Since 2014, US farmers have been deliberately flooding their fields to create habitat for migratory birds; a decade later, 180,000 acres of farmland have become temporary wetlands serving as vital habitat for millions of birds

The Pacific Flyway stretches for more than 4,000 miles along the western edge of North America, forming one of four major migration routes used by birds on their seasonal journeys. Around one billion birds travel along the flyway each year, making the wetlands, lakes and other habitats scattered along the route vital stopover points.

But some of those places to stop have been disappearing. In California’s Central Valley, one of the flyway’s important stopover regions, about 95% of the historical wetlands have been lost, primarily to agriculture, according to the conservation organization Ducks Unlimited. For birds that have already traveled thousands of miles, and still have thousands more to go, the shrinking supply of suitable habitat can turn migration into a race between exhaustion and survival.

Then came BirdReturns, an initiative launched in California in 2014 by the Migratory Bird Conservation Partnership to ‘high-quality wetland habitat where and when it is needed most and the results speak for themselves’. Rather than buying farmland or permanently converting agricultural land into wildlife habitat, the program pays farmers and private wetland managers to flood fields at specific times, to create a temporary habitat when migrating birds need it most.

Creating temporary wetlands from farms

The BirdReturns program describes itself as “a flexible, cost-effective wildlife habitat marketplace.” Instead of purchasing land, the program lets farmers and private wetland managers name a price they will accept for creating the desired habitat on their land by flooding their fields.

Technology helps determine where and when that habitat is most useful. Using big data, satellite imagery and observations from community scientists, BirdReturns can identify when and where birds are likely to land. Satellite imagery can then be used to verify that the promised habitat has actually been delivered.

The program was piloted in 2014 after three years of developing the concept with direct input from the rice-growing community and participation from willing farmers.

A decade later, the approach has expanded considerably. Around 20% of rice lands are participating in the program, providing 180,000 acres of wetlands for migratory birds to use when needed, according to BirdReturns.

For farmers, the arrangement provides compensation that can support their operations and help keep agricultural land in production. For birds, it creates a network of temporary wetlands across a landscape where permanent wetlands have largely disappeared.

The benefits go beyond birds

The unusual partnership has another dimension: the water used to create bird habitat can also benefit people.

Migratory birds can help control pests, disperse seeds and leave behind natural fertilizer. Flooded fields can also allow water to seep into underground aquifers, helping replenish groundwater supplies. That matters in California, where drought, water scarcity and growing demand have made groundwater increasingly important.

The Migratory Bird Conservation Partnership describes its approach as a way to deliver shallow-water habitat while also recharging underground aquifers, calling it “something that is vital to shoring up California’s water security and resilience.”

“When we help birds, they help us,” notes BirdReturns.

Ten years later, the idea is moving beyond California

The concept of deliberately flooding agricultural fields for wildlife is not limited to the Pacific Flyway.

West in the Mississippi Delta, US Department of Agriculture researchers have been studying managed flooding as a way to create temporary wetlands for migratory birds, while also examining potential benefits for soil and water quality.

Some Mississippi Delta farmers were already flooding their fields during winter to provide habitat for ducks. Researchers with the Agricultural Research Service and nonprofit Delta Wind Birds explored whether that same infrastructure could be used earlier in the year to support migrating shorebirds.

“Rather than waiting for November or December to flood fields for ducks, we are starting as early as September to flood for migratory shore birds,” said Jason Taylor, research ecologist at the ARS National Sedimentation Laboratory’s Water Quality and Ecology Research Unit in Oxford, in a US Department of Agriculture article in 2021. “These birds use the same Mississippi flyway to migrate from Canada and the Arctic to South America and Antarctic areas and rely on shallow mud flats to feed while migrating. It turns out a flooded cornfield can provide this critical habitat.”

The research found that managed flooding could potentially offer environmental benefits beyond providing birds with a place to feed.

This process can put Nitrogen back in the atmosphere

Flooding fields earlier in the fall can enhance denitrification, a microbial process that converts excess nitrogen into nitrogen gas before it can move into waterways through runoff.

“By flooding fields in September and before colder, winter temperatures occur, we enhance microbial processes like denitrification that convert excess nitrogen left on the field to nitrogen gas. This excess nitrogen would normally move in water runoff from fields into waterways during winter storms,” said Taylor.

“This process puts nitrogen back into the atmosphere from where we originally extracted it to create fertilizer. We are basically completing the loop by flooding fields and returning unused fertilizer back to the global atmospheric nitrogen pool.”

The future for wetlands and birds

BirdReturns now aims to scale up its work by 2030, with a goal of providing an additional 100,000 acres of flooded habitat during migration and creating a rapid-response system for maintaining habitat during drought.

The organization is working with the California Rice Lands Waterbird Foundation and its companion Bid4Birds program, while also looking to establish additional habitat markets in other agricultural and wetland communities around the Central Valley.