlight the urgency of protecting tropical forests and limiting the magnitude of global warming by carbon dioxide emissions.

Conservation strategies should focus on maintaining biodiversity to enhance resilience, and identifying species that have a greater potential to acclimate in a warming world.

Kristine Crous, Senior Lecturer, School of Science and Hawkesbury Institute for the Environment, Western Sydney University and Kali Middleby, Plant Ecophysiologist, James Cook University

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

Every year, tens of thousands of land birds make a long flight across Bass Strait – the stretch of water separating Tasmania from continental Australia.

Well known for its high winds and rough seas, crossing Bass Strait is no small feat for these migrant land birds. Migration is stressful for birds, as they encounter inhospitable environments, predators, and weather changes while expending peak energy.

But how exactly do these birds traverse this daunting stretch of ocean?

Understanding this is more crucial than ever. New developments proposed in Bass Strait, particularly offshore wind farms, may introduce challenges for migrating birds. And until now, no one has looked closely at the movement pathways of these little migrants.

Our new research tracked the migration paths of Tasmanian boobooks, Ninox leucopsis, as they crossed from Victoria to Tasmania.

We found the Tasmanian boobook was indeed a regular migrant across Bass Strait – making it Australia’s only migratory owl. Rather than island-hopping, these small owls completed the roughly 250 kilometre flight across the strait in a single night, in one continuous flight.

These insights may help us protect birds in a rapidly changing world.

Tagging and tracking the Tasmanian boobook

As their name suggests, Tasmanian boobooks are common across Tasmania and were once considered endemic to the island. Over time, they were occasionally spotted in mainland Australia, with scattered records in Victoria and elsewhere.

In recent years, a more consistent pattern was revealed when keen birdwatchers discovered small numbers of these owls perched on Cape Liptrap, southeast of Melbourne, in spring. Could these birds actually be migrants about to make the Bass Strait crossing after winter on the mainland?

With thermal cameras, special nets, and lightweight miniature GPS-tracking devices in hand, we travelled to the southeast Victorian coast to catch five Tasmanian boobooks at these headlands.

Once we attached the tracking devices, we could follow their movements for up to three weeks before the tags failed and were dislodged.

Facinating findings

We found the Tasmanian boobook is Australia’s only migratory owl. In fact, it is what’s known as a “partial migrant”. This means while some birds of the species migrate, many other individuals remain in Tasmania year-round.

Three of our tagged birds departed southeast Victoria in October and November. They began their nonstop journeys at dusk and arrived in northern Tasmania early the following morning.

Two continued moving further inland to central Tasmania over subsequent nights and eventually settled at elevations of around 750 metres.

These observations suggest the migrating Tasmanian boobooks may be fleeing harsh winter conditions at high elevation areas. This phenomenon, known as altitudinal migration, has been observed in other Tasmanian birds such as the flame robin and crescent honeyeater.

We also discovered unexpected variety in the Tasmanian boobook migration patterns. Some birds left from Cape Liptrap and others from Wilsons Promontory, at the southern tip of Victoria.

They also flew at varying speeds under a surprising range of weather conditions, including headwinds upon departure. This is in an impressive feat for an owl, which weighs just 210–240 grams and probably undertakes the crossing by continuously flapping its wings.

New clues and questions about other Bass Strait migrants

Bird migration in the southern hemisphere is little-studied compared with northern hemisphere migration.

In Australia, movement patterns are particularly complex and variable due to the vast scale of the continental landmass, the variable geography such as mountains, deserts, and islands, and unpredictable climate.

At least 24 species migrate across Bass Strait. They range from songbirds and raptors to the critically endangered orange-bellied parrot and swift parrot.

Much of what we know comes from limited land-based observations. The Tasmanian boobooks we tracked give us just a small insight into the many migratory journeys across Bass Strait.

However, the variation we observed in just three migratory tracks for a single species raises questions about other Bass Strait migrants.

Are islands less crucial as stopover points than previously thought? Even for species like the orange-bellied parrot, which does use islands, it remains plausible many individuals might cross Bass Strait in a single non-stop flight.

These unanswered questions about bird movement across Bass Strait is not just a matter of curiosity.

Hazards old and new

Migratory birds are exposed to a greater range of threats than non-migratory birds. Crossing Bass Strait means risking inclement weather, artificial lighting, and collision with boats or oil rigs. Now, new developments may also present novel challenges.

Australia is rapidly expanding its renewable energy sector, including offshore wind.

Several areas in Bass Strait have been declared by the federal government as priority areas for wind farm development and many projects are already being planned.

These developments are essential for reducing emissions and combating climate change. But how do we balance the necessary transition to clean energy, while minimising direct harm to biodiversity?

Offshore wind farms can displace birds from their routes, or worse, introduce collision risks.

Environmental assessments are a mandatory part of wind farm development in Australia, but they need to be informed by robust ecological data.

Understanding the basic ecology of land-bird migration is crucial. We need to know where the threats to migratory birds are highest, which species are at risk of collisions, and how to mitigate these threats as the transition to renewable energy continues.

Jessica Wei Zhou, Researcher in Ecology, Monash University and Rohan Clarke, Associate Professor, School of Biological Sciences, Monash University

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

Australians are no strangers to housing crises. Some will even remember the crisis that followed the second world war. As well as producing the popular mid-century modern style of architecture, these post-war decades were a time of struggle.

As the population grew quickly after the war, Australia faced an estimated shortage of 300,000 dwellings. Government intervention was needed. A 1944 report by the Commonwealth Housing Commission stated that “a dwelling of good standard and equipment is not only the need but the right of every citizen”.

