Climate change is now threatening 43% of natural World Heritage sites, surpassing all other threats, according to the new IUCN World Heritage Outlook 4 published today. Invasive alien species (IAS) remain the second most prevalent current threat, affecting 30% of all sites. The report also warns of a sharp rise in the risk from wildlife and plant diseases. In 9% of sites there is a high or very high threat posed by pathogens, up from just 2% in 2020.

The IUCN World Heritage Outlook 4 assesses 271 natural and mixed World Heritage sites. Complementing the official monitoring processes under the World Heritage Convention, the World Heritage Outlook offers the most in-depth analyses of threats facing natural World Heritage around the world and their protection and management status. It is based on the knowledge of hundreds of experts, site managers and partners and presents the main results for 2025, but also some longer-term trends based on the four data sets now available.