Goals

We review of the key issues facing several groups of wildlife that depend on rice fields. We consider the needs of each group in terms of (i) the amount of rice needed, (ii) management practices on those fields that are most beneficial, and (iii) locations within the Central Valley that might have the greatest value for conservation.  In doing so, we develop a footprint of the rice acreage needed to sustain multiple species of wildlife using ricelands in California.

Background

Rice agriculture, especially winter-flooded rice fields, provides surrogate wetlands that host a diversity of species in the Central Valley.  Rice fields are critical for Giant Gartersnakes, wintering waterfowl, wintering and breeding shorebirds, Sandhill Cranes, native fishes, and many other species.

However, uncertainties in climate, water availability, agricultural crop markets, and urban expansion are precipitating changes in management practices, increased variability and magnitude of fallowing, and, in some cases, crop conversion. These uncertainties raise several important questions for both the rice industry and wildlife conservation: (1) How much rice is needed to meet minimum requirements for species of conservation concern in the California Central Valley? (2) How much planted rice needs to be flooded in winter and/or managed in specific ways to continue providing ecological benefits? (3) Are there specific locations where rice is especially needed to maintain high levels of wildlife abundance and diversity? (4) Finally, in the face of continuing challenges to agricultural and managed wetland habitats, which management practices, or suites of practices, are economically feasible to implement and benefit the greatest number of species, without negatively impacting other species?

While many studies have examined the value of rice habitat to specific groups of wildlife species, few have done so in an integrated fashion – evaluating the benefits, constraints, and tradeoffs for multiple wildlife species simultaneously. This is a much more challenging task, requiring a synthesis of the ecological, agronomic, economic, and management influences on multiple taxonomic groups as well as a synthetic evaluation of potential mutual benefits or tradeoffs. This project represents an initial attempt to address these questions

Project Results

We first develop a single baseline mapping framework including multiple habitat components that could influence the abundance and distribution of various wildlife species. We then review the core needs of five key taxonomic groups (Giant Gartersnakes, wintering ducks, wintering and breeding shorebirds and Black Terns, Sandhill Cranes, and native fishes) with respect to ricelands. We go on to provide an estimate of the rice acreage, management actions, and locations that would be of greatest value to each group. We include an evaluation of the potential economic value of riceland habitats and wildlife to address potential social welfare gains from improved wildlife habitat populations. Finally, we synthesize key outcomes from our taxa-specific analyses to provide an evaluation of the rice footprint needed to support these taxonomic groups.

Our estimates of the planted rice acreage needed for these taxonomic groups include: 30,000 ac for native fishes (only Yolo and Sutter bypasses are considered in this report), 43,139 ac (Sandhill Cranes), 80,000 ac (Giant Gartersnake), 373,540 ac of winter-flooded rice and flooded fallow rice fields (non-breeding shorebirds), 472,794 ac of planted rice (to restore populations of Black Terns and support other breeding shore birds), and 500,000 ac (non-breeding ducks). A minimum rice footprint could be determined as that which satisfies the minimum needs of the species with the largest acreage requirement - any reduction of rice below that target would impact at least that one species. Under this premise, a minimum footprint of ~470,000– 500,000 acres would define the conservation footprint. We discuss several factors that will influence this estimate, and we consider a range of rice acreages where the amount of rice habitat is inadequate under all conditions (high risk), where there is risk of not meeting population objectives, especially when conditions are poor (insufficient), and where there is enough rice habitat to buffer populations under almost all conditions (sufficient).

We use our mapping analysis to identify rice locations that are high priority for multiple species. We emphasize that (1) these are not the only areas of conservation importance, (2) they are not weighted rankings of conservation value, and (3) they do not define the minimum footprint. Rather, we present these maps as tools for strategic conservation planning to identify focal areas where joint management may be most effective and/or where management tradeoffs for different species may occur.

Finally, we identify research needs for each taxonomic group. We also describe next steps to develop a more refined rice conservation footprint using multi-objective decision analysis, expanding the species groups considered, enhancing economic and ecological data integration, as well as modelling and engaging stakeholders in key priority areas.