When the Pacific Changes the World El Niño, Extreme Weather and the Fight for Wildlife

 

El Niño: The Climate Phenomenon 

That Can Reshape the World's Weather and 

Its Consequences for Wildlife

The words El Niño are increasingly appearing in weather forecasts and climate discussions. With forecasts during 2026 pointing towards a return of El Niño conditions in the tropical Pacific, concern is growing about the potential for another period of disrupted weather, heat, drought and flooding.

But what exactly is El Niño, how does it interact with our warming climate, and what could it mean for the wildlife with which we share the planet?

The answer is both fascinating and worrying.

What is El Niño?

El Niño is part of a natural climate system known as the El Niño–Southern Oscillation, or ENSO.

Under normal conditions, powerful trade winds push warm surface water westwards across the equatorial Pacific towards Indonesia and Australia. Cold, nutrient-rich water rises from deeper layers in the eastern Pacific, particularly off the coast of South America.

During El Niño, those trade winds weaken and the distribution of warm water changes. The consequences are not confined to the Pacific. Changes in tropical rainfall and atmospheric circulation can alter weather patterns thousands of miles away through what climatologists call teleconnections.

It is important not to think of El Niño as a simple weather forecast. It does not guarantee that every affected region will experience a particular event. Instead, it changes the probability of certain weather patterns occurring.

That distinction matters. El Niño can load the climatic dice without determining exactly where every flood, drought, storm or heatwave will occur.

El Niño in a warming world

This is where the story becomes more complicated.

El Niño is a natural cycle. Climate change did not create it. Indeed, the World Meteorological Organization states that there is currently no evidence that climate change increases the frequency or intensity of El Niño events.

However, climate change can make the world in which El Niño operates considerably warmer. A warmer atmosphere can hold more moisture, warmer oceans contain more energy, and background temperatures are already elevated because of increasing greenhouse gases.

In other words, El Niño may act as an additional push on a climate system that is already changing.

The World Meteorological Organization reported that 2024 was likely the first calendar year with a global average temperature around 1.5°C above the 1850–1900 average, at approximately 1.55 ± 0.13°C. The strong El Niño that peaked early that year contributed to the record warmth, although greenhouse gas emissions remained the primary driver.

The oceans are also absorbing enormous amounts of heat. Around 90% of the excess energy trapped by greenhouse gases is stored in the ocean, and 2024 saw the highest ocean heat content in the observational record.

That matters enormously because El Niño begins in the ocean but its consequences spread through the atmosphere, across continents and ultimately into ecosystems.

Where might the greatest impacts be felt?

Every El Niño is different, but certain broad patterns occur often enough to be useful in seasonal forecasting.

Flooding and intense rainfall

El Niño is frequently associated with increased rainfall in parts of:

• Western South America, including Peru and Ecuador
• Parts of East Africa during particular rainy seasons
• The southern United States

Heavy rainfall can cause catastrophic flooding, landslides, infrastructure damage and crop losses. When unusually warm air contains more water vapour, intense rainfall events can become even more damaging.

Drought and extreme heat

Other regions may experience the opposite problem.

El Niño is commonly associated with an increased risk of dry conditions in areas including:

• Indonesia
• Parts of Australia
• Southern Africa
• Parts of South Asia

Drought can devastate agriculture, reduce water supplies and dramatically increase wildfire risk.

Changing storm patterns

El Niño can alter the position of major atmospheric circulation systems and jet streams.

For example, it can influence winter storm tracks across North America and is generally associated with reduced Atlantic hurricane activity, while potentially increasing activity in parts of the central and eastern Pacific.

However, regional forecasts should always be treated carefully. ENSO is only one part of a complex climate system, alongside factors such as ocean temperatures elsewhere, atmospheric circulation, regional geography and long-term climate change.

Food, water and human consequences

The environmental consequences rapidly become human consequences.

Drought reduces crop yields and water availability. Floods can destroy farmland, roads and homes. Fisheries can collapse when changes in ocean circulation disrupt marine food chains.

One of the most important oceanographic effects of El Niño occurs off the coast of South America. Normally, cold water rising from the deep brings nutrients towards the surface. During El Niño, this upwelling can weaken, reducing primary productivity and affecting the entire marine food web, including commercially important fisheries.

The developing 2026 event is already raising concern about food supply chains, particularly where drought or excessive rainfall could affect major agricultural regions.

