Flooded rice fields in California's Central Valley offer important, often vital habitat to many wildfire species. Photo by Pansare from Pixabay

DAVIS, CA (MPG) - From ducks and cranes to giant garter snakes and salmon, flooded rice fields in California's Central Valley offer important, often vital habitat to many wildlife species. Yet uncertainties around crop markets, water and climate can prompt some growers to fallow rice fields or change their management practices.

Will today’s rice acreage under current practices be enough to meet key species’ needs? If not, how much rice is needed? Where should it be planted? And what management practices offer the greatest benefit for species of concern?

Scientists from the University of California, Davis, and Point Blue Conservation Science address these questions in a new report, “A Conservation Footprint for California Rice,” written for the California Rice Commission.

“This was a highly interdisciplinary effort that I don't think has been attempted at this scale for California rice or perhaps any other California agricultural crop working with wildlife,” said report co-lead John Eadie, a UC Davis professor emeritus in the Department of Wildlife, Fish and Conservation Biology who coordinated the 173-page effort among 13 authors. “I think this report provides the baseline for future work to come.”

The authors reviewed the core needs of key species living among the region’s rice fields. These include giant garter snakes, wintering ducks, wintering and breeding shorebirds, black terns, sandhill cranes and native fish. They developed a mapping framework of the species' habitat, as well as an estimate of the rice acreage, management practices and priority locations for rice that would most greatly benefit each wildlife group.

Over the past decade, rice acreage has ranged from 250,000 to 540,000 acres in California. The report found that approximately 470,000 to 500,000 acres defines the desired conservation footprint of rice for the most species of concern.

The needs for different species include 30,000 acres for native fish, 43,000 acres for sandhill cranes, 80,000 acres for giant garter snakes, 373,500 acres of winter-flooded rice and flooded fallow rice fields for non-breeding shorebirds, 473,000 acres of planted rice to restore populations of black terns and help support breeding shore birds, and 500,000 acres for wintering ducks.

Winter flooding critical

The authors emphasize that rice acreage alone, even as much as 500,000 acres, will not sustain these species unless water is available during the winter and during critical periods in the fall and spring. Winter flooding of the rice fields is especially critical for many of these species.

Historically, seasonal wetlands shaped the Central Valley's ecology and biodiversity. Beginning in the mid-1800s, these lands were largely drained for agriculture, flood control and development.

“In the absence of natural wetlands, rice has become essential surrogate habitat for an incredible diversity of California wildlife,” said report co-editor Daniel Karp, a UC Davis professor in the Department of Wildlife, Fish and Conservation Biology. “In the face of climate-induced droughts and escalating water prices, providing rice farmers with the support needed to continue flooding their fields in winter is absolutely essential to safeguard this incredible conservation success story.”

Priority locations and management solutions

For nearly all wildlife groups, the Colusa and Sutter basins rank as the highest priority locations for rice habitat, given their proximity to wetlands and wildlife refuges. The Yolo Basin, Consumnes-Mokelumne Rivers region, and parts of the Delta are especially important for shorebirds and sandhill cranes. The Yolo and Sutter bypasses also represent critical areas for fish in flooded rice fields.

The conservation value of these areas, however, largely depends upon how they’re managed. In addition to winter flooding and water availability, spatial location, managing vegetation, irrigation canals and post-harvest rice straw are just some of the considerations when managing rice for wildlife. The report outlines several strategies for each group.

“This kind of interdisciplinary work is challenging but so important to effective conservation,” said report co-author Kristen Dybala, a principal ecologist at Point Blue Conservation Science. “When we work together, we can identify opportunities for the same acres to contribute to multiple goals at once.”

The value of rice

In addition to providing habitat for wildlife, rice production creates about $1 billion of added economic value and up to 7,500 jobs for California’s Sacramento Valley.

“For decades now, our growers have seen firsthand how much their rice fields are used by wildlife all throughout the year,” said Tim Johnson, president and CEO of the California Rice Commission. “This Rice Footprint report by the University of California, Davis, details how these same fields that grow America’s sushi rice serve as the economic driver for our small communities and are also vital to our ecosystem in helping waterfowl, shorebirds, reptiles and fish thrive.”

The report was funded primarily by the California Rice Commission through a grant to the UC Davis Center for Watershed Sciences and to Point Blue Conservation Science.

Additional authors include Francisco Bellido-Leiva, Lee Burrows, Sean Fogenburg, Andrew Rypel and Brian Todd of the UC Davis Department of Wildlife, Fish and Conservation Biology; Robert Walsh of Point Blue Conservation Science; Bruce Linquist of UC Davis Plant Sciences; and Daniel Sumner and Jessica Xu from UC Davis Agricultural and Resource Economics.