Can Crayfish Combat Climate Change?

By Jonathan Kuba


            The tiny crayfish, a freshwater crustacean commonly known in the United States as “Louisiana crawfish,” “mudbugs” or “red swamp crayfish” (Procambarus clarkii) is native to North America and Mexico.  It’s larger cousin, another freshwater crustacean is native to Australia and commonly known as “yabbies” or “red claw crayfish” (Cherax quadricarinatus).  Though there are many species of crayfish, these two may be a three-pronged answer to climate change, malnutrition, and poverty alleviation in many developing countries.

It has been argued that rice is a major biogenic contributor of greenhouse gas emissions with some estimating it at 10% of global methane emissions.  However, since rice production has been occurring for thousands of years, it is unlikely that rice cultivation is the cause for the recent huge spike in global greenhouse gas emissions within the last fifty years.  Nevertheless, some lab and field studies have shown that flooded rice fields emit methane when organic matter is degraded by anaerobic bacteria feasting on decaying rice straw.

Enter the humble mud bug.  Crayfish are omnivorous but mainly eat plant matter and detritus.  In the southeastern states of America, crayfish have been cultivated for centuries within rice fields.  When the rice field is harvested and drained, the crayfish burrow into the mud and do not emerge until the field is flooded again.  When the field is flooded, the crayfish re-emerge, often with babies, and gorge themselves on the leftover rice straw or vegetation that grew during the dry period, now breaking down in the water.

So why is this crayfish/rice relationship important and how can it help with the three big problems of climate change, nutrition and poverty in developing countries?  If crayfish are used in the fields by the approximately 150 million smallholder paddy rice farmers around the world, then a significant amount of paddy rice straw can be consumed by the crayfish before the anerobic fermentative bacteria can process the rice straw into methane.

Furthermore, based on the experience of crayfish/rice farmers in Louisiana, crayfish can become a major contributor to smallholder farmers’ incomes and will bring the farmers more income than the rice harvest itself.  Also, as an added benefit for the farmers, the waste that the crayfish produce is a natural organic fertilizer that can add a decent percentage of nitrogen and a significant percentage of phosphorus to the soil, which saves on fertilizer cost and can improve rice yields.

Lastly, in many developing countries, malnutrition is still a big problem since protein production is expensive.  Crayfish production can be relatively low cost since rice straw is a free by-product feed for crayfish/rice farmers and animal feed is by far the largest cost in livestock production.  Given the protein rich content in crayfish meat, this can add a significant amount of protein to diets in crustacean eating countries around the world, or become a big export product for those who don’t consume crayfish.

To ensure farmers do not sacrifice carbohydrate production for protein production, it is important that the crayfish do not consume the growing rice itself.  So farmers will need to correctly time the addition of the crayfish to the paddies when the rice is strong enough to not be consumed by the clawed creatures.

One of the biggest challenges for adoption of any climate smart agricultural practice is making smallholder farmers change their habits.  However, when economic incentives align with the proposed habit change, then you have the recipe for success.  Like a good crawfish étouffée, let’s hope this practice satisfies the hunger of smallholder farmers around the world for climate smart solutions, a healthy diet, and a tasty bottom line.