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Some butterflies decline while others flourish in UK's warmer weather

A pearl-bordered Fritillary butterfly Getty Images

The pearl-bordered Fritillary butterfly has declined by 70%

When spring and summer come around, butterflies are a colourful common sight.

But while some species are flourishing, the numbers of other species are rapidly declining according to data from the UK Butterfly Monitoring Scheme (UKBMS).

59 native species were monitored. 33 have declined while 25 have improved.

Experts say one of the reasons is because the UK has seen sunnier and warmer weather over the past 50 years which has partly been caused by climate change.

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(L-R) A pearl-borded Fritilliary butterfly. A photo from the side with its wings closed. It is orange with darker orange, brown and white patterns; A common small tortoiseshell butterfly. It is laying with its wings out on a leaf has a brown furry body, mainly organge wings with blue and brown pattern aroiund the endge of its wings and black and white stripes at the top of its wings; a white-letter hairstreak is sat on a flower with its wings closed. It is mainly brown with some orange on the bottom tip of its wings and two thin white striped down its wings. Butterfly Conservation/Getty Images

(L-R) The pearl-bordered fritillary butterfly feeds on violets and has declined by 70% since UKBMS began.

The common small tortoiseshell has also declined by 87%

The white-letter hairstreak has fallen by 80%

The UKBMS has been monitoring the UK's butterfly species for 50 years.

From this, they're able to see how species populations are reacting to habitat loss, pollution and climate change.

Many species are continually declining, particularly those which live in a particular habitat like woodland clearings or chalk grasslands.

Habitat loss means they struggle to find a new place to live and breed in.

But even some of the more adaptable butterflies are struggling like the common small tortoiseshell which has seen an 87% decline.

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Meanwhile butterflies that can live in a wide range of environments are generally coping better.

Experts say the warmer weather due to climate change has a part to play in this.

Butterflies are cold blooded so are better suited to warmer conditions.

Butterfly expert Professor Jane Hill from the University of York said:

"Most British butterflies reach their northern range limit in the UK, so they have opportunities to expand further north into northern England and Scotland."

Common small tortoiseshell is laying with its wings out on a white flowered plant. It has a brown furry body, mainly orange wings with blue and brown pattern around the edge of its wings and black and yellow stripes at the top of its wingsGetty Images

While warmer weather is better for butterflies, the numbers of butterflies recorded in the UK haven't necessarily reflected this.

For example, the UK had its sunniest year on record in 2025, which butterflies would usually really like, but it was only an average year for sightings.

Conservationists are focusing on protecting and increasing the habitats butterflies need to survive.