Measuring the natural capital of Amazonian forests: A case study of the National Forest of Carajás, Brazil

• Using ecosystem functions and ecosystem services metrics provided a deeper comprehension of natural capital. • Amazon biodiversity and the benefits provided by it to human welfare are clearly linked to natural capital. • Understanding the value of forest can improve the effectiveness of conservation policy and decision-making. We propose an innovative approach that links nature and people to assess the natural capital of tropical forests in the Amazon. Our study location is a protected area inside Eastern Amazon forest, where we defined 14 sampling points and analyzed ten components, which encompass the maintenance of standing forests (nature to itself) and the provision of ecosystem services (nature to people). Five components were used to assess ecosystem functions and five components were used to assess ecosystem services. As for ecosystem functions, we registered 467 species of animals (122 bees, 53 butterflies, 292 birds) and 418 plant species, and a mean interaction diversity of 2.8 (from 480 bee-plant interactions). Based on functional traits, we found that at least 83 % of species must be preserved to guarantee resilience, and that functional diversity relies on 60 % of non-replaceable species. Eleven per cent of birds and 9 % of plants are endangered. As for ecosystem services, carbon storage in soil and vegetation is 41.6 and 173 MgC/ha (on average), respectively. One to four uses by Amazonian traditional communities were reported on 42 % of plants. In the vicinities of the protected area, we found that 66 % of crops (13 from 20 crop species) depend on pollinating bees, and the value of annual crop pollination service is US$4.5Mi. Regarding water protection and local climate regulation, data modelling has shown that the presence of protected forests leads to a 21 % increase in evapotranspiration and a decrease in temperature of 0.4 °C. Our framework showed a clear link between the megadiversity found in Amazonian tropical forest and the robust benefits provided to human welfare, highlighting forest conservation as a key element for sustainable development. Advances in understanding the value of forests stimulate significant new opportunities to improve the effectiveness and efficiency of forest conservation and management policies and decision-making.