World Heritage natural sites cover less than 1% of the planet’s surface, yet they host more than 20% of all species on Earth, including over 20,000 species threatened with extinction.
Endorsed by UNESCO, the United Nations organization dedicated to Science, Education and Culture, for their natural value and their relevance to nature conservation, there are now more than 270 natural sites on the World Heritage list.
However, a new assessment points to worrying trends in the state of these sites. According to the International Union for Conservation of Nature (IUCN), partner of UNESCO’s World Heritage Committee in the Nature sector, 43% of the 271 natural sites are threatened by climate change more than by any other factor. This reveals an increase from 33% in 2020.
Invasive alien species emerge as the second largest threat, affecting 30% of sites, and third are diseases, classified as a high or very high threat to 9% of sites, compared with 2% recorded in 2020.
The report “IUCN World Heritage Outlook 4” is the fourth in a series of comprehensive analyses conducted since 2014 on natural sites listed as World Heritage, and it also shows that, in the last 10 years, the proportion of sites with a positive conservation outlook has fallen to 57% in 2025, down from 62% in 2020.
“Protecting World Heritage is not only safeguarding iconic places, it is protecting the very foundations of life, culture and the identity of people around the world,” Grethel Aguilar, Director-General of the IUCN, warns in a statement.
Recalling that these are “some of the world’s most notable sites,” which host “extraordinary biodiversity and geodiversity” and are vital to many human communities, the official laments that the new report “shows that threats are growing and stronger efforts are needed.”
Experts warn that the threats faced by World Heritage natural sites are interconnected. Changes in temperature and precipitation patterns create fertile ground for the proliferation of invasive alien species, which, in turn, can alter environmental conditions and open space for the emergence of pathogens.
“Predicting and preventing these cascading impacts is crucial, not only for ecosystems, but also for human health,” warns IUCN, which considers that urgent investment is needed to strengthen the management of World Heritage natural sites.
This is because, according to the latest analysis, only half of the evaluated sites have effective protection and management measures. Moreover, it is estimated that 15% of natural sites are underfunded, putting their conservation at risk.
Yet not all news is bad, since 13 natural sites have improved their conservation status compared with the 2020 analysis, mainly thanks to strengthened anti-poaching measures, the establishment of local partnerships and the stabilization of important populations of wild animals.
“Ensuring the resilience of World Heritage natural sites requires long-term commitment at all levels, from local communities to international partners, supported by adequate funding,” says Tim Badman, head of the World Heritage Programme at IUCN.
