In 2009, scientists introduced the planetary boundaries framework, which identified nine critical Earth system processes—chemical pollution, climate change, and freshwater consumption among them—and established a stress limit, or boundary, for each. If a boundary is eclipsed, the Earth system could be irreversibly destabilized. For example, the current boundary for freshwater use is the point at which human water consumption disrupts environmental flow and impedes the global hydrological cycle; recent work has suggested potential additional subboundaries for groundwater, atmospheric water, soil moisture, and frozen water.
Planetary boundaries provide a conceptual scaffolding for understanding how humanity affects Earth’s systems—defining, in effect, humanity’s safe operating space within the environment. The challenge, however, lies in translating global limits into actionable local management. In a new study, Zipper et al. propose an integrated method for understanding and managing water resources across spatial scales.
The authors provide a local-global linkage by combining two water management approaches: the fair shares approach and the local safe operating space approach. The fair shares approach is a top-down strategy that sets a planetary boundary value and allocates water impacts locally. Those allocations could be doled out to political entities like nations or cities, or they could be assigned to individual companies or industrial sectors. In contrast, the local safe operating space approach works from the bottom up to identify the limits beyond which local water resources are disrupted. Under this system, each region could determine a limit on water cycle modification based on local socioenvironmental needs.
By combining the top-down and bottom-up approaches to water management, the authors suggest that their framework takes advantages of strengths of both while limiting each strategy’s drawbacks. By using both methods, the management framework is relevant for the global Earth system as well as for local communities. Furthermore, the strategy can be used to govern within both social (cities, nations, companies, and industries) and physical (watersheds, aquifers, continents) contexts.
In addition to laying out the proposed methodology, the new study includes a case study for its application focused on a Colombian watershed degraded by decades of human activity. Although it has not been field-tested, the researchers say the strategy serves as a useful guide to managing water that considers both local and global constraints. (Earth’s Future, https://doi.org/10.1029/EF001307, 2020)
—Aaron Sidder, Freelance Writer
This story is a part of Covering Climate Now’s week of coverage focused on Climate Solutions, to mark the 50th anniversary of Earth Day. Covering Climate Now is a global journalism collaboration committed to strengthening coverage of the climate story.