There is a more than 60% chance that a “super” El Niño will develop by the end of this year.

This is defined as the strongest El Niño event you can get, and happens when sea surface temperatures in the tropical Pacific Ocean rise by more than 2°C. During a super El Niño, the ocean gives off extra heat into the air, which helps raise global temperatures. Because climate change is already warming the planet, a super El Niño could push global temperatures to the highest levels ever recorded.

El Niño conditions have already begun this year, according to the US National Oceanic and Atmospheric Administration. While El Niño is a natural phenomenom, climate change means that El Niños are becoming stronger and more frequent.

Hotter sea surface temperatures could spell big problems for marine wildlife and fisheries alike. As the oceans warm, they become more layered, leading to warm, nutrient-poor water sitting on the surface, and cooler, nutrient-rich water trapped below. This layering makes it harder for nutrients to rise to the surface. As a result, there are fewer nutrients available for phytoplankton, the tiny plants that form the base of the marine food chain.

With less phytoplankton in the oceans, there is less food for zooplankton (drifting animals that eat phytoplankton), fish and larger animals including seabirds and marine mammals. This is even more pronounced for the tropical eastern Pacific. The Humboldt current usually brings cold, nutrient-rich water up to the surface, creating one of the most productive marine regions on Earth. But this current is disrupted and overwhelmed during an El Niño. This rich ecosystem supports both wildlife and important fisheries, making it one of the most biologically and economically important ocean regions in the world.

Dramatic effects on fisheries

Strong El Niño events are known to seriously affect Peruvian anchoveta stocks (Engraulis ringens). The super El Niño led a 55% decline in catch in 1972 and 51% on 1973, leading to severe economic hardship. The collapse was driven by El Niño combined with high fishing pressure, as fleets continued trying to maintain catch rates despite rapidly declining stocks. This forced government intervention in the fishery.

The Peruvian anchoveta (Engraulis ringens) is the basis of the world’s largest single-species fishing area, worth an estimated US$1-3 billion (£74.5 million-£2 billion) each year. Globally, this fishery accounts for about 20% of all fishmeal production, which in turn provides roughly half of the feed used in global aquaculture. This makes the species not only vital for Peru’s economy, but also essential for supporting fish farming and food production worldwide.

Reduced fishing quotas

These days El Niño conditions lead to reduced quotas and fishery closures. The anchovy fishery is currently closed due to El Niño. This has led to record-high fishmeal prices (US$2,500 per tonne) which will make aquaculture food more expensive and lead to higher fish farming costs globally.

While the Peruvian anchoveta fishery is perhaps one of the most severely effected and well-documented fisheries in response to El Niño, other fisheries across the globe are also affected by these changing ocean conditions. Along the Californian coast, squid landings plummet during El Niño years. Similarly, in the Indian Ocean, tuna catches appear to be at their lowest after a strong El Niño. Not all fish stocks decline, and some have been shown to increase in response to warmer temperatures. Declining and altered fish stocks during El Niño have been shown to lead to increased fish “wars” between countries in the South China Sea, as fishermen follow migrating fish stocks into other countries economic zones.

Dying coral reefs

El Niño can also have a major impact on marine habitats. One of the most widely recognised effects is on coral reefs, with warmer marine temperatures triggering bleaching, causing corals to expel the microscopic algae they rely on for energy, and in some cases die. During El Niño years, widespread bleaching becomes common across the tropical Pacific, Indian Ocean, south-east Asia and north-east Australia, highlighting the ripple effect of El Niño.

The recent 2023-24 El Niño triggered unprecedented heat stress across the globe, with extensive mortality documented in many countries (for instance Mexico, Australia and Costa Rica).

But it is not just coral reefs that are at risk. In the Galapagos Islands, seaweed and coral habitats have disappeared, or are extremely degraded, due to sensitivity to El Niño. Similarly, mangroves have suffered mortality in Australia, while in California, kelp populations have decreased by 50-70% during El Niño.

Starvation of seals and sea lions

Large marine animals have suffered during strong El Niño. Most notable has been the starvation of a large proportion of fur seals (Arctocephalus galapagoensis) and sea lions (Zalophus californianus wollebaeki) in the Galapagos, and the dramatic reduction in seabird populations in Peru. Many South American fur seals (Arctocephalus australis) and South American sea lions (Otaria byronia) along the southern coast of Peru died. The mother seals remained at sea for longer than ever recorded before, and this is likely to be because they were looking for food.

