The Natural History Museum (NHM) study found that biodiversity within protected areas declined by 2.1 percentage points between 2000 and 2020, slightly more than the 1.9-point decline in similar but unprotected regions. The study used the Biodiversity Intactness Index to gauge ecosystem health under human pressures, revealing that many protected areas, often aimed at conserving specific species rather than entire ecosystems, fail to maintain overall biodiversity.

According to Dr. Gareth Thomas, NHM's head of research innovation, while the 30x30 target is essential, protection alone isn't enough. "Most people would assume protected areas would at least conserve nature, but this research shows otherwise," he said. Thomas stressed that protections often fall short, as in the Republic of Congo's Conkouati-Douli National Park, where over 65% is under oil and gas concessions. Across regions such as the Amazon and Southeast Asia, hundreds of thousands of square kilometers of protected areas and Indigenous territories overlap with similar threats.

Other factors include climate impacts—like wildfires, droughts, and storms—which disregard protected boundaries. Research from the University of New South Wales highlighted that, in biodiversity-rich countries like Indonesia and Madagascar, corruption, political instability, and limited resources hamper conservation laws' enforcement.

Emma Woods, NHM's policy director, urged a shift beyond just increasing protected areas to 30x30, emphasizing that quality and enforcement matter. Exeter University's biodiversity economics professor, Ben Groom, praised the goal's widespread support but cautioned against shallow policy focused only on meeting targets.