A key recommendation was that the Australian government should encourage the building of more climate-responsive and healthy homes.

So, what happened? Why are so many homes today still not well-designed for the local climate?

Building small and for a sunny climate

The postwar period was a time of shortages and rationing. As well as meat, sugar, clothing and fuel, building materials were in short supply.

Government restrictions limited house sizes in general to around 110 square metres. That’s less than half the average size of new houses today. Building activity and the prices of materials were also regulated.

While people waited for building permits, many had to arrange temporary housing. Some lived in sleepouts or rented spare rooms from strangers. Others camped in tents or lived in caravans or temporary buildings erected on land bought before the war.

Looking at the published advice on housing design in the 1940s and 1950s, it’s clear passive solar design, small home sizes and climate-responsive architecture were topics of interest. A passive solar design works with the local climate to maintain a comfortable temperature in the home.

This preference was not driven by concerns about climate change or carbon footprints. Rather, the Commonwealth Housing Commission called for solar planning “for health and comfort”.

The commission’s executive officer, architect Walter Bunning, demonstrated how to go about this in his book Homes in the Sun. He translated government recommendations into a format appealing to home builders.

This was a time before most home owners could afford air conditioning. It was advised that homes be sited to capture prevailing breezes, have insulated walls and roofs, use window shading and overhanging eaves, and plantings of shade trees and deciduous creepers. External spaces, such as patios, and north-facing living spaces oriented to the sun, were also promoted.

Among the designs were plans for the “Sun Trap House”. This design applied passive solar design principles to a modest freestanding home.

‘New approach’ didn’t eventuate

Eventually, the housing crisis eased. However, this was not a result of Bunning’s hoped for “new approach to house planning”. Most of the new housing was traditionally designed and built suburban homes.

These came in the form of stock plans by builders and construction companies, with owner builders making up 40% of the homes constructed in 1953-54. Sponsored housing provision programs, including the War Service Homes Scheme and Soldier Settlement Scheme, were rolled out across the country.

At a state level, arms of government such as the South Australian Housing Trust and the Victorian Housing Commission provided not only houses for the rental market but also for purchase. These houses included imported prefabricated dwellings.

As a result, many homes built in the postwar housing crisis suffer from much the same problems as their predecessors. It led to a situation today where 70% of Australian houses have an energy rating of three stars or lower. That’s well short of the current seven-star standard for new homes.

It wasn’t for lack of architectural advice

In a time of shortage, most people were happy to have a roof over their heads no matter what the design. To architects, this seemed a wasted opportunity.

As a result, the Royal Australian Institute of Architects promoted architect-designed plans that people could buy for a nominal fee. In South Australia, these were available through the Small Homes Service.

House advice and plans for sale were featured in newspapers and magazines such as the Australian Home Beautiful. The institute also published brochures that promoted the idea that “better design considers climate and environment” and followed recommendations by the Commonwealth Experimental Building Station for maximum comfort.

Passive solar solutions are timeless

The energy-hungry mechanical heating and cooling of today’s houses often neglects passive solar and simple solutions such as insulation, eaves, window awnings, curtains and draught stoppers. These were common solutions in the post-war period.

The principles of passive solar design haven’t changed since then. The ideas advocated both in 1945 and today in design advice such as the Australian government’s Your Home guide to environmentally sustainable homes remain the same.

While our world today faces many crises affecting health, climate resilience, housing affordability and inequality, we have a chance to shape the solutions.

The federal government is developing a National Housing and Homeless Plan and has committed A$10 billion to its housing fund. The target is to build 1.2 million homes over the next five years. What better opportunity to learn from the past and build a brighter, more sustainable future?

Julie Collins, Research Fellow and Curator, Architecture Museum, University of South Australia and Lyrian Daniel, Associate Professor in Architecture, University of South Australia

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

Debate erupted this week over the growing number of beach tents, or “cabanas”, proliferating on Australian beaches. The controversy, which began on social media, was fuelled by Prime Minister Anthony Albanese who declared it was “not on” for beachgoers to reserve a spot on the sand by erecting a cabana then leaving it vacant for hours.

Albanese told Nine’s Today show “everyone owns the beach” and staking a claim on the sand was “a breach of that principle, really”.

Other critics deem beach cabanas an eyesore. And lifeguards say the structures can obscure their view of the water, which poses a safety risk.

Beach cabanas do, however, serve a valid purpose. They provide some protection against the sun’s harmful ultraviolet rays and, from a recreational perspective, can enable people to spend longer at the beach on hot days than they might have otherwise.

I’m a member of the University of NSW Beach Safety Research Group, and I’ve worked with local councils and national parks to address health and safety issues on beaches. So let’s look at how to strike the right balance between personal convenience and public safety when using a cabana.

A fair go for all?

In years past, Aussies came to the beach with a towel and maybe a book, stayed a little while then left.

But more recently, the use of beach tents and cabanas has grown. It’s likely the result of Australia’s growing coastal population, and a rising awareness of the dangers posed by sun exposure.

These days, it’s not uncommon to visit a popular beach in summer and find a village of cabanas stretching as far as the eye can see.

It’s great to see so many people using the beach. Beaches and oceans are health-giving places, though they come with inherent dangers.

And of course, in Australia the beach is free for all who wish to use it. It’s an approach in line with our supposedly egalitarian culture, in which everyone gets a “fair go”. Here, beaches are a place to be shared, no matter what your income or social status.

