The threats facing the sea—all serious on their own—are also combining to create new dangers. One surprising example is the proliferation of jellyfish, causing problems far beyond annoyance to swimmers.
Natural jellyfish predators are disappearing. Bluefin tuna has seen overfished almost to the point of extinction. Sea turtles, particularly leatherbacks and loggerheads, are also caught but mainly they are suffocating on all the plastic bags infesting the seas.
Meanwhile, jellyfish are finding increasingly abundant food sources. The agricultural fertilizers pouring into the sea from farms are encouraging the growth of plankton, while overfishing is depleting the stocks of small fish like sardines which would normally also feed on plankton.
In the absence of predators and competition for food, jellyfish populations are growing unchecked. The trend is amplified by climate change and increasingly warm waters. The latest scientific research has shown that in certain zones, such as along the coast of Namibia, the biomass of jellyfish has already exceeded that of the fish.
The jellyfish example shows how attacks on the marine ecosystem disturb the delicate equilibrium of the food chain, with cascading consequences making it very difficult for humans to find suitable solutions. The problem of marine resources must be tackled from many different angles.