Why turning old city bridges into new urban parks is such a great idea

Nick Dunn– Professor of Urban Design, Lancaster University

Castlefield Viaduct in 2020 as work on the newly opened sky park got underway. PA Images | Alamy

The recent opening of the Castlefield Viaduct Sky Park in Manchester, UK, has brought fresh attention to the growing number of projects that reuse urban infrastructures to create linear parks.

When the Promenade Plantée opened in 1993 on top of an abandoned railway viaduct in Paris, it was reportedly the first of its kind. It provided local residents a green escape, ten metres above the tarmac of the street below, and a beautiful, three-mile meander from the Bois de Vincennes to Bastille. The opening of New York’s fabled High Line, in 2009, further cemented this type of urban regeneration as something for cities to aim for.

Post-pandemic, finding innovative ways to eke out accessible green spaces in the urban environment is more urgent than ever. Doing so provides health and environmental benefits alongside economic ones, by promoting biodiversity, mitigating air pollution, and in some (though not all) cases, reducing the heat island effect.

Plantlife spills over the edges of an elevated railway above a busy intersection
The High Line in Manhattan. Krzysztof Stefaniak | Shutterstock

How a local approach to high lines is needed

Since the 2000s, city planners across the world have tried to replicate what has been called “the High Line effect”. Built on top of a disused stretch of elevated freight rail line in western Manhattan, the High Line garnered considerable press and media coverage from the outset. It has been rightly championed as a success story, attracting eight million visitors a year and fostering new economic activity.

But not everywhere else is wealthy Manhattan. By reinvigorating the industrial heritage and cultural identity of a place, this approach can increase tourism which can have mixed results.

Recent research has shown that without policies in place to ensure that lower-income local communities can enjoy the benefits of newly greened spaces, including health benefits, these projects can actually exacerbate inequality by raising property values and causing the displacement of long-term residents who can’t afford to stay. Urban planning experts talk about green gentrification, as has been noted in the case of the 606 linear park in Chicago, among others.

Instead of simply trying to copy what has been done elsewhere, this type of regeneration is best done when attuned to the local heritage. As Historic England has emphasised, the best way to steward heritage sites and the historic environment is by keeping people’s wellbeing in mind. In particular, it’s about giving local people a voice, a place to be active and a sense of belonging.

Signposts at a junction in a pedestrianised green space.
The 606 elevated trail in Chicago. Carlos Yudica | Shutterstock

Why reusing existing structures is best

Adapting existing infrastructure is an integral part of rethinking the city in an era of climate emergency. The era of grand visions for public parks is largely over, as most cities are already full. Both spatially and economically, forming large green spaces from scratch is not possible.

Reworking old railway lines and bridges into parks, conversely, contributes to a wider strategy of adaptive reuse and what designers term urban acupuncture. Since the 1960s, pocket parks have been created out of small, hidden or overlooked bits of land between existing buildings.

A pond set between planted beds in an elevated walkway.
The Promenade Plantée in Paris. Joao Paulo V Tinoco | Shutterstock

The hyper-local nature of this type of urban greening makes it easier for residents to access and benefit from these spaces. As pressure increases on how we use resources and keep carbon in the ground wherever possible, enabling everyone to have access to green space for health reasons is critical.

This can be challenging in those cities where a large proportion of residents do not have access to private gardens. Capitalising on a city’s vertical space – as elevated walkways do – is a huge advantage in high-density cities where significant pressure on ground-level space exists. What’s more, the structures being turned into parks are usually found in those parts of a city that are post-industrial and in need of regeneration.

In terms of environmental impact, these parks have great potential. Each year the High Line, for example, sequesters over 1.3 tons of atmospheric carbon and its tree canopies collect over 24,340 gallons of stormwater.

An overhead shot of an elevated park in a city centre.
The Seoullo 7017 Skygarden. Keitma | Shutterstock

Further, by reusing existing industrial structures rather than demolishing and replacing them, embodied carbon can be kept where it is. Research on the Seoullo 7017 Skygarden in Seoul, a linear park built atop a disused highway overpass which cuts across the city’s main rail station, has shown that rewilding and landscaping urban infrastructures is more cost effective and less environmentally impactful than completely replacing them.

There is growing evidence of how important biodiversity in cities is, not just during daylight hours but at night too. Reused infrastructure projects can play an important role in providing ecological corridors across cities for nocturnal creatures. Supporting both human and non-human life in this way is a valuable step towards improving the sustainability and resilience of places.

Linear parks thus weave nature into the flow of a city. They support wildlife. They encourage sustainable transport and physical activity (walking, biking, jogging). They are, as landscape architect Diana Balmori puts it in her 2010 book, A Landscape Manifesto, dynamic spaces: “not peaceful retreats but ways”.


In defence of pigeons

Steve Portugal– Reader in Animal Biology and Physiology, Royal Holloway University of London

Pigeons are widely treated with contempt by the public. Fercast/Shutterstock

If you ask people why they like their favourite animal, they will tell you about the incredible things the creature can do, its relatable characteristics or its interesting looks. Few would be likely to cite the pigeon as theirs. Many people think of them as vermin rather than wildlife.

People’s utter disdain for feral pigeons breaks my heart. Sit in a park at lunchtime, anywhere in the world, and you’re almost certain to witness people lashing out at pigeons.

I see people stamping their feet and kicking as the birds weave in and out of their legs to snaffle leftover crumbs. But few people stop to think why there are pigeons under the bench they’re sitting on. We brought them into our cities, yet so many despise them. It hasn’t always been this way; we have a rich and long relationship with the humble pigeon.

