(CNN) More than half of Europe's endemic trees -- species that are only found in the region -- are at risk of extinction because of diseases, pests and human activities, a conservation organization based in Geneva has said.

The International Union for Conservation of Nature (IUCN) Friday released its findings as part of its newly published European Red List of Trees.

While the European Red List had already assessed 15,000 species, including vertebrates, freshwater molluscs and trees, the latest study focused on the dangers to lesser-known species.

In total, 58% of Europe's endemic trees are at risk of dying out -- as well as more than two-fifths of the continent's 454 native species.

The horse chestnut -- native to Bulgaria, Greece, Albania and the Republic of North Macedonia but widespread elsewhere in Europe -- is among those in danger.

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