The math of the deep ocean has an almost cruel quality. The entire process, which may take a few hours, involves a mining vessel dragging equipment across the seafloor to remove nodules that took millions of years to form. The recuperation? These days, scientists think it might take a thousand or several thousand years. It’s not a typo. That isn’t a dramatic exaggeration. In fact, that is what the research indicates.
More than 5,400 invertebrate fossils extracted from a sediment core off the coast of Santa Barbara were examined in a seminal study headed by UC Davis scientist Sarah Moffitt, which was published in the Proceedings of the National Academy of Sciences back in 2015. A unique window into what happened to seafloor ecosystems during the last major deglaciation—a time of rapid warming, ice melting, and the expansion of low-oxygen ocean zones—was provided by the core, which covered a period of about 12,700 years. Moffitt discovered something startling and, to be honest, somewhat depressing. The recovery of seafloor biodiversity took place on a millennial scale, but the ecological disruption itself occurred quickly, with measurable drops in oxygen levels in less than a century. Not a hundred years. One thousand. “It commits us to thousands of years of recovery,” stated Moffitt. It’s the kind of statement that sticks in your mind.
The explanation for these startling timelines is not mysterious, but it does necessitate an awareness of the stark differences between the deep ocean and any environment that the majority of us will ever come into contact with. There, beneath two kilometers of water, food is hard to come by, the temperature is barely above freezing, the pressure is oppressive, and sunlight is nonexistent. Almost everything slows down as a result of life’s adaptation to these circumstances. growth, reproduction, and metabolism. The lifespan of deep-sea corals is more than 4,000 years. Some sponges live for 11,000 years. These are not anomalies. They are typical. It is more than just killing an animal when an industrial process destroys a coral colony that has existed since the Bronze Age. It’s destroying a structure that will take longer than human history to revert to its previous state, if it grows at all.
The numbers for sediment accumulation provide an equally bizarre narrative. In the deep abyss, seafloor sediment accumulates at a rate of less than 0.5 centimeters per thousand years. Deep-sea mining equipment leaves wide furrows in the seabed that don’t simply close up. As the surrounding ecosystem struggles to regain its equilibrium, they sit there in silence for decades and then centuries. When some researchers returned to mining test sites from experiments carried out in the 1980s, they discovered that the communities were still obviously disturbed and that the tracks were still clearly visible. The seafloor appeared to have been recently worked on, even though it had been more than 40 years.
A growing, if delayed, awareness of all of this may be reflected in some of the current developments in deep-sea policy circles. This kind of long-term thinking has been encouraged by the Deep-Ocean Stewardship Initiative’s documentation, which highlights the fact that human-built governance structures, such as committees, review cycles, and five-year plans, function on timescales that are essentially unrelated to those of the deep ocean. There is an uncomfortable fundamental mismatch. International organizations such as the United Nations’ International Seabed Authority are grappling with how to control commercial seabed mining before it reaches its full scale, but sometimes it’s like watching the wrong clock when organizations built for human-paced decision-making attempt to handle geological-paced repercussions.
An example of what happens when that mismatch is ignored is provided by the orange roughy. Before anyone realized how slowly it reproduced, this deepwater fish, which can live for more than 200 years, was heavily fished during the 1970s and 1980s. Populations had been decimated by the time the fishery failed. Decades later, stocks are still estimated to be only 10 to 30 percent of their initial size. In 2016, the European Union finally outlawed bottom trawling below 800 meters, but as is often the case, the lesson came late.
It’s difficult not to feel something change when you consider the scope of everything. The majority of the planet is covered by the deep sea. It cycles nutrients, stores carbon, and sustains biodiversity that has hardly been documented by science. Furthermore, it appears to be assumed in many industrial circles that it can absorb damage in the same way that a shallow reef might; things will recover with enough time and goodwill. The scientific community disagrees. It claims that the recovery, if it occurs at all, occurs over periods of time that make human civilization appear to be a fleeting disruption. When there are minerals down there that battery manufacturers want and political pressure to exploit them is increasing, it’s uncomfortable to accept that. For the next millennium, the ocean floor will remain in place. It is much less certain what will survive on it.