The approach contrasts to many destinations in Europe, the United States and elsewhere, where large sections of beaches are reserved for private use. At Waikiki beach in Honolulu, for example, people pay US$100 or more to hire an umbrella and chairs, and a place on the sand for the day.

To some naysayers, cabana use in Australia challenges the notion that the beach is for everyone. They question whether people should be allowed to mark out beach territory no-one else can use. That’s why in 2020, a bid by a private company to introduce paid cabanas on Sydney’s Bondi Beach prompted a public outcry.

Cabanas bring practical challenges, too. They represent an unplanned influx of temporary infrastructure into busy public spaces. Left unchecked, they could cause pedestrian congestion and become a flashpoint for disagreement between beachgoers.

The current debate may prompt Australian beach authorities to consider bringing in cabana regulation, similar to what’s in place for some beaches in the US.

In the meantime, here are five tips for safe and fair use of beach cabanas:

1. Placement: Erect your cabana at the back of the beach and away from lifeguard towers or lifesaver tents to avoid obstructing lifeguards’ views. Clear sightlines to the water are essential for ensuring timely emergency responses. This positioning also leaves space closer to the water for other beachgoers, including children playing at the water’s edge.

2. Tying down: Secure your cabana firmly in the sand to prevent it from being blown away by strong winds. Flying cabanas are a danger to other beach users, potentially causing injuries and damage to property.

3. Spacing: Avoid overcrowding by maintaining two to three meters between structures. This ensures free movement and accessibility for all beachgoers, and ensures families and groups can enjoy the beach without feeling cramped. Also, stay within the boundaries of your cabana and don’t claim territory outside its boundaries.

4. Emergency access: Keep pathways and access points clear at all times. This is crucial for lifeguard vehicles, ambulances and surf rescue teams. Unobstructed access can make the difference between life and death in an emergency.

5. Common sense: As with using any shared space, consider the needs of others and apply common sense. How would you feel if someone set up a structure right in front of you, blocking your view of the waves or ruining your vibe? Or if you or a loved one needed medical attention on a beach, would you want an ambulance crew obstructed by an unbroken line of tents?

Looking ahead

In the past, some have called for a ban on beach cabanas. But the structures appear here to stay – and that’s not a bad thing. Skin cancer affects more young Australians than any other cancer, and the Cancer Council applauds the use of cabanas.

It’s important to note, however, that cabanas do not provide complete protection from UV rays. If you’re at the beach all day, you might still get too much sun even under a tent.

When it comes to your next visit to the coast, by all means pack your cabana. But make sure you use it carefully and responsibly, so everyone’s day at the beach is safe and enjoyable.

Samuel Cornell, PhD Candidate, UNSW Beach Safety Research Group + School of Population Health, UNSW Sydney

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

When I (Nathan Brooks English) was six years old, I snuck a starfish home from the beach and hid it in my closet. I regret that now, as my parents did then when the smell of rotting starfish overwhelmed the house. I regret it also because that starfish had a place and a purpose – and dying in a hot, dark closet next to my Hot Wheels was not it.

Likewise, the beautiful shells and natural flotsam that decorate Australian beaches have a place and a purpose. For many of us, summer at the beach is a cherished memory and collecting seashells is probably a part of that memory.

On most beaches in Australia, collecting shells without living creatures in them is legal, but let me convince you there are better options that ensure future Sallies will still find seashells by the seashore.

Someone needs that shell more than you

For native wildlife, both occupied and unoccupied shells provide important shelter and sources of calcium and grit.

Taking that beautiful snail shell could increase the cost of housing for a hermit crab or the small shrimp that needs it next. The beautiful conch shell that calls to you is actually an octopus caravan.

For these reasons, never pick up shells in the water or in tidal pools; chances are they are being used or will be shortly.

Likewise, collecting shells in marine parks is strictly prohibited.

Shells have spiritual and cultural importance

For the island Woppaburra People of central Queensland, beaches and shells have spiritual and cultural importance as part of Dreaming stories, dance and ceremonies.

In addition to their place and purpose in my (Robert Muir) stories and culture, shells can also provide valuable insight and context to our history on the island.

Middens (deep piles of shells left on the beach after being used to produce food or tools) provide archaeological evidence that the islands have been occupied for at least the past 5,000 years.

Back then, Woppa (also known as Great Keppel Island, in Queensland) and its beaches could sustainably support the 100 to 200 people who lived on the island for more than five millenia.

Today, Woppa hosts tens of thousands of visitors a year on three small beaches. And while people are welcome to pick up, examine and play with the shells, to preserve their place and purpose they must be left on the shore where they were found.

If everyone took a shell…

Increasing pressure on beaches and their natural resources isn’t just felt on Woppa.

The global population now exceeds 8 billion people and our collective (pun intended) impact on beaches is magnified. That’s twice as many people as when I (Nathan Brooks English) was a child in the late 1970s.

For example, in 2019 Bondi Beach had more than 2.1 million visitors (not that anyone is looking at shells). If everyone took a shell, there’d be hardly any left.

Even smaller beaches need time to accumulate shells and a summer rush of collectors can quickly deplete beaches of shells until the next cyclone or winter storm washes more up.

What to do instead of collecting shells

So how do we balance wanting a tangible reminder of the beach in our own yards or homes (the destination of many shells) versus not damaging the natural beauty and function of beach ecosystems?

Instead of taking a shell, take a picture instead. You can photograph unoccupied shells in place along the beach where the tide has collected, or arrange them together for a photographic collage.

Include them in your sandcastles as gates, windows, or little people to populate the castle.

For your artsy children (or adults), use crayons or coloured pencils and a small sketch pad to draw the shells.

