Dryland Watershed Restoration With Rock Detention Structures: A Nature-based Solution to Mitigate Drought, Erosion, Flooding, and Atmospheric Carbon

Jennifer Gooden,Richard Pritzlaff

doi:10.3389/fenvs.2021.679189

Abstract

Historic land degradation is an ongoing threat to the Sky Islands of southern Arizona, US, and northern Sonora, Mexico, an area designated as a globally significant biodiversity hotspot. Land degradation has reduced ecosystem services provisioning, released carbon from disturbed soils into the atmosphere, and significantly diminished resilience to climate change. Private land managers in the region have developed methods to reverse degradation and restore biodiversity and ecosystem function. Land managers have used rock detention structures (RDS), technology adapted from traditional Indigenous practices in the region, as a tool for reversing desertification and watershed degradation. The structures were installed primarily for erosion control and water management, but they have had positive impacts on multiple biophysical systems. In this study, we analyze watershed-scale installation of RDS as a nature-based solution for climate change mitigation and adaptation. Case studies include four properties that offer examples of structures that have been in place over a period ranging from 1 to 40 years. We reviewed journal articles and other studies conducted at the four sites, supplemented with interviews, to catalogue the nature-based solutions provided by RDS. This study documents positive impacts on overall stream flow, reduction in peak runoff during inundation events, and increased sedimentation, which increase resilience to drought, erosion, and flooding. Data suggest potential impacts for climate change mitigation, though further research is needed. In addition, results suggest that watershed restoration with RDS offers a host of co-benefits, including an increase in biodiversity and wildlife abundance, an increase in vegetative cover, and increased surface water provisioning over time to support the land-based livelihoods of downstream neighbors. In the discussion, we consider barriers to replication and scalability using the strategy of the UN Decade on Ecosystem Restoration as a guiding framework, discussing issues of awareness, legislation and policy, technical capacity, finance, and gaps in knowledge.

Highlights

Ecosystems of the arid southwestern United States and northern Mexico have suffered extensive land degradation
We reported some information about the cost of constructing RDS, we lack sufficient documentation of the costs of watershed-scale restoration, information that is necessary to assess the financial viability of payments for ecosystem services (PES) programs and carbon market-financed restoration projects
Dryland watershed restoration was not included by Fargione et al (2018) as a natural climate solution for the United States

Summary

Introduction

Ecosystems of the arid southwestern United States and northern Mexico have suffered extensive land degradation. This degradation has been a continuing threat to the Sky Islands of southern Arizona and northern Sonora, an area that is both a biodiversity hotspot and a harbinger of the deleterious effects of climate change (Deyo et al, 2012; Falk, 2013). One of the most visible symptoms of land degradation in the Sky Islands has been the incision of streambeds and the declining health of the riparian areas that depend upon them. In the Sonoran Desert, dry washes occupy less than 5% of land area, but they support 90% of bird life, even though washes may carry water for only a few hours a year (Dimmit 2015)

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