Agricultural land retirement in the San Joaquin Valley: A novel conservation opportunity

The years 2021 to 2030 were recently declared the UN Decade on Ecosystem Restoration. This call to action by the UN General Assembly aims to ramp up the restoration of degraded ecosystems while enhancing food security, water supply, and biodiversity in the face of a changing climate. Agricultural lands, which account for up to 40 percent of global land surface, will prove central to this effort. As water resources grow scarcer because of climate change, taking certain lands out of production and facilitating their recovery through restoration represents a critical conservation opportunity.

California enacted its Sustainable Groundwater Management Act (SGMA) in 2014 in response to severely depleted groundwater resources across more than two million acres of irrigated agricultural lands. The Act requires groundwater basins to bring aquifers into balance by 2040, which means facilitating their recharge at a rate equal to or greater than the rate at which water is extracted. Achieving this will require taking more than 500,000 acres of irrigated agricultural lands out of production within the next two decades – a shift that is likely to have far-reaching impacts on agricultural output, although the extent of these consequences has yet to be realized.

California’s San Joaquin Valley is at the epicenter of this push. The San Joaquin Valley aquifer system underlies approximately half of California’s Central Valley – a region that currently contributes one-fifth of the United States’ agricultural food production. It is also home to one of the highest concentrations of threatened and endangered animal species in the country. Since ideal groundwater recharge sites do not always overlap with those sites most suitable for critical wildlife habitat, SGMA compliance has the potential to lead to a disjointed mosaic of barren fields. Alternatively, it could catalyze the creation of an integrated landscape that supports both high-quality agriculture and species conservation while meeting groundwater recharge targets.

Historically, the Central Valley landscape was dominated by arid and semi-arid grasslands, shrublands, and scrublands that played host to a myriad of unique desert-adapted species. The San Joaquin kit fox, the blunt-nosed leopard lizard, and the giant kangaroo rat are three such species, and their populations have suffered as a result of encroaching agricultural and industrial development. This habitat loss is compounded by drought and the proliferation of non-native grasses and animals – challenges harming native species across the region. Strategic agricultural retirement and restoration, then, represents a novel form of conservation – not because it aims to set aside the best lands for wildlife habitat but because it endeavors to recover “used” lands capable of supporting biodiversity.

Three recent articles published in Ecosphere, Science of the Total Environment, and Environmental Research Communications examine this moment of transition in land use and the opportunities and challenges therein.

In one study, Dr. Christopher Lortie and colleagues demonstrate that retired agricultural land is a viable asset for the San Joaquin kit fox, blunt-nosed leopard lizard, giant kangaroo rat, and other imperiled species. The results of their synthesis show that reducing the density of non-native plants, mediating drought, and – to the extent possible – prioritizing proximity to existing or former habitat significantly contribute to species recovery. Importantly, the researchers call attention to the fact that retired agricultural lands, when vegetation is managed properly, can further support species by connecting existing populations. The lesson here is that once plants are established, animals will follow. Towards this end, Lortie and his colleagues call for an ecologically-strategic approach to designating agricultural lands for retirement – one that takes soils, moisture, and native vegetation into consideration in assessing fields’ capacity to support endangered species.

In another study, Kelly Bourque and fellow researchers explore the ideal configuration of groundwater recharge projects in balancing groundwater management and biodiversity goals. The researchers examined agricultural fallowing as one groundwater management strategy, which entails taking agricultural fields out of production to reduce irrigation demand. They determined that prioritizing fields for retirement based solely on annual crop revenues can partially mitigate biodiversity threats. A significant percentage of endangered species habitat actually overlaps with the fields most desirable for fallowing from an economic perspective. However, this approach falls short of actually meeting biodiversity goals, and the costs of removing fields from production and reaching groundwater targets can vary dramatically when biodiversity conservation is weighted more heavily in the planning calculus.

In both of these articles, the authors identify a lack of research on specific restoration techniques and project implementation costs. This translates to uncertainty around how exactly to maximize habitat value for threatened and endangered species and, subsequently, what funding is available to landowners that succeed in generating these ecosystem benefits. When it comes to programs like the Central Valley Resilience Initiative, which aims to support land managers navigating the SGMA transition in delivering meaningful outcomes for wildlife, planning amidst this uncertainty is tricky. Producers are not necessarily equipped to factor habitat values into their land management decisions.

In a third article, however, Dr. Meredith Niles and Courtney Hammond Wagner found that an overwhelming majority of farmers (95 percent) feel confident in their abilities to manage their groundwater resources. Niles and Wagner analyzed individual farmers’ support for SGMA and found that 71 percent “also feel confident that they can achieve groundwater sustainability under SGMA.” If this level of confidence in groundwater management is complemented by a robust understanding of the habitat values that can be harnessed under different land management regimes, farmers can make more holistic decisions capable of delivering both environmental and community benefits. Towards this end, pilot programs with landowners and water managers that explore different land management regimes have the potential to fill a critical gap in understanding. Ultimately, these programs could catalyze new state and local funding programs to support farmers in the SGMA transition.

As we enter the UN Decade on Ecosystem Restoration, a biodiversity crisis is unfolding and demands on agricultural production are increasing, depleting already overtaxed water resources. The situation playing out in the San Joaquin Valley is not unique. Across the world, other drylands are facing similar pressures, and land managers are navigating similar challenges. While there is some natural overlap between cost-effective groundwater management and biodiversity conservation in the San Joaquin Valley, selecting and retiring agricultural lands with these dual goals in mind requires, first, understanding, and second, balancing economic and ecological tradeoffs. As California endeavors to bring its groundwater basins into balance, determining where and how these goals can align will prove critical to seizing the conservation opportunity in this moment of transition. The process unfolding here will offer lessons for other agricultural regions staring down similar challenges across the world.