Who holds Brazil’s biodiversity? The pivotal role of private landholders

The urgency of tackling the biodiversity crisis across the tropics is clear, yet governance structures such as land tenure can act as barriers or enablers for conservation. Here, we focus on Brazil, a megadiverse country that has made major efforts to link deforestation to individual properties through self-reported environmental registries. Yet, how these efforts support biodiversity explicitly, remains unclear. We paired up-to-date, parcel-level land tenure data with newly developed biodiversity models to assess patterns of species richness and endemism across tenure categories. Protected areas and indigenous lands hold higher biodiversity than other categories (Cohen’s d > 0.8), whereas private lands & claims have lower biodiversity on average (Cohen’s d < 0) – although biodiversity was higher when these properties potentially overlap with protected or undesignated lands. We further linked these tenure patterns to compliance-related biodiversity risks and opportunities. The Pantanal, Pampas, and Mata-Atlântica held some of the areas at greatest risk of biodiversity loss from legal deforestation, whereas restoration potential was highest along the Amazon-Cerrado border. Effective conservation requires identifying where biodiversity is most vulnerable and which actors matter most. Explicitly integrating land tenure and regulatory compliance into existing policy frameworks is a first step towards more effective and lasting biodiversity conservation.