Abstract
Irrigated agriculture has grown rapidly over the last 50 years, helping food production keep pace with population growth, but also leading to significant habitat and biodiversity loss globally. Now, in some regions, land degradation and overtaxed water resources mean historical production levels may need to be reduced. We demonstrate how analytically supported planning for habitat restoration in stressed agricultural landscapes can recover biodiversity and create co-benefits during transitions to sustainability. We apply our approach in California’s San Joaquin Valley where groundwater regulations are driving significant land use change. We link agricultural-economic and land use change models to generate plausible landscapes with different cropping patterns, including temporary fallowing and permanent retirement. We find that a large fraction of the reduced cultivation is met through temporary fallowing, but still estimate over 86,000 hectares of permanent retirement. We then apply systematic conservation planning to identify optimized restoration solutions that secure at least 10,000 hectares of high quality habitat for each of five representative endangered species, accounting for spatially varying opportunity costs specific to each plausible future landscape. The analyses identified consolidated areas common to all land use scenarios where restoration could be targeted to enhance habitat by utilizing land likely to be retired anyway, and by shifting some retirement from regions with low habitat value to regions with high habitat value. We also show potential co-benefits of retirement (derived from avoided nitrogen loadings and soil carbon sequestration), though these require careful consideration of additionality. Our approach provides a generalizable means to inform multi-benefit adaptation planning in response to agricultural stressors.
Highlights
Agriculture covers over one third of Earth’s land surface (FAO AQUASTAT, 2018), and while its expansion and intensification have brought many benefits to humanity, the same factors have had profound adverse impacts on biodiversity and ecosystem services (Foley et al, 2005; Cardinale et al, 2012)
The agricultural production and retirement statistics for the business as usual” (BAU) scenario are generated at the coarse regional scale by the Statewide Agricultural Production Model (SWAP) model, with retirement identified by comparing to a “No-Sustainable Groundwater Management Act (SGMA)” scenario modeled in SWAP
Comparing with the current agricultural footprint indicates that much of this fallowing would happen even in the absence of SGMA, due to natural and policy-driven variability in water available for agriculture, but we find SGMA to be responsible for a reduction of annual average cultivated area of ∼160,000 ha (Table SR1)
Summary
Agriculture covers over one third of Earth’s land surface (FAO AQUASTAT, 2018), and while its expansion and intensification have brought many benefits to humanity, the same factors have had profound adverse impacts on biodiversity and ecosystem services (Foley et al, 2005; Cardinale et al, 2012). Even as agricultural land use is expected to continue shifting and expand with human population growth and climate change, many existing cultivated regions are stressed due to water scarcity, soil degradation, and increased climatic extremes (Godfray et al, 2010; Elliott et al, 2014; Gibbs and Salmon, 2015). These stresses will require careful changes in landscape management to sustain agricultural production, and in certain regions, will necessitate retiring some lands from intensive production. Irrigation capabilities will play a key role in adapting to increased climate variability, though reliance on them will need to be considered among many interacting factors and stresses (Howden et al, 2007)
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