Taking a few shells at a time to your umbrella to sketch them and then returning them to the tide line will sate the urge to collect and leave the beach unchanged.

You may even find you have a gifted scientific illustrator on your hands.

When you’re done with the shells, leave them by the shore. Wind, tides and time (or tomorrow’s small visitor) will sweep them back into natural circulation, continuing their storied lives as creature homes or fine grit for our beautiful Australian beaches, their purpose and place preserved.

If you absolutely must pick something up and take it home, please pick up some of the vast amount of plastic found on Australian beaches.

Nathan Brooks English, Associate professor; Flora, Fauna & Freshwater Research Cluster Lead, CQUniversity Australia and Robert Muir, Project Officer at the Woppaburra TUMRA Aboriginal Corporation, Indigenous Knowledge

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

The size of the Antarctic ice sheet can be hard to comprehend. Two kilometres thick on average and covering nearly twice the area of Australia, the ice sheet holds enough freshwater to raise global sea levels by 58 metres.

Ice loss from this sheet is projected to be the leading driver of sea level rise by 2100, yet its contribution remains highly uncertain. While sea levels are certain to rise this century, projections of the contribution from Antarctic ice vary from a 44 cm rise to a 22 cm fall.

Much of this uncertainty is because the ocean processes that control the fate of the sheet occur on an incredibly small scale and are very difficult to measure and model.

But recently scientists have made significant progress in understanding this “ice-ocean boundary layer”. This progress is the subject of our new review paper, published today in Annual Reviews.

Shrinking, thinning and retreating

At the margins of the Antarctic ice sheet, glaciers flow into the Southern Ocean, forming floating ice shelves. These ice shelves act as keystones, stabilising the ice sheet. They’re also shrinking.

The ocean melts ice shelves from below – a process known as “basal melting”. Increased basal melting has led to the thinning and retreat of the ice sheet in some regions, raising global sea levels.

It has also slowed the deepest current in the global overturning circulation, a system of ocean currents that circulates water around the globe.

Like the glaciers that feed them, ice shelves are immense. Yet the ocean processes that control basal melting, and the fate of the entire Antarctic ice sheet, occur on the scale of millimetres. They happen in a thin layer of ocean, just beneath the ice.

The boundary layer between the ice shelf and the ocean is cold, miles from anywhere, and beneath very thick ice, so it’s no wonder it has hardly been measured at all.

Studying this layer with other techniques such as computer simulations is also a huge challenge. Until recently, the tiny motions within the ice-ocean boundary layer put accurate modelling of ice melt out of reach.

These twin challenges have long stymied efforts to answer the deceptively simple question: “How does the ocean melt Antarctic ice shelves?”

Modelling the micro-scale

Computer simulations of ocean processes aren’t new.

But only recently have simulations of the ice-ocean boundary layer become feasible, as computing resources grow and the cost of using them shrinks.

Several research groups around the world have taken on this problem, modelling the micro-scale ocean flow that supplies heat to the ice for melting.

Researchers are looking for a relationship between what the ocean is doing, and how quickly the ice melts. So far, they’ve uncovered not just one relationship but several, each indicating a different melt “regime”. Ocean conditions (temperature, salt content and the speed of ocean currents) and the shape of the ice determine which melting regime applies.

Ice sheet shape is key because meltwater is fresh and lighter than the surrounding ocean. Like hot air collecting at the top of a room, fresh, cold meltwater collects in hollows in the lower surface of the ice sheet, insulating the ice from the ocean water below and slowing melting.

For steeply sloping ice, the insulating effect is much less. The energetic flow of meltwater as it rises under steep ice leads to mixing with the warmer ocean waters. This increases melting.

Fast ocean currents have a similar effect, as they transfer heat to the ice.

Sonar-fitted robots

Recently, ocean robots, including autonomous underwater vehicles and tethered probes deployed by drilling through the ice, have provided unprecedented amounts of data on the environment beneath ice shelves.

Using sonar and cameras, these robots have revealed a weird and wonderful “icescape” on the underside of ice shelves.

This icescape is made of many different ice features, ranging from centimetres to kilometres in size. Some, like steep-sided crevasses, are formed by ice fracturing. Others, like dimpled depressions in the ice (often called “scallops”), stair-like “terraces”, mussel-shaped “scoops”, and larger basal channels, are thought to be formed by melt processes.

Our new knowledge of melting from computer simulations and robots sheds light on these features and how they form. The existence of melt regimes helps explain the evolution of steep-sided terraces, or why different features appear in distinct parts of an ice shelf.

For instance, in the warm, calm eastern part of the Dotson ice shelf in west Antarctica, an autonomous robot observed basal terraces. In the west of Dotson – which experiences cold, fast currents – large mussel-shaped scoops were discovered.

Uncertainties remain

Exactly how some of these features form is still unknown.

New simulations that allow the ice-water boundary to move in time show the “self-sculpting” behaviour of ice melt. This is similar to how dunes form and move in a desert.

However, new computer models are needed to simulate the formation and evolution of the whole icescape.

Some of the recent advances highlighted here are helping to reduce the uncertainty in our understanding of the contribution of the Antarctic ice sheet to global sea level rise.

However, incorporating our new understanding of basal melt, and the dynamic icescape it forms, into climate and ice sheet models still presents a huge challenge.

Overcoming this challenge is urgent. Accurate representation of melt in climate and ice sheet models will reduce the deep uncertainty in sea level rise projections, especially as ocean conditions – and ice shelf melt regimes – shift into the future.

