Grand Challenge for the Future of Freshwater Ecosystems

We live on a blue planet and, althoughmuch of the water is in the oceans, it can be argued that there is abundant freshwater to sustain human society: some 93,000 km3 is in lakes and rivers alone and much more is stored in groundwater or as ice1. However, freshwater is not distributed uniformly in space or time across the globe, nor often in relation to patterns of human settlement. To compound this problem, intensive human activities have further diminished available water supplies through overuse and pollution from point and non-point sources. As a consequence, 80% of the world’s population is exposed to high levels of threat to water security (Vorosmarty et al., 2010). In the developed world, massive investments in water infrastructure have beenmade to offset the threat to human water security (Vorosmarty et al., 2010). However, these technical and primarily “end-of-pipe” solutions have come at considerable cost to the natural environment and there has been no similar level of investment to protect aquatic ecosystems. As a result, the threat to freshwater biodiversity remains high in much of the developed and developing world. Declining water quality and quantity, habitat modification, overfishing, and biological invasions pose major threats across the globe (Dudgeon et al., 2006). These human pressures continue to grow with no sign of abating (Vorosmarty et al., 2013) and are likely to dominate the threats to most freshwater ecosystems over the next three decades (Settele et al., 2014). Climate change will compound these problems and is already affecting freshwater ecosystems in regions that until now have been relatively unimpaired by human activity. Rising water temperatures are driving shifts in freshwater species distributions and will worsen water quality problems, especially in systems with high loading of nutrients (Settele et al., 2014). Changes in precipitation will substantially alter ecologically important attributes of flow regimes in many rivers and wetlands (Doll and Bunn, 2014). Many of these environmental changes impact on important goods and services provided by freshwater ecosystems (e.g., clean water, fisheries) and will further compound the challenges for human water security. There is little dispute that we have entered the Anthropocene for freshwater ecosystems. Reference to “water shortages” began to rise in English publications at the start of the last century but declined in prevalence in the 1970’s, associated with an increase in the use of the term “water crisis” (Figure 1). Throughout this period, the term “water demand” has continued to increase in prevalence and “global water crisis” has emerged as a newmoniker for the twenty-first century. Our past approach to water management is unlikely to meet growing human water needs in the face of accelerated change to our freshwater ecosystems, let alone address the consequences of continuing environmental decline. The aim of this “grand challenge” article is to highlight what can be done to address these problems, from global scale governance initiatives to local-scale on-ground actions, aimed at tackling problems at their source. I also wish to explore what more we can do to