It is two decades since Facebook introduced the News Feed – letting loose a world in which algorithms would shape ever more of our lives.

In 2006, Facebook was facing something of a crisis. Its internal data suggested that for the first time since its launch two years earlier (as TheFacebook), the company had stopped growing. People weren’t joining, and existing users weren’t spending more time on the site.

The solution co-founder Mark Zuckerberg and colleagues came up with, the News Feed, meant individual users’ homepages would be automatically updated with information tailored to them – in particular, new posts their Facebook friends had added.

Up to then, users had to actively check their friends’ profiles to see what they were up to. Now, this information would automatically be sent to your homepage. With it, a new world of algorithmic interaction was born.

It might seem quaint now, but for many Facebook users at the time, these changes felt like a violation of their privacy and trust. If you were to change your relationship status from “in a relationship” to “it’s complicated”, for example, this could now be broadcast to all of your online friends.

The News Feed caused the first major protest against Facebook. Tens of thousands of users joined a group calling for the return of the original system. A spontaneous protest emerged outside Facebook’s office in the city of Palo Alto, California. For the first time, the company felt it had to hire security guards.

Zuckerberg issued a sort-of-apology, but he didn’t back down. What he and other Facebook engineers could see was that, rather than pushing people away from the site, the News Feed was driving more engagement – leading users to spend more and more time on the platform.

A revolution in media consumption

Twenty years later, we can understand this development as one of the most significant socio-technical changes of the entire digital revolution. It ushered in an age where algorithmic systems structured how people interacted, consumed news and conducted political activity.

Crucially, to enable this new “content pushing” approach, Facebook engineers had to build a new digital architecture that moved the site away from being a static social network, into an algorithmic system built around the extraction and analysis of user data.

Under this new system, in the words of researchers Christina Alaiamo and Jannis Kallinikos, Facebook users could be “computed on the basis of discrete and countable activities”, turning them into “identifiable, knowable and actionable objects”.

Facebook had thus shifted from a site primarily enabling social interaction to one concerned with the production and commercialisation of knowledge. With increasing accuracy, it understood what type of content kept users on the site longer – and what type of information could influence people’s behaviour outside and beyond the site.

Facebook could now continuously optimise the level of social interactions using its algorithmic ranking system, Edge Rank. With a tweak, it could switch from prioritising messages from close friends to content that generated greater interaction, or outrage.

This took power away from users towards the corporation, and raised concerns that users were spending more time on the site than they seemed to want to. (Eventually, this would lead to a “major overhaul” of the News Feed in 2018, with Facebook promising to re-prioritise “meaningful social interactions” over “relevant content”.)

But above all, Facebook’s innovation in 2006 enabled it to capture huge amounts of user data that would, over the next two decades, enable it to expand globally at an astonishing rate – and generate vast amounts of revenue in the process.

A very different algorithmic age

Twenty years on, Facebook’s parent company Meta and other big tech platforms face challenges far more powerful than spontaneous protests on the streets of Palo Alto. Across the world, there is sustained activity from democratic institutions and states to contain the power and perceived harm of the algorithmic systems that emerged from 2006.

In Australia, use of social media platforms by under-16s is banned, and this is potentially spreading to the UK. Meanwhile, courts in the US have forced Meta to restrict the amount of access that children have to their products. While less than 1% of Facebook’s revenue comes from teens, the precedents set by these legal cases appear significant.

However, we also live in a very different algorithmic age than the one heralded by the launch of the News Feed 20 years ago. While Meta continues to derive most of its revenue from its social network platforms, which also include Instagram and WhatsApp, recent investments and prospective AI product launches suggest its leadership believe future revenue streams will largely be tied to developments in machine learning, large language models and “superintelligence”.

The question is: will governments and other institutions react more quickly to the concerns raised by this new era of AI development than they did to the emergence of algorithms two decades ago? On past evidence, this looks unlikely.

Asher Kessler received funding from the Economic and Social Science Research Council.

Heatwaves claimed the lives of tens of thousands of people in Europe’s capital cities this summer, as they experienced record temperatures.

In London, emergency wards filled with elderly patients injured after fainting in the heat. Meanwhile, the dry weather created subsidence and left homes with cracks.

In Paris temperatures exceeded 40°C in late June and people struggled to carry on their lives, and in Madrid, heatwaves burned thousands of hectares on the outskirts of the city.

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Read more: Can the searing European summer put climate action back on the agenda – or will disaster response take over?