Madelaine Gamble Rosevear, Postdoctoral Fellow in Physical Oceanography, University of Tasmania; Ben Galton-Fenzi, Principal Scientist; Bishakhdatta Gayen, ARC Future Fellow & Associate Professor, Mechanical Engineering, The University of Melbourne, and Catherine Vreugdenhil, ARC DECRA Research Fellow in Fluid Dynamics, The University of Melbourne

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

The Arctic can feel like a far-off place, disconnected from daily life if you aren’t one of the 4 million people who live there. Yet, the changes underway in the Arctic as temperatures rise can profoundly affect lives around the world.

Coastal flooding is worsening in many communities as Arctic glaciers and the Greenland Ice Sheet send meltwater into the oceans. Heat-trapping gases released by Arctic wildfires and thawing tundra mix quickly in the air, adding to human-produced emissions that are warming the globe. Unusual and extreme weather events, pressure on food supplies and intensifying threats from wildfire and related smoke can all be influenced by changes in the Arctic.

In the 2024 Arctic Report Card, released Dec. 10, we brought together 97 scientists from 11 countries, with expertise ranging from wildlife to wildfire and sea ice to snow, to report on the state of the Arctic environment.

They describe the rapid changes they’re witnessing across the Arctic, and the consequences for people and wildlife that touch every region of the globe.

Pace of change in the Arctic accelerates

The Arctic of today looks stunningly different from the Arctic of even one to two decades ago. Over the Arctic Report Card’s 19 years, we and the many contributing authors to the report have watched the pace of environmental change accelerate and the challenges become more complex.

For the past 15 years, the Arctic snow season has been one to two weeks shorter than it was historically, shifting the timing and character of the seasons.

Shorter snow seasons can challenge plants and animals that depend on regular seasonal changes. Longer snow-free seasons can also reduce water resources from snowmelt earlier in spring or summer and increase the possibility of drought.

The extent of sea ice, an important habitat for many animals, has declined in ways that make today’s mostly thin and seasonal sea ice landscape unrecognizable compared with the thicker and more extensive sea ice of decades past.

With a shorter sea ice season, the dark ocean surface is exposed and can absorb and store more heat during summer, which then adds to air and ocean temperature increases. This aligns with observations of long-term warming for Arctic surface ocean waters. Sea ice-dependent animals can also be forced ashore or into longer fasting seasons. The Arctic shipping season is also lengthening, with rapidly increasing shipping traffic each summer.

Overall, 2024 brought the second-warmest temperatures to the Arctic since measurements began in 1900, and the wettest summer on record.

Arctic tundra becomes a carbon source

For thousands of years, the Arctic tundra landscape of shrubs and permafrost, or frozen ground, has acted as a carbon dioxide sink, meaning that the landscape was taking up and storing this gas that would otherwise trap heat in the atmosphere.

But permafrost across the Arctic has been warming and thawing. Once thawed, microbes in the permafrost can decompose long-stored carbon, breaking it down into carbon dioxide and methane. These heat-trapping gases are then released to the atmosphere, causing more global warming.

Wildfires have also increased in size and intensity, releasing more carbon dioxide into the atmosphere, and the wildfire season has grown longer.

These changes have pushed the tundra ecosystem over an edge. Susan Natali and colleagues found that the Arctic tundra region is now a source – not a sink, or storage location – for carbon dioxide. It was already a methane source because of thawing permafrost.

The Arctic landscape’s natural ability to help to buffer human heat-trapping gasses is ending, adding to the urgency to reduce human emissions.

Stark regional differences make planning difficult

The Arctic Report Card covers October through September each year, and 2024 was the second-warmest year on record for the Arctic. Yet, the experience for people living in the Arctic can feel like regional or seasonal weather whiplash.

Stark regional differences in weather can make planning difficult and challenge familiar seasonal patterns. These include very different conditions in neighboring areas or big changes from one season to another.

For example, some areas across North America and Eurasia experienced more winter snow than usual during the past year. Yet, the Canadian Arctic experienced the shortest snow season in the 26-year record. Early loss of winter snow can strain water resources and may exacerbate dry conditions that can add to fire danger.

Summer across the Arctic was the third warmest ever observed, and areas of Alaska and Canada experienced record daily temperatures during August heat waves. Yet, residents of Greenland’s west coast experienced an unusually cool spring and summer. Though the Greenland Ice Sheet continued its 27-year record of ice loss, the loss was less than in many recent years.

Ice seals, caribou and people feeling the change

Rapid Arctic warming also affects wildlife in different ways.

As Lori Quakenbush and colleagues explain in this year’s report, Alaska ice seal populations, including ringed, bearded, spotted and ribbon seals, are currently healthy despite sea ice decline and warming ocean waters in their Bering, Chukchi and Beaufort sea habitats.

However, ringed seals are eating more saffron cod rather than the more nutritious Arctic cod. Arctic cod are very sensitive to water temperature. As waters warm, they shift their range northward, becoming less abundant on the continental shelves where the seals feed. So far, negative effects on seal populations and health are not yet apparent.

On land, large inland caribou herds are overwhelmingly in decline. Climate change and human roads and buildings are all having an impact. Some Indigenous communities who have depended on specific herds for millennia are deeply concerned for their future and the impact on their food, culture and the complex and connected living systems of the region. Some smaller coastal herds are doing better.

Indigenous peoples in the Arctic have deep knowledge of their region that has been passed on for thousands of years, allowing them to flourish in what can be an inhospitable region. Today, their observations and knowledge provide vital support for Arctic communities forced to adapt quickly to these and other changes. Supporting Indigenous hunters and harvesters is by its very nature an investment in long-term knowledge and stewardship of Arctic places.

