The International Union for Conservation of Nature (IUCN) World Heritage Outlook 4, the most comprehensive assessment of all natural World Heritage sites globally, and for the first time reveals trends in the conservation prospects of these sites over a ten-year period.
In the last decade, the proportion of sites with a positive conservation outlook has fallen to 57% in 2025, down from 62% in 2020. Sites recognised for their biodiversity values are disproportionately affected.
“Protecting World Heritage is not just about safeguarding iconic places – it is about protecting the very foundations of life, culture, and identity for people everywhere,” said Dr Grethel Aguilar, IUCN Director General.
“The new IUCN World Heritage Outlook shows that threats are rising and stronger efforts are needed. We must come together with more committed action on the ground and greater investment to ensure these irreplaceable treasures endure – for nature, for people, and for the generations yet to come.” He explained
Climate change is the largest current threat to natural World Heritage globally and is now assessed as highly threatening in 43% of sites (117 of the 271), compared to 33% in 2020.
Invasive alien species (IAS) remain the second most prevalent current threat, whilst a surge in wildlife and plant diseases is now affecting nine percent of sites (23 out of 271 sites assessed), up from just two percent (five out of the 252 sites assessed) in 2020.
Diseases such as Ebola virus in primates (Virunga National Park, DRC), white-nose syndrome in bats (Mammoth Cave, USA), chytridiomycosis in amphibians (Tasmanian Wilderness, Australia), avian influenza (Península Valdés, Argentina) and top-dying disease in Sundarbans mangroves (Bangladesh) are impacting ecosystems and threatening keystone species.
Threats from invasive species and diseases are often interconnected and intensified by climate change. Shifting temperatures and precipitation can enable invasives to spread faster and further and can alter the conditions for pathogens. Unsustainable tourism, the third most widespread current threat, can also support their spread. Predicting and preventing these cascading impacts is critical, not only for ecosystems, but also for human health.
Signs of resilience, where management is effective
Effective management is essential to address the growing threats to natural World Heritage sites. However, the report finds that only half (50%) of all assessed sites have effective protection and management. The findings also reveal that one in seven sites (15%) are highly at risk from a lack of sustainable financing, compromising the resilience and prospects of the world’s most iconic places. The report urges governments, donors and international partners to step up collaboration and financing.
Against these trends, thirteen sites improved their conservation outlook between 2020 and 2025—proof that targeted investment and local engagement work. Four sites in West and Central Africa (Dja Faunal Reserve (Cameroon), Salonga and Garamba National Parks (DRC), and Niokolo-Koba National Park (Senegal)), moved from critical to significant concern thanks to strengthened anti-poaching efforts, local partnerships, and the stabilisation of key animal populations.
“The IUCN World Heritage Outlook 4 shows both the scale of the challenges and the power of effective management. Ensuring the resilience of natural World Heritage requires long-term commitment at all levels, from local communities to international partners, backed by adequate finance”, said Tim Badman, IUCN Director for World Heritage.
“The picture we see after a decade shows a new approach is needed to turn the tide for World Heritage and expand the small number of successes to the large number of sites in need.” He added