Understanding and conserving tropical freshwater ecosystems

A healthy water environment is essential to life. Freshwater ecosystems occupy less than 1% of the Earth's surface, make up only 0.01% of all water, yet host ca. 10% of all known species. They also deliver vital ecosystem services, such as climate regulation and the provision of food, fuel, fibre, and water resources. Besides sustaining a disproportionately high share of global biodiversity, freshwater ecosystems are far more imperilled than terrestrial or marine realms nonetheless remain largely overlooked. This is critical in tropical regions, which are under intensive pressure from land use change, one of the main drivers of global biodiversity loss. In the Amazon, the world's largest and most biodiverse river basin, knowledge on the impacts of anthropogenic activities is largely insufficient.

Spreading across nine South American countries, the Amazon is of local and global relevance for the provisioning of myriad ecosystem services that are vital for human well-being. For instance, it is responsible for rainfall generation across South America, global climate regulation, and for 1/5 of the world's freshwater that reaches the oceans. However, much of the Amazon region is now severely threatened - it holds much of the land that could be available for agricultural expansion, which is being facilitated by new strains of crops, climatic change, and infrastructure development such as new and improved roads. As Brazil holds more than 60% of the Amazon, representing 50% of its territory, it has a large responsibility in its management and conservation.

One of the most poorly studied elements of the Amazonian freshwater ecosystems is how stream biodiversity is affected by human activities in agriculture landscapes. Small streams are the most extensive and widespread freshwater ecosystem in the basin, connect terrestrial and aquatic systems, host an outstanding biodiversity, support local livelihoods, accumulate multiple impacts that occur in their catchments, and have cascading effects on larger rivers. Therefore, the future of the Amazon river basin is dependent on the integrity of headwater streams. The main objective of my proposal is to further our understanding of the consequences of human impacts on tropical headwater streams, propose solutions to promote their conservation, and influence conservation and land use policy and practice in the Amazon.

I will achieve this in four integrated work packages (WP). WP1 includes collecting multispecies (fish and aquatic invertebrates) data from multiple streams in the Brazilian Amazon, building on a large-scale survey I led in 2010 that resulted in important publications (e.g. Science, Journal of Applied Ecology). This repeated assessment will be the first comprehensive evaluation of temporal changes in tropical stream biodiversity in agriculture landscapes. In WP2, I will explore the potential of cutting-edge approaches such as environmental DNA (eDNA) and the quantification of pesticides as valuable tools to advancing our understanding of human pressures in tropical streams. In WP3 I will develop an ambitious and pioneering field experiment on stream fragmentation to better understand the impacts of roads (i.e. culverts and associated infrastructure), one of the most neglected drivers of stream degradation. This will be the first field manipulative experiment to measure the impacts of stream fragmentation by roads in the tropics. In WP4, I will promote transformational change in the Amazon by integrating the information from previous WPs to estimate the extent of stream degradation across the Amazon River basin, develop mechanisms to promote sustainable stream management, and inform policy. I expect to substantially contribute to the science and practice of stream conservation by bringing about a step-change in our understanding in the tropics and linking these findings to urgent policy and management challenges in the Brazilian Amazon.