Community-driven efforts to protect the pirarucu, one of the world’s largest freshwater fish, are delivering far-reaching conservation gains across Brazil’s western Amazon, but the financial burden of this success is being borne almost entirely by local families, a new study has found.
Research published in *Nature Sustainability* shows that by guarding a network of oxbow lakes along the Juruá River, Indigenous and riverine communities are indirectly conserving floodplains and upland forests on a scale far larger than the areas they directly monitor making it the largest community-based conservation initiative documented in the Brazilian Amazon.
Lake patrols protect forests far beyond their borders
Along the winding Juruá River, fishing families take turns guarding narrow lake entrances from small wooden watchtowers, preventing illegal harvesting of pirarucu (Arapaima gigas), a species vital to local food security and livelihoods. While patrols focus on specific lakes, their impact extends much further.
The study examined conservation efforts across 14 rural communities monitoring 96 oxbow lakes. Researchers found that by restricting access to these lakes, communities effectively protect floodplain areas nearly eight times larger than the lakes themselves. When seasonal fish movements into flooded forests were accounted for, the protected area expanded to 36 times the lake size. Indirect protection of nearby upland forests pushed the total conservation footprint to an average of 86 times the area under direct surveillance.
“These findings show that community protection of aquatic ecosystems creates ecological benefits that spill over into terrestrial landscapes,” said co-author Ana Carla Rodrigues, highlighting how local stewardship strengthens connectivity between rivers, floodplains and forests.
keystone fish anchors ecosystem recovery
The pirarucu plays a central ecological role in Amazonian floodplains. As a massive apex predator that can grow up to three metres long, it shapes aquatic food webs and supports biodiversity across connected habitats.
Community-led management along the Juruá has helped bring the species back from near collapse, with populations increasing by more than 400 per cent since the early 2000s. Traditional knowledge has been critical to this recovery. Because pirarucu surface to breathe, fishers rely on ancestral counting techniques that closely track fish behaviour and seasonal rhythms.
Controlled harvesting has also created a steady source of income, with a share of revenues reinvested into community needs such as healthcare access and infrastructure. Researchers say this has reinforced collective responsibility for conservation.
Conservation gains come at a steep economic price
Despite its success, the study highlights a major inequity: communities shoulder the full financial cost of protecting these ecosystems. Surveillance alone accounts for nearly one-third of fisheries management expenses and reduces household income by around 21 per cent. Guards patrol without pay, covering food and equipment costs themselves while risking confrontations with poachers.
Researchers estimate that protecting the lakes costs about $0.95 per hectare per year a significant burden for low-income communities. If labour were formally compensated, costs would rise to more than $5 per hectare annually.
The authors argue that payments for environmental services (PES) could help address this imbalance by directly compensating communities for the ecological benefits they provide. Discussions around pilot PES schemes took place at COP30 in Belém in 2025, with proposals to channel funds through local associations under transparent and accountable frameworks.
Shifting conservation from exclusion to equity
Beyond ecological gains, community-based fisheries management has begun reshaping social dynamics. Women, historically overlooked in conservation roles, are increasingly involved in fish counting, surveillance and leadership within local associations. Younger residents are also participating, helping counter migration to cities.
“For a long time, conservation science excluded local people,” said João Campos-Silva, a study co-author. “This research shows that there is no future for the Amazon without communities at the centre and that they must be recognised and rewarded for the services they provide.”
The study concludes that while community conservation is highly effective, its long-term sustainability depends on financial mechanisms that ensure dignity, equity and shared responsibility for protecting one of the planet’s most important ecosystems.