Integrating the Water Planetary Boundary With Water Management From Local to Global Scales

Abstract

The planetary boundaries framework defines the “safe operating space for humanity” represented by nine global processes that can destabilize the Earth System if perturbed. The water planetary boundary attempts to provide a global limit to anthropogenic water cycle modifications, but it has been challenging to translate and apply it to the regional and local scales at which water problems and management typically occur. We develop a cross‐scale approach by which the water planetary boundary could guide sustainable water management and governance at subglobal contexts defined by physical features (e.g., watershed or aquifer), political borders (e.g., city, nation, or group of nations), or commercial entities (e.g., corporation, trade group, or financial institution). The application of the water planetary boundary at these subglobal contexts occurs via two approaches: (i) calculating fair shares, in which local water cycle modifications are compared to that context's allocation of the global safe operating space, taking into account biophysical, socioeconomic, and ethical considerations; and (ii) defining a local safe operating space, in which interactions between water stores and Earth System components are used to define local boundaries required for sustaining the local water system in stable conditions, which we demonstrate with a case study of the Cienaga Grande de Santa Marta wetlands in Colombia. By harmonizing these two approaches, the water planetary boundary can ensure that water cycle modifications remain within both local and global boundaries and complement existing water management and governance approaches.

The water planetary boundary: interrogation and revision

“…The planetary boundary framework could complement existing tools for water-resource management by offering a unique approach for assessing water-cycle modifications as part of the wider human impact on the Earth System. 46 Thus, despite the well-founded criticism of the current freshwater use planetary boundary, we argue that the framework of a planetary boundary for water is useful and worth serious intellectual attention.…”

“…For the water planetary boundary to have practical value for water management, it needs to be operational and informative at the regional and local scales at which water is managed, such as basins or individual nations, 14,62,63 areas governed by multinational organizations such as the European Union, 13 or a company's supply chain. 10 Here, we only briefly introduce how the water planetary boundary may be integrated with existing water management and governance occurring at regional and local scales, which is the main focus of the companion paper by Zipper et al 46 Previous attempts at downscaling the planetary boundaries have largely focused on calculating a country's ''fair share'' of the global safe operating space ( Figure 2). H€ ayh€ a et al 12 identify three key dimensions to consider: (1) biophysical processes, which define the relevant scale at which the planetary boundary can be addressed-water-cycle processes are spatially heterogeneous so the global impacts of a change depend on site-specific factors; (2) socioeconomic considerations, which define the environmental impact a country has both inside and outside of its borders 64 -global accounting methods such as the water footprint 38 are tools for addressing this dimension, although regional opportunity costs need to be considered; 65 and (3) ethical considerations, which address differences among countries in environmental impacts caused by exceeding the control variable as well as their ability to respond to environmental challenges-equity-based allocation frameworks could address this dimension.…”

Ecological resource availability: a method to estimate resource budgets for a sustainable economy

“…For the moment, the ERA method is designed to calculate global budgets only. However, environmental circumstances on a regional level may be different compared to the global average (e.g., biodiversity – Chaudhary et al , 2016; land use – Gerten et al , 2020; water scarcity –Gleeson et al , 2020; Pfister & Bayer, 2014; Zipper et al , 2020) and therefore require regionalization. In principle, integrating regionalized boundaries is possible in the ERA method; however, this requires both the setting of regional boundaries as well as regionalized impact assessment.…”

Illuminating water cycle modifications and Earth system resilience in the Anthropocene

“…We suggest that the water planetary boundary provides an effective framework that can integrate with and complement existing water management approaches at subglobal scales such as watersheds, aquifers, or nations. Subglobal use of the water planetary boundary is the focus of separate work (Zipper et al, 2020), and we only briefly introduce it here to highlight the potential utility of the water planetary boundary. Previous work with the planetary boundary framework at subglobal scales has either attempted to 10.1029/2019WR024957 Water Resources Research calculate a "fair share" of the planetary boundary value allocated to a subglobal domain, for example, a nation (Häyhä et al, 2018) or use the control-response variable relationship foundational to the planetary boundary framework to develop local boundaries in a conceptually consistent manner (e.g., Dearing et al, 2014).…”