Feral pigeons are the descendants of wild rock doves. We domesticated them centuries ago, for food and their supreme navigation skills. They thrive in our cities because our tall buildings and window ledges mimic their natural home; caves and cliffs. Our waste provides ample food.

People are enthusiastic about homing pigeons but there isn’t much difference between homing pigeons and feral pigeons. It just depends on whether they live in someone’s loft as a captive pigeon or the local town square.

Who are you calling bird-brained?

The homing abilities of pigeons are legendary. We are still learning about how amazing these birds are. They can do basic maths, on a par with monkeys, and can distinguish real words from made up ones.

Homing pigeons can find their way using smell, landmarksEarth’s magnetic field and infrasound (sound waves with a frequency too low for humans to hear). They can also follow each other and are able to learn routes from one another. Feral pigeons generally mate for life, and they are very attentive parents. The adults produce a crop milk, which they gently drip-feed to their chicks.

Our fascination with their homing abilities continues today, with tens of thousands of pigeon races around the world every year. Pedigree winners sell for over £1 million.

Pigeons are found in large numbers in cities. PauliusPeleckis/Shutterstock

Image problems

We have such disdain for the pigeons living amongst us in our towns and cities. But not so long ago we were fascinated with these creatures. In the mid 1800s we started to appreciate pigeons for their good looks. During this period, many new breeds emerged, including fantails, Jacobins, tumblers and barbs.

Tumbler pigeon. Morrowind/Shutterstock

Their exaggerated features attracted the attention of Charles Darwin. He was a pigeon aficionado and used this dramatic example of diversity within a species to convey his ideas about natural selection in The Origin of Species. It is almost as if we have seen feral pigeons too often to appreciate their rainbow throat feathers and cute, plump bodies. These features would be prized in a rare species.

Warrior birds

Feral pigeons are true survivors. Having spent many hours observing pigeons in St James Park in London, I have seen them caked in oil, milk and human vomit. I have watched pigeons with one foot missing, both feet missing, with only one leg, or trapped in bits of litter. Yet they soldier on. The normal outpouring of sympathy towards animals in distress is absent for feral pigeons. Many people have told me that far from inspiring sympathy, pigeons’ battle scars only add to their dislike: the birds look “messy”. Feral pigeons are thought to be prone to losing toes and feet because human hair and netting tangles around them, cutting off the blood supply. They can also get their feet stuck in chewing gum. Our litter harms pigeons and then we treat them with contempt for the way it makes them look.

Pigeons are a common sight in cities. Ercan Mercankaya/Shutterstock

Pigeons are some of the most decorated animals in history. No less than 32 pigeons have won the prestigious Dickin Medal, the animal equivalent of the Victoria Cross. Homing pigeons were used intensively during both the first and second world wars, to deliver vital messages between battalions and fly with cameras on for reconnaissance missions. Perhaps the most famous war pigeon is Cher Ami, who in 1918 was awarded the French Croix de guerre medal, for delivering messages from an encircled battalion under heavy fire. Cher Ami was shot through the breast, blinded in one eye, and his right leg was only hanging on by a tendon by the time he delivered his messages.

There is not much difference between homing pigeons and feral pigeons. stockphoto mania/Shutterstock

For many people, feral pigeons are some of the only wildlife they interact with on a regular basis. These interesting birds live right on our doorsteps. Next time you’re outdoors, give pigeons 30 seconds of your time. Watch them. Witness their intricate social interactions and see the tender moments between pairs as they preen each other and bring nesting material as gifts. However, if you really don’t want them around during your lunchbreak the best advice is: be a less messy eater.


Thousands more species at risk of extinction than currently recorded, suggests new study

Lilly P. Harvey– PhD Researcher, Environmental Science, Nottingham Trent University

Amphibian species are particularly at risk. elementals / shutterstock

New research suggests the extinction crisis may be even worse than we thought. More than half of species that have so far evaded any official conservation assessment are threatened with extinction, according to predictions by researchers from the Norwegian University of Science and Technology.

Conservation resources are limited and it is not feasible or logical to protect every square kilometre of land and sea. So to mitigate the rapid loss of biodiversity, where should our conservation resources go? To answer this question we first need to know which species to protect.

The International Union for Conservation of Nature coordinates a network of scientists who have assessed biological information available for all sorts of species worldwide for more than 50 years, publishing their findings in the Red List of Threatened Species. Its goal has been to identify species that need protection with an assigned conservation category of extinction risk.

It’s the Red List that confirmed tigers are officially endangered, for instance, or that giant panda populations have recovered enough to move from endangered to merely vulnerable.

However, while species like pandas and tigers are well studied, researchers don’t know enough about some species to properly assess their conservation status. These “data deficient” species make up around 17% of the nearly 150,000 species currently assessed.

When analysing conservation data it is common for researchers to remove or underestimate assumptions of threat for these species, in order to control for unknown variations or misjudgements. Now, these researchers in Norway have tried to shed light on the black hole of unknown extinction risk by designing a machine learning model that predicts the threat of extinction for these data deficient species.

Machine learning for extinction assessment

When thinking of artificial intelligence and machine learning it is easy to imagine robots, computer-simulations and facial recognition. In reality, at least in ecological science, machine learning is simply an analytical tool used to run thousands of calculations to best represent the real-world data we have.

In this case, the Norwegian researchers simplified the Red List extinction categories into a “binary classifier” model to predict a probability of whether data deficient species are likely “threatened” or “not threatened” by extinction. The model algorithm has “learned” from mathematical patterns found in biological and bioclimatic data of those species with an already assigned conservation category on the Red List.