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How trees can help

Thami carried out preliminary research on the results of extreme heat on European cities this summer. The study looked into how many buildings have adequate shade from trees. The results were striking.

In London, Paris and Madrid over 90% of buildings did not have enough shade around them to prevent urban heat island effects. These were among the worst results in cities we studied, but even the best performers had a majority of residents without adequate heat protection – cities like Hamburg (56% unprotected) and Barcelona (70% unprotected).

This builds on past research that shows how major cities around the world – including in Europe – tend to struggle to reach useful levels of tree canopies to create shade close to homes and workplaces. It suggests that that homes should have a view of three trees and be within a 300 m walk of a park.

Early results for my research suggests that huge portions of European cities are exposed to avoidable heat island effects.

How urban heat islands work

On many days during summer 2026 it didn’t get much cooler in the evening. This is because of what is known as the urban heat island effect. Cities typically lack shade, due to high rates of tree removal, sparse planting, and poor tree health and there are vast amounts of asphalt, clay and concrete. These are almost the perfect materials to soak up and hold heat from all that direct sunshine. Unshaded asphalt can reach over 70°C on heatwave days.

Even after sunset, cities stay hot because roads, buildings and footpaths begin to radiate their absorbed heat back at us as they cool. The urban heat island effect can add significantly to ambient temperatures, making a day that is already very hot (perhaps 35°C) even more dangerous in high-asphalt, low shade locations (over 40°C).

What could help?

Tree shading is an effective strategy to address this urban heat, with a range of other mental and physical health benefits to local residents. Trees prevent solar radiation reaching heat-absorbing materials such as asphalt, and also keep the sun off our bodies. Tree shade has been shown to reduce the heat absorbed by pedestrians by up to 18°C.

Healthy trees also push water out of their leaves as they photosynthesise, which soaks up heat as it evaporates. This evaporative cooling effect adds an extra few degrees of cooling, in addition to shading people and preventing heat island effects, even during heatwaves as long as trees still have access to water.

Where trees are needed

Planting more trees in cities in the wake of this summer’s heatwaves is going to help cool urban areas down. The thinktank, the Create Streets Foundation, found the temperature on an exposed paved area in London during one heatwave was 55°C but was 25-30°C in a shaded area metres away.

Looking at a city such as London, you might argue that it already has plenty of trees: around 8 million.

But trees are only effective tools against urban heat when they’re close to homes. A lush shady park 800m away isn’t going to prevent dangerous localised heat island effects for you and your neighbours.

The other crucial factor is that there are thresholds of shade cover that have to be reached for trees to actually offer substantial cooling. A few isolated trees creating small islands of shade aren’t enough. Adding more tree canopy has been shown to be effective at preventing urban heat islands when it reaches 30-40% overall shade cover, within 60m of homes and workplaces.

It will also be important to plant trees that are best able to cope with increasingly hot temperatures in Europe.

Adding just a few degrees to an already hot day sharply ramps up the danger that heat poses. In locations where heat islands bump up the ambient air temperature from 33°C to 37°C, or 35°C to 41°C, there’s an increase in patients attending hospital admissions’ rooms due to heat related illness. When air temperature increases above 35°C the human body’s ability to manage the heat is greatly reduced; cardiovascular strain, dehydration, potentially leading to heatstroke and the need for medical intervention.

When it makes nights hotter there are other ramifications. It is during the cooler night hours that the body loses heat to reset for the following day. If the body is still trying to cope with warm temperatures, 24°C and above, this impacts recovery and impairs sleep quality. This means we start the next day in deficit, both physiologically and cognitively, to cope with another hot day. Repeated exposure to days of high heat mean that the deficit builds over time.

Adding more trees works

Medellin in Colombia is an example of what happens when more plants are added to urban streets.

In just a few years, millions of plants and over 12,500 trees were added to form a network of lush greenways across Colombia’s second largest city.

This project has resulted in significant drops in temperature (of 4.5°C in some areas, and 2°C citywide).

There are signs that Paris and London are aware they need to make changes. The recently announced Heat Ready London plan includes a focus on urban greening.

Paris is already starting to add more green space. The city’s school streets programme not only creates safe, car-free areas close to local schools, but also has added more trees. Evidence already suggests that surfaces in school streets are 5°C cooler than their traffic-heavy counterparts, with fewer trees.

As Europe prepares for more hot summers, planting trees close to homes needs to be high on the agenda to help people cope.