Action for the Arctic and the globe

Despite global agreements and bold targets, human emissions of heat-trapping gasses are still at record highs. And natural landscapes, like the Arctic tundra, are losing their ability to help reduce emissions.

Simultaneously, the impacts of climate change are growing, increasing Arctic wildfires, affecting buildings and roads as permafrost thaws, and increasing flooding and coastal erosion as sea levels rise. The affects are challenging plants and animals that people depend on.

Our 2024 Arctic Report Card continues to ring the alarm bell, reminding everyone that minimizing future risk – in the Arctic and in all our hometowns – requires cooperation to reduce emissions, adapt to the damage and build resilience for the future. We are in this together.

Twila A. Moon, Deputy Lead Scientist, National Snow and Ice Data Center (NSIDC), Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder; Matthew L. Druckenmiller, Research Scientist, National Snow and Ice Data Center (NSIDC), Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder, and Rick Thoman, Alaska Climate Specialist, University of Alaska Fairbanks

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What does the future hold for forests in a warmer, drier world? Over the past 25 years, trees have been dying due to effects of climate change around the world. In Africa, Asia, North America, South America and Europe, drought stress amplified by heat is killing trees that have survived for centuries.

Old trees may have grown through entire millennia that were wetter than the past 20 years. We are scientists who study forest dynamics, plant ecology and plant physiology. In a recent study, we found that trees can remember times when water was plentiful and that this memory continues to shape their growth for many years after wet phases end.

This research makes us optimistic that young trees of today, which have never known 20th-century rainfall, have not shaped their structure around water abundance and thus may be better equipped to survive in a chronically dry world.

What if we water the forest?

This study built on nearly 20 years of forest research in response to early warning signs of forest loss in the 1990s in the dry Rhône River Valley of the Swiss Alps. At that time, scientists observed that Scots pine trees that had stood for around 100 years were declining and dying. They wondered whether drought or other climate factors were driving this loss.

To tackle this question, researchers at the Swiss Federal Institute for Forest, Snow and Landscape Research designed an ecological experiment. To understand the impacts of drought, they would irrigate a mature forest, doubling natural summertime rainfall, and then compare how these water-rich trees fared in comparison with those receiving only natural precipitation.

The Pfynwald experiment, launched in 2003, has shown that trees survived at higher rates in irrigated plots. After 17 years of irrigation, the team found that irrigation didn’t just help trees survive dry phases – it also increased their growth rates.

Legacy effects are forests’ memories

Trees experiencing drought alter their leaves, wood and roots in ways that prime them for continued dry conditions. Wood under drought might have smaller cells that are less vulnerable to future damage, and roots might increase relative to leaf area. These structural changes persist after the drought has passed and continue to influence the tree’s growth and ability to tolerate stress for many years.

Known as “legacy effects,” these lingering post-drought impacts represent an ecological memory of past climatic conditions at the tree and forest level. Knowing that trees hold a persistent memory of past dry phases, researchers wondered whether they might also show structural changes in response to past wet periods.

Eleven years after summertime irrigation started in Pfynwald, scientists stopped irrigating half of each plot in 2013 to address this question. The formerly irrigated trees, which at this point were about 120 years old, had experienced a lasting period of irrigation – but now those times of plenty were over.

Would the trees remember? A decade later, we found out.

Trees, trains and particle accelerators

On an early March morning in 2023, two of us (Alana Chin and Marcus Schaub) met at Pfynwald to collect very fresh leaf and twig samples so that we and colleagues could look inside to search for signs of lasting effects of past water richness.

At the site, we climbed canopy access towers to collect newly grown treetop leaves and twigs from control trees that had never been irrigated; trees that had been irrigated every summer since 2003; and formerly irrigated trees that had not received irrigation water since 2013.

We took our samples to the Swiss Light Source, an intensely powerful synchrotron – a type of particle accelerator that produces the world’s most intense beams of light. This facility is the home of the TOMCAT, an extremely high-resolution X-ray that allowed us to look inside our leaves and twigs without disturbing their structure.

Scanning our samples took all night, but when we stumbled out of the building, we had images capturing every cell in exquisite detail.

The memory of water

We found that the new leaves of once-irrigated trees were different from both continually watered trees and never-watered control trees. Leaves carry out photosynthesis that fuels a tree’s survival and growth. Inside them, we could see the legacy of past water abundance, written in the size, shape and arrangement of cells.

Reading this cellular signature, we observed that, at the expense of structures promoting productivity, formerly irrigated trees showed every sign of chronic water stress – even more so than never-irrigated trees. In their anatomy, we saw why these trees that had it easy for 11 wet years were now growing slowly.

Every cell in a leaf comes with a trade-off. Trees must balance investments in rapid photosynthesis with others that promote leaf survival. Rather than building the cells used to harvest sunlight and ship sugar to the rest of the tree, leaves on the trees that had been irrigated showed every indication of drought stress we could think to measure.

After receiving extra water for an 11-year stretch and then losing it, the trees were producing new, tiny leaves that invested mostly in their own survival. The leaves were structured to protect themselves from insects and drought and to store water reserves. Compared with leaves on trees that had never known irrigation, these looked as though they were in the middle of the drought of the century.

While this memory of water might seem negative, it likely once helped trees “learn” from past conditions to survive in variable environments. The formerly irrigated trees did not know that humans had played a trick on them. Like trees experiencing climate change, they had no way of knowing that the water was not coming back.