Giant Panda webpage on IUCN Red List
The Red List assigns each species in one of seven conservation categories, or tags them as ‘not evaluated’ or ‘data deficient’. IUCN Red List

They found more than half (56%) of the data deficient species are predicted to be threatened, which is double the 28% of total species currently evaluated as threatened in Red List. This reinforces the concern that data deficient species are not only under-researched, but are at risk of being lost forever.

On land, these likely threatened terrestrial species are found across all continents, but live in small geographically restricted areas. This finding supports previous research with similar conclusions that species with small range sizes are particularly vulnerable to anthropogenic habitat degradation, such as deforestation or urbanisation.

At risk amphibians

Amphibians are the most at-risk group, with 85% of those data deficient species predicted as threatened (compared to 41% of those currently evaluated on the Red List). Amphibians are already a poster-child for the extinction crisis and are a key indicator for ecological health, as they depend on both land and water. We don’t know enough about what causes such catastrophic extinction of amphibians, and I am part of a science initiative trying to address the problem.

Black and yellow toad on green leaf
Dozens of harlequin toad species in Central and South America have been discovered and almost all are already critically endangered or extinct in only a few decades. goran_safarek / shutterstock

It’s a slightly different, but still tragic, story at sea. Data deficient marine species that are predicted to be facing extinction are concentrated along coasts, particularly in south-eastern Asia, the eastern Atlantic coastline and in the Mediterranean. When data deficient species are combined with fully-assessed species on the Red List, there is a 20% increase in the probability of extinction along the eastern coastlines of tropical Latin America.

What this means for global conservation

Two world maps
How data deficient species change conservation priorities: percent change in probability of a species being threatened by extinction once data deficient species are factored in. (a = marine species; b = non-marine) Borgelt et al / Communications Biology

Though it is likely that the need for conservation has actually been underestimated worldwide these probability predictions are highly variable across different areas and groups of species, so don’t be fooled into overgeneralising these findings. But these broad results do highlight why it is so important to further investigate data deficient species.

The use of machine learning tools can be a time-and-cost-effective way to enhance the Red List and help overcome the challenging decision of where and what to protect, aiding targeted conservation action and expanding protected areas in these black holes of biodiversity.


Houseplants don’t just look nice – they can also give your mental health a boost

Lauriane Suyin Chalmin-Pui– Wellbeing Postdoctoral Fellow with the Royal Horticultural Society, University of Sheffield

Houseplants can be an essential link to nature – especially for those without access to a garden. Syda Productions/ Shutterstock

For those of us without access to outside green space, houseplants are a stylish and affordable way of getting a nature fix. Alongside looking nice, indoor plants actually have several other perks – the biggest benefit of which could be improving your mental health. And the good news is you don’t need to be a self-professed “plant parent” to experience these benefits either.

One in eight UK households don’t have access to any kind of garden. Young people and those from minority ethnic backgrounds are among those least likely to have a garden.

Not having access to nature can have a number of effects on our health. It’s been linked to symptoms of depression and anxiety, as well as other health conditions, such as asthma, cardiovascular disease, and poor immune function. For many of us, houseplants are an essential link to nature.

While there’s not yet a robust body of research on the mental health benefits of houseplants specifically, plenty of studies have shown how beneficial green space and gardening are for mental health. For instance, one study found that people who garden daily have better wellbeing and lower stress levels compared to those who don’t.

Gardening also reduces symptoms of depression and anxiety and increases positive emotions to the same extent as biking, walking and eating out. Many of these outcomes are likely to be true of houseplants too.

A recent review of 42 studies demonstrates that even just being in the presence of indoor plants can improve mental and physical health. These experiments compared participants doing various activities in rooms with or without plants.

The presence of plants saw better performances on cognitive tasks involving focus, sorting or memory recall, greater pain tolerance when holding hands in ice cold water, and lower levels of physiological stress. Interestingly, the aesthetic appearance of plants is important too, with separate research showing that people tend to react more positively to lush, green plants with rounded and denser foliage.

But most of these studies are centred around the mere presence of plants. From research on the benefits of gardening, we can assume that caring for houseplants will bring out many more emotional benefits – such as pride, social connectionsatisfactionfascinationmental resilience in times of stress, and may even help you heal from past trauma.

Good for you

There are plenty of other reasons owning houseplants is beneficial for you.

Plants can remove pollutants such as carbon dioxide, nitrogen dioxide (from nearby traffic), fine particles (from dust) and volatile organic compounds (from air fresheners, cooking and cleaning). For people indoors for the majority of the day, indoor air quality is hugely important.

High concentrations of carbon dioxide can reduce cognitive performance (such as concentration and memory recall) while prolonged exposure to other indoor pollutants can cause long-term health problems – ranging from minor eye or throat irritations to respiratory problems and cancer.

But removing a meaningful quantity of indoor pollutants would require a lot of plants in a very bright room – something unrealistic for most people. If you do want to give it a try, plants with a high leaf area – such as an India rubber tree (Ficus elastic) or devil’s ivy (Epipremnum aureum) are your best bet.

A young woman wearing gardening gloves uses a spray bottle to water her houseplant.
Houseplants can be good for other aspects of your health, too. antoniodiaz/ Shutterstock

In theory, plants can also help increase indoor air humidity. Most of our buildings are too dry. Keeping humidity in an optimal range can prevent the spread of viruses, fungal growth, as well as eye, skin and nose dryness. Though dependent on other conditions in the room like size, light, and airflow, some of the best plants for increasing humidity are English ivy (Hedera helix), Devil’s ivy (Epipremnum aureum) and Peace Lily (Spathiphyllum).

Lifelong learning

You don’t need a green thumb to enjoy success with houseplants. Gardening is all about learning through trial and error, and even the most seasoned gardeners make mistakes. Indeed, not all plants will thrive everywhere – and some may struggle through infestations, won’t adapt to light or water conditions, and die. Try not to get hung up on this setback. It’s always worth trying again, perhaps with a different species and armed with more botanical knowledge.

