The population of fish and other ocean vertebrates has fallen by nearly half since 1970, says a new report released by the World Wildlife Fund.

The decline, much of which can be attributed to overfishing, could mean serious problems for the world’s human population, according to the new “Living Blue Planet Report,” released Tuesday.

“The picture is now clearer than ever: humanity is collectively mismanaging the ocean to the brink of collapse,” said Marco Lambertini, the director general of WWF International. “Considering the ocean’s vital role in our economies and its essential contribution to food security – particularly for poor, coastal communities – that’s simply unacceptable.”

The period from 1970 to the late 1980s showed the steepest decline in populations worldwide. Although the decreases leveled off in the 1990s and lasted into the new century, the decline of oceangoing vertebrates has again picked up pace, the WWF found.

The study looked at 5,829 populations of 1,234 species of mammals, birds, reptiles and fish, it said. Based on published scientific studies, it also utilized indices created by the Zoological Society of London.

Scombridae, the genus which includes tuna and mackerel, declined by 74 percent over the study period, the authors concluded.

But other species are seriously impacted. Sea cucumber harvests by humans skyrocketed during the study period. More than 50 percent of the species of sea turtles are now classified as endangered. And fish are not just being overfished, they’re also being reduced by loss of underwater habitat. For instance, sea-grass-living fish species have declined 70 percent, and coral-dependent species have declined by 34 percent since 1979. Both habitats are vanishing at a faster pace than previously understood – a third of seagrasses have already vanished worldwide, while a total of 20 percent of the world’s mangroves have disappeared, the WWF found.

Solutions could come in the form of no-take areas of the ocean to build back fish populations, the preservation of underwater habitat and the reduction of marine pollution – and even simple changes such as switching hooks for fishermen to ensure they don’t catch non-target species like sea turtles, according to the report.

An added pressure could be the 3- to 5-degree warming of the world’s oceans by the year 2100, the authors added. If that warming trend continues, coral reefs will disappear by 2050, they concluded.

Three billion people depend on fish as a major source of protein, the report added.

The WWF normally releases their report every other year. But they accelerated its release due to the international attention to environmental concerns – particularly with the coming climate-change conference in December in Paris.

The last Living Planet Report, released in 2014, estimated vertebrate population across the world had declined 52 percent over the same period, based on an analysis of more than 10,000 populations of more than 3,000 species.