The global trend toward increasing farmland retirement offers potential opportunities for biodiversity preservation in working landscapes worldwide (Stewart et al., 2019). Here we sought to understand how landscape changes driven by drought-induced fallowing in Kern County, California, US impacted landscape connectivity for the endangered San Joaquin kit fox, an umbrella species in the region (Williams & Fitton, 1997). Our analysis found that habitat connectivity for kit foxes peaked in 2015 with the highest total area of fallowed land, then slightly decreased with fallowing in 2017. Increases in connectivity from 2011 to 2015/2017 were apparent in reductions in average cost-weighted distances and effective resistances between core habitat areas. Additionally, despite least cost path lengths increasing from 2011 to 2015/2017, CWD-to-LCP ratios decreased in those timeframes, indicating that cumulative costs incurred by kit foxes travelling along LCPs decreased. These findings highlight that fallowed parcels may provide important conservation value by increasing landscape connectivity through an intensive agricultural landscape. While our work focused on one species, the San Joaquin kit fox, our findings have implications for other species of interest under the implementation of groundwater management policy.
Effective habitat conservation for the many endangered and endemic species in intensive agricultural regions necessitates corridors between sparse protected areas. Improved connectivity between core habitat areas prevents isolation of individual populations, helping to prevent inbreeding depression and facilitating annual or climate-driven migration and range shifts (Lino et al., 2019; Norén et al., 2016; Runge et al., 2014; Schwartz & Mills, 2005). Connectivity is especially critical for highly mobile species like kit foxes and other small canids, as dispersal within metapopulations across a fragmented landscape is vital to maintaining critical levels of genetic diversity (Hanski et al., 1996; Koopman et al., 2000; Stacey et al., 1997). Small improvements to connectivity in an agricultural landscape could significantly impact recovery for regionally threatened species and facilitate gene flow for many others (Gilbert-Norton et al., 2010; Kelsey et al., 2018; Schloss et al., 2012; Stewart et al., 2019; Williams & Fitton, 1997). Indeed, we saw fallowing double in the region from 45 kha in 2011 to 93 kha in 2015, yielding notable increases in connectivity for the San Joaquin kit fox across multiple metrics. More specifically, we find that the cost-weighted distance, effective resistance, and CWD to LCP ratio all decrease from 2011 to 2015/2017. In combination, these results indicate that kit foxes likely experienced less resistance to travel across western Kern County in 2015 relative to 2011, and also had more options for low resistance travel between core areas. Given the potential increase in permanent or rotational fallowing under the Sustainable Groundwater Management Act and the increasing need for species’ mobility in response to climate changes, such increases in connectivity present a promising conservation opportunity.
Conservation lands are often heavily skewed towards high elevation and poor soil areas (Aycrigg et al., 2013). The opportunity costs of developing permanent reserves or movement corridors in productive agricultural landscapes are high and far-reaching (Bourque et al., 2019) and cultural ties to farming often extend generations (Kelsey et al., 2018), making large-scale static conservation corridors in working landscapes implausible. Thus, strategic conservation in predominantly agricultural landscapes may require opportunistic options for increasing landscape connectivity, such as temporary corridors between established protected areas (Bengtsson et al., 2003). More specifically, temporary reserves that take advantage of ephemeral and semi-permanent land use changes, such as fallowing, may be a more viable solution for increasing conservation through connectivity in areas of high economic and ecological value (Ando & Hannah, 2011; Costello & Polasky, 2004; Moilanen et al., 2014). Besides being potentially more economically and socially viable, these dynamic corridors could also be more adaptive to temporal shifts in environmental conditions or species movement behavior, which is increasingly vital under compounding anthropogenic and climate stressors (D’Aloia et al., 2019; Jennings et al., 2020; Larsen & McComb, 2021; Zeller et al., 2020). Additionally, strategic placement of fallowed lands may have numerous co-benefits, including improved soil quality, increased water storage, increased yields post-fallowing, and reduced economic losses from forced fallowing (Bourque et al., 2019; Kremen & Miles, 2012; Larsen & Noack, 2021; Oliver et al., 2010). Collaboration between agricultural and conservation stakeholders with local Groundwater Sustainability Agencies (GSAs) could help provide spatially contiguous or connected habitat with temporary corridors composed of fallowed land, and help increase species mobility and recovery throughout working landscapes (Lortie et al., 2018; Maresch et al., 2008; Stewart et al., 2019), while also seeking to minimize or offset costs to farmers associated with implementation of SGMA.