Each plant has different requirements, so look for plants that are suited to the conditions in your home. You may even want to find plants that actually thrive on neglect. Some of the best options for beginners are the spider plant (Chlorophytum comosum), the parlour palm (Chamaedorea elegans), and anything in the cactus and succulent families, such as the zebra cactus (Haworthia) or the jade plant (Crassula ovata).

Growing herbs is also a cheap and useful starting point for beginners. There are also apps out there that can help make it easier for you to care for your plants, by giving you advice, reminders and a forum to ask questions.

Owning houseplants can have a range of benefits for our health – especially mental health. It can also be a great hobby that always teaches you something new, encourages self-expression – choosing and caring for plants –, and gives you a tangible sense of fulfilment.


Seven reasons Nordic walking is better for you than the normal kind

Lindsay Bottoms– Reader in Exercise and Health Physiology, University of Hertfordshire

Nordic walking may be a great way to boost the benefits of your regular strolls. Jacek Chabraszewski/ Shutterstock

Have you ever noticed people out walking with poles even on flat surfaces and wondered why they are doing it? This is known as Nordic walking, which is a little bit like cross country skiing but without the snow.

Walking with poles was first developed in Scandinavia and came to central Europe about 20 years ago. For some reason, it has not become particularly popular even though it has many health benefits.

Here’s why – alongside a few good reasons to give Nordic walking a try.

1. You burn more calories

As far back as 1995, researchers noticed that Nordic walking burned more calories than regular walking did. In fact, they found it burned up to 18% more calories than ordinary walking did.

Numerous studies have confirmed these findings since – which is why it’s suggested that Nordic walking could be a great form of exercise for those looking to lose weight. One study from Italy even found that overweight people lost weight faster doing Nordic walking compared to ordinary walking.

While Nordic walking doesn’t burn more calories than other, more intense forms of exercise – such as running – it can be a great low-impact exercise option, or a way to boost the benefits of your regular daily walks.

2. It may reduce limb pain

Using poles while you walk can distribute your weight through the arms and torso, placing less strain on your back, knees and hips. In theory, this has the potential to improve back pain while walking.

However, research is mixed, with some studies showing Nordic walking can reduce lower back pain and impact on the knees, while others show it’s no more helpful than ordinary walking.

If you’re someone who suffers from lower back, hip or knee pain, Nordic walking could be helpful to you since it redistributes your weight somewhat. But it’s worth discussing with your doctor first before giving it a try, and stopping if your pain still persists even while using the poles.

3. Improves upper body strength

Nordic walking engages your arms and shoulders more than regular walking does, and that could improve your strength. Research has shown that Nordic walking can not only increase hand grip strength but also increases muscle activity in the shoulders.

Upper body strength – including how strong your grip is – is important for many of the things we do everyday, from carrying our shopping to filling up the kettle. Increasing muscle strength is also important to help prevent injury as it helps stabilise the joints and protects them when moving under impact like carrying heavy shopping bags.

Read more: How strong your grip is says a lot about your health

4. Increases core strength

Nordic walking also engages the core muscles (including those in the abdomen and your back) more than ordinary walking does.

Greater engagement of the core muscles will help strengthen them, which may in turn improve posture. Better core strength can also improve your balance as well as your ability to move.

5. Reduce risk of falling

Unfortunately as we get older we are more likely to trip and fall when we are walking. This is mainly because of a decrease in muscle strength, balance issues and problems with the way we walk.

Two elderly ladies wearing winter coats stroll down a woodland path using walking poles.
Nordic walking may improve balance. Alexey Smyshlyaev/ Shutterstock

The benefit of Nordic walking is that you are placing the poles into the ground at the same time as you’re using your legs. This improves balance and makes you less likely to fall.

In fact, one study even showed that people who followed a Nordic walking training programme for three weeks had improved balance – even when walking without poles. It’s no wonder Public Health England recommends Nordic walking for improving balance in older people.

6. Boosts cardiovascular health

Research shows that Nordic walking can improve cardiovascular fitness in as little as four weeks.

Another study on obese women also showed Nordic walking was able to improve blood pressure, though only to a similar extent as ordinary walking. In addition, Nordic walking has been shown in postmenopausal women to improve resting blood sugar levels, which is important in preventing diabetes as well as improving cholesterol levels in the blood.

7. You can walk faster

Nordic walking can help you get where you want to be faster than ordinary walking can. In fact, a review showed Nordic walking increased average walking speed by up to 25% compared to ordinary walking. As a consequence of walking faster, you can then burn more calories. So if you went for a 30-minute Nordic walk, you’d be able to walk further and burn more calories than you might on a regular walk.

There seem to be clear advantages to doing Nordic walking. It may especially be good for people who don’t like other types of exercise – such as running – but still want to do something of a higher intensity than brisk walking.


James Lovelock: the scientist-inventor who transformed our view of life on Earth

Mark Maslin– Professor of Earth System Science, UCL

James Lovelock outside his home laboratory. Homer Sykes/Alamy Stock Photo

James Lovelock, the maverick scientist and inventor, died surrounded by his family on July 27 2022 – his 103rd birthday. Jim led an extraordinary life. He is best known for his Gaia hypothesis, developed with the brilliant US biologist Lynn Margulis in the 1970s, which transformed the way we think of life on Earth.

Gaia challenged the orthodox view that life simply evolved and adapted to the ever-changing environment. Instead, Lovelock and Margulis argued that species not only competed but also cooperated to create the most favourable conditions for life.

