Future of Freshwater Ecosystems in a 1.5°C Warmer World

Abstract

Freshwater ecosystems are highly vulnerable to global warming because 1) their chief drivers, water quality and flow regimes, are highly sensitive to atmospheric warming, and 2) they are already extremely threatened by a wide range of interacting anthropogenic pressures. Even relatively modest global warming of 1.5°C poses a considerable threat to freshwater ecosystems and the many critical services these provide to people. Shifts in the composition and function of freshwater ecosystems are widely anticipated with adverse consequences for ecosystem services, including those underpinning water and food security. While the extent and severity of effects is likely to be significantly reduced if global warming is limited to 1.5°C, concerted efforts to implement widely recognised priorities for policy and management are required to mitigate unavoidable impacts and reduce the likelihood of perverse outcomes of climate mitigation and adaptation efforts in other sectors—all of which rely on fresh water supply. Freshwater ecosystems and their services, including provision of fresh water, must therefore be considered first and foremost when developing and implementing any climate action.

An analysis of threats to endangered animal taxa in California's freshwater systems

“…All Mediterranean‐climate regions have experienced extensive habitat loss and land use change; the introduction of invasive species to freshwater systems; water pollution from agricultural or urban development; and high levels of associated water extraction, regulation and flow modification (Cooper et al, 2013; Groves & di Castri, 1991; Marr et al, 2013; Underwood et al, 2009). These threats are expected to intensify in Mediterranean climates, where precipitation is projected to decline with increased global warming (Capon et al, 2021). Continuing stressors in Mediterranean freshwater systems are also expected to be amplified by continued human development and responses to climate change, including increased surface water and groundwater withdrawals and inter‐basin transfers for agricultural, industrial, environmental and municipal provisioning (Gleick & Cooley, 2021; Gleick & Palaniappan, 2010; Filipe et al, 2012).…”

People need freshwater biodiversity

“…Freshwater biodiversity patterns can signal environmental stress on aquatic ecosystems, their services, and human well‐being (Lynch et al, 2016). Individual species respond, often predictably, to stress arising from eutrophication and pollution, flow modification, habitat degradation, loss of connectivity, non‐indigenous species, over‐exploitation, and climate change (Capon et al, 2021; Dudgeon et al, 2006; Tickner et al, 2020; Vörösmarty et al, 2010). Freshwater assemblages (e.g., phytobenthos, plants, invertebrates, fish, and even less visible ones like fungi or microbes) integrate individual, multiple, and cumulative effects of environmental stress throughout their catchments (Craig et al, 2017).…”

Editorial: Linking nitrogen cycling transformations to microbial diversity in freshwater ecosystems

“…Wet deposition of Nr, increased anthropogenic N inputs into natural environments, and accelerated climate warming are expected to cause major challenges for N-cycling transformations in freshwater ecosystems in the future (Capon et al, 2021 ). Although the importance of microbial activity to ecosystem function in aquatic ecosystems has been explored, the identification of abiotic and biotic factors driving changes in N-cycling, N-transformation rates, and N-cycling communities in freshwater ecosystems deserves more attention.…”

“…Increases in the availability of reactive nitrogen (Nr) in the environment due to human activities has altered the cycle of nitrogen (N) over the last century (Galloway and Cowling, 2021 ). Among global ecosystems, freshwater ecosystems (e.g., rivers and lakes) are considered suitable models to examine changes in processes related to the functioning of the N cycle as they are sensitive to nutrient loads across large spatial and temporal scales (Smith, 2003 ; Catalán et al, 2006 ; Capon et al, 2021 ; Medina-Sánchez et al, 2022 ). In mountain freshwater ecosystems, Nr is mainly introduced via wet deposition in the form of nitrate ( ), but human activities can also introduce N into aquatic ecosystems at lower altitudes (Castellano-Hinojosa et al, 2017 , 2022 ; Siles and Margesin, 2017 ).…”