Marengo, J. A., Espinoza, J.C., Esquivel Muelbert, A., Anderson, E., Armenteras, D., Bilbao, B., Fleischmann, A. S., Guayasamin, J. M., Lapola, D., Libonati, R., Mercado, L., Ribas, C. C., Sierra, J. P., Vilanova, E., Vale Wapichana, S. (2025) Chapter 1: Amazon connections from regional to global: impacts and vulnerabilities. In Amazon Assessment Report 2025 (eds Peña-Claros, M., Nobre, C. et al.) Science Panel for the Amazon, UNSDSN, New York, US. Available at: www.sp-amazon.org/ publications. DOI:10.55161/LSKV6581`

The Amazon is a complex system of vibrant and interconnected ecosystems and human cultures, housing the largest species diversity on Earth. The many connections across the Amazon, linking the biosphere and atmosphere, the hydrology and biodiversity, are fundamental for global biodiversity, the stability of the global climate, and this, the well-being of humanity. The Amazon forest recycles between 30–50 per cent of its rainfall and exports moisture that shapes precipitation patterns across South America via “aerial rivers”. The increases in deforestation, extreme wildfires, and the frequency of compound drought-heat events raise concerns around the possibility that large portions of the Amazon forest will experience significant degradation. These changes exacerbate the climate crisis at local, regional, and global scales that in turn compromise Amazonian connectivity and increase worldwide human vulnerability. The Amazon’s climate both influences and is influenced by large-scale atmospheric phenomena that link weather and climate across vast distances, known as teleconnections. The Amazon forest sustains other biomes and economic activities for regions such as the Pantanal wetlands, the La Plata River Basin, and the Orinoco River Basin (N-S and S-N connectivity). The Andean-Amazon hydroclimatic system (E-W and W-E connectivity) conforms to a two-way interacting system, whereby the Amazon exports water vapor to the Andes through aerial rivers, and the Andes export river flows, sediments, and nutrients to the low-lying Amazon. Decreased river connectivity during extreme droughts isolates local communities and compromises their food and water security; below average floods can also impair floodplain-dependent activities, such as fishing. Without actions that prevent further degradation, Amazon forests are approaching critical environmental thresholds that threaten its ecological functions, biodiversity, and cultural connections.

1. Introduction

The Amazon is a fundamental part of the Earth’s cycles. This vibrant system of interconnected ecosystems and human cultures links the biosphere and atmosphere in connections essential to the balance of energy, water, and carbon and to the life of humanity on Planet Earth. The Amazon forest contributes around 30 to 50 per cent of the rain that falls in the region through the process of evapotranspiration1. The Amazon River accounts for approximately 17–20 per cent of the world’s river discharge to the oceans2. This region contains more than 10 per cent of Earth’s terrestrial biodiversity and stores an amount of carbon equivalent to 15–20 years of global CO2 emissions (150–200 Gt C)3,4. The Amazon is home to more than 48 million people, including 2.2 million Indigenous Peoples of more than 400 ethnicities, as well as Afrodescendent and local traditional communities5. This beautifully interconnected system, the life it supports, and the functions it plays are under threat from climate change, forest loss and degradation (e.g., from illegal timber extraction, fire, hunting), illegal land-grabbing and illegal mining (see Chapter 2). The disruption of these connectivities will cause irreversible harm to the global climate, biodiversity, and human well-being6.

With the recent increase in deforestation, wildfires, droughts, heatwaves, and regional warming, concerns are growing about the potential collapse of the Amazon forest ecosystem. The Amazon River has experienced four “once-in-a-century” droughts in 2005, 2010, 2015–2016, and 2023–2024, and two “once-in-a-century” floods in 2012 and 2021, each progressively more severe than the previous one7,8. In turn, the damage to the Amazon forest further exacerbates the climate crisis at local, regional, and global scales, as well as at various levels, such as atmospheric, climatic, hydrological, and ecosystems1,2.

The Amazon is one of the most diverse regions on Earth. This enormous biodiversity is unique in having an exceptionally high level of regional and local endemism, meaning that many species—particularly among plants, birds, amphibians, and insects—are found nowhere else. There are between 6,000 and 16,000 tree species across the Amazon, most of them are still unknown. Amazonian biodiversity is heterogeneously distributed across the region, with many species found only in restricted areas or in specific environments9,10. Hence, the loss of connectivity between rivers, forests, and savannas can lead to local extinctions or compromise genetic flow and ecosystem resilience11. The continuity of forest cover across vast areas enables the movement of terrestrial fauna, including large mammals, birds, and seed-dispersing species. This movement is essential for maintaining forest regeneration and ecological balance. Free- flowing rivers are critical for the seasonal movement and genetic connectivity of biota restricted to floodplain and riverine habitats12. The ecological connectivity of the Amazon—linking forests, rivers, and wetlands across a mosaic of ecosystems— supports critical ecological processes and functions such as evapotranspiration and photosynthesis. The series of continental- scale corridors are essential to preserve the vast biodiversity of South America under climatic and anthropogenic pressures. Increasing connectivity and preserving these corridors is crucial for climate adaptation strategies13 and for maintaining fundamental ecological processes that enable forests to pump water from vegetation into the atmosphere through evapotranspiration. In this chapter, we synthesize the current understanding of the significance and threats to the physical, biological, and human connections, ranging from regional to global scales, providing a baseline for action to conserve the Amazon. Connectivity among the various terrestrial, seasonally flooded, and aquatic ecosystems is critical to the Amazon’s ecological integrity.