Earth is a self-regulating system maintained by communities of living organisms, they claimed. These communities adjust oxygen and carbon dioxide levels in the atmosphere, salinity in the ocean and even the planet’s temperature to keep them within the acceptable bounds for life to thrive.

Just like Charles Darwin before him, Lovelock published his new, radical idea in a popular book, Gaia: A new look at life on Earth (1979). It was an instant hit that challenged mature researchers to reassess their science and encouraged new ones. As my friend and colleague Professor Richard Betts at the Met Office Hadley Centre put it:

He was a source of inspiration to me for my entire career, and in fact his first book on Gaia was a major reason why I chose to work on climate change and Earth system modelling.

Not only did the book challenge the classical Darwinism notion that life evolved and prospered through constant competition and dogged self-interest, it founded a whole new field: Earth system science. We Earth system scientists study all the interactions between the atmosphere, land, ocean, ice sheets and, of course, living things.

Lovelock also inspired the environmental movement by giving his ideas a spiritual overtone: Gaia was the goddess who personified the Earth in Greek mythology.

This antagonised many scientists, but created a lot of fruitful debate in the 1980s and 1990s. It is now generally accepted that organisms can enhance their local environment to make it more habitable. For example, forests can recycle half the moisture they receive, keeping the local climate mild and stabilising rainfall.

But the original Gaia hypothesis, that life regulates the environment so that the planet resembles an organism in its own right, is still treated with scepticism among most scientists. This is because no workable mechanism has been discovered to explain how the forces of natural selection, which operate on individual organisms, birthed the evolution of such planetary-scale homeostasis.

An aerial view of morning mist over a rainforest.
Organisms alter their environment to make it more favourable to life. Avigator Fortuner/Shutterstock

An independent scientist

There was much more to James Lovelock, who described himself as an “independent scientist since 1964”, because of the income generated from his invention of the electron capture detector while studying for a PhD in 1957.

This matchbox-sized device could measure tiny traces of toxic chemicals. It was essential in demonstrating that chlorofluorocarbons (CFCs) in the atmosphere, which originated in aerosols and refrigerators at the time, were destroying the ozone layer. It also showed that pesticide residues exist in the tissues of virtually all living creatures, from penguins in Antarctica to human breast milk.

A small device resembling a spindle with a white band in the middle.
The electron capture detector Lovelock invented for measuring air pollution. Science Museum LondonCC BY-SA

The money he earned from the electron capture detector gave him his freedom because, as he was fond of telling people, the best science comes from an unfettered mind – and he hated being directed. The detector was just the start of his inventing career and he filed more than 40 patents.

He also wrote over 200 scientific papers and many popular books expanding on the Gaia hypothesis. He was awarded scientific medals, international prizes and honorary doctorates by universities all around the world.

Dr Roger Highfield, the science director at the London Science Museum, summed Jim up perfectly:

Jim was a nonconformist who had a unique vantage point that came from being, as he put it, half-scientist and half-inventor. Endless ideas bubbled forth from this synergy between making and thinking. Although he is most associated with Gaia, he did an extraordinary range of research, from freezing hamsters to detecting life on Mars … He was more than happy to bristle a few feathers, whether by articulating his dislike of consensus views, formal education and committees, or by voicing his enthusiastic support for nuclear power.

Jim was deeply concerned by what he saw humanity doing to the planet. In his 1995 book The Ages of Gaia, he suggested that the warm periods between ice ages, like the current Holocene, are the fevered state of our planet. Because over the last two million years the Earth has shown a clear preference for a colder average global temperature, Jim understood global warming as humanity adding to this fever.

Jim did despair at humanity’s inability to look after the environment and much of his writing reflected this, particularly his book The Revenge of Gaia in 2006. But at the age of 99, he published Novacene: The Coming Age of Hyperintelligence (2019), an optimistic view which envisaged humanity creating artificially intelligent life forms that would, unlike us, understand the importance of other living things in maintaining a habitable planet.

His dwindling faith in humanity was replaced by trust in the logic and rationality of AI. He left us with hope that cyborgs would take over and save us from ourselves.


Exercise can reduce stress and improve sleep – particularly for women with breast cancer

Len De Nys– PhD researcher, Stress, Healthy Ageing and Physical Exercise, University of Stirling Anna Catriona Whittaker– Professor of Behavioural Medicine, University of Stirling

Regulating cortisol levels simultaneously improves sleep quality. Rido/ Shutterstock

When you’re suffering from stress, it can affect almost every aspect of your life – even down to how well you sleep at night. While it’s normal to experience stress over things every now and again, if it continues to affect your sleep in the long-term it can lead to poorer quality sleep and even insomnia.

This may, in turn, lead to other health problems, such as depression, cancer relapse and early death.

But our recent review suggests that physical activity may be key to improving both stress levels and sleep.

To conduct our review, we looked at all possible studies ever published on this topic. Around 60% of the studies we looked at happened to be done on women with breast cancer, while the other 40% were done on a more diverse range of participants, including men and women without breast cancer. It’s uncertain why so many studies in this area looked at women with breast cancer, but it may be to do with the fact that chemotherapy causes a lot of side effects – such as stress and poor sleep.

Our findings suggest that, in general, exercise was effective for reducing stress levels and improving sleep. Other studies that have looked at a more diverse group of participants have also shown that physical activity can help lower stress and can help people get a better night’s sleep. Research also suggests exercise may be beneficial for people with other health conditions such as depression or sleep disturbances.

Cortisol is an essential hormone in the body. It works with our brain to regulate a number of important body processes including mood, immune system function and metabolism. It also triggers our “fight-or-flight” response when we encounter things that are scary or stressful – hence why it’s often called our “stress hormone”.

