White storks (Ciconia ciconia) are a majestic bird with a two-metre wingspan and an enormous circular nest.

The recent release of these stunning birds at multiple sites in England, with more releases planned and a public consultation under way has kicked off a debate about whether non-native birds should be part of rewilding projects.

The government advising body Natural England says it does not consider white storks to be native birds. But some experts disagree and say it is a native species and was hunted into extinction in the 1400s.

What is a native species?

In the UK, native species are those which have been present throughout the last 12,000 years. This includes migratory species which breed in or visit the UK. It also includes species which have been eradicated by humans but reintroduced.

In England, a licence is needed to introduce any species which is not ordinarily resident, or a regular visitor, to England. This is partly because these species could become invasive, a term used when a species cause substantial environmental or socioeconomic harm.

But even when species are not native, they can have value for rewilding projects. The white stork’s biggest contribution to rewilding is likely to be their ability to inspire the public interest in nature. Storks in Europe are so popular that there are special stork villages which are managed for tourism, and people can see these iconic species up close.

White storks are definitely regular visitors to England, and rare but present in the subfossil record (the last 4000 years). This status as a regular visitor means they fall somewhere between a native and non-native species – they are not considered a priority for introduction, but no license is required for their release.

Introduced non-native species can cause problems. A good example is Japanese knotweed (Reynoutria japonica), brought to the UK by the Victorians as an ornamental plant. It rapidly spreads and causes damage to the structure of buildings and essential services such as water and drainage pipes. Controlling it now costs the UK £247 million each year.

Introduced species are also a major conservation challenge, such as the damage to seabird populations by invasive cats, rats and other animals feeding on their eggs and chicks. If a rewilding project introduces a non-native species, it could become invasive and cause serious disruption to native species already in the landscape.

But evaluating the impact of adding new species to the landscape is important even when a species is considered native. The Scottish beaver trial was conducted to evaluate the impact of introducing beavers (Castor fiber) from Norway in 2008. Eighteen years later, beavers are a key part of many rewilding projects, from London to large estates in Scotland.

What can white storks add?

White storks are charismatic species which are viewed positively by most people, and this could increase engagement with nature. In Poland, tourists travel hundreds of kilometers to visit white storks, making them valuable for rewilding projects which use tourism to raise funds.

Non-native species are also introduced as “ecological analogues” which means they provide the same ecological function as extinct species. The steppe bison (Bison priscus) which roamed the UK in the Pleistocene period were mixed feeders, which means they ate a combination of grasses, leaves and the woody parts of plants. By feeding on a variety of plants and plant parts, mixed feeders like bison can encourage a patchwork of habitats in a landscape. The native steppe bison is extinct in the UK, but projects like Kent Wildlife Trust’s Wilder Blean project have introduced the related, but non-native, European bison (Bison bonasus) to provide these functions.

Adapting to warming climate

Better adaptation to future climates is another reason to include non-native species in rewilding projects. As the UK’s climate changes, species are moving from places where they are considered native to new areas which suit them better. The southern small white butterfly (Pieris mannii) has spread northwards in Europe and was first seen in the UK in 2025. This small butterfly has successfully made the journey over the ocean, but other species may require human help to move to new areas with more suitable climates.

As an island nation with many locally extinct species, the introduction of species has formed a key part of UK conservation, including rewilding projects. It does matter whether a species is native or not. Although both could benefit rewilding projects, non-native species carry greater risks to local environments and have higher regulatory requirements.

The white stork’s status as a regular visitor could allow them to sidestep the regulatory requirements for non-native species, though impact on the environment should also be considered.

But as their nests can attract birds such as swallows and martins, introducing white storks could have broader benefits to the landscape.

Sarah Papworth 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.

It may seem like we are on the verge of discovering alien life. In 2025, a press release stated that we have the “strongest hints yet” of extraterrestrial life on the exoplanet K2-18b. And when talking about a collected sample from a rock named “Cheyava Falls” on Mars, Nasa Administrator Sean Duffy said this was the “closest we have ever come” to discovering life on the red planet.

Such moments capture the imagination. But they also raise an important question: what do the majority of scientists actually think?

