| Abstract | The aim of this study is to assess the global occurrence of large submarine canyons to provide context and
guidance for discussions regarding canyon occurrence, distribution, geological and oceanographic significance
and conservation. Based on an analysis of the ETOPO1 data set, this study has compiled the first inventory of
5849 separate large submarine canyons in the world ocean. Active continental margins contain 15% more
canyons (2586, equal to 44.2% of all canyons) than passive margins (2244, equal to 38.4%) and the canyons are
steeper, shorter, more dendritic and more closely spaced on active than on passive continental margins. This
study confirms observations of earlier workers that a relationship exists between canyon slope and canyon
spacing (increased canyon slope correlates with closer canyon spacing). The greatest canyon spacing occurs in
the Arctic and the Antarctic whereas canyons are more closely spaced in the Mediterranean than in other
areas.
River-associated, shelf-incising canyons are more numerous on active continental margins (n=119) than on
passive margins (n=34). They are most common on the western margins of South and North America where
they comprise 11.7% and 8.6% of canyons respectively, but are absent from the margins of Australia and
Antarctica. Geographic areas having relatively high rates of sediment export to continental margins, from
either glacial or fluvial sources operating over geologic timescales, have greater numbers of shelf-incising
canyons than geographic areas having relatively low rates of sediment export to continental margins. This
observation is consistent with the origins of some canyons being related to erosive turbidity flows derived
from fluvial and shelf sediment sources.
Other workers have shown that benthic ecosystems in shelf-incising canyons contain greater diversity and
biomass than non-incising canyons, and that ecosystems located above 1500 m water depth are more
vulnerable to destructive fishing practices (bottom trawling) and ocean acidification caused by anthropogenic
climate change. The present study provides the means to assess the relative significance of canyons located in
different geographic regions. On this basis, the importance of conservation for submarine canyon ecosystems
is greater for Australia, islands and northeast Asia than for other regions.
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