When trees experience a drought event, recovery can mean reaching a “new normal” state, in which they are prepared to survive the next drought, with smaller, less vulnerable cells and increased energy reserves to ‘save up’ for future dry periods. They may have deeper roots or a smaller pool of leaves to support, helping them prepare for an unstable environment.

We wanted to know whether the same was true of trees that had experienced water abundance. Were they waiting in distress for the water to return?

Hard times may make tough trees

In some temperate forests, like the ones we studied in Switzerland, old trees once knew levels of water abundance that now are gone, thanks to climate change. That past abundance may have locked into place structural and epigenetic changes in the trees that are mismatched to today’s drier world. If this is true, then some of today’s devastating global tree mortality events may be, in part, due to the legacy effects of past water abundance.

In most of the world’s temperate forests, however, the current cohort of young forest trees – those sprouting in the past 15 to 20 years – has managed to establish itself under conditions that once would have been considered chronic drought. Those young trees, which have survived an endless dry period, will form the forests of the future.

In all, our observations in Pfynwald have provided us some room for hope that young trees currently taking their place in many forests worldwide may be better prepared to cope with the world as humans have shaped it. Climate shifts in recent decades have primed them for hard times, without the lingering memory of water.

Alana Chin, Assistant Professor of Plant Physiology, Cal Poly Humboldt ; Janneke Hille Ris Lambers, Professor of Environmental Systems Science, Swiss Federal Institute of Technology Zurich, and Marcus Schaub, Group Leader, Forest Dynamics and Ecophysiology, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL)

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

The UK is currently one of the world’s most biodiversity-depleted countries. Urbanisation is a known driver of the nature crisis. This means that the planning system, which regulates development in the UK, plays a crucial role in protecting nature from harm.

On paper, things look positive. Over the past 20 years, a growing list of international, national and local laws and policies have been passed to ensure that the planning system protects ecologically sensitive sites. In spring 2024, England’s new biodiversity net gain policy came into effect, requiring all new residential developments to achieve and maintain a 10% increase in biodiversity, secured for 30 years.

In practice, this means that when developers seek planning permission to build new housing, they have to conduct ecological surveys of their proposed site. The local planning authority reads these reports and lists a set of planning conditions, which are binding: in theory, the developer must adhere to them. This includes providing habitat for wildlife on the land used for development, minimising the harms to nature associated with the change of land use, from farmland to urban areas, for example.

However, in the summer of 2024, we audited 42 new developments across five local planning authorities in England to see whether developers were complying with these ecological conditions on the ground. We found just 53% of the ecological features that should have been there were actually present. When we excluded street trees, this fell to 34%.

Our report, which has not yet been peer reviewed, was commissioned and published by Wild Justice. This not-for-profit environmental campaigning organisationwas co-founded by broadcaster Chris Packham, author and conservationist Mark Avery and Ruth Tingay, a columnist who campaigns against raptor persecution – their work is funded by public donations. We wrote the report together with Sarah Postlethwaite, a senior planning ecologist who works for a local authority.

To research every site, we downloaded relevant documents from each council’s planning portal, including landscaping maps. We visited every street and public open space within each development and measured whether the planning conditions had been met on the ground. We walked over 291 hectares of land, surveyed nearly 6,000 houses and searched for 4,654 trees and 868 bird boxes.

More than half (59%) of wildflower grasslands were sown incorrectly or damaged, and 48% of hedges were missing, along with 82% of specialist woodland edge grassland.

Statistics were even worse for species-specific mitigations: 83% of hedgehog highways were absent, along with 75% of bird and bat boxes. Some swift and bat boxes had even been installed upside down, making them useless to their intended occupants.

This pattern was surprisingly similar across the country, for all sorts of property developers, sizes of development and location. Given that we looked at many local, regional and national housebuilders, this strongly suggests a systemic issue across the planning and development system.

Lack of enforcement

So why is this happening? One simple reason is a lack of effective regulation. Planning consents are supposed to be enforced by specialist teams in local planning authorities.

Ideally, they would visit every new development and do similar checks, but enforcement budgets have been subjected to severe cuts since 2010, leaving them unable to deal with anything but the most serious breaches. Assessing the presence of ecological features also requires a specialist skillset that most people working in planning enforcement do not have. Alongside a resources problem, there is a skills and knowledge gap that needs to be filled.

But there’s also something more worrying going on. The planning system is focused on the processing of applications, paying little attention to the “concrete” outcomes of the system, in both senses of that word.

A great deal of the private sector consultancy that surrounds ecological mitigations (that includes the work of ecologists, landscape architects and private sector planners) is about producing documents that are prospective and virtual.

Hardly any effort is spent checking up on whether any of this activity equates to outcomes on the ground that genuinely help the natural world. With nobody checking whether conditions are met in practice, developers can simply break ecological planning conditions, and get away with it without consequences.

How to avoid irreparable harm

The situation urgently requires action because the government recently announced a huge increase in housing targets. Their assumption is that the ecological harms associated with this level of urbanisation will be mitigated by existing ecological policy and protections. Our work shows that these systems are simply not working in practice on development sites around the country. If nothing changes, what looks like a biodiversity net gain on paper could become a loss.

The government has sought to downplay the severity of this situation, presenting housing as a battleground between environmental and social goals, between newts on the one hand and desperate victims of the housing crisis on the other But, presenting this as a direct conflict is a deeply unhelpful and old-fashioned framing. In reality, human and ecological wellbeing are irrevocably intertwined and biodiversity loss has so many hidden social costs. The key is to find affordable and effective solutions to both dimensions.