Groundwater overdraft in the San Joaquin Valley has resulted in the largest groundwater deficit of any region in California (Hanak et al., 2018). In order to meet SGMA guidelines by 2040 it has been suggested that upwards of 300 kha of agricultural land may need to be fallowed, with a yet to be determined mix of rotational and permanent fallowing (Bryant et al., 2020; Hanak et al., 2018). It is anticipated that many farmers will have options to temporarily fallow some fields, bringing them into production as short-term climate conditions yield sufficient surface water supply. Strategic collaboration as to which fields different farmers choose to temporarily fallow could provide important dynamic habitat connectivity throughout the San Joaquin Valley. Furthermore, temporary corridors paired with increased protection and restoration of quality habitat, via permanently fallowed land, could create dynamic reserve networks that help achieve both short- and long-term conservation objectives (Bengtsson et al., 2003; D’Aloia et al., 2019). Incentives provided to farmers who temporarily or permanently fallow particular fields based on objectives of these dynamic reserves could offset opportunity costs they would incur by not selecting fields with the lowest economic value. Funding mechanisms that seek to capitalize on the biodiversity conservation potential of fallow land under SGMA while decreasing costs to farmers have grown in recent years. Broadly speaking, agri-environmental schemes for biodiversity conservation have been used successfully across the US and globally, including direct payments and subsidies to farmers who adopt environmentally beneficial practices and fallowing rotations (Bourque et al., 2019; Henderson et al., 2000; Herzon et al., 2010; Kuussaari et al., 2011; Oñate et al., 2007; Ribaudo et al., 2008, 2010; Sanz-Pérez et al., 2019; Tarjuelo et al., 2020; Toivonen et al., 2013). In California, conservation payments could tap into available funding mechanisms and environmental initiatives, such as USDA funded conservation initiatives, Sustainable Groundwater Planning Grant Program funding for projects that increase sustainable groundwater, and state funding from California’s newly established Biodiversity Collaborative (Bourque et al., 2019; California Department of Water Resources, 2021; Office of Governor Gavin Newsom, 2020). In 2020, the California Department of Conservation (DOC) initiated a Watershed Coordinator Grant Program providing a total of $1.5 million in funding to five different Watershed Coordinators, some of whom are expected to use funding to incentivize retirement of agricultural land that will benefit wildlife (California Department of Conservation, 2019). More recently, Assembly Bill (AB 252) was proposed in California under which the DOC would be required to provide funding to GSAs that could then provide payments to farmers who agree to repurpose land for specific conservation and restoration projects (AB-252 Department of Conservation: Multibenefit Land Repurposing Incentive Program: Administration, 2021).
To derive the requisite benefits from tax payer funded agri-environmental schemes necessitates a thorough understanding of the socio-ecological system. Our study adds to understanding of how temporary reserves may function to improve connectivity in working landscapes, yet has several limitations of note. First, our case study focuses on one species in one agriculturally-dominated county. Second, we lack data on species movement to validate our connectivity models. Further examination of strategic fallowing and its potential co-benefits at a larger spatial scale and inclusion of ground-validation of species movement is needed to understand cost-effectiveness of opportunistic fallowing. Strategic corridors of fallowed lands could be functional for kit foxes, who have been historically documented living near and foraging in fallow and less intensive agriculture fields. Indeed, the species recovery plan suggests farmland areas periodically set aside for more than 2–3 years would be useful for maintaining connectivity corridors in our study region (Williams & Fitton, 1997). However, this schema may not be generalizable to other species or regions. More research is needed to understand how connectivity benefits and co-benefits scale with fallowing duration.
Strategic, yet temporary conservation actions have the potential to reduce the conflict between biodiversity preservation and agricultural production in agricultural landscapes. Here we show that an increase in temporary fallowing from 2011 to 2015/2017 in western Kern County likely increased landscape connectivity for the San Joaquin kit fox. These results illustrate the potential for co-benefits to be derived amidst significant land use changes associated with drought conditions and the impending implementation of SGMA. Though the opportunity costs of fallowing to farmers under SGMA will likely be high, those costs have the potential to be partially offset by tapping into the conservation potential of dynamic reserves comprised of permanent and temporary conservation corridors made available by such actions. Given the ubiquity and influence of productive landscapes on human and natural systems and the increasing preponderance of uncultivated land therein, strategic and coordinated fallowing paired with dynamic and opportunistic conservation may be key to biodiversity conservation in agricultural landscapes.