Cortisol also plays an important role in sleep. Cortisol levels change throughout the day, but are generally at their peak in the morning, around 30-45 minutes after waking up, helping us feel alert and ready to take on the day. But gradually these levels decline throughout the day, which helps us feel tired and fall asleep at night.

But in times of stress you may experience higher cortisol levels in the evening – which makes it harder to get a good night’s sleep. Poor sleep in turn increases stress by affecting the way the body produces cortisol.

According to our review, physical activity counterbalances this negative spiral by regulating cortisol levels – which simultaneously improves sleep quality. We found that light-to-moderate intensity exercise (such as running and yoga) seem to be the most beneficial in improving stress and sleep. But our study also suggests that exercise works best at reducing stress and improving sleep when it’s tailored to each person’s preference.

A diagram showing how much exercise, the intensity of it, and how many times a week is needed to improve stress levels and sleep quality.
This is the formula for less stress and a better night’s sleep, according to our review. Len De Nys, Author provided

Why exercise works

Previous research suggests a couple of possible reasons why exercise is so good for reducing stress and improving sleep.

First, exercise can be seen as a “hormetic” stressor. Hormesis is that sort of good stress that keeps your body alert. During exercise, your body is exposed to various forms of stress – such as the stress your muscles experience because of the extra demand placed on them. These stressors simulate existing mechanisms that your body uses to withstand greater stress.

Either too little or too much exposure to exercise stressors can lead to poor health. It’s that sweet spot that regulates cortisol and improve sleep (and overall health). But this sweet spot differs from person to person – and may even be affected by your own mental state when you exercise.

Second, it’s important to consider the type of exercise you do – as this can determine whether or not it makes you feel relaxed or more stressed. This is why it’s essential that you enjoy the exercise you do. You may also want to change the intensity of the exercise you do depending on the time of day.

Since exercise releases cortisol (especially more intense types of exercise, such as weightlifting or high-intensity interval training), morning exercise can help your body feel more energised during the day and help you feel more tired in the evening. For this same reason, if you’re someone who likes to exercise in the evening it’s best to choose exercises – such as yoga or tai chi – that help you wind down and don’t spike cortisol levels too much.

But of course, not everyone can exercise first thing in the morning. The good news is that exercise almost any time of day can help reduce your stress levels and improve sleep – and this is true of almost every type of exercise, too.


Cities: how urban design can make people less likely to use public spaces

Jose Antonio Lara-Hernandez– Senior Researcher in Architecture, University of Portsmouth

We only feel free to use spaces that we can identify with. Vagengeim | Shutterstock

Urban beautification campaigns are usually sold to local residents as a way to improve their daily lives. Design elements – from lighting systems to signs, benches, bollards, fountains and planters, and sometimes even surveillance equipment – are used to refurbish and embellish public spaces.

Designers refer to these elements as “urban furniture”. And the projects they’re used in are usually aimed at increasing social interaction, heightening safety, improving accessibility and generally making life in the city better.

Some research argues, however, that such beautification campaigns can result in public urban spaces becoming more exclusive. Despite the promises with which they are marketed, if these projects disregard what local people need, they can feel less able, or willing, to make use of these spaces.

An urban canal pathway seen at sunset.
Cheonggyecheon canal, in Seoul, South Korea. PixHound | Shutterstock

Cities aren’t only identified by their monuments or signature buildings. You can tell New York City and Palermo apart just by looking at what people are doing in public. A New York scene is more likely to feature someone on a skateboard eating a burrito, while a Palermo image might include a group of men in a street watching a football match on television through a shop window.

Urban space is where city children learn and play, students read and people work, walk and relax. It is through these different activities that any single city’s urban culture is created.

Quite what city spaces look like is down to urban design, a powerful tool.

Architects, infrastructural and spatial designers carefully configure the built environment – the constructed fabric of our cities – and this has a lasting effect on how we use or inhabit them.

In cities around the globe – from Algiers, Auckland and Chicago to Hanoi, Mexico City and Seoul – research shows that transforming public spaces markedly affects the diversity of what people do in them, and whether they use them.

In Algiers, the Algerian capital, neighbourhoods were formally designed in the 1970s in a rigid modernist style. Design elements including shady trees, benches and lights at night made people feel comfortable carrying out activities such as playing cards or gathering to chat, but huge buildings, wide streets and large spaces also caused people to feel insecure and lost. Further, the land was landscaped in the kind of homogenous way characteristic of other big cities including Los Angeles, Auckland and Sydney. These large-scale and non-contextual designs have also been linked to antisocial behaviour.

A large urban park and high-rise buildings.
Alameda Central Park, Mexico City. Diego Grandi/Alamy Stock Photo

Research conducted in the historic Alameda Central Park neighbourhood of Mexico City highlight similar patterns of exclusion caused by how a neighbourhood was redesigned.

After the area was transformed in 2013, there was a notable decline in the diversity of the activities people undertook there (family and religious gatherings; street art; music; informal vendors). Instead, the law now prioritises touristic activity over local people’s everyday needs and allows the authorities to operate a zero-tolerance approach towards anything deemed disruptive. Vendors have become nomadic, packing up and hiding as soon as the police are nearby.

In the Cheonggyecheon-Euljiro area of Seoul, South Korea, meanwhile, redevelopment led to 50-year-old workshops being torn down. This in turn has threatened the historical and cultural values of the local population and disrupted social networks.

How cities are co-created

In his 1968 book, The Right to the City, the French Marxist philosopher and sociologist Henri Lefebvre described the city as a co-created space. This contrasts with the more capitalist definition in which urban space is a commodity to be bought and sold, Lefebvre saw it as a meeting place where citizens collectively built urban life.