For millions of people, particularly those already living with water insecurity or dependence on seasonal agriculture, the difference between an ordinary rainy season and a failed one can be profound.

But perhaps the most overlooked consequences are those experienced by wildlife.

The Natural World Under Pressure

Wildlife has always adapted to changing weather. Migration, hibernation, dispersal and breeding strategies have evolved over thousands of years.

The problem today is not simply change.

It is the speed, intensity and combination of changes.

A species may be capable of surviving a drought. It may survive a heatwave. It may survive habitat loss.

But what happens when all three occur together?

That is increasingly the challenge facing biodiversity.

The IPCC concludes with very high confidence that extreme climate events are already occurring beyond conditions to which many species are adapted. Local population losses have been widespread, while marine heatwaves have caused extensive mortality among corals, kelps, seagrasses and mangroves.

Birds: disrupted migration and collapsing food supplies

Birds are particularly vulnerable because many species depend on extremely precise timing.

A migratory bird may arrive at its breeding grounds expecting an explosion of insect life. But what happens if a warm spring causes insects to emerge several weeks earlier?

The birds may arrive on time according to their inherited migratory timetable but too late for the food.

This is known as a phenological mismatch.

Extreme weather can also directly affect birds.

Drought can dry wetlands and reduce feeding habitat. Flooding can destroy nests. Marine heatwaves can alter fish populations, leaving seabirds struggling to find sufficient food.

El Niño's disruption of nutrient-rich upwelling in the eastern Pacific can cascade through marine ecosystems. Reduced plankton productivity affects fish, which in turn affects seabirds and marine mammals.

For long-lived seabirds, repeated poor breeding seasons can be particularly damaging. A population may survive one bad year. Several consecutive years of food shortages can be far more serious.

Migratory birds face an additional challenge: their annual journey connects multiple continents. A drought in Africa, a heatwave in Europe or flooding at a critical stopover site can all affect the same individual population.

The journey is only as strong as its weakest link.

Mammals: heat, drought and shrinking habitat

Mammals are affected both directly and indirectly.

Extreme heat can cause direct mortality, particularly among animals unable to escape high temperatures. The IPCC notes documented mass mortality events associated with extreme heat, including fruit bats.

Drought can be equally destructive.

As water sources disappear, animals are forced to travel further. Competition increases. Predators and prey may become concentrated around the remaining water. Livestock and wildlife may compete for increasingly scarce resources.

In some ecosystems, the problem becomes a vicious circle.

Drought reduces vegetation.

Reduced vegetation means less food.

Animals weaken and reproduce less successfully.

Wildfire may then destroy what habitat remains.

Large mammals may be able to travel, but only if suitable habitat exists elsewhere. For species living in increasingly fragmented landscapes, moving is not always an option.

A changing climate can therefore turn roads, cities, farmland and fences into barriers that prevent wildlife from responding naturally.

Insects: the hidden foundations of ecosystems

When people think about climate disasters, insects are rarely the first organisms that come to mind.

Perhaps they should be.

Insects pollinate plants, recycle nutrients and provide food for countless birds, mammals, amphibians and fish.

Extreme drought can reduce flowering plants and therefore nectar resources. Heat can alter development rates and survival. Heavy rainfall can destroy vulnerable life stages.

The consequences can move rapidly through the food web.

Fewer insects may mean less food for breeding birds.

Fewer pollinators may mean reduced reproduction in wild plants.

Changes in insect distribution may also bring new pests and diseases into areas where ecosystems have little experience of them.

Not every insect will decline. Some species may benefit from warmer conditions and expand their range.

That is another important point: climate change is not simply a story of everything disappearing.

It is also a story of ecosystems being rearranged.

The winners and losers may not be evenly distributed.

Plants: drought, fire and changing landscapes

Plants cannot simply walk away.

A woodland may survive decades of gradual climatic change. But repeated drought, heatwaves, wildfires and pest outbreaks can push it beyond a tipping point.

At higher levels of warming, entire ecosystems may begin to shift.

The IPCC warns that biodiversity risks increase with every increment of global warming. Beginning around 1.5°C, natural adaptation increasingly encounters hard limits, with growing risks of population decline, mortality and extinction.

Plants face particular problems when climate changes faster than they can disperse.

A tree may produce seeds that eventually colonise cooler areas further north. But this process takes time. Climate zones can move more quickly than some species can follow.

Meanwhile, plants dependent on very specific soil types, mountain environments or isolated habitats may simply have nowhere to go.

