Ensuring effective protection and restoration for tropical freshwater ecosystems

Healthy freshwater ecosystems are crucial to life. Despite hosting approximately 10% of all known species and providing vital ecosystem services, from climate regulation to food supplies, they are often neglected by research. Global changes add more pressure to freshwater ecosystems, which are more endangered than terrestrial or marine ones. While the freshwater biodiversity crisis remains hidden beneath the water's surface, one-quarter of freshwater fish are currently threatened with extinction.
Tropical freshwater ecosystems are especially vulnerable as the region experiences some of the world's most intensive agriculture and infrastructure development, alongside additional impacts from climate change. My research centres on the Amazon, the largest and most biodiverse river basin globally, which hosts 40% of the world's remaining free-flowing rivers. Despite its vital importance, deforestation, climate change, and infrastructure development are causing rapid transformations in the Amazon. These terrestrial impacts reach Amazonian rivers via a large network of headwater streams, which constitute the most widespread and extensive freshwater ecosystem in the basin. Recently, ecological restoration has gained traction in the Amazon as a solution to reverse its widespread degradation. However, ensuring that restoration initiatives also benefit and safeguard Amazonian watercourses has largely been overlooked.
Amazonian streams host an outstanding biodiversity and provide irreplaceable ecosystem services to 40 million people, including clean water, leisure and fish. Small streams are thought to be home to half of the basin's fish species. However, streams are the most understudied components of Amazonian and other tropical freshwater ecosystems, with fisheries in larger river channels attracting most research to date. The future of the Amazon River basin relies on the health of its headwater streams. My main goal is to address significant knowledge gaps about tropical freshwater ecosystems and promote biodiversity conservation in the world's largest river basin.
I will achieve this by building on the efforts made during the first phase of my Future Leaders Fellowship and collecting new data to address my long-term research objectives. First, I will conduct the second phase of a pioneering field experiment on stream fragmentation. Road-associated infrastructures, such as culverts, are a major driver of freshwater degradation and biodiversity loss worldwide. Road culverts block and fragment streams, disrupting the movement of water, nutrients, and species. Despite their ubiquity in the Amazon, the effects of road culverts on stream habitats and fauna are poorly understood. I will evaluate stream resilience to fragmentation after experimentally removing culverts and restoring hydrological connectivity. This is the first field manipulative experiment to examine the impacts of road-induced stream fragmentation in the tropics. Second, I will combine the findings obtained during both phases of my FLF to estimate the extent of stream degradation across the Amazon River basin and identify priority areas for restoring the hydrological connectivity of streams. I will use this evidence to integrate freshwater conservation into current environmental policies in Brazil and inform policies that regulate the maintenance and decommissioning of road-associated impoundments. I anticipate making a significant contribution to the science and practice of stream conservation by advancing our understanding in the tropics and linking these findings to urgent policy and management issues in the Brazilian Amazon.