This idea that public space is a public good that belongs to everybody has been increasingly challenged in recent years, with the rise of privately owned public space. Most of the parks in London (roughly 42 kilometres squared) of green space in total) are owned by the City of London Corporation, the municipal body that governs the City of London, but increasingly squares within new developments are owned by corporations.

A stone-tiled public space in an office development.
The More London development near Tower Bridge, London, is privately owned public space. UrbanImages / Alamy Stock Photo

Urban theorists have long noted the connection between how a city is designed and how life is conducted within it. The US scholar Jane Jacobs is famous for highlighting that cities fail when they are not designed for everyone. And Danish architect Jan Gehl’s output has consistently focused on what he has termed the “life between buildings”.

As Gehl has explained, for a city to be good to its residents, those in charge of designing it have to be aware of how it is being used: what people are doing in its spaces. To be successful, urban designs have to be focused on and geared towards people’s daily lives. Gehl has explained that designing a city for pedestrians – at a walkable scale – is how you make it healthy, sustainable, lively and attractive.

When we use public spaces, even if only on a short-term basis, we are effectively appropriating them: urban designers and architects talk about “temporary appropriation” to describe the individual or group activities with which we invest these spaces.

Research has also highlighted how democratic this can be. But it is contingent on those spaces being designed in consort with residents. When a public space, by contrast, is overly designed without people’s needs being taken into account, it does not get used.

Since the 1970s, urban theorists have highlighted that we only make use of those public spaces where we feel represented. For urban design to work, paying heed to what local people actually think of their city is crucial.


Hedgehog conservation: how to make a garden nest box appealing – new research

Abi Gazzard– PhD in Ecology and Conservation, University of Reading


When large patches of woodland are swallowed by urban sprawl or when households replace long grass with artificial turf or refurbish buildings to repair cracks and crevices, wildlife populations are robbed of potential places to rest, breed and hibernate. That’s why conservation groups urge homeowners, where possible, to create wildlife-friendly habitats on their own land.

One artificial refuge that has long adorned gardens is the bird box. It is estimated that there are 4.7 million of them in gardens across the UK. Some studies have reported that nest boxes (or bricks) can help birds to produce more chicks and boost their populations compared with birds nesting in areas without artificial refuges.

But whether and how animals actually use these refuges depends on their design, where they are placed and the conditions of the wider landscape. In the wrong setting – or with the wrong design – wildlife can suffer harm or an increased risk of being captured by predators.

A tit perched at the entrance of a wooden bird box mounted on a tree.
Artificial refuges such as bird boxes create nesting sites where natural options are limited. Nadezhda Kulikova/Shutterstock

Relatively little is known about what makes a house a home for species other than birds, or how effective artificial refuges are for conserving a species. Even so, garden centres and other retailers offer a wide variety, ranging from ceramic houses for toads to wood and concrete roosts for bats. Many of these are made and installed with mammals in mind.

One such mammal is the nocturnal, ground-dwelling hedgehog. Hedgehogs have undergone a long-term decline and are listed as vulnerable on Britain’s red list of mammals: some parts of the countryside may have seen numbers crash by up to 75% over the past 20 years. Where populations persist, hedgehogs often make use of residential gardens, and it is here where the public – by providing nest boxes (or “hedgehog houses”) – could play a significant role in their conservation.

In a new study, I found that you might be able to improve the chances of a hedgehog taking up residence in your garden nest box by, among other things, thinking carefully about where you position it and leaving out food and bedding material.

A hedgehog surrounded by autumn leaves.
Hedgehog numbers have declined by between 30% and 75% across different parts of the UK countryside since 2000. Colin Robert Varndell/Shutterstock

The hedgehog housing census

Charming images and videos of hedgehogs using nest boxes (both homemade and shop-bought) abound on social media. Yet very little is known about how best to choose, make or install these refuges. That’s partly because people are advised to avoid disturbing nesting hedgehogs.

To resolve this, researchers at the University of Reading (including myself) and specialists at the conservation campaign group Hedgehog Street launched the hedgehog housing census: an online questionnaire which gathered information on how nest boxes are used across the UK.

More than 5,000 surveys were returned. Using this data we examined how hedgehogs use boxes for different types of nesting. Hedgehogs typically build distinct nests for somewhere to rest during the day, somewhere to rear young and somewhere to hibernate over winter, and may move between more than one nest in each instance. For each type of nesting, we modelled how the use of a nest box appeared to have been influenced by its design and dimensions, plus features of the garden and environment.

For most seasons, the study showed that hedgehogs were more likely to have used a nest box where food – such as meaty pet food – and bedding were provided. Some gardeners left piles of dry leaves in a corner of the garden which hedgehogs could gather and drag into the box.

Hedgehogs were also more likely to use nest boxes where there was access between the front and back gardens, highlighting the importance of connections between habitats. This may be possible by cutting a hole in the bottom of a fence or leaving a gap beneath a gate to form a hedgehog highway. Additionally, the likelihood of a hedgehog inhabiting a box tended to increase when they were placed under shelter such as shrubs, or on hard surfaces such as patios, and with the entrances oriented away from wide open spaces.

A composite image showing eight different hedgehog house designs.
Artificial hedgehog refuges come in a variety of designs. Abi Gazzard, Author provided

The presence of dogs seemed only to have a negative effect during the vulnerable period of hibernation, which typically occurs between November and April. Surprisingly, badgers or foxes did not seem to deter hedgehogs from nesting in a box, though few people reported having seen either species in their garden. We also found that, during hibernation, nest boxes were more often used when the boxes were south-facing and within five metres of a building. This may be because these spots were warmer, and cosier nesting chambers help hibernating hedgehogs burn less energy. Too warm and hedgehogs could wake up more frequently, though. The optimum nest box temperature for hedgehogs – and the design features that might influence this – are not well understood.

