Environmental Defense Fund Applauds the IUCN’s Decision to Protect the Critically Important Mesopelagic Zone

The International Union for the Conservation of Nature (IUCN) voted to pass motion 035, “Protection of mesopelagic ecosystem integrity” at the World Conservation Congress in Abu Dhabi. This motion calls for a precautionary approach on the expansion of fishing and other industrial activity until this ecosystem is better understood.

The mesopelagic zone, also known as the Ocean Twilight Zone, is located between 200 and 1,000 meters deep and is home to, by some estimates, 90 percent of the ocean’s biomass. Each night, many of these organisms make a key contribution to the ocean’s ability to absorb excess CO₂ by helping to sequester 2-6 GT of carbon per year when they migrate daily from the surface to feed and then back to the mesopelagic. 

“The mesopelagic zone plays a key role in the ocean’s biological carbon pump and therefore helps to stabilize our climate. The species in the mesopelagic zone are also critical for a healthy, functioning ecosystem, serving as prey for many ecologically and commercially important marine species. That’s why it is so important to take a precautionary approach when it comes to this vital ecosystem, and the passage of this motion puts us on the right track. 

“With the passage of this motion, we can develop data-backed policies and practices that sustainably balance human and ecosystem needs. This comes on the heels of another win for ocean conservation: the adoption of the high-seas treaty. It’s clear that the international community has recognized the value of our ocean’s biodiversity and are working together to make real progress in ocean conservation and sustainability.” 

• Kristin Kleisner, Associate Vice President & Lead Senior Scientist, Ocean Science