By Dr. Becker
“… Humanity is collectively mismanaging the ocean to the brink of collapse,” according to Marco Lambertini, director general of WWF International. WWF’s new report, “Living Blue Planet 2015,” presents a sobering picture of the state of our planet’s oceans, and as Lambertini put it, it is not for the faint-hearted.
The Living Planet Index (LPI), which measures trends in population sizes of mammals, birds, reptiles, amphibians and fish, was highlighted in WWF’s 2014 “Living Planet Report.” That report found a 52 percent decline in vertebrate species between 1970 and 2010.
The 2015 report includes the marine LPI, which measures trends in the populations of more than 1,200 mammal, bird, reptile and fish species. The marine LPI similarly showed a 49 percent decline between 1970 and 2012.1
Some Fish Species Have Declined by 74 Percent
Among the species faring the worst are those people depend on for food. Populations of tuna and mackerel, for instance, declined by 74 percent during the study period.
Exploitation is the main threat, although habitat degradation and loss, pollution and climate change are also mentioned. A number of marine species are highlighted as threatened, including:
| Sea turtles |
Pinnipeds |
| Seabirds and shorebirds |
Sea snakes |
| Manatees |
Sharks |
Certain sea cucumber populations have declined by a shocking 98 percent, the report noted. While these marine animals aren’t widely known in the U.S., they’re considered a luxury food item in Asia. As such, they’ve been extensively overfished in the last 25 years.
This alone represents a sharp blow to the marine ecosystem, as sea cucumbers play a role in regulating water quality, turning over sediment, recycling nutrients and are a major source of prey for crustaceans.
With their numbers declining, they’ve left certain areas uninhabitable for other organisms.2 Other species highlighted in the report include:
- Sharks and rays: Catches of sharks, rays and related species rose more than three-fold from the 1950s to 2003, and have been falling since (but likely only because of population declines). Loss of apex predators like sharks is thought to present a serious risk to ecosystem health.
- Marine turtles: Four turtle species (hawksbill, Kemp’s ridley, green and loggerhead) are endangered or critically endangered. They face threats from human consumption, bycatch in fisheries, climate change, marine debris, loss of nesting sites and more.
Populations of leatherback turtles in the Eastern Pacific, for instance, have declined by 97 percent in the last three generations.
The report also noted concerning declines in fish species in the North Atlantic Ocean, where deep-sea fish populations declined 72 percent in the last four decades, with no signs of recovery.
Loss of Habitat Poses a Major Threat to Marine Life
Human exploitation, including overfishing, is the major cause of declining marine species. However, habitat loss and degradation also play a role. According to the report, the following habitat losses may be particularly damaging:
- Coral reefs: Three-quarters of the world’s coral reefs are threatened. The reefs provide homes to more than 25 percent of marine species, but are threatened by increased fishing, agricultural pollution, deforestation, coastal development and shipping, and rising ocean temperatures.
The report noted, alarmingly, that “at current projected levels of warming and acidification, coral reefs could be lost altogether by 2050.”
- Seagrass: In the last 100 years, seagrass coverage has declined by 30 percent. Populations of fish living in seagrass habitats have declined by more than 70 percent from 1970 to 2010.
Loss of seagrass is concerning as it provides habitat for many fish species, stores vast amounts of carbon (more than land-based forests) and also provides grazing for manatees, dugongs and green turtles.
- Mangroves: Mangrove cover declined by nearly 20 percent from 1980 to 2005, largely due to being converted to other uses like aquaculture, agriculture, infrastructure or tourism.
Many species use mangroves for spawning grounds, nurseries, food and shelter, while they also provide coastal protection, carbon sequestration and other benefits to humans.
Pollution presents another threat to marine life. More than 5 trillion plastic pieces (estimated to weigh more than 250,000 tons) are in the world’s oceans. Run-off from agriculture and industry is leading to oxygen-depleted dead zones.
And seabed mining licenses also cover 1.2 million square kilometers of the ocean floor. To date no commercial mining operations have occurred in the deep sea, but interest is growing since it represents an untapped source of metals and mineral deposits.
No one knows what impacts such mining may have on the environment if and when it occurs. Sadly, only 3.4 percent of the ocean is protected, and even this area is not always protected the way it should be. As the report noted:
“For centuries, people have regarded the ocean as an inexhaustible source of food and a convenient dumping ground, too vast to be affected by anything we do.
But in the space of just a few decades, it has become increasingly clear that the ocean has limits and that in many important parts of our seas the sustainability thresholds have been well and truly breached.
… [P]opulations of marine species have fallen dramatically and vast areas of vital habitats have been degraded and destroyed, with implications that we are only just beginning to comprehend.”
Warming Seas Allow Shell-Crushing Predators to Reach New Seas
The world’s oceans are being threatened from all angles, including the introduction of predators to areas where they haven’t lived for tens of millions of years.
In the journal Proceedings of the National Academy of Sciences, researchers described how cold water has kept skeleton-breaking predators like king crabs away from the continental shelf surrounding Antarctica.3 However, rapidly warming seas off the western Antarctic Peninsula may soon change this.
King crabs have been discovered on the adjacent continental slope, with researchers speculating they may soon (within the next few decades) move upward onto the outer shelf, especially since no barriers (such as salinity levels or food resources) are standing in their way.
“Emergence of king crabs on the shelf could have catastrophic consequences for the unique seafloor communities of Antarctica,” the researchers explained. Phys.org further reported:4
“The overall effect of the migration of king crabs to shallower waters, explained postdoctoral scientist and study co-author Kathryn Smith of Florida Institute of Technology, would be to make the unique Antarctic ecosystem much more like ecosystems in other areas of the globe, a process ecologists call biotic homogenization.
Such changes, the researchers conclude, would fundamentally alter the Antarctic sea-floor ecosystem and diminish the diversity of marine ecosystems globally.”
While the outlook for the marine environment looks bleak, WWF noted that it’s not too late to save our seas.
They recommend a need to establish increased protected marine areas and sustainable fisheries, costal development and tourism, while also engaging in sustainable seafood consumption, responsible tourism and efficient use of energy and materials.
By working together, the report notes, governments, business and industry and society as a whole can secure a living ocean for all.