The oceans: perhaps the greatest warning sign

The oceans may provide the clearest illustration of what happens when natural climate variability collides with long-term global warming.

Corals are already under immense pressure from rising sea temperatures.

During periods of exceptional ocean warmth, corals can bleach expelling the microscopic algae that provide much of their energy. If stressful conditions persist, entire reef systems can suffer widespread mortality.

The IPCC reports widespread and extensive impacts from marine heatwaves on habitat-forming species including corals, kelps, seagrasses and mangroves.

El Niño can add further warmth to already overheated oceans.

This is one of the reasons scientists are particularly concerned about the combination of short-term climate cycles and long-term warming.

A natural event that might once have been damaging can become considerably more dangerous when it occurs on top of an already elevated temperature baseline.

What about the United Kingdom?

The effects of El Niño on British weather are considerably less direct and less predictable than in parts of the tropical Pacific.

It would therefore be wrong to say that El Niño automatically means a particular type of British winter or guarantees storms, floods or drought.

The UK sits within a complicated North Atlantic weather system influenced by the Atlantic Ocean, the jet stream, the North Atlantic Oscillation and numerous other atmospheric factors.

Nevertheless, the wider effects of El Niño can influence global atmospheric circulation and may alter the probability of certain weather patterns reaching north-west Europe.

For British wildlife, however, the more significant issue may be the global nature of interconnected ecosystems.

Many of the birds seen in Britain migrate through or winter in regions vulnerable to drought, extreme rainfall and changing food availability. What happens thousands of miles away can ultimately influence the birds arriving on our shores in spring.

A wetland bird seen at Sandwich Bay or Pegwell Bay may have spent the winter in Africa.

A seabird feeding in the North Sea may depend on a marine ecosystem already responding to changes in sea temperature.

Climate change does not recognise national boundaries.

Neither does wildlife.

The bigger picture

The most important lesson from El Niño is that we should not look at climate change as a single event.

It is a changing background against which natural climatic cycles continue to operate.

El Niño will eventually weaken. Another phase of ENSO will follow.

But the greenhouse gases warming the planet do not simply disappear when El Niño ends.

The World Meteorological Organization makes the distinction clearly: El Niño is a natural source of climate variability, while human activity is driving the long-term warming trend. Climate change may amplify the impacts of ENSO because warmer oceans and a warmer atmosphere provide more energy and moisture for extreme weather.

That combination should concern us.

A drought occurring in a warmer world may be more severe.

Heavy rainfall occurring in a warmer atmosphere may produce more intense downpours.

Marine ecosystems already experiencing record ocean heat may be less able to withstand another period of exceptional warming.

Wildlife populations already fragmented by habitat loss may have fewer places to retreat.

A test of resilience

The coming years will not simply test our ability to forecast weather.

They will test the resilience of ecosystems.

For conservationists, this means protecting and reconnecting habitats, restoring wetlands, allowing rivers room to flood naturally, creating wildlife corridors and maintaining ecosystems capable of absorbing shocks.

A nature reserve cannot exist as an isolated island.

Species need landscapes through which they can move.

Wetlands need water.

Rivers need space.

Woodlands need resilience.

And conservation increasingly needs to consider not only the species that are present today, but those that may arrive tomorrow.

El Niño may be temporary.

The environmental pressures it exposes are not.

The real question is whether we can learn from these increasingly dramatic events and build landscapes and ecosystems capable of surviving a world in which the climate is becoming less predictable.

For wildlife, there is no emergency plan, no insurance policy and no second planet.

There is only the resilience of the natural world and increasingly, the decisions we make to protect it.

Key facts at a glance

• El Niño is a natural warming phase of the El Niño–Southern Oscillation.
• It changes tropical Pacific ocean temperatures and atmospheric circulation.
• Its effects can include increased risks of flooding, drought, heatwaves and changes to storm patterns.
• 2024 was likely the first calendar year around 1.5°C above pre-industrial temperatures, with El Niño contributing to the record warmth but human-driven greenhouse gases remaining the primary cause.
• Around 90% of excess heat trapped by greenhouse gases is absorbed by the oceans.
• Extreme weather is already causing widespread impacts on biodiversity, including mortality and ecosystem degradation.
• El Niño can disrupt marine food chains by reducing nutrient-rich upwelling in parts of the Pacific.
• There is no established evidence that climate change increases the frequency or intensity of El Niño itself, but a warmer world can amplify many of its impacts.