The census also revealed where hedgehogs might prefer to make their own nests in gardens. Survey respondents reported evidence of 2,546 other nests used by hedgehogs in their gardens, including nests built under vegetation, such as long grass or shrubs, (46%), sheds (21%), woodpiles (15%), compost heaps (6%) and decking (6%).

Nest boxes – and gardens more broadly – provide important nesting habitats for the declining hedgehog. But there is still much we don’t know about how these artificial refuges compare to natural nests. This a field in which researchers must delve deeper, by untangling how nest box design affects occupancy and by trying to understand the consequences of using artificial refuges on hedgehog health, behaviour and abundance. For now, it’s clear that simple actions can improve the chances of a hedgehog using a nest box – a potentially critical part of nurturing the recovery of this species.


Climate crisis: even temporarily overshooting 2°C would cause permanent damage to Earth’s species

Joanne Bentley– Postdoctoral Researcher in Molecular Ecology, African Climate & Development Initiative, University of Cape Town Alex Pigot– Research Fellow, Genetics, Evolution & Environment Division of Biosciences, UCL Andreas L. S. Meyer– Postdoctoral Research Fellow in Ecology & Evolutionary Biology, University of Cape Town Christopher Trisos– Senior Research Fellow in Climate Change Risks, University of Cape Town

Ondrej Prosicky/Shutterstock

The history of climate change is one of people slowly coming to terms with the truth. None but a small minority still question whether it’s real and caused by humans. Now most grapple with the reality of trying to slow down catastrophic warming, and the difference between solutions and false hope. The concept of climate overshoot is the next thing we will need to get to grips with.

Unless urgent action is taken, emissions are expected to cause the planet to continue heating rapidly over the next few decades, prompting the global average temperature to overshoot the Paris agreement’s target, which aimed to limit warming to between 1.5°C and 2°C. A period of higher temperatures will occur in the middle of this century as a result. Then, the idea goes, new but yet unproven technologies and techniques for pulling greenhouse gases from the atmosphere will eventually bring temperatures back down to a safer level.

Until now, scientists were unsure what temporarily overshooting (and then boomeranging back below) the Paris agreement’s temperature target would entail for nature. So, for the first time, we studied the consequences of allowing Earth’s temperature to exceed these precautionary limits, then fall below them again, for marine and land-based life. In other words, we looked at how damaging the journey of overshooting the 2°C temperature target would be, and not just the destination itself.

The results suggest that a temporary overshoot would cause waves of irreversible extinctions and lasting damage to tens of thousands of species. This is what the world can expect if humanity fails to make deep emission cuts this decade, and relies instead on future technologies to remove emissions later.

Harm arrives fast and leaves slowly

Our study modelled the impact of global temperatures exceeding 2°C for around 60 years between 2040 and 2100 on over 30,000 species that live on land and in the sea. We looked at how many of them would be exposed to temperatures that could hinder their reproduction and survival, and how much time they would be exposed to this risk.

A line graph depicting
In this scenario in which the world overshoots the 2°C target, emissions do not peak until 2040. Meyer et al. (2022), Author provided

Harm would be fast to arrive and slow to disappear for nature, even after temperatures fall again. Just a few years of global temperatures above 2°C could transform the world’s most important ecosystems. Take the Amazon basin, for example. Some species would remain exposed to dangerous conditions long after the global average temperature stabilised – with some remaining exposed as late as 2300. This is because some species, especially those in the tropics, live closer to the limit of heat they can tolerate and so are sensitive to relatively small changes in temperature. And while global average temperatures may return to safer levels eventually, local temperature changes might lag behind.

The consequences of this exposure could be irreversible and include the tropical forest turning into savanna. The world would lose a critical global carbon sink, leaving more planet-warming gases in the atmosphere.

The Coral Triangle in the western Pacific Ocean is one of the most species-rich marine ecosystems and home to many reef-building corals, sea turtles, reef fish and mangrove forests. Our modelling showed that in some communities, all or most of the species would be exposed to dangerous conditions simultaneously for at least a few decades and as much as two centuries. As well as disrupting a source of food for millions of people, disappearing corals and mangroves would remove a natural barrier protecting coastal towns and villages from rising seas and worsening storms.

A variety of corals growing in shallow water with a tropical island in the background.
Tropical corals exist at the limit of their thermal tolerance and are especially vulnerable to climate change. Ethan Daniels/Shutterstock

No way home

The consequences of overshooting 2°C for the survival of species have been neglected by policymakers. Our analysis indicates that it cannot be assumed that life will simply recover once temperatures fall below 2°C again. We found that 3,953 species will have their entire population exposed to temperatures outside the range they evolved in for more than 60 consecutive years. The Philippine porcupine will be exposed for 99 years, and the Mawa clawed frog for an astonishing 157 years. Surviving this length of exposure is a stern challenge for any species.

Relying on carbon dioxide removal and so-called negative emissions technologies to lower greenhouse gases in the atmosphere over several decades is too risky to contemplate. Some of this technology, like carbon capture and storage, hasn’t yet been shown to work at the scale needed. Other techniques have negative effects on nature, such as bioenergy, where trees or crops are grown and then burned to generate electricity. Rolling out vast plantations at the same time as temperatures overshoot the internationally agreed “safe” limit would leave species reeling from a hotter climate and shrinking natural habitat.

Delaying drastic cuts to emissions will mean the world overshooting 2°C is a best-case scenario. This overshoot would come at an astronomical cost to life on Earth that negative emission technologies will not reverse. The effort to stop temperatures rising isn’t an abstract attempt at bending curves on a graph: it’s a fight for a liveable planet.