El Niño can trigger harmful algal blooms, which occur when tiny algae in the water grow really fast and produce toxins that can harm animals and people. These blooms have led widespread deaths of whales when they feed in affected areas near the coast.

It’s hard to determine what the extent of a super El Niño will be on marine life. But with our oceans already struggling under climate change, and little time for marine populations to recover from the last El Niño of 2023-24, it could be the most devastating one yet.

Samantha Garrard currently receives funding from a UKRI policy fellowship

Digital icons are everywhere – and usually, we interpret these visual symbols in the blink of an eye. Who today doesn’t know that a wastebasket means “delete” and a magnifying glass means “search”?

Yet icons’ meanings can be deeply shaped by culture, experience and technological history. So what seems obvious to one person may be confusing to another.

They were originally designed to make computers look friendlier and less intimidating to the few people who had access to them. For example, the icons below first appeared in 1975 in the Pygmalion visual programming system.

Years later, they attained much wider visibility thanks to the Xerox Star 8010, a pioneering office computer that introduced many graphic interface concepts that are still used today.

Research my colleagues and I conducted examines how people perceive, understand and evaluate digital icons – including which visual characteristics make icons easier to learn and use. Pygmalion’s pioneering icons worked because they relied on existing knowledge of the office world.

This meant they reduced cognitive effort by relying on recognition rather than recall. The icons looked like the physical objects they were representing – and critically, objects the computer’s users were already familiar with.

Five secrets of a good icon

The designer Susan Kare, creator of many of the original Macintosh icons, said a good icon should either be instantly recognisable or so easy to remember that a user only needs to learn it once.

To Kare, designing icons was about solving “the little puzzle of making an image fit a metaphor”. More than 40 years later, that challenge remains.

Research, including work by my colleagues and me, suggests the most successful icons tend to share key characteristics that guide us from seeing to understanding almost instantaneously. Here are five of them.

1. They depict things we already know

Early computer icons worked because they borrowed from the office world that people already knew: folders, bins, documents, calculators, floppy disks. Psychologists refer to those as “concrete” icons because people to use their knowledge of the everyday world to interpret them.

However, only a limited number of functions can be represented as identifiable objects, and getting a close fit between pictures and functions is not always easy. The more complex the meaning becomes, the harder it is to design concrete icons.

To test this, can you guess the meaning of these four icons? (Answers at the end of the article.)

2. They mean what we think they mean

Psychologists talk about “semantic distance” – how closely an image matches its intended meaning. An abstract symbol for “privacy settings” or “cloud syncing” has a much larger semantic distance than using a bin to mean “delete”.

As digital functions become more complex, designing icons that communicate their meaning quickly becomes increasingly difficult.

3. They feel familiar

Another important feature of successful icons is consistency of use over time – which leads to familiarity. The icons shown below are widely used even though the objects depicted are no longer so widely in use. This highlights the point that icons are partly informative signs and partly shared learned conventions, whose success is based on collective familiarity.

Take the floppy disk “save” icon (below left). Younger users recognise the meaning without ever having seen the physical object that the icon originally represented. The same is true of traditional telephone handsets and perhaps even envelopes (now widely used to denote “email”). While the objects have been superseded, the icons remain.

4. They look good

A well-designed object can have a positive effect on our behaviour – and the digital world is no different. Well-designed icons are more likely to attract downloads, help us perform tasks more efficiently, and learn better and faster. They even make digital environments feel more pleasant to use.

Think of the difference between an app icon that feels cluttered and amateurish and one that looks clean, balanced and professional. Even before we know what the app does, the icon’s design can influence expectations of how well the app will work.

5. They are tested with real users

Although icons and symbols are on the rise as a global visual language, it’s important not simply to assume that icons work globally – and to understand what makes a good digital icon across languages, cultures, ages and digital experiences.

This is why the International Standards Organisation (ISO 9186) demands comprehensibility testing – because symbols should be understood without explanatory text whenever possible.

A bridge between perception and meaning

As we spend more of our lives in digitally mediated environments, icons do two jobs simultaneously. They help us interact with technology more efficiently, and shape how we feel about the experience.

A digital icon is not simply a small picture. It is a bridge between perception and meaning. The best icons make interfaces feel less intimidating, more intuitive and more approachable – creating a global visual language that crosses barriers of language and culture.

In other words, good icons do more than help us find our way around a digital world. They help make that world feel understandable, welcoming and human.

Icon quiz answers: 1. cloud syncing; 2. privacy settings; 3. algorithmic recommendations; 4. generative AI.

Irene Reppa does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.