Planetary health requires a better understanding of the reciprocal negative effects and mutual benefits between the environment, environmental change and degradation, and human health and well-being. This applies to all geographic and temporal scales and to all levels of decision-making. Local communities in low- and middle-income countries, living in transboundary areas, suffer the negative effects of environmental change and degradation on their health and well-being, and are often in a vulnerable situation due to their reduced access to health resources and greater distance from the main decision-making centers in their respective countries. If these populations are provided with the necessary tools to interpret and exploit complex, multi-thematic information about their environment, they will be able to more easily identify and understand the impacts of the environment on their well-being and develop locally acceptable and sustainable adaptation and mitigation solutions. However, knowledge about the knock-on effects of the environment on the lifestyle, health, and well-being of local communities must be clearly established and shared. In general, it is observed that these communities have limited access to information and do not necessarily possess the scientific skills (literacy) essential to make the most of it. In this context, the MOSAIC project aims to design and implement open, multimodal, and replicable information ecosystems to support cross-border communities in expanding their understanding of the environment in which they live and its relationship to their well-being, with the goal of collaborating to create a health-promoting environment that influences public debate and the design of healthy public policies. This project is based on the principles of open science, in particular: i) the joint mobilization of participatory science, open access principles, open access data infrastructures, as well as ecological and health sciences, ii) the co-production and use of data and knowledge by all project stakeholders, with shared values. The MOSAI project will consider two regions particularly affected by climate change, extreme weather events, and vegetation cover degradation: East Africa and the Amazon. More specifically, it will focus on three cross-border study areas: the triple border between Brazil, Colombia, and Peru; the border between French Guiana and Brazil; and the border between Kenya and Tanzania. These study sites will enable testing of the reproducibility and reusability of methods, data, and tools, and will facilitate interdisciplinarity and transdisciplinarity through the joint mobilization of a multidisciplinary team. The research will be divided into six work packages (WPs), each with specific tasks that can be carried out simultaneously.