Since January, I am one of the lucky few people who has twice heard Dr. Boone Kauffman of Oregon State University present his analysis of the carbon impact of shrimp farming on converted mangroves in southeast Asia.
His most recent talk at AAAS last week in Vancouver has been getting a lot of play this week, helping bring attention to an abhorrent practice in SE Asia and the associated climate change impacts - or the "Land Use Carbon Footprint" as he calls it.
Here's the rundown on his talk "What's the Jumbo Carbon Footprint of a Shrimp."
The “Land Use Carbon Footprint” is the carbon emissions that arise from the conversion of an ecosystem to another land cover type in order to provide some commodity.
Shrimp farming in SE Asia is a dominant cause of mangrove deforestation. Productivity in a converted shrimp pond is 50 to 500kg / hectare / year. The productive life of a shrimp pond is 3 to 9 years due to disease, and then it is abandoned.
Based on data from 24 mangrove sites, the calculation of the Land Use Carbon Footprint of a 100g shrimp cocktail takes into account:
- 100% loss of the above ground carbon stored in the mangrove trees,
- 100% loss of the below ground tree carbon (roots), and
- 100% loss of the surface soil carbon in the mangrove soil when it is piled into banks to create the shrimp pond.
Using an average productivity and life of the shrimp pond, a 100g shrimp cocktail has the staggering Land Use Carbon Footprint of 198 kg CO2. This means that for every kg of shrimp meat produced, the carbon footprint is 1,980 kg CO2 - nearly two metric tons, or more than 4,300 pounds. This is a conservative estimate and does not include the carbon costs of establishing the shrimp pond, feeding the shrimp, fertilizers, medicines, processing, or shipping.
The direct land use impact of every kg of shrimp meat produced is the destruction of 13.4 m2 of mangrove. With the loss of these mangroves there is a corresponding loss of ecosystem services such as storm protection, water quality, and essential fish habitat.
You might be wondering how this compares to other foods that have been identified as contributing to global climate change, such as a steak raised on pasture clear cut in the Amazon rain forest. Using a parallel method, Dr. Kauffman calculates the Land Use Carbon Footprint of a one pound steak to be one-tenth of an equivalent amount of shrimp from a converted mangrove.
One more comparison. If we assume a Prius gets 50 miles/gallon, knowing that each gallon of gas contains 8.8kg CO2, we can estimate that you would have to drive your Prius 1,125 miles to emit as much CO2 as the emissions related to the 100g shrimp cocktail. Depending on where you live, you could potentially drive to the Gulf of Mexico, buy shrimp from a local fisherman, and prepare them fresh yourself.
This is a striking and compelling analysis, and I am grateful to Dr. Kauffman for his excellent work. It is my hope that presenting the impact of shrimp farming in mangroves in this light will help to improve management of these critically important ecosystems, which are being lost at rates exceeding 2% per year.
Dr. Kauffman also ran one more calculation - estimating that with a price of carbon at $4/ton, it would be more cost effective to use carbon markets to protect the mangroves than to allow their continued destruction for cheap shrimp. And remember, this did not take into account all of the other carbon impacts of shrimp farming in converted mangroves.
*A disclaimer - the information presented here is from notes I took during Dr. Kauffman's presentations at the European Parliament in January, and at the AAAS meeting last week in Vancouver. I believe the information to be accurate, but this work has not yet been published.