...How do sharks affect atmospheric carbon? (click here)
Coastal predators such as sharks protect and enhance blue carbon (carbon stored in coastal and marine ecosystems) by limiting grazing on seagrass meadows and kelp forests. These ecosystems are precious not only to the plethora of species they support but also in the role they play in the absorption of carbon due to photosynthesis. For example, tiger sharks frequent shallow seagrass meadows. They prevent overgrazing in concentrated areas from turtles and other prey species, resulting in increased and more evenly distributed seagrass. The increase in meadow mass directly helps rising carbon levels, as seagrass captures carbon from the atmosphere 35 times faster than tropical rainforests.
Large fish such as shark, tuna, mackerel and swordfish are comprised of ~10 to 15% carbon. When they die naturally, their bodies act as direct carbon sinks through 'carcass deadfall'. The carbon held in their bodies is sequestered into the sediment. Put simply, if a carcass is removed from the sea its corresponding carbon is released into the atmosphere but if left to die at sea that carbon is buried. Luckily, these animals are also useful to the climate crisis when they stay alive!
Whaling and Sharks?
The global biomass of whales is less than 25% of pre-whaling times. A study by Pershing et al. shows the implications of removing large marine species on the oceans ability to store carbon. If efforts were increased to restore populations, whales could remove 8,700,000 tonnes of carbon from the environment. That's the equivalent of 110,000 hectares of forest, an area the same size as the Rocky Mountain National Park. If blue whale populations alone were restored they could sequester 3,600,000 tonnes of carbon. The same amount achieved by 43,000 hectares of forest, an area the same size as Los Angeles. But this isn’t the end of the story...
