The horse-chestnut, or conker tree, along with just over half of the other species unique and native to Europe risk becoming extinct, a new study suggests.

The decline of the iconic European tree is said to be mainly due to the leaf-miner moth, an invasive species originally from the Balkans that has spread round the continent. Logging, forest fires and tourism are also said to be leading causes.

In its 'Red List' report of threated species, the International Union for Conservation of Nature says that 42 percent of the 454 trees native to Europe could disappear from the continent.

And 58 percent of the trees endemic to Europe – meaning they can only be found there –  are now considered under threatened of extinction.

The report claims that 15 percent, around 66 species of tree, are deemed "critically endangered" meaning they are only a step away from extinction.

The situation has been described as "alarming" by the International Union for Conservation of Nature (ICUN), with pests and disease, urban development, and the introduction of invasive plants by humans said to be fuelling the decline.

"Trees are essential for life on earth," said Craig Hilton-Taylor, who heads the organisation's Red List Unit.

"And European trees in all their diversity are a source of food and shelter for countless animal species such as birds and squirrels and play a key economic role."

He called for better efforts "to ensure their survival," saying the threatened species needed to be integrated into regular conservation planning and land management.

Among the species said to be affected, 170 types of tree and shrub that belong to the Sorbus genus, or rose family, are particularly threatened – including the Crimean Rowan and Mountain-Ash.

The report comes amid a growing sense of urgency to address environment issues, such as fires in the Amazon, and the UN warning that climate change, habitat loss and other factors are pushing one million plant and animal species to the brink of extinction.

While declining numbers of animals such as African elephant or rhinos gain attention from the public and the media, the IUCN says that lesser-known species need more consideration in conservation planning.

Many lesser-known species were evaluated in the latest edition of the Red List report, which says that nearly half of all shrubs and vast numbers of types of mollusc and moss are threatened by extinction.

The IUCN said that many of these species were often overlooked but were crucial to ecosystems, providing air and playing an important role in the food chain.

Luc Bas, head of their Europe Office, said: "The impact of human-led activities is resulting in population declines and a heightened risk of extinction of important species across Europe.”

Speaking about the report, he said it shows "how dire the situation is for many overlooked, undervalues species that form the backbone of Europe's eosystem and contribute to a healthy planet."