Alongside climate change, the current rapid loss of biodiversity is one of the biggest threats that humanity faces to its own survival (1). With up to a million species at risk of disappearing within decades, human activities are reshaping life on Earth with no precedent in recent history. Biodiversity encompasses all life forms and their variation across the landscape. As one of the most important measures of environmental quality, high biodiversity is often linked with better provision of ecosystem services (2) and also helps assist and promote ecological conservation. Natural parks, national reserves, protected areas, and other measures for preserving the natural world are concerned first and foremost with the protection of biodiversity. But there is a critical and overlooked aspect of this important concept: its link with human cultural and linguistic diversity. Indigenous and traditional cultures and languages are the backbone of biodiversity conservation across the globe. Nonetheless, the rich knowledge found in these languages and cultures is not used in standard monitoring or conservation projects, and they face constant perils from parts of society with economic and political power. ( Top Left ) Evenki reindeer herders, Russia. ( Top Right ) Skolt Saami old growth forests Finland. ( Bottom ) Guarani community and local ecosystem vegetation, Brazil. Recent studies reveal how cultural and language diversities are intrinsically linked to the protection of biological diversity (3⇓⇓–6). Some of the largest countries on Earth, including Canada, Brazil, and Australia, are home to hundreds of languages and cultures, many of which are endangered. But the Indigenous-controlled lands represent only 6% and 13% of the territory in Canada and Brazil, respectively, and 52% in Australia. Still, these indigenous-controlled lands typically contain much higher biological diversity than that found in non–Indigenous-controlled areas, both protected and nonprotected, in the same countries (7). Languages and cultures … [↵][1]1To whom correspondence may be addressed. Email: andre.frainer{at}nina.no. [1]: #xref-corresp-1-1