Surprisingly, we usually don’t know. When a scientific controversy or breakthrough dominates headlines, press officers and journalists often quote a handful of experts. These views may be insightful, but they rarely tell us what the wider scientific community thinks. And yet public discussions frequently rely on phrases such as “the science says” or “scientists believe”, as if there were a clear and measurable answer.

In reality, systematic evidence about scientific opinion is often missing. My colleagues and I recently tried to change that in the domain of astrobiology. Shortly after the two major announcements of possible extraterrestrial life in 2025, we surveyed astrobiologists to understand how expert judgment was distributed across the field.

The first case concerned the exoplanet K2-18b. In April 2025, researchers reported possible traces of molecules called dimethyl sulfide and/or dimethyl disulfide. On Earth, these are associated with biological activity. Media coverage was extensive, with many reports framing the finding as an extraordinary advance in the search for alien life.

The second case came in September, when Nasa announced that Cheyava Falls appeared to preserve a potential biosignature – so-called “leopard spots” which are mineral rings that on Earth are often formed by microbial activity. Again, headlines, and Nasa officials themselves, suggested something momentous.

What scientists actually thought

We surveyed hundreds of astrobiologists from across the global research community, within days of each announcement. We asked a simple question: did scientists think extraterrestrial life had probably been found?

The results revealed a rather cautious picture. For K2-18b, only 6.6% of surveyed astrobiologists agreed that scientists had probably found extraterrestrial life. Nearly two-thirds disagreed, while 28.0% remained neutral. For the Mars case, confidence was higher but still cautious: 15.1% agreed, disagreement fell to 44.6% and neutrality rose to 40.3%.

Looking only at agreement and disagreement, however, misses an important part of the story. The proportion of astrobiologists who strongly disagreed fell dramatically, from 35.1% in the K2-18b case to just 11.1% for Mars. Much of the movement was therefore not from rejection to endorsement, but from strong rejection towards more tentative positions.

In other words, expert opinion moved in structured ways. The shift from K2-18b to Mars was not a simple movement from “no” to “yes”. Instead, the community became more open to the possibility without embracing it outright.

One possible reason is that the two cases involved different kinds of evidence. The K2-18b claim relied on possible atmospheric signatures detected from across interstellar distances, whereas the Martian case concerned a rock that could be studied directly and in much greater detail. At the same time, astrobiologists have long been aware that apparently lifelike features can sometimes arise through non-biological processes. Often, the challenge is not imagining how life could produce a signal, but understanding all the ways nature might produce something similar without life.

Scientific opinion is rarely binary. Public discussion often treats science as though communities either agree or disagree. But the distribution of opinion matters too. Strong agreement, agreement, neutrality, disagreement and strong disagreement can each tell us something different about how a scientific community is responding to a claim.

A large neutral response can indicate several things. Scientists may judge the evidence genuinely inconclusive. They may hold an intermediate level of confidence. Or they may regard a claim as too speculative to endorse or reject decisively. Likewise, movement from strong disagreement towards ordinary disagreement may signal a softening of attitudes even when overall disagreement remains high. Treating scientific opinion as simply “for” or “against” risks flattening these important distinctions.

Beyond extraterrestrial life

The broader lesson extends well beyond extraterrestrial life. In areas such as climate science, pandemics, artificial intelligence or medical research, public conversations frequently invoke scientific consensus.

Sometimes strong agreement genuinely exists. Sometimes it does not. But we often lack systematic ways of measuring what scientists actually think, especially where evidence is emerging or uncertainty remains substantial. Instead, discussions rely heavily on selective quotation, vocal individuals or assumptions about community views.

Efforts to do this more systematically are beginning to emerge. At Durham University, our research group, C-Scope (the Centre for Scientific Community Opinion Polling and Evaluation), studies how expert opinion is distributed and how it changes over time. We are not trying to replace evidence with polling, nor to treat majority opinion as truth. Our aim is to better understand how scientific communities respond to uncertainty.

Scientific knowledge advances through uncertainty, disagreement and gradual revision. If public discussion, and perhaps political will, increasingly turns on claims about what scientists think, we should make more effort to find out.

Peter Vickers 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.