Thami Croeser has previously recieved funding from The Australian Research Council, Greenlife Australia, and the European Union's Horizon 2020 program. He is a Director of the Australasian Green Infrastructure Network, a not-for-profit peak body. He occasionally provides urban forest advisory and analytics services in a private consulting capacity.

Simon Hodder has previously received funding from the European Union's Horizon 2020 program and UKRI, Engineering and Physical Sciences Research Council (EPSRC).

Amy, a 27-year-old software developer, has struggled with disordered eating since she was a teenager. “But after learning to code, I got much better,” she said in a research interview. “I often code for ten or more hours without stopping.” Her psychiatrist, however, worried that Amy has replaced one compulsive behaviour with another.

“Digital addiction” is often used to describe our relationship with smartphones, social media and other digital technologies. This way of thinking suggests that people get “hooked” on digital activity because their body becomes “addicted” to dopamine. It borrows from models of substance addiction: the focus is on the physical need to keep using a substance because the body has adapted to it, despite harmful consequences. The implied solution is straightforward: abstinence, which translates into practices like digital detox.

But Amy’s story, which forms part of our ongoing research, points to a more complicated reality of our relationship with digital technology. Coding consumed much of her time and attention, yet it also helped her earn an income and build a professional identity. Like many forms of digital engagement, it was not just a distraction but a way of navigating life.

As research shows, for many people digital technologies are not only a source of entertainment but key components of their education, work and social mobility. Unlike in the case of addictive substances, opting out of digital life is easier said than done when schools, banks and public services increasingly require it.

How people relate to digital technology isn’t just about them as individuals. It’s shaped by their personal vulnerabilities, but also by digital environments intentionally built to hook us, and by the wider social conditions people live in.

So comparing smartphones to substances like alcohol, tobacco or drugs can be misleading. It overlooks the fact that digital devices have become a kind of essential infrastructure for daily life. Given how we have built our lives around them, these technologies are now very difficult to live without.

How, then, do we develop a sustainable relationship with technologies such as smartphones that are both indispensable and potentially harmful?

The sugar model

Amy’s story with disordered eating may be useful here. Recovery from an eating disorder isn’t about eliminating food altogether, but about learning to live with it.

In the same way that we cannot remove food from our lives, it is also difficult to remove digital technologies from our everyday. So the challenge becomes developing ways of living with them.

Take, for example, sugar. In many countries, foods high in sugar are subject to a wide range of public health measures. Think national food safety standards, public health interventions, school nutrition policies, limits on advertising. So it’s not about focusing on one thing only. Rather, it’s the interaction between all of these interventions that shapes patterns of consumption and impacts wellbeing.

A similar approach is needed for digital technologies. At the level of state and industry governance, this includes regulation of platform and design – particularly when it is aimed at capturing and holding users’ attention.

Just as food labels describe ingredients, nutrition and additives, digital products could disclose what data they collect, what algorithms they run on and what psychological techniques keep their users engaged.

The UK’s decision to ban social media for under 16s while continuing to expand digital literacy and coding education reflects an important point: not all digital technologies are the same.

“Digital use” cannot be treated as a single category to be either embraced or banned. Like sugar, the question is not whether children should have it at all, but what kinds, in what quantities, and in what conditions.

Beyond counting calories and screen hours

Just as sharing a meal with family affects people differently from eating alone, playing games with friends is not the same as scrolling endlessly through social media. Both count as screen time, but they create very different social and emotional experiences.

Reflecting on our own digital habits remains important. But tracking screen time is like counting calories: it tells us how much, but not necessarily why. We have to ask ourselves what role digital technologies play in our lives.

Are they helping us work, connect, rest, escape, cope, feel less or more alone? Without this kind of reflection, self-tracking risks turning a complex social issue into a matter of individual self-control.

Understanding digital technologies through the lens of food rather than addiction shifts the emphasis in important ways. Both are domains where necessity, pleasure, risk and social obligation are intertwined, which is why abstinence may not be an adequate, long-term response.

Instead of treating excessive technology use as a matter of personal discipline, approaching them like some foods locates it within broader systems of design, industry governance, state policy and social practices. The challenge then is to integrate these different levels to make life with digital technologies sustainable.

Tanja Ahlin receives funding from the Dutch Research Council (NWO), Grant number VI.Veni.241S.150, https://doi.org/10.61686/EWUXQ23921

Xin Zhan receives funding from the University of Cambridge.