Habitat degradation is now predicted to lead to a drop in UK GDP of between 6-12% by the 2030s, a financial impact that could end up being greater than the financial crisis or COVID-19. Research suggests that delivering 300,000 homes a year would blow the entire carbon budget for England.

Other, far less environmentally harmful measures can provide a more meaningful solution to housing provision: building social housing on sites with low ecological value, retrofitting existing building stock and controlling the use of housing as an asset for investment to reduce the number of second homes would be a start.

Effective regulation is desperately needed. With the development industry making “supernormal” profits from the construction of housing, there is no excuse for failing both nature and people in this way.

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Kiera Chapman, Postdoctoral Research Fellow, Faculty of English, University of Oxford and Malcolm Tait, Professor of Planning, School of Geography, University of Sheffield

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Measured from ground level to the top of its highest tower, the Millau Viaduct in France is the tallest bridge in the world. At 343 metres, it’s taller than the Eiffel Tower or indeed any skyscraper in western Europe.

The two kilometre long bridge, which recently celebrated its 20th birthday, spans an entire valley and is an astonishing feat of architecture and engineering. But it also has a climate impact.

A megaproject like this, with several skyscraper-sized concrete and steel towers, involves a lot of carbon emissions. Yet the gains it has offered in operational efficiency – a shorter, straighter route, with fewer traffic jams – will probably offset these emissions within ten years. Given that the viaduct is now two decades old, it has far surpassed its carbon break-even point.

How to calculate the emissions impact of a bridge

The viaduct’s architect, Lord Norman Foster, estimates its annual CO₂ emissions savings from heavy goods vehicles alone at 40,000 tonnes. The methodology behind this figure is not fully transparent and it doesn’t appear to be based on peer-reviewed research. (Foster and Partners did not respond to a request for further detail). But, as an academic expert in sustainable energy and transport, I can make some rough calculations that show the Foster figure is at least plausible.

The viaduct forms part of the A75 motorway, a critical north-south route connecting Paris to the city of Montpellier and on to Barcelona. Before it was built, vehicles travelling on the A75 had to navigate a winding, congested route through the Tarn Valley and the town of Millau itself, adding a few stop-start miles to their journey.

The viaduct instead means vehicles can traverse the valley directly, cutting six kilometres from the journey. With about 4.7 million cars and 400,000 trucks using the A75 and the viaduct each year, all those savings add up.

We can estimate the emissions saved using standardised emissions factors of around 150 grams of CO₂ per kilometre for cars and 800 grams per kilometre for trucks. In all, it means the total savings from distance reduction alone amount to several thousand tonnes of CO₂ each year.

But there is more. Larger trucks who previously wanted a simpler and straighter drive generally took a different route through Lyon, a large city to the east, adding more than 60km to a journey from Paris to the south coast. The viaduct means these trucks can take the more direct route, saving perhaps 20,000 tonnes of CO₂. Of course it is hard to quantify exactly which trucks using the A75 would have taken which alternative route, but this is probably where the bulk of Lord Foster’s number comes from.

Before the viaduct was built, Millau was the main bottleneck on the French north-south motorway axis and experienced severe traffic congestion. The viaduct alleviated this congestion.

Research indicates that alleviating traffic congestion can reduce emissions by up to 25%. This is because vehicles consume less fuel when operating at steady speeds compared to frequent acceleration and deceleration in congested conditions. By applying this 25% reduction factor to the emissions saved from the 26km distance of the worst affected area, we can estimate the additional emissions savings attributable to improved traffic flow: a few thousand tonnes of CO₂ per year.

All considered, we can estimate the general emissions savings to be in the order of 25,000 tonnes of CO₂ per year, not too far from Lord Foster figure.

Construction costs vs efficiency savings

While the calculations provide a robust estimate of the viaduct’s emissions savings, it is only part of the story. For example, improved conditions on the A75 could mean more cars and trucks make the journey, partially offsetting the per vehicle fuel savings. This is an example of what’s known as a rebound effect.

That said, the rebound effect appears to be stronger for cars and individual people. For goods vehicles, who were mostly going to make these journeys anyway, research tends to show that new infrastructure like bridges mostly redirect and optimise traffic and do not generate a significant overall increase.

In a celebrated engineering feat at the time, the viaduct used structural components prefabricated off-site. This reduced on-site construction activities and limited the movement of heavy machinery and materials, minimising the impact on local biodiversity and the emissions associated with transportation and on-site operations.

The viaduct required 205,000 tonnes of concrete and 65,000 tonnes of steel. Concrete production emits approximately 75kg of CO₂ per tonne, while steel emits around 1,400kg. Based on these figures, the viaduct’s construction generated roughly 105,000 tonnes of CO₂.

To get a more complete picture of the viaduct’s environmental impact, we’ll need a comprehensive “lifecycle assessment” which would also look at maintenance, repairs, and its eventual decommissioning in 80 years time. For now, we can point to preliminary studies which estimate that around 40% of the carbon footprint of a bridge like this lie in the maintenance and decommissioning. So the bridge will still create a lot more atmospheric carbon in the rest of its lifetime.

Yet, even if the figures in this article are rough estimates, it seems clear that the emissions savings from the straighter and easier journey have already easily offset the carbon used to build and maintain the bridge. This shows how transport infrastructure policy can have a direct impact on decarbonisation. The Millau Viaduct has already prevented more atmospheric carbon than it has generated. From here on, those savings will only grow.

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Florimond Gueniat, Associate Professor in Mechanical Engineering, Birmingham City University

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