The deep ocean may be the least-known place on Earth. From the sea floor upward, the oceanic water column represents the overwhelming majority of living space on the planet – 90%, by one recent estimate. Yet very little of the dark blue expanse has been explored by humans. Seemingly each deep sea research voyage discovers alien organisms with features or abilities we have never imagined before, much less seen.

In July, UNESCO released a report that is the most comprehensive attempt so far to classify the open ocean into a set of general bioregions. (The report, Global Open Oceans and Deep Seabed [GOODS] Biogeographic Classification, is available at Although the classification of 30 broad bioregions remains a work in progress and is very light on information about the deeper water column, it provides a basis for conservation planning of the open ocean in general. As the report points out, it is a first step toward planning a representative system of MPAs in this little-known realm.

A call for surveys, protected areas

In 2004, the Conference of the Parties to the Convention on Biological Diversity adopted the objective of establishing “comprehensive, effectively managed and ecologically representative systems of [marine] protected areas” by the year 2012. While nations have pursued this objective with varying degrees of commitment in their own waters, there has been only slow progress on MPAs in marine areas outside national jurisdiction.

A significant limiting factor has been the lack of a global framework for establishing representative networks of MPAs on the high seas (see “Recent Developments toward System of High-Seas MPAs”, MPA News 8:1). But the relative lack of biophysical information on those waters has also presented a challenge. Although the UNESCO report aims to help address that, its classification system covers only the upper pelagic realm (from the sea surface down to 200 m) and the deep seabed, with virtually no coverage of the deep pelagic waters in-between (all waters below 200 m). Information on the deep pelagic realm simply remains too poor. Thus the question is raised, how can you plan to protect something, or somewhere, about which you know very little? Would you know what you were protecting? Or whether it even needed protection?

In a paper published this year in Conservation Biology, Bruce Robison of the Monterey Bay Aquarium Research Institute (U.S.) addresses that last question. His paper “Conservation of Deep Pelagic Biodiversity” says the open ocean’s “incomparable reservoir of biodiversity” is being impacted by a growing number of factors, including climate change and acidification among others. Together, he suggests, these impacts are leading to restructuring of pelagic ecosystems, including changes in the geographical ranges of many species. (The abstract of Robison’s paper is at

Robison calls for baseline surveys and protected areas as the primary policy goals for addressing these threats. The concept of MPAs in the open ocean is not new. Researchers have proposed various strategies for siting high seas MPAs that account for the dynamic nature of marine systems. In a paper inConservation Biology in 1998, Claudia Mills and Jim Carlton proposed placing MPAs in the center of great ocean gyres, which are believed to have maintained their biodiversity for tens of millions of years (the paper is available at Graduate student Chris Van Assen at the University of Amsterdam this year proposed marine fronts – the boundaries between major water bodies – as appropriate MPA sites, due to their general association with high productivity. (For his paper “The importance of the Argentine shelf for conservation in the South Western Atlantic”, e-mail The Convention on Biological Diversity has also adopted criteria for identifying areas of significance in the open ocean and deep sea that recognize the need for protecting such pelagic features.

Vulnerability and irreplaceability

Even with such rule-of-thumb suggestions and the UNESCO bioregional classification system, though, an MPA-planning process for the deep ocean would look much different than for a coastal MPA. For one thing, there would be vastly less scientific data or traditional knowledge to inform decisions.

Graeme Kelleher, author of Guidelines for Marine Protected Areas (, says it would be a mistake, however, to allow the lack of biophysical data to delay planning of MPAs in the deeper water column. Quoting the Guidelines, he says, “It is better to have an MPA that is not ideal in the ecological sense but which meets the primary objective than to strive vainly to create the ‘perfect MPA’. There will usually be sufficient information to indicate whether an MPA is justified ecologically and to set reasonable boundaries.”

Jeff Ardron, who co-edited the UNESCO report, says that protecting places we do not yet know in the deep ocean comes down to managing uncertainty. “I very much believe that we should protect ‘what we do not know’, since we know rather little,” he says. “And indeed there are practical approaches to do so, borrowing from the management of uncertainty in other fields, such as economics and medicine.” Ardron briefly discussed in the June 2007 MPA News how both fields have developed adequate methods for decision-making based on incomplete information (“Challenges Faced by the Global MPA Field”, MPA News 8:11).

He cautions, however, about focusing too much on areas that may ultimately not require urgent protection. “There is a lot to be said for protecting places before they become degraded,” says Ardron. “That said, some conservation issues are more pressing than others. The deep pelagic is a vast realm. Fundamental to systematic conservation planning are the notions of irreplaceability and vulnerability. In assessing conservation priorities, they should be considered together.”

Data that would be useful for planning

Les Watling of the University of Hawai`i, who co-authored the UNESCO report, says there are certain types of data that would be useful for deep pelagic MPA planning. He says it would be especially valuable to know:

  1. How widespread deep sea species are, including at very low depths (e.g., bathypelagic [1000-4000 meters deep] and abyssopelagic [4000-6000 m]); and
  2. Whether species at those depths follow specific water masses, or if they cruise the depths based on tolerances to temperature or other conditions.

“If we can get data to hint at the answers to these questions, we could then use the physical data – such as water temperature, salinity, oxygen – as proxies for the large areas of the globe where animal data are non-existent,” says Watling. “With that framework, we could make some biogeographic projections upon which deep-sea pelagic MPAs could be built.”

Until such data become available, Kristina Gjerde of the High Seas MPA Task Force supports the idea of extending existing deep seabed protected areas – areas closed to bottom fishing – upward to include the water column above. This would be done on a precautionary basis to protect the entire ecosystem, she says. Then assessments, as suggested by Robison, could be done to determine what biogeographic regions are not represented in the MPAs. In addition, says Gjerde, a set of international requirements is needed to require impact assessments of activities that have the potential to affect oceanic and seafloor biodiversity beyond national jurisdiction. “As with Resolution 61/105 by the UN General Assembly, which pertains to high-seas bottom fishing, activities would need to be managed to prevent significant adverse impacts,” says Gjerde. “And one would hope to also see a mechanism to facilitate the planning and establishment of MPA networks beyond national jurisdiction.”

When the planning of deep sea MPAs eventually begins, Dan Laffoley, Marine Vice Chair of the World Commission on Protected Areas, would prefer to see planners err on the side of protecting larger areas of the ocean in MPAs rather than smaller. “[Having less than optimal data] never stopped us from designating very large areas many years ago – the Great Barrier Reef, Yellowstone, the Grand Canyon, etc.,” he says. “That was before we really knew much about them other than they were wild, had many amazing species, and should be protected for everyone forever. In fact we probably regret not protecting much more back then, and we will probably feel the same way in many decades about the ocean.”

For more information:

Graeme Kelleher, IUCN Global Marine Programme, Canberra, Australia. E-mail:

Jeff Ardron, Marine Conservation Biology Institute, Washington, D.C., U.S. E-mail:

Les Watling, Department of Zoology, University of Hawai’i at Manoa, U.S. E-mail:

Kristina Gjerde, IUCN Global Marine Programme, Chylice, Poland. E-mail:

Dan Laffoley, WCPA – Marine, Peterborough, U.K. E-mail: