An international study coordinated by the University of Barcelona and published in the journal Oryx revealed that, between 1940 and 2020, the average body mass of birds in indigenous territories and local communities in Africa, Latin America, and Asia decreased by 72%. The research, which integrated scientific knowledge and local ecological memory, shows how large birds were replaced by small species, with far-reaching ecological and cultural consequences.
Data and Methodology
- In the 1940s, the average body mass of birds exceeded 1,500 grams.
- By 2020, the figure barely reached 535 grams.
- The study was based on 7,000 records of 283 species, collected through surveys of 1,434 adults from ten communities in Bolivia, Chile, Mexico, Brazil, China, Ghana, Kenya, Madagascar, Mongolia, and Senegal.
- Residents were asked to identify the most common birds from their childhood and compare them with current ones, reconstructing numerical trends and local experiences.
Regional Patterns
The phenomenon was statistically significant in territories such as:
- Tsimane (Bolivia).
- Timucuy (Mexico).
- Vavatenina (Madagascar).
- Ordos Desert (China).
In contrast, no significant variations were recorded in Lonquimay (Chile) and Bulgan soum (Mongolia).
Identified Causes
Communities pointed out factors such as:
- Hunting pressure: intensive hunting of wild species.
- Habitat loss due to agricultural expansion and infrastructure.
- Extensive livestock farming and power lines, affecting the survival of large birds.
Local testimonies illustrate the magnitude of the change:
- An elder Daasanach in Kenya: “All the large birds are gone now”.
- A resident of the Bolivian Amazon: “Many animals have disappeared because loggers hunt more”.
- A shepherd in Mongolia: “Now we have too much livestock, there are fewer nests, and large birds die on the power lines”.
Ecological and Cultural Consequences
The disappearance of large birds implies the loss of key functions:
- Seed dispersal.
- Pest control.
- Forest regeneration.
Moreover, it affects the diversity and balance of entire ecosystems, threatening biodiversity and environmental health.
Culturally, large birds have occupied a central place in the identity and collective memory of indigenous peoples. Their disappearance deteriorates ceremonial practices, stories, and intergenerational connections with nature.
Value of Indigenous Knowledge
Researcher Álvaro Fernández-Llamazares (ICTA-UAB) emphasized that the global bird extinction crisis is also reflected in the memory of communities with strong territorial roots. The study’s authors advocate for an equitable dialogue between science and traditional knowledge, urging conservation policies to actively incorporate indigenous experience.
The reduction of the average body mass of birds in indigenous territories indicates a double risk: ecological degradation and the erosion of cultural memory. The disappearance of large birds signifies the loss of essential environmental functions and cultural connections that have given meaning to the history and future of many communities.
